Patent Publication Number: US-2023158596-A1

Title: Electrode assembly for arc welding

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
     This application claims the benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63/264,358, entitled ELECTRODE ASSEMBLY FOR ARC WELDING, filed Nov. 19, 2021, and to U.S. Provisional Patent Application No. 63/370,430, entitled ELECTRODE ASSEMBLY FOR ARC WELDING, filed Aug. 4, 2022. The entirety of each of the above applications is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Field 
     The disclosed technology generally relates to welding technologies and more particularly to electrode assemblies for arc welding, e.g., submerged arc welding. 
     Description of the Related Art 
     Various welding technologies utilize welding wires that serves as a source of metal. For example, in metal arc welding, an electric arc is created when a voltage is applied between a consumable weld electrode wire, which serves as one electrode that advances towards a workpiece, and the workpiece, which serves as another electrode. The arc melts a tip of the metal wire, thereby producing droplets of the molten metal wire that deposit onto the workpiece to form a weldment or weld bead. 
     Technological and economic demands on welding technologies continue to grow in complexity. For example, the need for higher bead quality in both appearance and in mechanical properties continues to grow, including high yield strength, ductility and fracture toughness. Simultaneously, the higher bead quality is often demanded while maintaining economic feasibility. Some welding technologies aim to address these competing demands by improving the consumables, e.g. by improving the physical designs and/or compositions of the electrode wires. 
     Submerged arc welding (SAW) can provide highly economic solutions for some applications. The high deposition rates attained with submerged arc are chiefly responsible for the economies achieved with the process. 
     SUMMARY OF THE INVENTION 
     In an aspect, an electrode assembly for submerged arc welding (SAW) comprises a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode. The extension portion is elongated in a wire feed direction and is configured to electrically insulate the consumable electrode from a work piece during welding with an insulating sleeve surrounding the consumable electrode. The electrode assembly is configured such that, during SAW with consumable electrode inserted therethrough, a ratio between an electrical stick-out distance, which is measured between a contact tip portion disposed at an end of the head portion and the arcing tip of the consumable electrode, and a diameter of the electrode exceeds 30. 
     In another aspect, an electrode assembly for submerged arc welding, comprises a head portion and an extension portion arranged serially with the head portion, wherein the head portion and the extension portion are configured to feed a consumable electrode therethrough. The extension portion is configured to be disposed closer to an arcing tip of the consumable electrode relative to the head portion and comprises an envelope formed of a nonmagnetic material and an insulating sleeve disposed within the envelope and comprising a solid insulating material configured to surround the consumable electrode. 
     In another aspect, an extension portion configured for a submerged arc welding electrode assembly comprises an envelope formed of a nonmagnetic material and an insulating sleeve disposed within the envelope and comprising a solid insulating material configured to surround a consumable electrode. The extension portion is configured to be arranged serially with a head portion of the electrode assembly and to receive a consumable electrode from the head portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    schematically illustrates a submerged arc welding (SAW) system according to embodiments of the present technology. 
         FIG.  2    illustrates a conventional electrode assembly for a SAW system. 
         FIG.  3 A  illustrates a conventional electrode assembly for a SAW system over a workpiece having a shallow groove. 
         FIG.  3 B  illustrates a long stick-out (LSO) electrode assembly for a SAW system over a workpiece having a shallow groove. 
         FIG.  4 A  illustrates a conventional electrode assembly for a SAW system over a workpiece having a deep groove. 
         FIG.  4 B  illustrates an LSO electrode assembly for a SAW system over a workpiece having a deep groove. 
         FIG.  5    is a graph showing an experimental comparison of deposition rates versus current for both conventional SAW assemblies and LSO SAW assemblies. 
         FIGS.  6 A- 6 C  depict perspective views of an LSO electrode assembly having an extension portion according to embodiments of the present technology. 
         FIG.  7 A  is an isometric view of an LSO extension portion according to embodiments of the present technology. 
         FIG.  7 B  is an exploded view of the LSO extension portion depicted in  FIG.  7 A . 
         FIG.  7 C  is a perspective view of an envelope or nozzle body for an LSO extension portion according to embodiments of the present technology. 
         FIG.  7 D  is a cross-sectional view of the envelope or nozzle body depicted in  FIG.  7 C  taken along line A-A. 
         FIG.  7 E  depicts a perspective view of an insulating sleeve for an LSO extension portion according to embodiments of the present technology. 
         FIG.  7 F  is a cross-sectional view of the nozzle body depicted in  FIG.  7 E  taken along line B-B. 
         FIG.  8    is a cross-sectional view of an LSO extension portion according to embodiments of the present technology. 
         FIGS.  9 A and  9 B  show multi-arc LSO SAW assemblies according to embodiments of the present technology. 
     
    
    
