Patent Description:
The top of a railway rail frequently comes in contact with the wheels of trains, trams, trolleys, etc., thus is subject to extensive wear. In sidings where the rails are exposed to lower traffic frequency they might be subject to excessive corrosion, e.g., rust formation. Thus, rails in sidings are often welded (e.g., with zigzag weld beads) to increase lifetime and limit corrosion and ensure electrical conductivity for a signaling system of railroad road crossings. In general, when rail steel grades are welded, they need to be heated up to <NUM> - <NUM>° C temperature in order to avoid detrimental microstructure transformations that may cause rail breaks and may result in train, tram and/or trolley derailment. Thus, heating (called preheating prior to rail welding) is typically mandatory at every Railway Administration when the rail steel is subjected to welding. Additionally, when a rail head's top (or running) surface is welded on relatively long sections of rail (above <NUM> in length), the rail steel usually becomes distorted without pre-stretching. Typically, the distortion value can be around <NUM>-<NUM>/meter rail length.

Accordingly, improved rail head manufacturing methods and/or systems that can ameliorate the above described problems in a reliable, efficient and cost effective manner are desired.

<CIT> discloses a step-wise cladding method that utilizes a narrow preceding electrode and a wide following electrode. <CIT> (describing the preamble of claims <NUM> and <NUM>) discloses a cladding operation that pre-heats a rail before repair welding or cladding.

According to first and second aspects of the present invention there are provided methods of cladding a rail as recited in claims <NUM> and <NUM> respectively.

An example embodiment of the invention described in the present disclosure fulfills the above needs by employing an electroslag strip cladding (ESSC or ESC) technique that utilizes a twin-strip electroslag strip cladding (ESSC or ESC) welding process to deposit a layer of cladding material on the top of rails. By using the twin-strip ESSC welding process, the layer of cladding material can be deposited atop a region of the top surface (i.e., a running surface) of the rails at a relatively quick welding speed (e.g., a minimum welding speed of approximately <NUM>/minute) with less distortion (e.g., less than <NUM>/meter, such as <NUM>/m). Moreover, the twin-strip ESSC welding process requires no preheating of the rail steel prior to welding while reducing rail distortion below <NUM>/m (e.g., <NUM>/m).

According to another example embodiment of the present invention presented herein, the ESSC welding process uses stainless steel strip (however, other corrosion resistant alloy material may be used as well) as the cladding material since stainless steel can prevent and/or eliminate the formation of rust on the rail head after cladding.

In one example embodiment of the present invention presented herein, improved welding speed can be achieved by moving an ESSC welding head along a rail (e.g., on a rail car) or pulling a rail through a space under the ESSC welding head. When a pull-through type rail transfer system is employed, the ESSC welding head is stationary above the rail and a pull-through system may grab a long rail (e.g., an <NUM> long rail) and pull the rail through under the twin-strip ESSC welding head while the cladding is conducted continuously. Either way, the cladding material deposited atop the rails provides electrical connectivity, and sound damping for the rail.

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only.

Like numerals identify like components throughout the figures.

Cladding is a fundamental process to the manufacturing and fabrication industries and is used across many applications, including petrochemical, oil and gas, pressure vessel and boiler making. The process of cladding involves putting a new layer on top of an existing work piece - sometimes to repair items, other times to improve the wear resistance or corrosion properties of the piece.

The process of cladding is often used when there is a need to use mild or low-alloy steel for the main structure with a specially alloyed material applied to a certain portion of the work piece to accommodate necessary properties. It is more cost effective to apply the special alloy layer only where needed, rather than fabricating the entire structure from the more expensive specially alloyed material. Strip cladding processes offer an effective solution in these situations, especially electroslag strip cladding (ESSC) processes since ESSC offers a high disposition rate, particularly where the part to be cladded can accommodate the higher rate of deposition and heat input.

Before detailing aspects of the example embodiments of the present invention, an exemplary electroslag strip cladding (ESSC) process will be described below to provide a better understanding of the process.

Basically, electroslag strip cladding (ESSC) is a development of submerged arc strip cladding that is based on the ohmic resistance heating of an electrically conductive slag to create a pool of molten slag. During ESSC operations, there is no arc between the strip electrode and the parent or base material (i.e., the work piece). Instead, heat generated by the pool of molten slag (which, in some instances, is referred to as a welding bath) melts the surface of a base material, an edge of a strip electrode submerged in the molten slag, and flux (which protects the molten slag pool and degasses a welding head being used for the ESSC process). In order to operate with the molten slag pool, which may be maintained at a temperature of approximately <NUM>,<NUM>, a plating or cladding head is utilized to guide one or more metal strips to the molten pool of slag. The plating (cladding) head is usually a water-cooled, heavy duty head. The plating (cladding) head also usually includes a motorizing driving roll for strip feeding.

The utilization of a molten slag pool, as opposed to an arc, makes ESSC a reliable high deposition rate process suitable for cladding operations (which apply welded deposits over a large surface area). By comparison, submerged arc cladding creates significantly more dilution than the <NUM>-<NUM>% dilution typically produced with ESSC (e.g., <NUM>-<NUM>% more dilution than ESSC for the same heat input). Moreover, ESSC provides a higher deposition rate (i.e., the rate at which weld metal is actually deposited onto the work piece surface) and creates less penetration as compared to submerged arc cladding. For at least these reasons, ESSC may be preferable to submerged arc cladding when surfacing or cladding flat and curved objects such as heat exchangers, tubes, tube sheets and various pressure vessels. That being said, ESSC is still quite expensive and, thus, any improvements to the efficiency, productivity, dilution, etc. of ESSC are desirable.

More specifically, ESSC costs are typically driven by the cost of the equipment, most notably the plating head and feeding system, and the material utilized for the cladding. In fact, cladding techniques primarily exist because forming a part, vessel, plate, etc. entirely from a cladding material is often considerably more expensive than forming the part from an inexpensive material and cladding the part with the cladding material. Consequently, any developments in equipment or feeding systems that increase efficiency, quality, productivity, or otherwise minimize the amount of time and material required for cladding are highly desirable.

