Patent Publication Number: US-2020276627-A1

Title: Systems and methods for production of metallurgically bonded clad billet and products thereof, and metallurgically bonded clad billet

Description:
CONTINUITY DATA 
     This application claims the benefit of U.S. Provisional Application No. 62/812,488, filed on Mar. 1, 2019. The disclosure of the prior application is hereby incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to methods and systems for producing a clad billet composed of solid carbon or low-alloy steel (CS) and a corrosion resistant alloy (CRA), and products thereof. 
     BACKGROUND 
     Commodity hot rolled carbon or low-alloy steel (CS) bars have widespread applications. One major application of (CS) bars is for reinforcing concrete, a popular and versatile construction material due to its high compressive strength among other properties. Due to concrete&#39;s relatively low tensile strength and inability to deform without breaking, (CS) bars (commonly referred to as “rebar”) have been placed inside concrete slabs before curing. The internal (CS) bars help the cured concrete resist tensile stresses and avoid structural failure of the concrete. 
     Such reinforced concrete is used for buildings, marine structures, roads, bridges, and other transportation projects. In some geographic locations, chloride salts are often applied to concrete road surfaces during cold temperatures to limit icing on the roads for safety purposes. The chloride/salt solution permeates through the porous concrete and reacts with the (CS) bar, creating rust as a corrosion product. Rust weakens the (CS) bar by reducing the amount of load bearing material that provides strength. Also, rust has approximately 30% more volume than the carbon steel it replaces, and so the increased volume of the (CS) bar causes internal stress and cracking of the concrete, making the whole concrete pavement and structure prone to deterioration over time. As a result, the concrete may fail to provide a required service life. Similarly, reinforcing (CS) bar can deteriorate over time due to corrosion by being exposed to marine atmospheres, oxidizing gases, or other corroding elements, resulting in catastrophic failure. Maintenance and repair of such concrete roads currently in service have been estimated by the National Association of Corrosion Engineers (NACE) to cost around $8 billion per year. In other applications, chlorides and other corroding elements are known to attack (CS) rods by corrosion, such as (CS) sucker rods exposed to sour oil wells containing H 2 S and chlorides that cause corrosion and reduce the required service life. 
     Attempts have been made to develop a cost effective corrosion resistant (CS) bar to provide the required service life for the applications discussed above, as well as others. Corrosion resistant coatings have represented the simplest solutions, and coating systems which spray a coating material onto the (CS) bar have been developed and implemented. Such coatings, however, represent only a partial solution to the corrosion problem, due to inherent porosity in the coating and other property issues. Upgrading with solid corrosion resistant alloy (e.g., a solid stainless steel rebar) may help solve the corrosion problem, but that solution is very expensive, and drives up the cost beyond potential economic feasibility. 
     Attempts to produce a metallurgically bonded clad bar have been made, as an optimum material for a long term corrosion solution. For example, stainless clad rebar (SCR), in which the carbon steel core provides the mechanical properties and stainless steel surface resists the chloride corrosion, provides an optimum solution for concrete applications at a fraction of the cost of solid stainless bars. Similarly, other (CRA) claddings can provide design service life for other applications at a fraction of the solid (CRA) bar cost. Development of stainless clad rebar (SCR) with metallurgical bonding has been attempted over the years. One such process for manufacturing stainless clad steel products involves tightly wrapping a stainless steel sheathing over a carbon steel bar, with placement of various substances added at the ends and sealed to help maintain clean opposing surfaces of the bar and sheathing that form the billet. To create such a bond requires: (i) clean, un-oxidized surfaces of both the carbon steel bar and the stainless steel sheathing; (ii) lack of oxygen between the contact surfaces for bonding to minimize or eliminate oxidation; and (iii) high pressure at high temperature applied to the bonding surfaces. The sheathing is formed around the carbon steel bar as tightly as possible to minimize the gap between the two materials. However, the tighter the gap the more difficult it is for the protective mechanism to work deep into the relatively long, e.g., 40 foot length of the sheathing. As the sealed billet is heated to rolling temperature, any surface areas left unprotected inside the billet oxidize and fail to bond, even though substantial reduction occurs on the billet at high temperature and pressure going through the stages of the rod rolling mill. This process has shown variability in metallurgical bonding from point to point within each billet, and from billet to billet, resulting in poor bonding reliability, non-uniform cladding thickness, and other issues in production, such that the resulting product fails to meet minimum metallurgical bond requirements. 