     DETAILED DESCRIPTION 
     In processes using a consumable electrode, the electrode or the wire melts to provide an additive metal that fills a gap to form a weld joint that joins two metal workpieces. The welding processes using consumable electrodes include shielded metal arc welding (SMAW), gas metal arc welding (GMAW) or metal inert gas (MIG) welding, flux-cored arc welding (FCAW), metal-cored arc welding (MCAW), and submerged arc welding (SAW), among others. 
     Submerged Arc Welding 
       FIG.  1    schematically illustrates a submerged arc welding (SAW) system  100  for depositing a filler or weld metal onto a workpiece  102 . The system  100  includes a bare metal electrode wire  104  having a tip  106 , a contact tip  110  coupled to the electrode  104 , and a power supply  108 , which is electrically coupled to the contact tip  110  and the workpiece  102 . The system  100  also includes a flux delivery system  112 , which is configured to dispense flux  114  onto the workpiece  102  during the SAW process. The electrode  104  generally comprises a metal or alloy while the flux comprises granular fusible material. During the SAW process, heat is derived from an arc  116  between a bare metal electrode  104  and a workpiece  102 . The arc is shielded by a blanket of the flux  114  which is placed over the joint area ahead of the arc  116 . Filler metal is obtained primarily from the electrode wire  104  which is continuously fed through the blanket of flux  114  into the arc  116  and pool  122  of molten flux. Additional filler metal may be obtained by adding cold wire to the weld pool  122  or from metal powder contained in the flux  114 . Accordingly, in SAW, unlike the other fluxed processes, two consumables (the electrode wire  104  and the flux  114 ) are used and these two consumables may be supplied separately. 
     The distinguishing feature of SAW is the flux  114 , which covers the weld area and prevents arc radiation, sparks, spatter and fumes from escaping. The flux  114  allows for achieving high deposition rates and high quality weld deposit characteristics. In addition to shielding the arc  116  from view, the flux  114  provides a slag  118  which protects the weld metal  120  as it cools, deoxidizes and refines the weld metal  120 , insulates the weld to reduce the cooling rate and helps shape the weld contour. 
     During the SAW process, the heat of the arc  116  melts some of the flux  114  along with the tip  106  of the electrode  104  to form a weld pool  122 , as illustrated in  FIG.  1   . The tip  106  of the electrode  104  and the welding zone are always surrounded and shielded by molten flux  114 , which is itself covered by a layer of unfused flux  114 . The electrode  104  is held a short distance above the workpiece  102  with the arc  116  forming between the electrode  104  and the workpiece  102 . As the electrode  104  progresses along the joint, the lighter molten flux  114  rises above the molten metal in the weld pool  122  as slag  118 . The molten metal in the weld pool  122 , which has a higher melting (freezing) point, solidifies while the slag  118  above it is still molten. The slag  118  then freezes over the newly solidified weld metal  120 , continuing to protect the metal  120  from contamination while it is very hot and would react with atmospheric oxygen and nitrogen. After cooling and removing any unfused flux  114  for reuse, the solidified slag  118  may be easily removed from the weld. 
     The power supply  108  generates a voltage and current for the system  100  and the voltage and current are applied to the workpiece  102  and the electrode  104 . The current is applied to the electrode via the contact tip  110 . High currents can be used in submerged arc welding and extremely high heat can be generated. Because the current is applied to the electrode  104  a short distance above its tip  106 , relatively high amperages can be used on small diameter electrodes. This results in extremely high current densities on relatively small cross sections of electrode. Currents as high as or exceeding 600 amperes can be carried on electrodes as small as 64″, giving a density in the order of 100,000 amperes per square inch six to ten times that carried on stick electrodes. 
     Because of the high current density, the melt off rate is much higher for a given electrode diameter than with stick-electrode welding. The melt-off rate is affected by the electrode material, the flux  114 , type of current, polarity, and length of wire beyond the point of electrical contact in the gun or head. 
     Submerged arc welding may be performed with either DC or AC power. Direct current gives better control of bead shape, penetration, and welding speed, and starting is relatively easier. Bead shape is usually best with DC electrode positive (DCEP or reverse polarity), which also provides maximum penetration. Highest deposition rates and minimum penetration can be obtained with DC electrode negative (DCEN). Alternating current minimizes arc blow and gives penetration between that of DCEP and DCEN. 
     The insulating blanket of flux  114  above the arc  116  prevents rapid escape of heat and concentrates it in the welding zone. Not only are the electrode  104  and base metal of the workpiece  102  melted rapidly, but the fusion is deep into the base metal. The deep penetration allows the use of small welding grooves, thus minimizing the amount of filler metal per foot of joint and permitting fast welding speeds. Fast welding, in turn, minimizes the total heat input into the assembly and, thus minimizes problems of heat distortion. Even relatively thick joints can be welded in one pass by submerged arc welding. 
     Welds made under the protective layer of flux  114  have good ductility and impact resistance and uniformity in bead appearance. Mechanical properties at least equal to those of the base metal are consistently obtained. In single-pass welds, the fused base material is large compared to the amount of filler metal used. Thus, in such welds the base metal may greatly influence the chemical and mechanical properties of the weld. For this reason, it is sometimes unnecessary to use electrodes of the same composition as the base metal for welding many of the low-alloy steels. However, the chemical composition and properties of multipass welds are less affected by the base metal and depend to a greater extent on the composition of the electrode, the activity of the flux, and the welding conditions. 
     Through regulation of current, voltage, and travel speed, the operator can exercise close control over penetration to provide any depth ranging from deep and narrow with high-crown reinforcement, to wide, nearly flat beads with shallow penetration. Beads with deep penetration may contain on the order of 70% melted base metal, while shallow beads may contain as little as 10% base metal. In some instances, the deep-penetration properties of submerged arc welding can be used to eliminate or reduce the expense of edge preparation. 
     The flux serves several functions in submerged arc welding. These include covering the molten weld metal to protect it from the atmosphere and acting as a slag which refines the molten deposit by scavenging oxides and other non-metallic inclusions. Metallic additions to the flux can add to the alloy content of the deposit and deoxidize it. 
     There are four types of fluxes based on their method of manufacture; fused, bonded, agglomerated and mechanically mixed. 
     Fluxes are also identified as basic, acid, and neutral. Basic fluxes contain oxides of metals which dissociate easily while acidic fluxes contain oxides which dissociate to a small extent. A neutral flux does not add or subtract from the composition of the weld deposit. Fluxes having a ratio of CaO or MnO to SiO 2  which is greater than one are considered basic, those near one are considered neutral, and those less than one are acidic. 
     With proper selection of equipment, submerged arc is widely applicable to the welding requirements of industry. It can be used with all types of joints, and permits welding a full range of carbon and low alloy steels, from 16-gage sheet to the thickest plate. It is also applicable to some high-alloy, heat-treated, and stainless steels, and is a favored process for rebuilding and hard surfacing. Any degree of mechanization can be used—from the hand-held semi-automatic gun to boom or track-carried and fixture held multiple welding heads. 
     The high quality of submerged arc welds, the high deposition rates, the deep penetration, the adaptability of the process to full mechanization, and the comfort characteristics (no glare, sparks, spatter, smoke, or excessive heat radiation) make it a preferred process in steel fabrication. It is used extensively in ship and barge building, railroad car building, pipe manufacture, and in fabricating structural beams, girders, and columns where long welds are required. Automatic submerged arc installations are also key features of the welding areas of plants turning out mass-produced assemblies joined with repetitive short welds. 
     Other factors than deposition rates enter into the lowering of welding costs. Continuous electrode feed from coils, ranging in weight from 60 to 1,000 pounds, contributes to a high operating factor. Where the deep-penetration characteristics of the process permit the elimination or reduction of joint preparation, expense is reduced. After the weld has been run, cleaning costs are minimized, because of the elimination of spatter by the protective flux. 
     When submerged-arc equipment is used properly, the weld beads are smooth and uniform, so that grinding or machining are rarely required. Since the rapid heat input of the process minimizes distortion, the costs for straightening finished assemblies are reduced, especially if a carefully planned welding sequence has been followed. Submerged arc welding, in fact, often allows the pre-machining of parts, further adding to fabrication cost savings. 
     Because of these and other advantages provided by SAW, there is a desire and need to further improve various aspects of SAW, including even higher productivity and weld quality. For example, as one of the technical advantages of SAW derives from preheating the consumable electrode, there is a desire and need to further improve the preheating arrangement through improved electrode assembly design. 
     Long Stick-Out Electrode Assembly for Submerged Arc Welding 