For example, in order to increase productivity, some cladding heads now accommodate two strips and introduce both strips into the same molten slag pool. Introducing two strips into the molten slag pool may extend the length of the molten slag pool (e.g., the introduction of a second strip may extend a slag pool approximately <NUM>-<NUM>) so that the molten slag pool begins to solidify approximately <NUM>-<NUM> after the trailing strip (i.e., the second strip). This may encourage the formation of flat beads and proper links during ESSC. Moreover, a head that accommodates two strips may increase the deposition rate (thereby increasing productivity), decrease dilution, and allow for unique cladding compositions (e.g., by mixing different strips).

Turning to <FIG>, an example cladding environment <NUM> in which the techniques presented herein may be employed will now be described. In environment <NUM>, various components of a cladding apparatus <NUM> are illustrated performing ESSC operations on a work piece <NUM> (e.g., a low alloy carbon steel rail head). The apparatus <NUM> is a twin ESSC apparatus (i.e., a twin ESSC plating or cladding head; also referred to herein as an ESSC welding head) and thus, is configured to guide or feed a first strip of cladding material <NUM> and a second strip of cladding material <NUM> towards the work piece <NUM>. More specifically, in the depicted embodiment, the apparatus <NUM> includes a first strip feeder <NUM> that is configured to feed the first strip <NUM> to a contact jaw <NUM> and a second strip feeder <NUM> that is configured to feed the second strip <NUM> to the same contact jaw <NUM>. The contact jaw <NUM> then guides strips <NUM> and <NUM> towards the work piece <NUM>. However, in other embodiments, the strips need not be fed to the same contact jaw (or even be fed through the same cladding head) and, instead, may be fed to separate jaws (or heads). Along the same lines, in other embodiments, that apparatus may guide or feed more than two strips to the work piece <NUM>. In fact, in some embodiments, any number of strips may be fed to any number of jaws/heads, with any combination of strips being fed to any of the jaws/heads (e.g., two strips for each of two heads that each include a single jaw).

In the depicted embodiment, strips <NUM> and <NUM> are arranged as "twin strips" because the strips are fed in parallel, as a double strip arrangement. However, the term parallel is not intended to imply that strips <NUM> and <NUM> are fed at the same rate by their respective feeders <NUM> and <NUM>. Instead, as is explained below, strips <NUM> and <NUM> may be fed at different rates. In order to feed strips <NUM> and <NUM>, feeders <NUM> and <NUM> may each include any parts or components that move strips <NUM> and <NUM> towards the work piece <NUM> (via the jaw <NUM>). For example, feeders <NUM> and <NUM> may include grooved wheels driven by a driving unit, such as an electric motor. In embodiments utilizing grooved wheels, two grooved wheels may engage either side of each strip and rotate in opposite directions to move a strip towards the work piece <NUM>. The grooved wheels may be coupled to driving motors via any desirable drive shaft, power train, gearing arrangement, or other such mechanical coupling that allows rotational energy to be imparted to the feeders.

Moreover, in the depicted embodiment, the first strip of material <NUM> and the second strip of material <NUM> are each provided as spools or coils of cladding material (e.g., spools of metal strips with a width of <NUM> and a thickness of <NUM>). Consequently, the first feeder <NUM> and second feeder <NUM> unwind or unspool the first strip <NUM> and the second strip <NUM> as the feeders <NUM> and <NUM> feed strips <NUM> and <NUM> to the work piece <NUM> via the contact jaw <NUM>. Although not shown, in some embodiments feeder <NUM> and/or feeder <NUM> may include or be coupled to a straightener or straightening unit configured to straighten and/or align a strip as it is drawn from its coil/spool (i.e., as strip <NUM> or <NUM> approaches grooved wheels of feeder <NUM> or <NUM>, respectively). However, in other embodiments, the strips can be fed from any desirable reservoir and feeders <NUM> and <NUM> need not unwind or unspool strips <NUM> and <NUM> while feeding the strips.

Once strips <NUM> and <NUM> are fed to the contact jaw <NUM>, the contact jaw <NUM> aligns strips <NUM> and <NUM> in the welding direction D1 so that the apparatus guides strips <NUM> and <NUM> to the same portion of the work piece <NUM> as the cladding operations move in the welding direction D1. That is, strips <NUM> and <NUM> are spaced a distance from each other in the welding direction D1, insofar as "welding direction" is the direction in which a weld is intended to run (e.g., the welding direction may be the direction of movement of a cladding head). Consequently, the first strip <NUM> may be referred to as the leading strip <NUM> and the second strip <NUM> may be referred to as the trailing strip <NUM>. However, in other embodiments, two or more strips can be arranged in various settings or formations. For instance, strips can be disposed along an axis that is perpendicular to the welding direction D1, spaced different distances from each other in the welding direction, or a combination thereof.

In the event two or more strips are spaced along an axis that is perpendicular to the welding direction D1 (i.e., spaced along a "transverse axis"), the strips may be positioned side by side, for example, to clad a wide span at once. By comparison, when the strips are aligned in the welding direction D1 (like strips <NUM> and <NUM>), the strips may perform different roles in a single cladding pass and/or form a cladding layer with a mixed composition (e.g., if the different strips are different materials). Still further, in some embodiments, a plurality of strips may be arranged in a grid-like arrangement so that at least some of the plurality of strips are spaced along a transverse axis and other strips are aligned in the welding direction D1 (e.g., to provide a specific welding composition over a wide span).