     Another technique for producing stainless steel clad rebar was developed utilizing the “Osprey Process,” in which a molten, atomized stream of stainless steel is deposited onto a rotating, heated carbon steel bar in an evacuated chamber to build up the required stainless steel thickness. Once the required thickness is achieved, the bar is rolled through the mill to produce stainless steel clad rebar. A problem with this process is that the deposit inherently has porosity even when applied with high velocity guns. Moreover, the molten particles do not create a metallurgical (e.g., atom-to atom) bond with the carbon steel bar. The molten particle on impact is immediately quenched on hitting the carbon steel bar, creating a surface that fails to bond. Once the metallurgical bond is not formed on deposition, further processing through the mill will likewise not create the metallurgical bond. The “Osprey Process” has not been further developed for this application. 
     SUMMARY 
     There is a critical need for a process that produces high quality, 100% metallurgically bonded (CRA) clad bars that are resistant to corrosion and do not suffer from the problems encountered with the conventional manufacturing techniques discussed above. A further need exists for corrosion resistant bars, pipes, sucker rods, shafts, etc., that provide a required service life in environments that are subject to corrosive materials. 
     In embodiments of the present disclosure achieve these needs. 
     Generally, stainless clad (CS) bars provide an optimum material at a fraction of the cost of solid stainless bars for resisting corrosion in concrete. The stainless clad (CS) bars have a carbon or low-alloy steel core for mechanical properties, and stainless steel cladding surface to resist corrosion problems in applications such as, for example, pavements and highways, marine structures, and other areas that are prone to corrosive materials such as chloride. The same is true for stainless clad (CS) pipes, i.e., having a cylindrical hollow (CS) material for a core. The ability to produce corrosion resistant alloy (CRA) clad bars and pipes through the integrated operations of today&#39;s rod rolling mills and cold pilger/cold draw mills, respectively, provides opportunities in maintaining productivity and controlling production cost to obtain final products of (CRA) clad bars and pipes. 
     Embodiments of the methods, processes and billets discussed herein provide a significant improvement over the previous attempts to produce clad billet products, such as stainless clad rebar (SCR) and stainless clad pipes, because the disclosed methods and processes assure the formation of a 100% metallurgical bond (atom-to-atom), with a uniformly distributed clad thickness, on a consistently repeatable basis, thereby avoiding the conventional problems of metallurgical bonding failures and non-uniform cladding. 
     The present disclosure relates to methods and systems for producing a composite billet assembly, composed of a carbon or low-alloy steel (CS) core and a corrosion resistant alloy (CRA) pipe/tube/cylinder on the outer diameter of the (CS) core, for co-extrusion. Upon co-extrusion, the composite billet assembly forms a metallurgically bonded (atom-to-atom) clad billet that can be directly fed to a rod rolling mill for production of various clad bar products, or that can be directly fed to a cold pilger/cold draw mill for production of various clad pipe products. That is, the clad billet comprises a carbon or low-alloy steel core with a metallurgically bonded corrosion resistant alloy cladding on the outer diameter of the steel core. This 100% metallurgically bonded clad billet works either as a final product or as an intermediate product, which may be fed to a rod rolling mill or a cold pilger/cold draw mill for further reductions to produce a variety of other finished clad products such as, Stainless Clad Rebar (SCR), Clad Sucker Rods, Clad Shafts, Clad Pipes, and other applications. 
     According to one embodiment, a method of producing a clad billet, comprises: heating a corrosion resistant alloy cylinder, the corrosion resistant alloy cylinder including a hollow interior, an inner diameter, and an outer diameter, wherein the heating expands at least the inner diameter; inserting a solid carbon or low-alloy steel material into the hollow interior of the heated corrosion resistant alloy cylinder so that an outer surface of the solid carbon or low-alloy steel material faces the inner diameter of the corrosion resistant alloy cylinder; cooling the heated corrosion resistant alloy cylinder to contract at least the inner diameter of the corrosion resistant alloy cylinder so that the inner diameter shrinks onto the outer surface of the solid carbon or low-alloy steel material creating an interference fit at an interface with the outer surface and resulting in a composite billet assembly; and extruding the composite billet assembly to reduce the size of the composite billet assembly by reducing a thickness of each of the corrosion resistant alloy cylinder and the solid carbon or low-alloy steel material and form the clad billet having a metallurgical bond between the solid carbon or low-alloy steel material and the corrosion resistant alloy cylinder. 