       FIG.  2    illustrates an electrode assembly  200  defining an electrical stick-out and positioned over a workpiece  202 . The electrode assembly  200  includes a head portion  204  configured to receive a consumable electrode  206 . The head portion  204  includes a contact tip  210 , an electrode guide tube  212 , and an insulated guide  214 . The contact tip  210  is disposed radially around the electrode  210  and is configured to transfer current from a power source (e.g., power source  108  shown in  FIG.  1   ) to the electrode  206 . The electrode  206  includes a tip portion  208  configured to extend beyond the head portion  204 . The portion of the electrode  206  that extends between the end portion  208  and the end of the head portion  204  is referred to as the visible stick-out  218  while the portion of the electrode  206  that extends between the tip portion  208  and the contact tip  210  is referred to as the electrical stick-out or electrical electrode extension  216 . Unless stated otherwise, a stick-out length as used herein refers to the length of the electrical stick-out  216 , which is the parameter predominantly affecting the electrical response of the electrode assembly  200 . During operation of the electrode assembly  200 , the tip portion  208  is positioned adjacent to the workpiece  202  and the distance between the contact tip  210  and the workpiece  202  is referred to as the contact tip to work distance (CTWD)  220 . 
     The electrical stick-out  216  of the electrode wire  206  is preheated by Joule heating. If the electrical electrode extension  216  is not sufficiently long, the electrode wire  206  may not be sufficiently preheated. On the other hand, an increase of the length of the electrical stick-out  216  increases the electrical resistance of the circuit, which in turn increases the heating and hence the temperature of the tip  208  of the electrode  206 , leading to increased melting and deposition rate. The length of the electrical stick-out  216  in turn controls the dimensions of the weld bead since the length of the filler wire extension affects the burn-off rate. Further, electrical electrode extension  216  exerts an influence on penetration through its effect on the welding current. As the length of the electrical electrode extension  216  is increased, the preheating of and the voltage drop across the electrode wire  206  increases. The greater voltage drop can result in the bead shape being more convex, which can be overcome by increasing the input voltage by 2-5 volts. The length of the electrical stick-out  216  distance can be approximately 3-10 times a diameter of the electrode  206  depending on the type of steel being welded, for traditional steel welding processes. 
       FIG.  3 A  depicts an electrode assembly  300 A positioned over a workpiece  302  having a groove  303 . In the illustrated configuration, the stick-out portion  316 A of the electrode  306 A extends a conventional distance beyond the contact tip  310 A (e.g., 3 to 12 times the diameter of the electrode). The electrode assembly  300 A is positioned such that the head portion  304 A is positioned over the groove  303  and the tip  308 A of the electrode  308 A is within the groove  303 . More specifically, the head portion  304 A is positioned such that the tip  308 A is adjacent to the bottom of the groove  303  without the head portion  304 A contacting the workpiece  302 . In the illustrated embodiment, the tip  308 A is positioned within the groove such that the CTWD  320 A is about 25 mm. Positioning the tip  308 A closely adjacent to the bottom of the groove  303  allows for better and more consistent arcing between the tip  308 A and the workpiece  302 , thereby resulting in a more consistent deposition of filler metal into the groove  303  and improved weld quality and efficiency. 
     To further improve upon submerged arc welding (SAW) technology, a long stick-out (LSO) or extended stick-out technology developed by Lincoln Electric company may be employed. Long stick-out SAW refers to SAW processes in which the length of the wire that sticks out (“stick-out length”) of the electrode contact tip, or the contact-to-work distance (CTWD), is increased relative to conventional SAW processes, e.g., longer than about 25 mm. As used herein, LSO refers to an electrode configuration in which the electrical stick out exceeds about 10 times a diameter of the electrode  306 A. The longer stick-out length allows for a greater length of the electrode to be preheated prior to melting at the electrode tip. The preheating allows for melt-off rate to increase as a result, as it is easier to melt a preheated electrode wire for a given current density. The LSO SAW process can provide significant improvement in productivity and can provide up to 100% increase in submerged arc welding deposition rates over traditional SAW processes. The LSO SAW process can reduce or eliminate arc striking problems by allowing complete tailoring of the arc start characteristics. The LSO SAW can also provide improved control over the input of energy into the weld, lower heat input (less distortion), flux/wire ratio reduction. 
       FIG.  3 B  depicts an electrode assembly  300 B positioned over the groove  303  in workpiece  302 . The electrode assembly  300 B employs an LSO technology such that the electrical stick-out  316 B extends beyond the contact tip  310 B by substantially more than the stick-out  316 A extending beyond the contact tip  310 A ( FIG.  3 A ). For example, in some embodiments, the stick-out  316 B can have a length between 10 and 40 times the diameter of the electrode  308 B. In some embodiments, the stick-out  316 B can have a length that is more than 40 times the diameter of the electrode  308 B. The increased length of the stick-out portions  316 B allows for a greater length of the electrode  306 B to be preheated prior to melting at the electrode trip, thereby allowing for increased melt-off and deposition rates, as explained above. 
     The increased length of the stick-out portions in LSO SAW systems also allows for the LSO systems to be used to easily fill grooves that conventional SAW systems are either incapable of filling or can only fill using extremely precise arrangements and high operator skill. Specifically, while conventional SAW systems can be used with wide and/or short grooves, conventional SAW systems typically cannot be easily used with deeper and/or narrower grooves.  FIGS.  4 A and  4 B  depict electrode assemblies  400 A,  400 B positioned over a workpiece  402 , where the electrode assembly  400 A is generally similar to the assembly  300 A shown above in connection with  FIG.  3 A  and electrode assembly  400 B is generally similar to the assembly  300 B shown in above in connection with  FIG.  3 B . The workpiece  402  has a groove  403  which is substantially deeper and narrower than the groove  303  shown in above in  FIGS.  3 A and  3 B . Accordingly, when the assemblies  400 A and  400 B are placed over the groove  403 , the head portions  404 A,  404 B are positioned further from the bottom of the groove, resulting in the CTWD  420  being substantially longer than 25 mm. For example, in some embodiments, the CTWD or the electrical stick-out can be 125 mm or longer. When the electrode assembly  400 A is positioned over the workpiece  402  such that the tip  408 A is within the groove  403 , the size and shape of the head portion  404 A prevents it from being positioned further within the groove  403  without contacting and interacting with the workpiece  402 . As a result, the tip  408 A is spaced excessively far from the bottom of the groove  403 , which results in poor arcing between the electrode  406 A and the workpiece  402 , thereby resulting in a poor filler metal deposition rate and poor weld quality. Accordingly, the conventional stick-out length  416 A of the electrode assembly  400 A prevents the electrode assembly  400 A from forming high-quality welds within deep and/or narrow grooves. In contrast, when the electrode assembly  400 B is positioned over the workpiece  402 B such that the tip  408 B is within the groove  403 , the increased stick-out length of the assembly  400 B allows for the tip  408 B to be adjacent to the bottom of the groove. The reduced distance between the tip  408 B and the bottom of the groover  403  results in better arcing between the electrode  406 B and the workpiece  402 . Accordingly, in addition to improving weld quality and deposition rates due to allowing for additional preheating of the electrode prior to arcing, LSO SAW techniques also allow for the deposition of filler metal into the deeper and narrower grooves than conventional SAW techniques. 
     According to various embodiments, the LSO SAW electrode assemblies are capable of achieving significantly higher deposition rates compared to conventional SAW electrode assemblies for the same current. During the welding process, current is transferred into the electrode by the contact tip at a specific amperage and voltage. As the current flows through the electrode toward the tip of the electrode, the voltage drops and the electrode heats up. At the tip of the electrode, the current arcs to the workpiece. For LSO SAW assemblies, the increased length of the electrode results in a higher fraction of the total voltage drop occurring within the electrode than in conventional SAW assemblies. In some embodiments, the LSO SAW assemblies can be configured such that the voltage drop between the contact tip and the tip of the consumable electrode is at least 5%, at least 10%, at least 15%, or at least 20% (or is a value in a range defined by any of these values) of a total voltage drop across the total CTWD. In other embodiments, the electrode assembly is configured such that the voltage drop between the contact tip and the tip of the consumable electrode represents at least 1/30 of the total voltage drop across the CTWD, 1/15 of the total voltage drop across the CTWD, 1/10 of the total voltage drop across the CTWD, 1/7 of the total voltage drop across the CTWD, ⅕ of the total voltage drop across the CTWD, or a value in a range defined by any of these values. For example, in a conventional SAW electrode assembly where the total voltage drop along the CTWD is 30V, only about 1V of that total voltage drop may occur within the consumable electrode while the rest (about 29V) may drop across the arc length. In contrast, for an LSO SAW system of the same total voltage drop of 30V, about 4V of may drop occurs across the CTWD while the rest (about 26V) may drop cross the arc length. The increased voltage drop through the longer electrode results in the electrode being heated to a higher temperature than the electrode in a conventional SAW configuration and, as a result, the deposition rate increases. 
     Experiments have shown that the deposition rate per current for LSO SAW assemblies can exceed 0.05 lbs./hr./A, 0.06 lbs./hr./A, 0.07 lbs./hr./A, 0.08 lbs./hr./A, or a value in range defined by any of these values during welding.  FIG.  5    illustrates an experimental comparison of deposition rates versus current for both conventional SAW assemblies and LSO SAW assemblies, where the dashed lines represent the deposition rates for conventional SAW assemblies and the solid lines represent the deposition rates for the LSO SAW assemblies. In this experiment, the CTWD for the conventional SAW assembly was 1.25″, the CTWD for the LSO SAW assembly was 5″, and the diameter of the electrode was 5/32″. Three different power delivery methods were used: positive constant DC power, balanced square wave AC power, and 25% balanced square wave AC power. For the LSO SAW assemblies, a deposition rate exceeding 35 lbs./hr. can be achieved with current less than about 900 A, 850 A, 800 A, 750 A, 700 A, or in a range defined by any of these values, e.g., at about 700 A-750 A. For conventional SAW electrode assemblies, however, similar deposition rates are only projected to be achieved at a current exceeding about 900 A. Advantageously, the improvement in deposition rate over conventional SAW electrodes increases at higher current, as Joule heating (FR) varies as a square of current. That is, the relative improvement in deposition rate is projected to increase with increasing current. 