Still referring to <FIG>, the apparatus <NUM> also includes a flux hopper <NUM> that is a repository for flux <NUM> and is configured to selectively deliver flux <NUM> to a flux drop <NUM> disposed adjacent to the contact jaw <NUM>. Fluxes are generally granular fusible minerals typically containing oxides of manganese, silicon, titanium, aluminum, calcium, zirconium, magnesium and other compounds, such as calcium fluoride. The role of the flux <NUM> in ESSC is described in further detail below, but, generally, the flux <NUM> helps to produce a metal weld <NUM> with a specific chemical composition and specific mechanical properties under a layer of slag <NUM>. That is, the flux <NUM> is specially formulated to be compatible with a given strip or strips of cladding material so that the combination of flux and the strip(s) produces desired mechanical properties. In the depicted embodiment, flux <NUM> is delivered by a nozzle of the flux drop <NUM> on the leading edge of the contact jaw <NUM> to produce a protective layer <NUM> over a molten slag pool, as is described in further detail below. Additionally or alternatively, flux may be delivered to the trailing edge of the contact jaw <NUM> to provide a layer of flux over any molten slag included above the metal weld <NUM> (e.g., the apparatus <NUM> may include a second or repositioned hopper <NUM> and drop <NUM>).

The apparatus <NUM> also comprises a power source <NUM>, a controller <NUM>, and one or more sensors <NUM>. These components are each shown in dashed boxes connected to the dashed box of apparatus <NUM> because these components may be included in apparatus <NUM> (e.g., included during manufacturing of apparatus <NUM>) or connected thereto (e.g., retrofitted to the apparatus <NUM> and/or connected via a wired or wireless connection). For example, the operations of controller <NUM> may be executed by components included in the power source <NUM> (e.g., the controller <NUM> may be a user interface and the power source <NUM> may regulate feed speed of strips <NUM> and <NUM>). Each of these components is addressed in turn below.

First, the power source <NUM> may be included in or connected to the apparatus <NUM> and may include any number or type of power sources, such as a welding converter, a welding transformer, a rectifier, a thyristor controlled rectifier or an inverter. As an example, power source <NUM> may include two parallel direct current (DC) power sources <NUM> and <NUM> that are each connected to the apparatus <NUM>. Regardless of how the power source <NUM> is provided, the power source <NUM> provides a current to the contact jaw <NUM> that flows into any strip(s) fed therethrough. The current is transferred to the entire surface area of the strip(s) in contact with the contact jaw <NUM> and, importantly, the current is applied individually to each strip of material passing through a cladding head. However, since the current is from a single source (even if the source comprises multiple components in parallel, like source <NUM>), each strip receives the same magnitude of current. That is, strip <NUM> and <NUM> may receive approximately equal amounts of current individually (dependent on localized resistance levels in the molten slag). The current from each strip passes into the layer of electrically conductive slag <NUM> and, as is described in further detail below in connection with <FIG>, the resistance of the slag <NUM> generates heat as the slag <NUM> receives current to effectuate the cladding process (e.g., the temperature of the slag adjacent the strip(s) providing current may be approximately <NUM>,<NUM>).

Second, the controller <NUM> is connected to the apparatus <NUM> and configured to control the first feeder <NUM> and the second feeder <NUM> in the manner described in connection with <FIG> discussed in <CIT>, the entire disclosure of which is incorporated herein by reference. More specifically, the controller <NUM> includes a memory <NUM> with a strip feed speed regulation module <NUM> and the strip feed speed regulation module <NUM> is configured to perform the operations discussed in connection with <FIG> of the aforementioned U. Patent Application Publication. In some embodiments, the controller <NUM> is local to the apparatus <NUM>; however, in other embodiments, the controller <NUM> may be remote from the apparatus <NUM> and may be connected thereto via a network connection (e.g., a network connection formed by a communication interface included in the controller <NUM>, as is described in further detail in connection with <FIG> of the aforementioned U. Patent Application Publication. An example computing device that is representative of controller <NUM> is described in connection with <FIG> of the aforementioned U. Patent Application Publication.

Third, the apparatus <NUM> may include or be coupled to one or more sensors <NUM>. The sensor(s) are configured to measure the feed speed of at least the leading strip <NUM>, but may also measure the feed speed of two or more strips, such as the leading strip <NUM> and the trailing strip <NUM>. The sensor(s) <NUM> may measure the feed speed by measuring the speed with which a strip passes through the contact jaw <NUM>, the speed with which a spool of the strip unwinds (e.g., a pulse sensor may count rotations of a strip coil), or any other parameter that is indicative of speed, such as motor parameters (e.g., motor parameters of motors in feeders <NUM> and <NUM>), welding current, etc. Sensor(s) <NUM> may also measure or monitor any welding parameters, which are described in further detail in the aforementioned U. Patent Application Publication, including voltage, current, and other electrical parameters. For example, sensor(s) <NUM> may include one or more shunts in the power source to measure electrical parameters. The sensor(s) <NUM> may send any data to the controller <NUM> so that the controller <NUM> can determine a feed speed of one or more strips and/or any welding parameters. Information measured or collected by sensor(s) <NUM> is advantageously sent to the controller as soon as it is measured/collected, to prevent unnecessary delays in feed speed regulation/adjustment.

Now referring to <FIG>, but with continued reference to <FIG>, the apparatus <NUM> is generally configured to clad a work piece <NUM> with at least one of the first strip <NUM> and the second strip <NUM> in accordance with ESSC principles. That is, the physical principles that control the ESSC processes effectuated by apparatus <NUM> are substantially the same as the physical principles used for known ESSC methods, except, here, current is delivered to the strips individually and the feed rates of the strips are precisely controlled to control the rate at which the known physical principles create a cladded surface (e.g., the welds are controlled based on feed rate of the strips).