     According to an embodiment, the method further comprises cleaning the outer surface of the solid carbon or low-alloy steel material and the surface of the inner diameter of the corrosion resistant alloy cylinder, before inserting the solid carbon or low-alloy steel material into the hollow interior of the heated corrosion resistant alloy cylinder. 
     According to an embodiment, the cleaning removes at least one of oxides, oils and rust. 
     According to an embodiment, the method further comprises welding each opposite end of the composite billet assembly at the interface, before extruding the composite billet assembly, to create a seal against oxidation of the interface. 
     According to an embodiment, the composite billet assembly comprises an outer diameter of 3 inches to 45 inches, and the clad billet comprises a cross-sectional dimension of 1 inch to 20 inches after the extruding. 
     According to an embodiment, the method further comprises hot-rolling the clad billet to form a clad rod. 
     According to an embodiment, the method further comprises at least one of cold pilgering and cold drawing the clad billet to form a clad pipe. 
     According to an embodiment, the solid carbon or low-alloy steel material is a bar. 
     According to an embodiment, the solid carbon or low-alloy steel material is a hollow cylinder. 
     According to an embodiment, the extruding shapes the clad billet to have a cross-sectional shape is one of a circle, cylinder, a rectangle, and a square. 
     According to an embodiment, the metallurgical bond is an atom-to-atom bond between the solid carbon or low-alloy steel material and the corrosion resistant alloy cylinder. 
     According to another embodiment, a system for producing a clad billet, comprises: a corrosion resistant alloy cylinder including a hollow interior, an inner diameter, and an outer diameter; a solid carbon or low-alloy steel material including an outer surface; a heater for heating the corrosion resistant alloy cylinder to expand at least the inner diameter of the corrosion resistant alloy cylinder; an insertion device for inserting the solid carbon or low-alloy steel material into the hollow interior of the heated corrosion resistant alloy cylinder so that the outer surface of the solid carbon or low-alloy steel material faces the inner diameter of the corrosion resistant alloy cylinder; an area to allow cooling of the heated corrosion resistant alloy cylinder to contract at least the inner diameter of the corrosion resistant alloy cylinder so that the inner diameter shrinks onto the outer surface of the solid carbon or low-alloy steel material and creates an interference fit at an interface with the outer surface, resulting in a composite billet assembly; and an extruder for extruding the composite billet assembly to reduce the size of the composite billet assembly by reducing a thickness of each of the corrosion resistant alloy cylinder and the solid carbon or low-alloy steel material and form the clad billet having a metallurgical bond between the solid carbon or low-alloy steel material and the corrosion resistant alloy cylinder. 
     According to an embodiment, the system further comprises a cleaning device for cleaning at least one of oxides, oils and rust from the outer surface of the solid carbon or low-alloy steel material and the surface of the inner diameter of the corrosion resistant alloy cylinder. 
     According to an embodiment, the system further comprises a welding device for welding each opposite end of the composite billet assembly at the interface to create a seal against oxidation of the interface. 
     According to an embodiment, the system further comprises at least one of: a hot-rolling device for hot-rolling the clad billet to form a clad rod; and a cold pilgering/cold drawing device for at least one of cold pilgering and cold drawing the clad billet to form a clad pipe. 
     According to a further embodiment, a clad billet comprises: a carbon or low-alloy steel core; and a corrosion resistant alloy outer layer covering the carbon or low-alloy steel core, wherein the corrosion resistant alloy outer layer has a metallurgical bond with the carbon or low-alloy steel core defined by an atom-to-atom bond between the corrosion resistant alloy outer layer and the carbon or low-alloy steel core. 
     According to an embodiment, the clad billet further comprises a length of 20 feet to 60 feet; and a cross-sectional dimension of 3 inches to 10 inches. 
     According to an embodiment, a cross-sectional shape of the composite billet assembly is one of a circle, a cylinder, a rectangle, and a square. 
     The foregoing is intended to give a general idea of the embodiments, and is not intended to fully define nor limit the invention. The embodiments will be more fully understood and better appreciated by reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the detailed description of various embodiments usable within the scope of the present disclosure, presented below, reference is made to the accompanying drawings, in which: 
         FIG. 1A  illustrates an embodiment of a corrosion resistant alloy cylinder. 