     In LSO SAW systems, the consumable electrode (e.g., electrodes  306 B,  406 B) extends beyond the end of the head portion (e.g., head portions  304 B,  404 B) such that the arcing tip (e.g., tips  308 B,  408 B) is visible. As previously discussed, the portion of the electrode that extends beyond the contact tip portion is referred to as the electrical stick-out. In some embodiments, the electrical stick-out is measured based on the diameter of the electrode. The length of the electrical stick-out in SAW can depend on the type of steel being welded, e.g., whether the steel being welded is a low alloy steel containing less than about 8 wt. % of non-iron elements or a high alloy steel containing greater than about 8 wt. % of non-iron elements. In conventional SAW for welding low and mild steel, the electrical stick-out length can be approximately 7-10 times the diameter of the electrode. In conventional SAW for welding high alloy steel, the electrical stick-out length can be approximately 3-5 times the diameter of the electrode. For example, in embodiments where the diameter of the electrode is 5/32″, the visible stick-out length can be approximately 1-1.5 inches. In contrast, in LSO SAW according to various embodiments, a stick out-to-diameter ratio, or a ratio between an electrical stick-out distance, measured between a contact tip portion disposed at an end of the head portion and the arcing tip of the consumable electrode, and a diameter of the electrode exceeds 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 or has a value in a range defined by any of these values. For example, these ratios can be obtained by electrical stick-out distance exceeding 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm, 155 mm, 160 mm, 165 mm or a value in a range defined by any of these values, and a diameter of the electrode having any value between 2.5 mm and 5.0 mm. For instance, for an electrical stick-out length of 155 mm and an electrode diameter of 3.2 mm, the stick out-to-diameter ratio is about 48, whereas for an electrical stick-out length of 125 mm and an electrode diameter of 4.0 mm, the stick-out-to-diameter ratio is about 31. 
     While increased stick-out length can advantageously provide certain advantages, such as higher deposition rate, various problems can arise for stick-out lengths exceeding, e.g., 25 mm, when conventional electrode assemblies are used. For example, the heated wire can move out of alignment and wander in the welding groove as the stick-out distance increases. This can pose a problem especially in welding deep and narrow grooves that may be used to minimize time and cost of joining thick sections, as LSO welding electrode assemblies can be too bulky to reach the bottom of the groove. To address this and other challenges, some electrode assemblies include an extension portion that serves as an insulated guide for the electrode. The extension portion provides, among other things, electrical and thermal insulation as well as mechanical rigidity to the heated electrode. However, some extensions may not be suitable for some applications, e.g., for filling narrow and deep grooves such as a triangular or U-shaped groove having a depth exceeding 4 inches and having an angle of an apex that is 16 degrees or less. Some designs of the electrode assemblies that include extension portions may be insufficient with respect to one or more of: optimized vertical and lateral dimensions, thermal and electrical insulation, arc instability caused by magnetic materials and compact flux delivery. In contrast various embodiments of the electrode assembly for submerged arc welding described herein address these and other needs. 
     Long Stick-Out Electrode Assembly with Covered Insulating Extension Portion 
     Disclosed herein are various electrode assemblies for improved LSO SAW and method of manufacturing and using the same.  FIGS.  6 A and  6 B  depict an example electrode assembly  600  configured for long stick-out submerged arc welding, according to various embodiments. The electrode assembly  600  according to various embodiments comprises a head portion  602 , an extension portion  604 , and a bracket  612 . The head portion  602  and extension portion  604  are arranged serially and configured to feed a consumable electrode  606  therethrough. The bracket  612  is fixedly attached to and electrically insulated from the head portion  602  and the extension portion  604  and is configured to securely hold the extension portion  604  such that the extension portion  604  remains aligned with the head portion  602 . The electrode  606  includes a tip configured to be positioned adjacent to a workpiece during the welding process. The head portion  602  includes a contact tip  610  that is in electrical contact with the electrode  606  and is configured to provide power to the electrode  606  during welding. The consumable electrode  606  is fed through the head portion  602  with a wire guide and exits at the contact tip  610 . The consumable electrode  606  is subsequently fed through the extension portion  604 , which is elongated in a wire feed direction. During SAW, the head portion  602  is disposed to be distal to the tip  608  of the electrode and the extension portion  604  is disposed to be proximal to the tip  608 . 
     In the illustrated example, the serially arranged head portion  602  and extension portion  604  are arranged serially and do not have vertically overlapping portions. While in the illustrated configuration the head portion  602  and the extension portion  604  are physically separated and exposes the consumable electrode  606  therebetween, embodiments are not so limited. In other arrangements, the contact tip portion and the extension portion may contact each other. It will be appreciated that, in the illustrated embodiment, because of the serial arrangement of the head portion  602  and the extension portion  604 , the contact tip  610  and the extension portion  604  are also serially arranged, such that no portion of the extension portion  604  overlaps the contact tip  610 . Further, the outer surface of the extension portion  604  forms the outermost surface of the electrode assembly  600  adjacent the arcing tip of the exposed consumable electrode  606 . 
     In some embodiments, the electrode assembly  600  also includes a flux delivery system  614 . The flux delivery system  614  is configured to deposit flux onto the workpiece during the SAW process. Advantageously, the flux delivery system  614  is configured such that the flux delivery system  614  does not limit the dimensions of a groove of a workpiece the extension portion  604  is capable of being inserted into. In the illustrated embodiment, the flux delivery system  614  is fixedly attached to the extension portion  604  with the bracket  612 . In other embodiments, however, the flux delivery system  614  can be fixedly attached to the extension portion  604  in some other way. In still other embodiments, the flux delivery system  614  may not be fixedly attached to the extension portion  604 . Instead, in some embodiments, the flux delivery system  614  may be fixedly attached to some other portion of the electrode assembly  600  or may not be attached to any portion of the electrode assembly  600 . Additionally, because the electrode assembly  600  is configured for SAW, embodiments of the electrode assembly  600  are configured to be used in SAW systems without the use of a shielding gas. 
     The extension portion  604  is configured to electrically insulate the consumable electrode  606  from a work piece during welding with an insulating sleeve formed of a solid insulating material, e.g., a ceramic material, surrounding the consumable electrode. In some implementations, the solid insulating material may be a composite or layered insulator, e.g., a composite or layered ceramic. During welding, the consumable welding electrode  606  is preheated in the insulated extension portion  604  by Joule heating, prior to being melted at the arcing tip  608  of the consumable electrode  606 . In some embodiments, the electrode assembly  608  is configured to heat the consumable electrode within the extension portion to a temperature up to 600° C., up to 700° C., up to 800° C., up to 900° C., or to a temperature in a range defined by any of these values. 
       FIG.  6 C  depicts the electrode assembly  600  positioned within a groove  616  formed in a workpiece  618 . In various embodiments, the extension portion  604  is configured to electrically insulate the consumable electrode  606  from the workpiece  618  and has a shape, length and a lateral dimension such that the extension portion  604  is configured to be capable of being inserted into narrow grooves  616  as shown in  FIG.  6 C . The insulating sleeve formed of a solid insulating material such as a ceramic material surrounding the consumable electrode  606  inside the extension portion  604  allows the lateral dimension of the extension portion  604  to be significantly reduced without increasing the likelihood of shorting the electrode and the workpiece. For example, in some embodiments, while the contact tip  610  can have a width up to 30 mm (or about 1.18 inches), the extension portion  604  can have a width of about 16 mm (or about 0.79 inches). Additionally, in some embodiments, the extension portion can have a length of 110 mm (or about 4.33 inches). In these embodiments, the head portion  602  is spaced sufficiently far apart from the tip  608  of the electrode such that, during welding, the wider head portion  602  can positioned outside of the groove  616  in the workpiece  618  while the narrower extension portion  604  is disposed within the groove. As a result, the narrower extension portion  604  is configured to not contact a sidewall of narrow grooves  616  such as a triangular trench having a depth exceeding 4 inches, 5 inches, 6 inches, 7 inches, or a value in a range defined by any of these values, and having an angle  620  of an apex that is less than 16 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, or a value in a range defined by any of these values, while the tip  608  of the consumable electrode  606  contacts the apex. It will be appreciated that shallower the groove  616 , the narrower the apex angle  620  can be. For example, the relationship may follow an example dependence such as that shown in TABLE 1, without limitation. It will be appreciated that the grooves or trenches may not have a triangular shape in cross section. Instead, some grooves may have, e.g., a rectangular or tapered rectangular shape. In these geometries, the “apex” angle  620  or the acceptance angle can be defined by an arctan of a width over depth of the trench. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Groove Depth 
                 Apex Angle 
               