By way of example, initially, the flux drop <NUM> releases flux <NUM> and a molten slag pool <NUM> is formed from the first strip <NUM>, the work piece <NUM>, and pulverized flux <NUM>. Once the slag pool <NUM> is large enough for ESSC operations (e.g., once the "stick out" of the slag pool, which is illustrated as "S" in <FIG>, is sufficient to extinguish an electrical arc used to initially create a molten slag pool), the apparatus <NUM> can begin cladding operations. That is, once the slag pool is large enough, the apparatus <NUM> can move in the welding direction D1 and/or the work piece <NUM> can be moved in direction opposite to D1 to initiate ESSC operations. However, this start-up process is described only by way of background and it is to be understood that the techniques presented herein are intended for use during a welding or cladding phase, which may be a phase during which cladding action is carried out. That is, the welding phase may be the phase between a start-up phase (creation of the molten slag pool and stabilization of welding parameters) and a stop phase (termination of the welding process).

During ESSC operations, current (shown as "I") is introduced to the first strip <NUM> and second strip <NUM> at the contact jaw <NUM>. The leading strip <NUM> is then brought into contact with the slag layer <NUM> and the current flows through the first strip <NUM> strip and into the layer of electrically conductive slag <NUM>. More specifically, the current flows through the first strip <NUM> into a molten portion <NUM> of the slag layer <NUM>. The resistance of the molten slag <NUM> generates heat that keeps the welding process going (e.g., the slag temperature remains at approximately <NUM>,<NUM>, at least adjacent the strips). Consequently, as the ESSC operations proceed in the welding direction D1, the first strip <NUM> and work piece <NUM> are melted by the molten slag pool <NUM> and form a molten metal that is eventually deposited on the work piece <NUM> as a metal weld <NUM>. The flux <NUM> also melts, at least in part, as the first strip <NUM> and work piece <NUM> are melted, creating the protective layer of slag <NUM> over the metal weld <NUM>. However, at least a portion of the slag layer <NUM> that is extending over the weld is molten slag, as indicated at <NUM>.

That is, molten slag <NUM> extends over a molten metal weld <NUM>, so that the molten slag <NUM> includes a portion above the metal layer <NUM> and a molten slag pool at the leading edge of the metal weld <NUM>. Eventually, the molten slag layer <NUM> above the metal weld <NUM> solidifies, as is shown at <NUM>; however, in the depicted embodiment, the second strip <NUM> is quickly introduced to (i.e., incorporated or mixed into) the molten slag <NUM> before the molten slag <NUM> hardens (as indicated at <NUM>). In fact, the trailing strip <NUM> actually rides on top of the slag layer <NUM> and since current is running through the second strip <NUM>, the second strip <NUM> extends the length of the molten slag <NUM>. For example, in the depicted embodiment, the molten slag <NUM> may begin to solidify approximately <NUM> - <NUM> after the second strip, or even <NUM> - <NUM> after the second strip. Consequently, the resultant metal weld <NUM> may be formed from a combination of the material of the first strip <NUM> and the material of the second strip <NUM>. More specifically, the resultant weld may include a small buffering layer formed from the first strip <NUM> and the remaining weld <NUM> may be formed from a desired mix or composition of the first strip <NUM> and the second strip <NUM>. Throughout this process, a layer <NUM> of pulverized flux protects the leading edge of the molten slag pool <NUM>.

Now turning to <FIG>, for a description of an example twin ESSC apparatus <NUM> (i.e., a cladding head <NUM>) with which the techniques described herein can be utilized. In <FIG> and <FIG>, the leading edge is illustrated on the right, whereas in <FIG> the leading edge is illustrated on the left (i.e., <FIG> and <FIG> illustrate an apparatus from the right side and <FIG> illustrates the apparatus from the left side); however, the embodiments are otherwise largely the same. Consequently, apparatus <NUM> has been labeled with at least some of the same reference numerals used in <FIG> and <FIG> to illustrate how the features of apparatus <NUM> correspond to the features discussed above. For example, the apparatus <NUM> includes a contact jaw <NUM> configured to receive a leading strip <NUM> and a trailing strip <NUM>. More specifically, the cladding head <NUM> includes a leading passage <NUM> configured to receive and guide the first strip <NUM> to a work piece and a trailing passage <NUM> configured to receive and guide the second strip <NUM> to the same work piece. The apparatus <NUM> also includes a flux drop <NUM> configured to create a protective layer on the leading edge of the cladding head. In this particular embodiment, the leading passage <NUM> and the trailing passage <NUM> are each configured to receive strips of a maximum width of approximately <NUM> and a maximum thickness of approximately <NUM>; however, in other embodiments, the cladding head <NUM> may receive strips of any size. The contact jaw <NUM> is also configured to transfer a current from a power source to the entire surface area of strips <NUM> and <NUM> disposed within the leading passage <NUM> and trailing passage <NUM>.

Referring now to <FIG>, an example embodiment of a rail <NUM> cladded by the techniques presented herein is shown and will now be described. The rail <NUM> comprises a rail head portion <NUM> which includes a top head portion <NUM>, side head portions <NUM>, and a rounded corner head portion <NUM> located between the top head portion <NUM>, and each side head portion <NUM>. A region <NUM> of the top head portion <NUM> extending in a direction into the page of <FIG> will be referred to as the head (or running) surface of the rail. This region of the rail is the region which most frequently comes in contact with the wheels of trains, trams, trolleys, etc., thus is subject to extensive wear and excessive corrosion, e.g., rust formation, if not patterned or coated with a specially alloyed material, such as, for example, stainless steel or nickel alloy steel.

Still referring to <FIG>, the region <NUM> of the top head portion <NUM> defining the head (or running) surface of rail <NUM> includes a machined-out groove (depression) <NUM>. In addition, the rail <NUM> of the present example embodiment further includes a foot portion <NUM> and a neck portion <NUM> connecting foot portion <NUM> to rail head portion <NUM>. The rail <NUM> is typically formed from rail steel grade, e.g., a mild or low-alloy steel, in an extruder (not shown). A layer of wear resistant alloy material (i.e., a cladding layer) <NUM> is deposited on the head (or running) surface of the rail head portion <NUM>, e.g., within groove (depression) <NUM>, to improve wear resistance, electrical connectivity, and sound damping of rail <NUM>. The layer of wear resistant alloy material (i.e., the cladding layer) <NUM> may further reduce and/or eliminate the wear on the head (or running) surface of rail head portion <NUM>. The layer of corrosion resistant (stainless) alloy material (i.e., the cladding layer) <NUM> may further reduce and/or eliminate the corrosion on the head (or running) surface of rail head portion <NUM>.