         FIG. 1B  illustrates an embodiment of a solid carbon or low-alloy steel material. 
         FIG. 1C  illustrates another embodiment of a solid carbon or low-alloy steel cylinder material. 
         FIG. 1D  illustrates an embodiment of a composite billet assembly. 
         FIG. 2  illustrates a perspective view of the composite billet assembly according to an embodiment. 
         FIG. 3  illustrates a cross-sectional view of the composite billet assembly according to an embodiment. 
         FIG. 4  illustrates an embodiment of an extrusion press. 
         FIG. 5  illustrates an embodiment of an extrusion process. 
         FIG. 6  illustrates the stages of a composite billet assembly, a clad feedstock billet, and a clad bar, according to an embodiment. 
         FIG. 7  illustrates the stages of a composite billet assembly, a clad mother pipe, and a clad pipe, according to an embodiment. 
         FIG. 8  illustrates the steps associated with a method of producing a clad billet and products thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before describing selected embodiments of the present disclosure in detail, it is to be understood that the present invention is not limited to the particular embodiments described herein. The disclosure and description herein is illustrative and explanatory of one or more presently preferred embodiments and variations thereof, and it will be appreciated by those skilled in the art that various changes in the design, organization, means of operation, structures and location, methodology, and use of mechanical equivalents may be made without departing from the spirit of the invention. 
     As well, it should be understood that the drawings are intended to illustrate and plainly disclose presently preferred embodiments to one of skill in the art, but are not intended to be manufacturing level drawings or renditions of final products and may include simplified conceptual views to facilitate understanding or explanation. As well, the relative size and arrangement of the components may differ from that shown and still operate within the spirit of the invention. 
     Moreover, it will be understood that various directions such as “upper”, “lower”, “bottom”, “top”, “left”, “right”, “first”, “second” and so forth are made only with respect to explanation in conjunction with the drawings, and that components may be oriented differently, for instance, during transportation and manufacturing as well as operation. Because many varying and different embodiments may be made within the scope of the concept(s) herein taught, and because many modifications may be made in the embodiments described herein, it is to be understood that the details herein are to be interpreted as illustrative and non-limiting. 
       FIGS. 1A to 1D  illustrate embodiments of a corrosion resistant alloy (CRA) cylinder  10 , a solid carbon or low-alloy steel (CS) material  12 , and a composite billet assembly  14  formed by inserting the (CS) material  12  into the (CRA) cylinder  10 . The (CRA) cylinder  10 , as shown in  FIG. 1A , may be formed of alloys including, but not limited to, all grades of Stainless Steels, Nickel based alloys, Copper based alloys, Titanium and Ti Alloys and other corrosion resistant alloys. The (CRA) cylinder  10  may have a substantially cylindrical shape, meaning that the (CRA) cylinder  10  has a hollow interior  11  extending throughout a length of the (CRA) cylinder  10 , an inner diameter  13 , and an outer diameter  15 . In this regard, the (CRA) cylinder  10  may be shaped as a pipe, tube, cylinder, sleeve, channel, or conduit. In a preferred embodiment, the cross-sectional shape of the (CRA) cylinder  10  is circular. However, other polygonal cross-sectional shapes, such as rectangular, pentagonal, hexagonal, octagonal, etc., are within the scope of the present embodiments. The length of the (CRA) cylinder  10  is not particularly limiting, and in a preferred embodiment the length may be about 3 feet to 5 feet. In other embodiments, the length may range from 2 feet to 6 feet. The outer diameter  15  of the (CRA) cylinder  10  is not particularly limiting, and in a preferred embodiment the outer diameter  15  may be about 4 inches to 24 inches. In other embodiments, the outer diameter  15  may range from 3 inches to 50 inches. The thickness of the (CRA) cylinder  10  is not particularly limiting, and in a preferred embodiment the thickness may be about 0.5 inches to 1.5 inches. In other embodiments, the thickness may range from 0.375 inches to 5.0 inches or more. 