               
                   
                   
               
             
            
               
                   
                 &gt;2 in. 
                  &lt;8 deg. 
               
               
                   
                 &gt;3 in. 
                 &lt;10 deg. 
               
               
                   
                 &gt;4 in. 
                 &lt;12 deg. 
               
               
                   
                   
               
            
           
         
       
     
     In various embodiments, the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding while having an outer surface formed of a substantially non-magnetic material surrounding the consumable electrode.  FIG.  7 A  depicts an extension portion  700  and  FIG.  7 B  depicts an exploded view of the extension portion  700 . The extension portion  700  has opposing first and second ends  702 A,  702 B and an opening  704  that extends between the first end  702 A and the second end  702 B. The extension portion  700  further includes an envelope or nozzle body  706 , an insulating sleeve  708  disposed within the nozzle body  706 , a c-clamp  710 , and a nut  712 . As will be discussed in greater detail elsewhere in the application, the insulating sleeve  708  can have a generally cylindrical shape that defines the opening  704 . The extension portion  700  is configured to be fixedly attached to the head portion of an electrode assembly (e.g., head portion  602  of electrode assembly  600  shown in  FIGS.  6 A- 6 C ) such that the first end  702 A is proximal to a contact tip within the head portion (e.g., contact tip  610 ) while the second end  702 B is distal to the contact tip. During the SAW process, the extension portion  700  receives a consumable electrode (e.g., electrode  606  in  FIGS.  6 - 6 C ) from the head portion and the electrode is disposed within the opening  704  such that it extends between the first and second ends  702 A,  702 B of the extension portion  700 . The insulating sleeve  708  is configured to directly surround the consumable electrode without an intervening structure or feature other than air. 
     In some embodiments, the extension portion  700  is fixedly attached to the head portion with a bracket (e.g., bracket  612  in  FIG.  6 B ) and the c-clamp  710  and nut  712  can be used to fixedly attach the extension portion  700  to the bracket. However, this is merely one possible method of fixedly attaching the extension portion  700  to the head portion and other suitable attachment mechanisms may be used instead. For example, in some embodiments, the extension portion  700  can be fixedly attached to the bracket by welding the nozzle body  706  to the bracket. In these embodiments, the extension portion  700  may not include the c-clamp  710  and nut  712 . 
       FIG.  7 C  is a perspective view of the envelope or nozzle body  706  and  FIG.  7 D  is a cross-sectional view of the envelope or nozzle body  706  taken along line A-A. The envelope or nozzle body  706  includes first and second ends  714 A,  714 B and a cavity or opening  716  that extends between the first and second ends  714 A,  714 B and that is configured to receive and house the insulating sleeve  708  therein. In various embodiments, the envelope or nozzle body  706  can have a generally cylindrical shape having at least a portion that tapers inwards toward the second end  714 B. As will be discussed in greater detail elsewhere in the application, the tapered second end  714  advantageously allows multiple electrode assemblies to be positioned more closely adjacent to each other when used in a multi-arc configuration. 
     According to embodiments, the envelope or nozzle body  706  functions as an outer envelope for the extension portion  700  and can be formed of a non-magnetic material. When the envelope  706  is formed of a magnetic material, it can exert or modify the magnetic field in its vicinity, thereby degrading, modifying or blowing the arc plasma. Furthermore, a magnetic material can become magnetized or demagnetized over time, thereby resulting in a drift of the arc characteristics. To address these and other concerns, in some embodiments, the envelope  706  is formed of a non-magnetic material such as a non-magnetic steel. As described herein, a non-magnetic steel refers to a steel having a low ferrite content and a high austenitic content, e.g., a steel having a ferrite number (FN) less than about 8. For example, the non-magnetic steel can be a high Cr-content steel, such as a stainless steel. Forming the nozzle body  706  out of a non-magnetic material advantageously improves the consistency of the magnetic field around the consumable electrode and reduces arc instability and welding defects. The non-magnetic material also reduces any instability of the welding parameters that may be caused by magnetization of the extension portion  706  over time. 
       FIG.  7 E  is a perspective view of the insulating sleeve  708  and  FIG.  7 F  is a cross-sectional view of the insulating sleeve  708  taken along the line B-B. The insulating sleeve  708  includes first and second ends  718 A,  718 B and has a generally cylindrical shape that forms the opening  704  through which the consumable electrode passes. In representative embodiments, the insulating sleeve  708  is formed of an insulating material that thermally and electrically insulates the electrode as it passes through the extension portion  700 . Advantageously, forming the insulating sleeve  708  from an insulating material allows for increased preheating of the consumable electrode during the welding process because the insulating material reduces dissipation of heat generated by the preheating electrode to the surrounding. Instead, the insulating sleeve  708  increases the relative amount of heat that remains trapped within the extension portion  700 , thereby increasing the efficiency of preheating of the electrode, which in turn results in higher deposition and melt off rates and higher productivity. 
     Furthermore, the insulating sleeve  708  allows the extension portion  700  to contact groove sidewalls of the workpiece without risking an electrical short between the electrode and the workpiece. When the electrode is heated to above-described temperatures during welding, the insulating material may lose some of its resistivity. To ensure that voltage drop caused by such contact remains relatively low, the solid insulating material is formed of an insulating material and configured to sustain a voltage difference of at least 5V, 10V, 15V, 20V, 25V or a value in range defined by any of these values, without substantially conducting when an outer surface of the extension portion  700  contacts the workpiece. 
     In some embodiments, the insulating sleeve  708  is formed from an insulating ceramic material. For example, in some embodiments, the insulating sleeve  708  is formed of alumina (Al 2 O 3 ) or silicon carbide (SiC). In other embodiments, however, other insulating materials can be used. For example, in some embodiments, the insulating sleeve  708  comprises silicon nitride, magnesia-stabilized zirconia, yttria-stabilized zirconia, magnesium oxide, or a zirconia-toughened alumina. The ceramic insulating sleeve  708  can be manufactured using various methods such as powder pressing, cold isostatic pressing, hot pressing, injection molding and slip casting. Additionally, in some embodiments, the ceramic insulating sleeve  708  is not machined. 
     In various embodiments, the extension portion  700  is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the length of the electrical stick-out between the contact tip portion (e.g., contact tip  610  shown in  FIGS.  6 A- 6 C ) and the tip of the consumable electrode (e.g. electrode  606  shown in  FIGS.  6 A- 6 C ) is substantially longer than in conventional SAW electrode assemblies. For example, in some embodiments, the extension portion  700  has a suitable length for supporting the electrical stick out length described herein. For example, as described above, the electrical stick out can be 125 mm or longer. Accordingly, the extension portion  700  has a length that can be up to approximately 110 mm. The visible stick-out, which corresponds to the portion of the consumable electrode that extends beyond the extension portion  700 , can have a length that is a difference between these two values. With this configuration, the length of the electrical stick-out, which includes the portions of the electrode within the extension portion  700  and the visible stick-out, can be at least as large as the sum of the visible stick-out length and the length of the extension portion  700 . Accordingly, during welding, the extension portion  700  can cause the electrical-stick-out to exceed 100 mm, 125 mm, 150 mm, 175 mm, or a length in a range defined by any of these values, e.g., 150-160 mm. For example, in some embodiments, the electrode assemblies can have an electrical stick-out of about 155 mm. Advantageously, the longer electrical stick-out substantially improves the deposition rate for a given current density, due to longer Joule-heated region provided by the extension portion  700 . 
     In addition, the insulating sleeve  708  enables, among other things, the shape and width of the extension portion  700  to be optimized for inserting the extension portion  700  into narrow grooves as described herein. According to various embodiments, the maximum width of the extension portion  700  at upper, untampered portions thereof can be less than 20 mm, 18 mm, 16 mm, 14 mm, 12 mm, or a value in a range defined by any of these values. Additionally, in some embodiments, the extension portion  700  can have a generally cylindrical shape having at least a portion that tapers inward towards the second end  714 B such that the width of the extension portion  700  at the second end  714 B is less than a maximum width of the extension portion  700 . In the illustrated configuration, the extension portion  700  is tapered at a lower portion thereof, while an upper portion of the extension portion  700  is substantially straight. However, embodiments are not so limited and in other configurations, the extension portion  700  can be tapered substantially throughout its entire length. For example, in some embodiments, the extension portion  700  can have a maximum width of 16 mm that tapers to a width of 10.8 mm at the second end  714 B. In other embodiments, however, the tapered second end  714 B can have a different width. For example, in some embodiments, the width of the extension portion  700  at the second end  714 B can be 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, less then 8 mm, or a value in a range defined by any of these values. In some embodiments, the extension portion  700  can taper inwards at the second end  714 B at an angle of 2°, 3°, 4°, 5°, 6°, 7°, 8°, more than 8°, or a value in a range defined by any of these values. For illustrative purposes only, roughly one third of the length of the illustrated extension portion  700  is tapered. However, it will be appreciated that any suitable fraction of the length may be tapered, including substantially the entire length, e.g., greater than 20%, 40%, 60% or 80%, 100%, or a value in a range defined by any of these values. It will be further appreciated that the tapered sidewall may not be straight, but the degree of tapering may vary with length. For example, the degree of tapering may vary, e.g., continuously or discontinuously, throughout the tapered portion. As configured, the extension portion  700  can be configured to not touch the sidewalls of a narrow groove such as a generally triangular trench as described elsewhere in the application. Any portion of the tapered portion can be configured such that tangents of the exterior sidewalls form a triangle or a cone having an angle of an apex that is less than 16 degrees, 12 degrees, 10 degrees, 8 degrees, 6 degrees, or a value in a range defined by any of these values. Advantageously, the shape and dimensions of the extension portion  700  as described can enable its insertion into narrow grooves without contacting the sidewalls thereof. Additionally, as will be discussed in greater detail elsewhere in the application, the tapered second end  714 B advantageously allows multiple electrode assemblies to be positioned more closely adjacent to each other when use din a multi-arc configuration. 