In the depicted embodiment of rail <NUM> illustrated in <FIG>, the cladding layer <NUM> is formed on the head (or running) surface of rail head portion <NUM>, e.g., within the machined-out groove (depression) <NUM>, utilizing a twin-strip electroslag strip cladding (ESSC) process, as previously described herein. The process utilizes a cladding apparatus <NUM> to perform ESSC operations on the head (or running) surface of rail head <NUM> according to the techniques presented herein. Specifically, the apparatus <NUM> uses a twin ESSC plating or cladding head <NUM> configured to guide or feed a first strip of cladding material <NUM> and a second strip of cladding material <NUM> towards the head (or running) surface of the rail head <NUM>, as discussed herein. Utilizing the twin-strip ESSC head <NUM> enables the layer of cladding material <NUM> to be deposited atop the entire head (or running) surface of rail head <NUM> at a relatively quick welding speed of at least about <NUM>/minute.

Furthermore, in the depicted <FIG> embodiment, the example rail <NUM> may have a height (h) between approximately <NUM> and <NUM>; rail head portion <NUM> may have a width (w) of approximately <NUM> and a thickness (t) of approximately <NUM>; foot portion <NUM> may have a width (w<NUM>) of approximately <NUM>; and neck portion <NUM> may have a height (hi) of about <NUM>. The cladding layer <NUM> deposited on the head (or running) surface of the rail head <NUM> (i.e., the region <NUM> of the top head portion <NUM> including machined-out groove (depression) <NUM>) by the twin ESSC plating or cladding head <NUM> may have a thickness (t<NUM>) of generally about <NUM>. However, the previously mentioned portions of rail <NUM> may have other suitable dimensions, as required, and the thickness of cladding layer <NUM> on the head (or running) surface of rail head <NUM> may be increased or reduced as necessary.

Turning now to <FIG> and <FIG>, example embodiments of transfer systems which may be utilized to move ESSC head <NUM> along rail <NUM> or, in the alternative, convey rail <NUM> under ESSC head <NUM> for deposition of a cladding material onto the head (or running) surface of rail head <NUM> will now be described.

With reference to <FIG>, an embodiment of a transfer system <NUM> is shown in which the ESSC cladding head <NUM> is secured to a support structure <NUM> configured to permit travel of the ESSC cladding head at a predetermined speed of progression over a rail <NUM> sitting atop a workstation <NUM>, with its rail head <NUM> uppermost, as depicted by directional arrow D2 shown in <FIG>. In this embodiment, the support structure <NUM>, while only illustrated in a schematic manner, is intended to serve as a characteristic example (but not limited thereto) of a motorized trolley (carriage) movable along an overhead track, rail or beam, a mobile robotic apparatus, an articulated boom assembly, a self-propelled traveling gantry, a motor-powered railcar, etc. Even though the predetermined speed of travel of ESSC cladding head <NUM> may vary, the travel speed of the cladding head over rail head <NUM> should typically be selected such that the minimum welding speed of at least approximately <NUM>/minute is maintained.

Furthermore, the support structure <NUM> of the <FIG> embodiment (e.g., the motorized trolley/carriage, the mobile robotic apparatus, the articulated boom assembly, the self-propelled traveling gantry, the motor-powered railcar, etc.) may comprise a power source, a controller, and one or more sensors (not shown). These components may be included in support structure <NUM> (e.g., included during manufacturing of the motorized trolley/carriage, the mobile robotic apparatus, the articulated boom assembly, the self-propelled traveling gantry, the motor-powered railcar, etc.) or connected thereto (e.g., retrofitted to the support structure, and/or connected via a wired or wireless connection). For example, the operations of the controller may be executed by components included in the power source (e.g., the controller may be a user interface and the power source may regulate the speed of progression the support structure <NUM> - e.g., the motorized trolley/carriage, the mobile robotic apparatus, the articulated boom assembly, the self-propelled traveling gantry, the motor-powered railcar, etc. - is moved over example rail <NUM>).

Turning now to <FIG>, an example embodiment of another transfer system <NUM> is shown in which the ESSC cladding head <NUM> is secured to a stationary support structure <NUM> configured to permit a rail <NUM> to be advanced through a space under the ESSC cladding head <NUM>, as depicted by directional arrow D3 shown in <FIG>. In this embodiment, example rail <NUM> may be conveyed at a predetermined speed of progression under ESSC cladding head <NUM> by a rail feeder assembly <NUM>. The rail feeder assembly <NUM>, while only illustrated in a schematic manner in <FIG>, may represent (but is not limited to) an elongate, horizontally disposed feeder bench having an approach-end section A, a run-out end section B, and a center section C at which the ESSC cladding head <NUM> is provided between sections A and B. The rail <NUM>, with its rail head <NUM> uppermost (i.e., facing upward), may be conveyed along the feeder bench in a feeding direction from the approach-end section A to the runout-end section B, and is subjected to an electroslag operation at ESSC cladding head <NUM> located intermediate those sections to provide cladding metal layer <NUM> on the head (or running) surface of rail head <NUM>.