       FIG. 1B  illustrates an embodiment of the solid carbon or low-alloy steel (CS) material  12 . The carbon or low-alloy steel (CS) material  12  is described herein as being a “solid”, meaning that the structure or nature of the carbon or low-alloy steel (CS) material  12  is substantially rigid, as opposed to a liquid, molten or powder form. The material forming the carbon or low-alloy steel includes, but not limited to, carbon and low alloy structural grade steels, chrome moly steels, typically as covered by ASTM, ASME, AISI, API, ISI specifications and other such equivalent specifications defining design, manufacturing, and building standards. In the embodiment of  FIG. 1B , the (CS) material  12  is shaped as a bar, or block of material. In an alternative embodiment shown in  FIG. 1C  however, the (CS) material  12  is shaped as a hollow cylinder including a hollow interior extending throughout a length of the (CS) cylinder, an inner diameter  16 , and an outer diameter  17 . In the alternative embodiment, the (CS) material  12  may be shaped as a pipe, tube, cylinder, sleeve, channel, or conduit. The cross-sectional shape of the (CS) cylinder may be circular. In either embodiment (bar or hollow cylinder), the length of the (CS) material  12  may be the same as the length of the (CRA) cylinder  10 . The outer diameter  17  of the (CS) material  12  may have a dimension designed for an interference fit with the inner diameter  13  of the (CRA) cylinder  10 . In the embodiment having a hollow cylinder (CS) material, the thickness of the cylinder may range from 0.50 inches to 3.00 inches or higher. 
       FIG. 1D  illustrates an embodiment of a composite billet assembly  14  that is formed by inserting the (CS) material  12  into the (CRA) cylinder  10  according to the following process. To begin with, the (CS) material  12  and the (CRA) cylinder  10  may be machined as required to meet strict dimensional tolerances for a designed interference fit. Next, the mating surfaces, i.e., the inner diameter  13  of the (CRA) cylinder  10  and the outer diameter  17  of the (CS) material  12  cleaned of all contaminants and deleterious elements, such as oxides, oils, and rust, grease, industrial dust and particulates. The cleaning may be performed by a cleaning device  18 , such as an abrasive blaster using an abrasive media to remove deleterious materials and leave a fresh, un-oxidized surface. Other types of cleaning devices  18  may include machining devices used to form the (CRA) cylinder  10  and the (CS) material  12  to specified tolerances, and may include solvents that remove oils and grease without leaving a residue. 
     The (CRA) cylinder  10  is then heated with a heater  19  to expand at least the inner diameter  13  of the (CRA) cylinder  10 . The heater  19  may be a furnace, or other device that produces heat via infrared or electric resistance. Alternatively, the heater  19  may be an optical lamp source. The heater  19  may be positioned to heat the inner diameter  13  directly, or may be positioned to heat from the outer diameter  15 . Heating temperatures required to expand at least the inner diameter  13  of the (CRA) cylinder  10  range from 300° F. to 1400° F. As the (CRA) cylinder  10  heats, a gap is produced between the inner diameter  13  of the (CRA) cylinder  10  and the outer diameter  17  of the (CS) material  12 , allowing the (CS) material  12  to be inserted into the (CRA) cylinder  10  without resistance. The insertion may be performed with a lift device (not shown). The (CS) material  12  is then inserted into the hollow interior  11  of the heated (CRA) cylinder  10  so that the outer diameter  17  (outer surface) of the (CS) material  12  faces the inner diameter  13  of the (CRA) cylinder  10 . Once the (CS) material  12  has been inserted into the heated (CRA) cylinder  10 , heater  19  is turned off and the (CRA) cylinder  10  is allowed to cool. The cooling may simply be the result of turning off the heater  19  so that the (CRA) cylinder  10  is no longer subjected to the heat from the heater  19 . In the cooling process, the (CRA) cylinder  10  should cool uniformly. For instance, the (CRA) cylinder  10  may cool simply by being subject to room temperature or ambient atmosphere. In other embodiments, the cooling may be accelerated by a cooling device (not shown), such as one producing forced air, that is turned on after the heater  19  is turned off. Cooling of the (CRA) cylinder  10  causes at least the inner diameter  13  of the (CRA) cylinder  10  to contract so that the inner diameter  13  shrinks onto the outer surface or diameter  17  of the (CS) material  12 , creating a tight interference fit at an interface  20 , or mating area of the inner diameter  13  of the (CRA) cylinder  10  and the outer surface or diameter  17  of the (CS) material  12 . The mated (CS) material  12 /(CRA) cylinder  10  creates a composite billet assembly  14  having a core formed by the (CS) material  12  and an outer cladding formed by the (CRA) cylinder  10 . The interference fit at the interface  20  may be protected from oxidation by welding the interface  20  at opposite ends (i.e., top and bottom ends) of the composite billet assembly  14  with a welding device  21 . The resulting welds  22  create a seal against oxidation of the interface  20  during heating of the composite billet assembly prior to extrusion. 