     Another benefit of the electrode assembly  700  is that flux-to-wire consumption ratio is lower than conventional SAW assemblies because the electrode deposition rate increases while the flux consumption remains constant. 
     As previously discussed, the insulating sleeve  708  is disposed within the envelope or nozzle body  706 . In some embodiments, the insulating sleeve  708  is placed within the nozzle body  706  without an adhesive or other material such that any gaps that may exist between the inner surfaces of the nozzle body  706  and the outer surfaces of the insulating sleeve  708  are filled with air and the insulating sleeve  708  can move or rotate relative to the envelope or nozzle body  706 . In other embodiments, however, the insulating sleeve  708  may be securely attached to the nozzle body  706  with an intervening material. For example, in some embodiments, the insulating sleeve  608  is disposed within the nozzle body  706  with a suitable sealant or adhesive. In these embodiments, the suitable sealant may be disposed between the nozzle body  606  and the insulating sleeve  708  such that the sealant fills any gap that may exist between the inner surfaces of the nozzle body  706  and the outer surfaces of the insulating sleeve such that the insulating nozzle  708  is immobilized with respect to the nozzle body  706 . In these embodiments, the suitable sealant may be a relatively soft material and may serve as a shock absorbing layer between the insulating sleeve  708  and the nozzle body  706  such that cracking of the insulating sleeve  708  under mechanical or thermal stress is suppressed or prevented. In other embodiments, a different material can be used to securely attach the insulating sleeve  708  within the nozzle body  706 . For example, in some embodiments, the insulating sleeve  708  and the envelope or nozzle body  706  may be attached using a brazed metallic joint. In other embodiments, the insulating sleeve  708  and the envelope or nozzle body  706  may be attached using a non-metallic sealant or adhesive such as a polymeric adhesive material or epoxy. 
       FIG.  8    is a top-down cross-sectional view of an extension portion  800 . The extension portion  800  includes an opening  802  through which a consumable electrode is configured to slidingly pass through, an envelope or nozzle body  804 , and an insulating sleeve  806  disposed within the envelope or nozzle body  804 . In the illustrated embodiment, the insulating sleeve  806  is attached to the envelope  804  using a sealant layer  808 . The sealant layer  808  is formed from a suitable sealant that may be a relatively soft material and may serve as a shock absorbing layer between the insulating sleeve  806  and the envelope or nozzle body  804  such that cracking of the insulating sleeve  806  under mechanical or thermal stress is suppressed or prevented. Furthermore, even when the insulating sleeve  806  cracks, the suitable sealant can effectively prevent loose pieces form coming off and falling on the workpiece. In some implementations, insulating sleeve  806  is brazed into the envelope or nozzle body  804  and the suitable sealant comprises a suitable brazing material. The suitable brazing material has a melting temperature that is substantially lower than a melting temperature of the envelope or nozzle body  804 . Without limitation, suitable brazing metals include copper-based alloy, e.g., Cu/Sn alloys. In some other implementations the suitable sealant comprises a suitable glass sealant that has a glass working temperature that is substantially lower than a melting temperature of the metallic sheaths. Without limitation, suitable sealants include a doped silica, e.g., a doped aluminosilicate glass or a heavily doped sodium silicate glass. Other sealants may be possible, e.g., high-temperature epoxy that can withstand the outer temperature of the insulating sleeve. Advantageously, securing the insulating sleeve  806  to the envelope  804  using a suitable sealant improves the durability, reliability and lifespan of the extension portion  800 . 
     One additional advantage of utilizing the relatively narrow extension portion as described herein is that it facilitates using multiple electrode assemblies in multi-arc set-ups. When welding large pieces of metal together, it is sometimes desirable to use multiple electrode assemblies at the same time to further increase the filler metal deposition rate. During multi-arc welding, the tips of multiple electrodes should be positioned closely adjacent to each other such that each of the electrode tips is disposed within the same weld pool. However, it is often difficult to use conventional SAW electrode assemblies in a multi-arc set-up. This is because the large diameter of the head portions (e.g., head portions  204  ( FIG.  2   ),  304 A ( FIG.  3 A ),  304 B ( FIG.  3 B )) of conventional electrode assemblies makes it difficult for multiple electrode assemblies to be placed sufficiently close to each other to facilitate multi-arc welding. Additionally, the short length of the electrode stick-out portions (e.g., stick-out portions  316 A,  416 A) used in conventional SAW assemblies may require that the welding torches be arranged at a high angle with respect to each other to allow for the arcing tips of the respective electrodes to be sufficiently close to each other to be positioned within the same weld pool. Accordingly, it is challenging to use conventional SAW electrode assemblies in multi-arc set-ups because the large size of the head portions and the short stick-out length limit the number of electrode assemblies that can be used in multi-arc set-up while also making it difficult to position the torches when trying to weld within a groove. These and other challenges can be mitigated with extension portions according to embodiments having relatively narrow extension portions, as described herein. 
       FIG.  9 A  depicts a multi-arc SAW system  900 A having first and second electrode assemblies  902 A,  902 B. The first electrode assembly  902 A includes a head portion  904 A having a contact tip  906 A, an electrode  908 A having a tip  910 A, an extension portion  912 A, and a flux delivery system  914 A. Similarly, the electrode assembly  902 B includes a head portion  904 B having a contact tip  906 B, an electrode  908 B having a tip  910 B, an extension portion  912 B, and a flux delivery system  914 B. The electrode assemblies  902 A,  902 B are generally similar to the electrode assembly  600  described above in connection with  FIGS.  6 A- 6 C  and the extension portions  912 A,  912 B may be generally similar to the extension portions  700  and  800  described above in connection with  FIGS.  7 A- 7 F  and  FIG.  8   . As previously discussed, while the contact tips  906 A,  906 B can have a width up to 30 mm (or about 1.18 inches), the extension portions  912 A,  912 B can have a width of about 16 mm (or about 0.79 inches) and a length of about 110 mm (or about 4.33 inches), which allows for the electrode assemblies  902 A,  904 A to each have an electrical stick-out greater than 125 mm (or about 4.92 inches). 
     With this configuration, the first and second electrode assemblies  902 A,  902 B can be positioned such that a distance  916  between the tips  910 A,  910 B of the electrodes  908 A,  908 B is sufficiently small to allow for efficient multi-arc welding. Specifically, the shape, length, and width of the extension portions  912 A,  912 B as described herein allows for the extension portions  912 A,  912 B to be simultaneously positioned within narrow and deep grooves such that the tips  910 A,  910 B are disposed within the same weld pool during the SAW process without the extension portions contacting the sidewalls of the grooves. For example, in some embodiments, the first and second electrode assemblies  902 A,  902 B can be positioned such that, during welding, the distance  916  between the tips  910 A,  910 B is 15 mm while the angle  920  between the electrode assemblies  902 A,  902 B is 20 degrees. However, this is only one example. In other embodiments, the electrode assemblies  902 A,  902 B can be positioned such that, during multi-arc welding operations, the distance  916  between the tips  910 A,  910 B is less than 30 mm, 25 mm, 20 mm, 15 mm, or a value in a range defined by any one of these values, and the electrode assemblies  902 A,  902 B are oriented such that the angle  920  between the electrode assemblies  902 A,  902 B is less than 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, 15 degrees, 10 degrees, 5 degrees, or a value in a range defined by any one of these values. 
       FIG.  9 B  depicts another multi-arc SAW system  900 B having three electrode assemblies  902 A,  902 B, and  902 C, where each of the electrode assemblies  902 A,  902 B, and  902 C is configured as described above in connection with  FIG.  9 A . The size, shape, and width of the extension portions  912 A,  912 B,  912 C for the electrode assemblies  902 A,  902 B,  902 C as described herein allows for extension portions  912 A,  912 B,  912 C to be simultaneously positioned with narrow and deep grooves such that the electrode tips  910 A,  910 B,  910 C are all disposed within the same weld pool during the SAW process without the extension portions contacting the sidewalls of the groove. For example, in the illustrated embodiment, the electrode assemblies  902 A,  902 B,  902 C are positioned such that the distance  916  between the first and second tips  910 A,  910 B is 26 mm, the distance  918  between the second and third tips  910 B,  910 C are spaced apart from each other by 15 mm, the angle  920  between the first and second electrode assemblies  902 A,  902 B is 5 degrees, and the angle  922  between the second and third electrode assemblies  902 B,  902 C is 20 degrees. However, this is only an example. In other embodiments, the electrode assemblies  902 A,  902 B,  902 C can be positioned such that, during multi-arc welding operations, the distances  916 ,  918  between adjacent tips  910 A,  910 B,  910 C is less than 30 mm, 25 mm, 20 mm, 15 mm, or a value in a range defined by any one of these values, and electrode assemblies  902 A,  902 B,  902 C are oriented such that the angles  920 ,  922  between adjacent electrode assemblies  902 A,  902 B,  902 C is less than 40 degrees, 35 degrees, 30 degrees, 25 degrees, 20 degrees, 15 degrees, 10 degrees, 5 degrees, or a value in a range defined by any one of these values. 
     Still referring to  FIGS.  9 A and  9 B , according to embodiments, each of the first, second (and third) electrode assemblies  902 A,  902 B (and  902 C) is configured such that each of the multiple electrodes independently receives power from a dedicated power supply (e.g., power supply  108  shown in  FIG.  1   ). With this arrangement, each of the electrode assemblies can receive an independently controlled power, which allows for more consistent and efficient deposition of filler metal. Additionally, the current provided to each electrode assemblies can be varied for each electrode assembly such that individual electrode assemblies can receive different currents. In other embodiments, however, each of the electrode assemblies used in a multi-arc set-up can be coupled together in parallel such that each of the electrode assemblies shares the same current. 
     ADDITIONAL EXAMPLES 
     1. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding with a solid insulating material surrounding the consumable electrode.       