In an example embodiment, the feeder bench structure of rail feeder assembly <NUM> may include a plurality of conveyor rollers (not illustrated for purposes of clarity) to assist with conveyance of example rail <NUM> from approach-end section A to the runout-end section B. In a further example embodiment, a rail feeder arrangement, such as, for example, a variable speed motorized drive unit (not shown), may be provided at the approach-end section A of the feeder bench to push rail <NUM> toward ESSC cladding head <NUM>, while another rail feeder arrangement, such as, for example, a variable speed motorized drive unit (not shown) similar to the above mentioned drive unit, may be provided at the runout-end section B to pull the rail through the ESSC cladding head <NUM>, as described herein. Each rail feeder arrangement should be configured to convey rail <NUM>, with its rail head <NUM> uppermost (i.e., facing upwardly), along the feeder bench in a feeding direction from the approach-end section A, through the ESSC cladding head <NUM>, to the runout-end section B at a predetermined speed of progression which is selected to permit the minimum welding speed of at least approximately <NUM>/minute to be maintained. The rail feeder arrangements may be configured to function in unison or separately to convey the rail <NUM> under the ESSC cladding head <NUM>. However, either one of the rail feeder arrangements may be eliminated if it is not needed for conveyance of rail <NUM> through ESSC cladding head <NUM>.

While the example transfer system embodiment <NUM>, depicted in <FIG>, permits rail <NUM> to be conveyed at the predetermined speed of progression under ESSC cladding head <NUM>, other transfer systems may be utilized as well. That is, any pull-through, push-through, or other such systems now known or developed hereafter may be used to convey rail <NUM> at a predetermined speed of progression under ESSC cladding head <NUM>. For example, the ESSC welding head <NUM> may include a feed mechanism (not shown) which enables the welding head to grab a long rail (e.g., an <NUM> long rail) and pull it through under the twin-strip ESSC welding head while the cladding layer <NUM> is continuously deposited on the head (or running) surface of the rail <NUM>.

Furthermore, the rail feeder arrangements and the feed mechanism of the <FIG> embodiment (e.g., the rail push-through arrangement at approach-end section A, the rail pull-through arrangement at run-out end section B, and the feed mechanism included as part of the ESSC welding head <NUM>) may comprise a power source, a controller, and one or more sensors (not shown). These components may be included in the rail feeder arrangements, as well as the feed mechanism, (e.g., included during manufacturing of the rail push-through arrangement, the rail pull-through arrangement, and the rail feed mechanism of the ESSC welding head) or connected thereto (e.g., retrofitted to each of the push-through and pull-through rail feeder arrangements, as well as the rail feed mechanism of the ESSC welding head, and/or connected via a wired or wireless connection). For example, the operations of the controller may be executed by components included in the power source (e.g., the controller may be a user interface and the power source may regulate the speed of progression the rail feeder arrangements push or pull rail <NUM> under ESSC cladding head <NUM>, or the rail feed mechanism of the ESSC cladding head pulls rail <NUM> under ESSC cladding head <NUM>).

Moreover, the ESSC welding head <NUM> of the <FIG> and <FIG> embodiments may further include a reversible stepping motor unit (not shown) that permits the ESSC welding head <NUM> to be vertically adjusted towards and away from workstation <NUM> or the feeder bench of rail feeder assembly <NUM>, respectively. Vertically moving the ESSC welding head towards and away from the workstation of the <FIG> embodiment and the feeder bench of the <FIG> embodiment permits the working space under the ESSC cladding head <NUM> and/or the working space above the head (running) surface of rail head portion <NUM> to be controlled such that rails of various sizes (e.g., rails of different heights) may be accommodated and the region defining the running surface can be cladded under appropriate operating conditions.

With reference now to <FIG>, a description is provided of a method <NUM> for electroslag welding operations utilizing twin feed strips. For clarity, the operations depicted in <FIG> are described as being performed by ESSC apparatus <NUM> utilizing twin feed strips <NUM>, <NUM> according to the techniques described herein; however, this is not intended to be limiting and, in other embodiments, these operations may be performed, executed, or caused to execute by any other suitable entity.

Initially, at step <NUM>, a rail to be cladded, e.g., a rail having a configuration such as example rail <NUM> with a machined-out groove (depression) <NUM>, as illustrated in <FIG> (but without cladding layer <NUM>) is positioned atop a workstation, e.g., workstation <NUM> depicted in <FIG>, or a rail feeder assembly, e.g., feeder bench, <NUM> depicted in <FIG>. As described herein and shown in <FIG>, the example rail <NUM> comprises a rail head portion <NUM> which includes a top head portion <NUM>, side head portions <NUM>, and a rounded corner head portion <NUM> located between the top head portion <NUM>, and each side head portion <NUM>. In at least some embodiments, a surface region <NUM> of the top head portion <NUM>, between the corner head portions <NUM> and extending in a direction into the page of <FIG>, defines a head (or running) surface of example rail <NUM>. The head (or running) surface, as mentioned herein, may include a groove (depression) <NUM> machined into the top head portion <NUM>. In addition, the example rail <NUM> further comprises a foot portion <NUM> and a neck portion <NUM> connecting foot portion <NUM> to rail head portion <NUM>.

Thereafter, at step <NUM>, the example rail <NUM> and twin-strip ESSC plating or cladding head <NUM> are aligned such that the running surface of example rail <NUM> (i.e., the surface region <NUM> of the top head portion <NUM> with groove (depression) <NUM>) may subsequently have a metal alloy cladding layer <NUM> deposited and fused thereto by the ESSC welding process described herein.

Next, at step <NUM>, the cladding process is initiated with the ESSC cladding head <NUM> according to the techniques described herein. In one embodiment of the present invention depicted in <FIG>, movement of support structure <NUM> is commenced to transport ESSC plating or cladding head <NUM> at a predetermined speed of progression (e.g., a controlled rate to maintain a welding speed of at least approximately <NUM>/minute) over example rail <NUM> sitting atop workstation <NUM>, with its rail head <NUM> uppermost, to overlay and fuse cladding material <NUM>, such as (but not limited to) stainless steel or nickel alloy steel, to the running surface of example rail <NUM> at a deposition rate of, for example, approximately <NUM>-<NUM>/hour utilizing the abovementioned electroslag surfacing process, which yields a continuous, seam-free cladding (overlay) across the running surface of example rail <NUM>. As mentioned herein, the support structure <NUM> may be (but is not limited to) a motorized trolley (carriage) movable along an overhead track, rail or beam, a mobile robotic apparatus, an articulated boom assembly, a self-propelled traveling gantry, a motor-powered railcar, etc..