       FIG. 2  illustrates a perspective view of the composite billet assembly  14 . In the illustrated embodiment, the composite billet assembly  14  includes a bar-shaped (CS) material  12  core, and so the composite billet assembly  14  has the form of a composite billet bar assembly. However, in the embodiment in which a hollow cylinder (CS) material  12  is used as the core, the composite billet assembly  14  would form a composite billet pipe assembly (not shown).  FIG. 3  illustrates a cross-sectional view of the composite billet assembly  14  of  FIG. 2 .  FIG. 3  shows a cross-sectional view of the (CS) material  12  core, the outer (CRA) cylinder  10  layer, and the welds  22  at the end of the composite billet assembly  14  that seal the interface  20 . 
       FIG. 4  illustrates an embodiment of an extruder, such as an extrusion press  23  for extruding the composite billet assembly  14  at high temperatures to reduce the size of the composite billet assembly  14  and form a clad feedstock billet  27  (see  FIG. 6 ). For forming a clad mother pipe  29  (see  FIG. 7 ) from the composite billet assembly  14 , the extrusion press  23  is fitted with a cylindrical mandrel (not shown), which is inserted into the inner cylindrical opening of the composite billet assembly  14 , and extends beyond the die opening  26  of the die  25  for some length to form the inner diameter of the extruded clad mother pipe. The composite billet assembly  14  is first heated in a furnace (not shown) to a predetermined high temperature and rapidly transferred to the extrusion press  23  so as to not cool below the preset extrusion temperature, and extruded at the extrusion press  23 . The extrusion press  23  includes a press ram  24  that presses the composite billet assembly  14  through the die opening  26  of a die  25 . During extrusion, the composite billet assembly  14  undergoes significant cross-sectional size reduction by passing through the die opening  26 , as shown in  FIG. 5 , under very high pressures, such as 20,000 psi to 70,000 psi, depending on the capacity of the press, applied at high temperatures, such as 1800° F. to 2400° F. The size of the composite billet assembly  14  is reduced by the extrusion press  23  reducing a thickness of each of the (CRA) cylinder  10  and the solid (CS) material  12 . The proportion of the thickness reduction of the (CRA) cylinder  10  and the solid (CS) material  12  is the same throughout the cross-sectional area of the composite billet assembly  14  and along the length of the of the composite billet assembly  14  as it passes through the die opening  26 . As the size of the composite billet assembly  14  is reduced through the die opening  26 , clean, fresh, new un-oxidized surfaces of the composite billet assembly  14  are created at the interface  20  between the (CS) material  12  and the (CRA) cylinder  10  and forced to metallurgically bond at the interface  20  as the composite billet assembly  14  elongates to its new shape. The metallurgical bond is an atom-to-atom bond between the (CS) material  12  and the (CRA) cylinder  10 . In the composite billet assembly interface  20 , the material of the (CS) material  12  is in intimate contact with the material of the (CRA) cylinder  10 , with no gaps therebetweeen to entrap oxygen and oxidize upon heating. Thus, when the new surfaces are being created as the composite billet assembly  14  undergoes significant reductions at high pressures and temperatures, a 100% metallurgical bond is created between the material of the (CS) material  12  and the material of the (CRA) cylinder  10 . The metallurgical bond is a critical factor for determining success or failure of the resulting clad feedstock billet  27  (see  FIG. 6 ) and the clad mother pipe  29  (see  FIG. 7 ). Once the bond is created, it is nearly indestructible, with the two materials of the (CS) material  12  and the (CRA) cylinder  10  joined to become one unitized material and perform just like any other solid material. This allows the clad feedstock billet  27  to then be hot rolled to a clad bar  28  (see  FIG. 6 ) in the form of, for example, rebar, sucker rods, shafts and other products that can be easily bent, fabricated in a shop and the field, and welded as needed, to provide excellent service and design life in corrosive environments. Similarly, the clad mother pipe  29  is then cold pilgered and/or cold drawn to a clad pipe  30  (see  FIG. 7 ) that can be easily bent, fabricated in a shop and the field, and welded as needed, to provide better service and design life in corrosive environments. It is noted that the thickness of the (CRA) cylinder  10  before extrusion is drastically reduced proportionately after extrusion, so that the (CRA) cylinder  10  forms a relatively thin clad material layer around the outer diameter of the clad feedstock billet  27  (see  FIG. 6 ) and the clad mother pipe  29  (see  FIG. 7 ). 