     2. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the extension portion is configured to capable of not contacting a sidewall of a triangular trench having a depth exceeding 4 inches and having an angle of an apex that is less than 16 degrees while the tip of the consumable electrode contacts the apex.       

     3. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding while having an outer surface formed of a substantially non-magnetic material surrounding the consumable electrode.       

     4. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that a contact-to-work distance (CTWD) between the head portion and the tip of the consumable electrode during welding exceeds 125 mm.       

     5. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding; and   a flux delivery system fixedly attached to the extension portion and configured such that the flux delivery system does not limit dimensions of a groove of a workpiece the extension portion is capable of being inserted into.       

     6. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to achieve a deposition rate per current exceeding 0.05 lbs./hr./A during welding.       

     7. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to achieve a deposition rate exceeding 35 lbs./hr. at a current less than 900 A during welding.       

     8. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to drop at least 5% of a total voltage drop cross a contact-to-work distance (CTWD) between the head portion and the tip of the consumable electrode.       

     9. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to drop at fraction exceeding 2V of a total voltage drop cross a contact-to-work distance (CTWD) between the head portion and the tip of the consumable electrode.       

     10. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to heat the consumable electrode by Joule heating within the extension portion to a temperature up to 800° C.       

     11. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding with a solid insulating material, wherein the solid insulating material has sufficient resistance such that it is configured to sustain a voltage difference of at least 5V without substantially conducting when an outer surface of the extension portion contacts the work piece.       

     12. An electrode assembly for submerged arc welding, comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion comprises an insulating tip portion formed of a solid insulating material configured to electrically insulate the consumable electrode from a work piece during welding by surrounding the consumable electrode.       

     13. The electrode assembly according to any of the above examples, wherein the solid insulating material comprises a ceramic material. 
     14. The electrode assembly according to any of the above examples, wherein the solid insulating material comprises an insulating sleeve configured to pass the consumable electrode therethrough. 
     15. The electrode assembly of any one of the above examples, wherein the extension portion is formed of a material selected from the group consisting of silicon nitride, magnesia-stabilized zirconia, yttria-stabilized zirconia, silicon carbide, magnesium oxide, alumina or a zirconia-toughened alumina. 
     16. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the extension portion is configured to be capable of not contacting a sidewall of a triangular trench having a depth exceeding 4 inches and having an angle of an apex that is less than 16 degrees while the tip of the consumable electrode contacts the apex. 
     17. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding while having an outer surface formed of a substantially non-magnetic material surrounding the consumable electrode. 
     18. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that a contact tip-to-work distance (CTWD) between the contact tip portion and the tip of the consumable electrode during welding exceeds 125 mm. 
     19. The electrode assembly of any one of the above examples, further comprising a flux delivery system fixedly attached to the extension portion and configured such that the flux delivery system does not limit dimensions of a groove of a workpiece the extension portion is capable of being inserted into. 
     20. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to achieve a deposition rate per current exceeding 0.05 lbs./hr./A during welding. 
     21. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to achieve a deposition rate exceeding 35 lbs./hr. at a current less than 900 A during welding. 
     22. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the consumable electrode drops at least 5% of a total voltage drop cross a contact-to-work distance (CTWD) between the contact tip portion and the tip of the consumable electrode. 
     23. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that a stick-out portion of the consumable electrode drops at least 2V of a total voltage drop cross a contact-to-work distance (CTWD) between the contact tip portion and the tip of the consumable electrode. 
     24. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece and has a shape, length and a lateral dimension such that the electrode assembly is configured to heat the consumable electrode by Joule heating within the extension portion to a temperature up to 800° C. 
     25. The electrode assembly of any one of the above examples, wherein the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding with a solid insulating sleeve, wherein the solid insulating sleeve has sufficient resistance such that it is configured to sustain a voltage difference of at least 5V without substantially conducting when an outer surface of the extension portion contacts the work piece. 
     26. An electrode assembly for submerged arc welding (SAW), comprising:
         a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein during welding, the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode,   wherein the extension portion is elongated in a wire feed direction and configured to electrically insulate the consumable electrode from a work piece during welding with an insulating sleeve surrounding the consumable electrode, and   wherein the electrode assembly is configured such that, during welding with the consumable electrode inserted therethrough, a ratio between an electrical stick-out distance, measured between a contact tip portion disposed at an end of the head portion and the arcing tip of the consumable electrode, and a diameter of the electrode exceeds 30.       

     27. The electrode assembly of example 26, wherein the extension portion has an outer surface formed of a substantially non-magnetic material surrounding the insulating sleeve. 
     28. The electrode assembly of example 27, wherein the insulating sleeve is formed of a ceramic material that is enveloped by a substantially non-magnetic steel-based envelope forming the outer surface of the extension portion. 
     29. The electrode assembly of example 28, wherein the insulating sleeve and the non-magnetic steel-based envelope are held together by an adhesive layer. 
     30. The electrode assembly of example 29, wherein the adhesive layer comprises a brazed joint comprising a metallic filler material. 
     31. The electrode assembly of example 26, wherein the extension portion has a length greater than 100 mm. 
     32. The electrode assembly of example 31 wherein the electrode assembly is configured for the electrical stick-out distance exceeding 125 mm. 
     33. The electrode assembly of example 32, wherein the electrode assembly is configured for the diameter of the electrode exceeding 3 mm. 
     34. The electrode assembly of example 32, wherein the extension portion has an elongated shape such that, when fully inserted into a triangular trench having a depth exceeding 4 inches and having an angle of an apex that is less than 16 degrees such that the tip of the consumable electrode contacts the apex of the triangular trench, no part of the extension portion contacts a sidewall of the triangular trench. 
     35. The electrode assembly of example 32, wherein the electrode assembly is configured to achieve a deposition rate per current exceeding 0.05 lbs./hr./A during welding. 
     36. The electrode assembly of example 32, wherein the electrode assembly is configured to achieve a deposition rate exceeding 35 lbs./hr. at a current less than 900 A during welding. 
     37. The electrode assembly of example 32, wherein the electrode assembly is configured to drop at least 5% of a total voltage drop across a distance between the head portion and the arcing tip of the consumable electrode. 
     38. The electrode assembly of example 32, wherein the electrode assembly is configured to heat the consumable electrode by Joule heating within the extension portion to a temperature up to 800° C. 
     39. The electrode assembly of example 26, wherein the insulating sleeve has sufficient resistance such that it is configured to sustain a voltage difference of at least 5V without substantially conducting when an outer surface of the extension portion contacts the work piece. 
     40. The electrode assembly of example 39 wherein the insulating sleeve is formed of a ceramic material selected from the group consisting of silicon nitride, magnesia-stabilized zirconia, yttria-stabilized zirconia, silicon carbide, magnesium oxide, alumina, or a zirconia-toughened alumina. 
     41. The electrode assembly of example 26, further comprising:
         a flux delivery system fixedly attached to the extension portion and configured such that the flux delivery system does not limit a lower limit of a width of a groove of a workpiece the extension portion is capable of being inserted into.       