In another embodiment of the present invention depicted in <FIG>, at step <NUM>, the example rail <NUM> is pushed or pulled through a space under stationary ESSC cladding head <NUM> at a predetermined speed of progression (e.g., a controlled rate to maintain a welding speed of at least approximately <NUM>/minute) by a rail feeder assembly <NUM>, which may include an elongate, horizontally disposed feeder bench as described herein, so that overlay material (cladding) <NUM>, such as (but not limited to) stainless steel or nickel alloy steel, may be deposited and fused to the running surface of example rail <NUM> at a deposition rate of, for example, approximately <NUM>-<NUM>/hour utilizing the abovementioned electroslag surfacing process, which yields a continuous, seam-free cladding (overlay) across the full width of the running surface. However, other suitable rail feeder assemblies may be employed as needed.

At step <NUM>, the ESSC start-up phrase is initiated by guiding first and second strips of cladding material <NUM>, <NUM> towards the workpiece (e.g., exemplary rail <NUM>); transferring a current to at least one of the first and second strips of cladding material <NUM>, <NUM> to melt flux <NUM>, one or more of the strips <NUM>, <NUM>, and a portion of the workpiece to be cladded (e.g., head/running surface of rail head <NUM>), as described above in connection with <FIG>, to create a molten slag pool <NUM> on the workpiece (e.g., head/running surface of rail head <NUM>) that is sufficient to initiate the cladding phrase; and feeding the first strip of cladding material <NUM> towards the molten slag pool <NUM> at a first variable feed speed and the second strip of cladding material <NUM> towards the molten slag pool <NUM> at a second variable feed speed that is different from the first variable feed speed to continuously deposit seam-free cladding material <NUM> atop the workpiece (e.g., across the full width of the running surface of rail head <NUM>).

More specifically, the cladding material <NUM> is continuously deposited seam-free by ESSC cladding head <NUM> into the machined-out groove (depression) <NUM> in region <NUM> of the top head portion <NUM>. For example, cladding material <NUM> may be deposited within groove (depression) <NUM> to a height which is slightly higher than the original head (or running) surface of the head rail <NUM> (e.g., a thickness which may be slightly greater than generally about <NUM>), as shown in <FIG>, such that the cladding material may, thereafter, be milled down to form a smooth contoured surface that substantially conforms to the contour of the original head (running) surface of the top head portion <NUM> of rail head <NUM>, as shown in <FIG>. However, the thickness of cladding layer <NUM> deposited within groove (depression) <NUM> on the head (or running) surface of rail head <NUM> may be increased or reduced as necessary. Further, it may be possible to utilize the ESSC cladding head <NUM> to deposit cladding material <NUM> within the machined-out groove (depression) <NUM> that conforms to the contour of the original head (running) surface of the top surface portion <NUM> of rail head <NUM> without a subsequent milling operation.

Notably, as previously mentioned herein, the rail <NUM> does not need to be preheated prior to cladding rail head <NUM> with cladding material <NUM> and <NUM>. This is because ESSC processes generate enough (sufficient) heat to ensure proper microstructure formation in the cladding layer and, more importantly, in a heat affected zone (HAZ) of the rail head (illustrated by the dashed line in <FIG>) without preheating. In <FIG>, a dashed line in <FIG> generally depicts the HAZ as surrounding the cladding material layer <NUM> and machined-out groove (depression) <NUM>; however, typically, the HAZ will include a high temperature area or layer and a lower temperature area or layer, which are not illustrated for purposes of clarity. Generally, the thickness of the HAZ generally may be within a range of about <NUM> - <NUM>. However, the thickness of the HAZ could be slightly greater or less than <NUM> - <NUM> depending on production and fabrication requirements, as well as operating efficiency.

Regardless of the specific size of the HAZ, due to the intense heat generated during cladding with ESSC cladding head <NUM> (as mentioned above, the slag pool may be maintained at a temperature of approximately <NUM>,<NUM>), the example rail <NUM> will be heated with sufficient heat to provide a cooling time that will not create defects in the microstructures (e.g., molecular bonds) of the cladding layer <NUM> and the HAZ of the rail steel. That is, the heat input from the ESSC will be high enough to cause a natural avoidance (or at least discourages) austenite-to-martensite transformation and the detrimental phase transformations associated therewith. Notably, although martensite phase steel is exceptionally hard, it may also be brittle (owing to the needle-shaped features of the martensite microstructure). Thus, in rails, martensite phase steel may provide a point at which a crack or other such unwanted defect can initiate.

Put still another way, the high heat input of the ESSC naturally slows the cooling rate of the HAZ, which prevents or at least discourages austenite-to-martensite transformation. Specifically, austenite is generally only evident between approximately <NUM> and <NUM> and martensite transformation generally occurs under approximately <NUM>; thus, the intense <NUM>,<NUM> slag pool will prevent or discourage cooling in the HAZ (or at least the high temperature HAZ) that causes austenite-to-martensite transformation. Instead, due to the intense heat input of the ESSC, the HAZ will experience ferritic, pearlitic and bainitic transformations, which provide a less brittle microstructure as compared to martensite phase steel. Notably, pearlite may be formed during the slow cooling of austenite and can begin at a temperature of <NUM> to <NUM>, while ferrite can form within a subset of the temperature ranges of pearlite by the slow cooling of austenite. Bainite is typically formed at cooling rates slower than that for martensite formation and faster than that for ferrite and pearlite formation.

That said, in some instances, the example rail <NUM> might be preheated to prevent distortion along the length of the rail; however, this preheating may be less intensive and have minimal impact on the microstructure formation in the cladding layer. Moreover, preheating may be unnecessary for rails <NUM> of shorter lengths and may only be helpful for rails of substantially longer lengths (e.g., rails longer than <NUM>, longer than <NUM>, etc.).