     The cross-sectional shape of the clad feedstock billet  27 , shown in  FIG. 6 , after the extruding process is not particularly limiting, and in preferred embodiments the cross-sectional shape is one of a circle, a cylinder, a rectangle, and a square. The cross-sectional shape is determined by the shape of the die opening  26 , and so the die opening  26  may have a shape that is one of a circle, a cylinder, a rectangle, and a square. Other polygonal cross-sectional shapes are possible, and depend on the shape of the die opening  26 . That is, the die opening  26  may have a polygonal or angular shape other than a circle, a cylinder, a rectangle, and a square. Thus, the clad feedstock billet  27  can be produced to the exact feedstock dimensional requirements of a rod rolling mill. The cross-sectional shape of the clad mother pipe  29 , shown in  FIG. 7 , after the extruding process is circular according to a preferred embodiment. The clad mother pipe  29  can be produced to the exact dimensional requirements of a cold pilger/cold draw mill. 
     As used herein, the term “clad billet” refers to the intermediate product of both a clad feedstock billet, such as the clad feedstock billet  27  shown in  FIG. 6  and used to form clad bars, and to a clad mother pipe, such as the clad mother pipe  29  shown in  FIG. 7  and used to form clad pipes. That is, a “clad billet” as used herein may be a clad feedstock billet, or may be a clad mother pipe. The cross-sectional area of the clad billet discussed herein is not particularly limiting, and may be a function of the cross-sectional area of the die opening  26 . In a preferred embodiment, a circular cross-sectional area of the clad billet may result from a diameter of 3 inches to 10 inches of the clad billet; or from a length and width of from 3 inches to 10 inches for a square cross-sectional area. In other embodiments, the dimension (e.g., diameter, length or width) used for the cross-sectional area of the clad billet may be from about 1 inch to 20 inches after extruding. The length of the clad billet after extrusion may be from about 20 feet to 40 feet long, or may be up to about 60 feet long in some instances. These lengths of clad billets can produce an equal mass of the required extruded clad billet product. For example, the clad bar  28  shown in  FIG. 7  (e.g., rebar) having a diameter of about 0.375 inches to 1.75 inches may have a length of, for example, 2500 feet, and be formed in a hot-rolling process at, for instance, a rod rolling mill. 
     Reductions of the clad feedstock billet  27  through multiple stages of the rod rolling mill, which reductions change the shape and form of the billet at each stage, further consolidates the metallurgical bond and makes clad thickness uniform around the circumferential (outer diameter) surface, to produce stainless clad rebar (SCR), sucker rods, and other finished clad bar products. Similarly, the clad mother pipe  29  formed by hot extrusion of the clad billet assembly  14  will be processed through multiple stages of reduction in a cold pilger mill and/or a cold draw bench to reduce the diameter and thickness of the composite wall at each stage. It may be necessary to provide intermediate stress relieving steps prior to resuming further cold reducing steps to arrive at the final dimensions of outside dimension and wall thickness of the clad pipe. 