     42. An electrode assembly for submerged arc welding, comprising:
         a head portion; and   an extension portion arranged serially with the head portion in a wire feed direction, wherein the head portion and the extension portion are configured to feed a consumable electrode therethrough, wherein the extension portion is configured to be disposed closer to an arcing tip of the consumable electrode relative to the head portion and comprises:
           an envelope formed of a nonmagnetic material; and   an insulating sleeve disposed within the envelope and comprising a solid insulating material configured to surround the consumable electrode.   
               

     43. The electrode assembly of example 42 wherein:
         the extension portion comprises opposing first and second ends separated in the wire feed direction,   the head portion comprises a contact tip portion configured to apply a voltage and pass current to the consumable electrode and configured to be proximal to the first end of the extension portion and distal to the second end of the extension portion,   when the consumable electrode is fed through the electrode assembly, an arcing tip of the consumable electrode is configured to be proximal to the second end of the extension portion and distal to the first end of the extension portion, and   the extension portion is disposed between the arcing tip and the contact tip portion.       

     44. The electrode assembly of example 43 wherein the electrode assembly is configured for an electrical stick-out distance, measured between a contact tip portion disposed at an end of the head portion and the arcing tip of the consumable electrode, exceeding 125 mm. 
     45. The electrode assembly of example 44, wherein the electrode assembly configured such that a ratio between an electrical stick-out distance, measured between a contact tip portion disposed at an end of the head portion and the arcing tip of the consumable electrode, and a diameter of the electrode exceeds 30. 
     46. The electrode assembly of example 42 wherein the solid insulating material comprises a ceramic material. 
     47. The electrode assembly of example 42 wherein the insulating sleeve is fixedly attached to the envelope by an adhesive layer. 
     48. The electrode assembly of example 47 wherein adhesive layer comprises a brazed metallic joint. 
     49. An extension portion configured for a submerged arc welding electrode assembly, the extension portion comprising:
         an envelope formed of a nonmagnetic material; and   an insulating sleeve disposed within the envelope and comprising a solid insulating material configured to surround a consumable electrode,   wherein the extension portion is configured to be arranged serially with a head portion of the electrode assembly and to receive a consumable electrode from the head portion.       

     50. The extension portion of example 49, wherein the extension portion has a length greater than 100 mm. 
     51. The extension portion of example 49, wherein the extension portion is configured for a diameter of the consumable electrode exceeding 3 mm. 
     52. The extension portion of example 51, wherein the extension portion is configured such that during welding with the consumable electrode inserted therethrough, a ratio between an electrical stick-out distance, measured between a contact tip portion disposed at an end of the head portion and an arcing tip of the consumable electrode, and the diameter of the electrode exceeds 30. 
     53. The extension portion of example 49, wherein the insulating sleeve is formed of a ceramic material. 
     54. The extension portion of example 49, wherein the envelope is formed of a substantially non-magnetic steel-based material. 
     55. The extension portion of example 54, wherein the envelope is formed of a stainless steel. 
     56. The extension portion of example 49, wherein the insulating sleeve and the envelope are held together by an adhesive layer. 
     57. The extension portion of example 56, wherein the adhesive layer comprises a brazed joint comprising a metallic filler material. 
     58. A method of welding a workpiece, comprising:
         providing a submerged arc welding electrode assembly, the electrode assembly comprising:   a head portion and an extension portion arranged serially and configured to feed a consumable electrode therethrough, wherein:
           the head portion is disposed to be distal to an arcing tip of the consumable electrode and the extension portion is disposed to be proximal to the arcing tip of the consumable electrode, and   the extension portion is configured to electrically insulate the consumable electrode from a work piece during welding with a solid insulating material surrounding the consumable electrode;   
           positioning the electrode assembly over the workpiece such that the arcing tip is adjacent to the workpiece;   adjusting the electrode assembly such that a distance between the head portion and the arcing tip of the consumable electrode during welding exceeds 125 mm; and   providing a current to the electrode assembly.       

     59. The method of example 58 wherein the extension portion has a length greater than 100 mm 
     60. The method of example 58 wherein:
         the workpiece comprises a triangular trench having a depth exceeding 4 inches and having an angle of an apex that is less than 16 degrees,   positioning the electrode assembly over the workpiece comprises positioning the electrode assembly such that the extension portion is within the groove and the arcing tip contacts the apex.       

     61. The method of example 60, further comprising:
         moving the electrode assembly through the groove without the extension portion contacting a sidewall of the triangular trench while the arcing tip contacts the apex.       

     62. The method of example 58 wherein the electrode assembly is configured to achieve a deposition rate per current exceeding 0.05 lbs./hr./A. 
     63. The method of example 58 wherein the electrode assembly is configured to achieve a deposition rate exceeding 35 lbs./hr. at a current less than 900 A. 
     64. The method of example 58 wherein the electrode assembly is configured to drop at least 5% of a total voltage drop across a distance between the head portion and the arcing tip of the consumable electrode. 
     65. The method of example 58 wherein the electrode assembly is configured to heat the consumable electrode by Joule heating within the extension portion to a temperature up to 800° C. during welding. 
     66. A multi-arc welding system for submerged arc welding within a groove on a workpiece, wherein the groove has a depth exceeding 4 inches and an angle of an apex that is less than 16 degrees, the system comprising:
         a first electrode assembly, wherein the first electrode assembly comprises:
           a first head portion; and   a first extension portion arranged serially with the first head portion, wherein the first head portion and the first extension portion are configured to feed a first consumable electrode therethrough, wherein the first extension portion comprises a first nozzle body formed from a nonmagnetic material and a first insulating sleeve disposed within the nozzle body and comprising a solid insulating material configured to surround the first consumable electrode; and a second electrode assembly, wherein the second electrode assembly comprises:   a second head portion; and   a second extension portion arranged serially with the second head portion, wherein the second head portion and the second extension portion are configured to feed a second consumable electrode therethrough, wherein the second extension portion comprises a second nozzle body formed from the nonmagnetic material and a second insulating sleeve disposed within the second nozzle body, wherein the second insulating sleeve comprises the solid insulating material that is configured to surround the second consumable electrode,   
           wherein, during welding, the first and second electrode assemblies are configured to be positioned within the groove such that tips of the first and second consumable electrodes are closely adjacent to the apex of the groove and closely adjacent to each other without the first and second extension portions contacting a sidewall of the groove.       

     67. The system of example 66 wherein, during welding, the first and second electrode assemblies are configured to be positioned within the groove such that a distance between the tips of the first and second consumable electrodes is less than 30 mm and an angle between the first and second electrode assemblies is less than 40 degrees. 
     68. The system of example 66, further comprising:
         a third electrode assembly, comprising:
           a third head portion; and   a third extension portion arranged serially with the third head portion,   
           wherein the third head portion and the third extension portion are configured to feed a third consumable electrode therethrough,   wherein the third extension portion comprises a third nozzle body formed from the nonmagnetic material and a third insulating sleeve disposed within the second nozzle body,   wherein the third insulating sleeve comprises the solid insulating material that is configured to surround the second consumable electrode, and   wherein, during welding, third electrode assembly is configured to be positioned within the groove such that a tip of the third consumable electrode is closely adjacent to the tips of the first and second consumable electrodes without the third extension portion contacting the sidewall of the groove.       

     69. The system of example 66, wherein:
         the first electrode assembly comprises a first flux delivery system securely attached to the first head portion,   the second electrode assembly comprises a second flux delivery system securely attached to the second head portion,   the first and second flux delivery systems are configured to deposit flux into the groove, and   during welding, the first and second flux delivery systems do not contact the sidewall of the groove.       

     70. The system of example 66 wherein the first and second extension portions each have a length greater than 100 mm. 
     Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” “include,” “including” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Likewise, the word “connected”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number, respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. 
     Moreover, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or whether these features, elements and/or states are included or are to be performed in any particular embodiment. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. For example, while blocks are presented in a given arrangement, alternative embodiments may perform similar functionalities with different components and/or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these blocks may be implemented in a variety of different ways. Any suitable combination of the elements and acts of the various embodiments described above can be combined to provide further embodiments. The various features and processes described above may be implemented independently of one another, or may be combined in various ways. All possible combinations and subcombinations of features of this disclosure are intended to fall within the scope of this disclosure.