Moreover, during step <NUM>, the cladding techniques presented herein (e.g., employing twin strip ESSC welding processes utilizing a twin-strip ESSC welding head <NUM>) may deposit a cladding layer (formed from the two or more strips of cladding material, for example, first cladding material strip <NUM> and second cladding material strip <NUM>) that is maximum <NUM> wide and <NUM> to <NUM> thick through the variation of welding speed of approximately <NUM> to <NUM>/minute and a deposition rate of at least approximately <NUM>-<NUM>/hour. By comparison, known welding processes cannot provide a cladding layer of similar dimensions at the above noted welding speed and disposition rate. For example, known welding processes cannot provide welding speeds higher than <NUM>/minute and a deposition rate higher than about <NUM>-<NUM>/hour if a cladding material of approximately <NUM> wide and a minimum of approximately <NUM> thick is to be deposited on a workpiece. Furthermore, during step <NUM>, the cladding techniques presented herein may only generate <NUM>/meter or less of distortion (e.g., approximately <NUM>/m of distortion). By comparison, known welding processes may generate minimum <NUM>-<NUM>/meter of distortion or more.

At step <NUM>, the cladded rail <NUM> is subsequently permitted to cool and, thereafter, removed from workstation <NUM> or rail feeder assembly <NUM> for later use as transit rails for trains, trams, trolleys, etc. Thus, the rail <NUM> with its metal cladding layer <NUM> (e.g., stainless steel or nickel alloy steel) deposited atop the running surface of rail <NUM> provides performance enhancements, such as much improved corrosion (rust) resistance.

To summarize, the embodiments of the present invention are directed to an ESSC process and system which utilizes twin-strips of cladding material to deposit (i.e., weld) a metal cladding layer onto the head (or running) surface of a rail. The head (or running) surface of the rail may include a machined-out groove (depression) therein, as shown in <FIG> and <FIG>. Moreover, the disclosed twin ESSC process/system offers many advantages over previous rail cladding processes, for example: quicker welding speeds (e.g., minimum welding speed of approximately <NUM>/minute) with less distortion (e.g., less than <NUM>/meter); higher deposition rates (e.g., <NUM>-<NUM>/hour); reduced dilution of base material (e.g., about <NUM>%); none or lower preheating temperature; and lower flux consumption (e.g., about <NUM>/kg of strip). In addition, the higher deposition rate, combined with increased travel speed, reduces welding (cladding) time and improves productivity for manufacturing and fabrication applications.

Thus, in one form, a method is provided comprising: (a) positioning on a workstation or a rail feed assembly a rail with a rail head portion having a head (running) surface with a machined-out groove (depression) therein; (b) aligning a twin-strip ESSC welding head above the machined-out groove (depression) of the head (running) surface of the rail; (c) guiding a first strip and a second strip towards the rail; (d) transferring a current to at least one of the first strip and the second strip to create a molten slag pool on the head (running) surface of the rail sufficient for initiation of a cladding phase; (e) feeding the first strip towards the molten slag pool at a first variable feed speed; (f) feeding the second strip towards the molten slag pool at a second variable feed speed that is different from the first variable speed; (g) advancing the ESSC welding head at a predetermined travel speed of progression along the rail positioned on the workstation or, in the alternative, advancing the rail positioned on the rail feeder assembly through a space under the ESSC welding head at a predetermined travel speed of progression; and (h) continuously depositing seam-free metal cladding material across the full width of the machined-out groove (depression) in the region defining the head (running) surface of the rail.

In yet another form, a system is provided comprising: (a) an ESSC welding head which includes a first strip feeder configured to guide a first strip towards a rail, and a second strip feeder configured to guide a second strip towards the rail; (b) a power source configured to transfer a current to at least one of the first strip and the second strip to create a molten slag pool on a head (running) surface of the rail sufficient for initiation of a cladding phase; (c) a transfer system configured to permit travel of the ESSC cladding head at a predetermined speed of progression over the rail or, in the alternative, to permit the rail to be advanced through a space under the ESSC cladding head; and (d) a controller configured to: (i) cause the first strip feeder to feed the first strip towards the molten slag pool at a first variable feed speed, (ii) cause the second strip feeder to feed the second strip towards the molten slag pool at a second variable feed speed that is different from the first variable speed, and (iii) cause metal cladding material to be continuously deposited seam-free across the full width of a machined-out groove (depression) in the region defining the head (running) surface of the rail.

Claim 1:
A method (<NUM>) of cladding a rail (<NUM>), comprising:
providing a rail (<NUM>) including a rail head portion (<NUM>) having a region (<NUM>) defining a running surface;
and characterized in that the method further comprises:
aligning (<NUM>) an electroslag strip cladding (ESSC) welding head (<NUM>) having twin strips (<NUM>) (<NUM>) of cladding material above the rail head portion (<NUM>), wherein the twin strips (<NUM>) (<NUM>) define a first strip of cladding material (<NUM>) and a second strip of cladding material (<NUM>);
guiding the first strip (<NUM>) and the second strip (<NUM>) towards the rail head portion (<NUM>);
transferring a current to at least one of the first strip (<NUM>) and the second strip (<NUM>) to create a molten slag pool (<NUM>) on the rail head portion (<NUM>) sufficient for initiation of a cladding phase; and
advancing the ESSC welding head (<NUM>) at a predetermined travel speed of progression along the rail head portion (<NUM>) during the cladding phase to deposit a cladding layer (<NUM>) comprised of the first strip (<NUM>) and the second strip (<NUM>) across the region (<NUM>) defining the running surface of the rail head portion (<NUM>),
and wherein the cladding layer (<NUM>) is deposited across the region (<NUM>) defining the running surface of the rail head portion (<NUM>) without preheating the rail (<NUM>).