     A system for producing a clad billet may include the components and devices discussed herein. For example, the system may include a (CRA) cylinder  10  including the aspects discussed herein; and a solid (CS) material  12  including the aspects discussed herein. The system may further include a cleaning device  18  including the aspects discussed herein for cleaning at least one of oxides, oils and rust from the outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12  and the surface of the inner diameter  13  of the (CRA) cylinder  10 . A heater  19  including the aspects discussed herein is provided in the system for heating the (CRA) cylinder  10  to expand at least the inner diameter  13  of the (CRA) cylinder  10 . The system may include an insertion device for inserting the solid (CS) material  12  into the hollow interior of the heated (CRA) cylinder  10  so that the outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12  faces the inner diameter  13  of the (CRA) cylinder  10 . The system further includes an area, such as a room, open space, a platform to allow cooling, as discussed herein, of the heated (CRA) cylinder  10  to contract at least the inner diameter  13  of the (CRA) cylinder  10  so that the inner diameter  13  shrinks onto the outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12 , creating an interference fit at an interface  20 , as discussed herein, with the outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12 , resulting in a composite billet assembly  14  having the aspects discussed herein. The system may also include a welding device  21 , as discussed herein, for welding each opposite end of the composite billet assembly  14  at the interface  20  to create a seal against oxidation of the interface  20 , as discussed herein. The system further includes an extruder  23 , as discussed herein, for extruding the composite billet assembly  14  to reduce the size of the composite billet assembly  14  and form a clad billet having a metallurgical bond, as discussed herein, between the solid (CS) material  12  and the (CRA) cylinder  10 . The clad billet may be a clad feedstock billet  27  (see, e.g.,  FIG. 6 ) or a clad mother pipe  29  (see, e.g.,  FIG. 7 ). The system may comprise a hot-rolling device, such as in a rod rolling mill or pipe mill as discussed herein, for hot-rolling a clad feedstock billet  27  to form a clad bar  28 , as discussed herein. The system may comprise a cold pilgering/cold drawing device, such as in a cold pilgering/cold drawing mill, for cold pilgering/cold drawing a clad mother pipe  29  to form a clad pipe  30 , as discussed herein. 
       FIG. 8  illustrates a flow chart representing steps associated with a method for producing a metallurgically bonded clad billet and products thereof. The method may include the embodiments and aspects discussed herein. The process may being with a solid (CS) material  12  and a (CRA) cylinder  10  that have been machined as required to meet the dimensional tolerances for a designed interference fit, as discussed above. In step  30 , the outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12  and the inner diameter  13  of the (CRA) cylinder  10  may be cleaned, as discussed herein, to remove at least one of oxides, oils, rust, and other deleterious elements. The solid (CS) material  12  may be a bar, or may be a hollow cylinder, as discussed herein. In step  31 , the (CRA) cylinder  10  is heated to expand at least the inner diameter  13  of the (CRA) cylinder  10 , as discussed herein. In step  32 , the solid (CS) material  12  is inserted into the hollow interior  11  of the (CRA) cylinder  10 , so that an outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12  faces the inner diameter  13  of the (CRA) cylinder  10 , as discussed herein. In step  33 , the (CRA) cylinder  10  is cooled, or allowed to cool, as discussed herein, in order to contract at least the inner diameter  13  of the (CRA) cylinder  10  so that the inner diameter  13  shrinks onto the outer surface (e.g., outer diameter  17 ) of the solid (CS) material  12 , creating an interference fit at an interface  20  with the outer surface (e.g., outer diameter  17 ), as discussed herein, resulting in a composite billet assembly  14 . In step  34 , each opposite end of the composite billet assembly  14  may be welded at the interface  20 , as discussed herein, to create a seal against oxidation of the interface  20 . In step  35 , the composite billet assembly  14  is hot extruded, such as with the extrusion press  23  discussed herein, to reduce the size of the composite billet assembly  14  and form a clad billet having a metallurgical bond between the solid (CS) material  12  and the (CRA) cylinder  10 , as discussed herein. The clad billet may be a clad feedstock billet  27  or a clad mother pipe  29 , as discussed herein. As discussed herein, the metallurgical bond is an atom-to-atom bond between the solid (CS) material  12  and the (CRA) cylinder  10 . The process then proceeds to either step  36  or step  37 . In step  36 , the clad feedstock billet  27  is fed to a hot-rolling device, such as at a rod rolling mill as discussed herein, to form a clad product. Hot-rolling a clad feedstock billet  27  having a bar-shaped solid (CS) material  12  forms a clad bar  28 . On the other hand, in step  37  the clad mother pipe  29  is fed to a cold pilgering/cold drawing device, such as at a cold pilgering/cold drawing mill as discussed herein, to form a clad pipe. That is cold pilgering/cold drawing a clad mother pipe  29  having a hollow cylinder-shaped solid (CS) material  12  forms a clad pipe  29 . 
     While various embodiments usable within the scope of the present disclosure have been described with emphasis, it should be understood that within the scope of the appended claims, the present invention may be practiced other than as specifically described herein.