ELEVATED TEMPERATURE FORMING METHODS FOR METALLIC MATERIALS

INVENTORS

Njall Stefansson

Andrew Nichols

Michael Cleppe

BACKGROUND OF THE TECHNOLOGY FIELD OF THE TECHNOLOGY

[0001] The present disclosure is directed to methods of forming hard-to-form metallic materials, i.e., metals and metal alloys, using localized direct or indirect induction heating.

DESCRIPTION OF THE BACKGROUND OF THE TECHNOLOGY

[0002] It is generally known that certain metals and metal alloys, including, for example, titanium, titanium alloys, nickel-base alloys, and specialty steels {e.g., stainless steel, high-strength low-alloy steel (HSLA), armor steel alloys, and the like), are difficult to form. Such metallic materials are generally referred to herein as "hard-to- form" metallic materials. Hard-to-form metallic materials are generally more difficult to form as their thickness, width, and/or length increase. Many hard-to-form metallic materials cannot be effectively and efficiently formed into desired shapes or

components without the use of an extensive and costly set of processing steps.

Conventional techniques of making parts from hard-to-form metallic materials may include: welding together multiple pieces; machining or hogging out whole sections to provide desired shapes; and advanced forming techniques, such as net shape casting, forging, super-plastic forming, and the like. Many conventional part making techniques have limitations due to degradation of metal properties that exclude the techniques from use with hard-to-form metallic materials. For example, a heat affected zone my result from welding, and machining and casting defects may exist that are not readily detectable. Conventional forming of hard-to-form metallic materials normally involves significant post-forming operations for surface repair, flatness control, dimensional stability, cosmetic repair, and adjustment/ recovery of desired mechanical properties.

[0003] Fabricators have employed direct heating of hard-to-form metals and metal alloys with classic open torch technology, such as rose-bud torch technology. These methods, however, have met with only mixed success and generally are less successful as the size of the component or part increases. Poor temperature control and poor uniformity of heating is a common drawback of such methods. The use of open torch technology to heat a bend region of alpha+beta titanium alloy plate, for example, can produce undesirable phase transformations due to poor temperature control, resulting in beta phase at the surface of the plate, with an increasing

concentration of alpha+beta phase microstructure moving toward the plate centerline.

[0004] Other known methods for bending hard-to-form metallic materials generally involve high temperature heating prior to and/or during forming. Such processes may require multiple heating steps to enable forming of a part. In addition, high temperature forming usually requires post-forming operations such as annealing, surface conditioning, pickling, dimensional stabilization, and/or additional rework. Also, such high temperature work can require a large furnace, depending on part size and dimensions of the formed component. Logistics, feasibility, and expense may render such processing impractical from an operational, scheduling, and cost perspective. [0005] Attempts have been made to develop improved techniques for forming of hard-to-form metallic materials. For example, U.S. Patent No. 6,071 ,360 discloses a method for superplastic forming of thick titanium alloy plate. The plate is heated to superplastic temperatures, e.g., 1650°F (898.9°C), and forming takes place using a press ram. Completion of a part is accomplished by machining the formed plate. The '360 patent states that a 7.87 inch (20 cm) thick plate can be bent to about 130° with a 5 inch (12.7 cm) to 6 inch (15.24 cm) inner radius bend. In an embodiment of the '360 patent, a 2 inch (5.08 cm) thick plate was formed with a complex curvature exceeding a 12 inch (30.48 cm) depth over an area of 30x60 inches (76.2.x152.4 cm). One drawback of the method described in the '360 patent is the high temperature and specialized equipment required to achieve superplasticity in the alloy plate. [0006] In light of the above discussion, there is a need for improved methods to bend and otherwise form hard-to-form metallic materials.

SUMMARY

[0007] According to one aspect of the present disclosure, a method of forming a metallic article comprises inductively heating a localized region of a metallic article to a forming temperature. In a non-limiting embodiment, the forming temperature is in a forming temperature range of 0.20 to 0.50 of a melting temperature of the material from which the metallic article is comprised. After inductively heating the localized region, the metallic article is formed in the localized region. In non-limiting embodiments, forming the metallic article comprises at least one of bending, drawing, punching, stamping, and roll forming the metallic article. In certain non-limiting embodiments, the metallic article comprises a material selected from a titanium alloy, a nickel-base alloy, a stainless steel alloy, a high-strength low-alloy steel, and an armor steel alloy. [0008] According to another aspect of the present disclosure, a method of bending a metallic plate includes inductively heating a lineal region of the metallic plate to a bending temperature. In a non-limiting embodiment, the bending temperature is in a bending temperature range of 0.2 to 0.5 of a melting temperature of the metallic material from which the metallic plate is comprised. After inductively heating the lineal region of the metallic plate, the plate is bent along (i.e., in) the lineal region. In non- limiting embodiments, the metallic material from which the metallic plate is comprised is a material selected from a titanium alloy, a nickel-base alloy, a stainless steel alloy, a high-strength low-alloy steel and an armor steel alloy.

[0009] According to yet another aspect of the present disclosure, a method of forming a metallic material includes placing a metallic article comprising a material selected from a metal and a metal alloy on a ferrous alloy surface. The ferrous alloy surface is inductively heated to a predetermined temperature in a localized region of the ferrous alloy surface that is in contact with a localized region of the metallic article, and the localized region of the metallic article is thereby conductively heated to a forming temperature within a forming temperature range. The metallic article is formed in the localized region. In non-limiting embodiments, the metallic article comprises a metallic material selected from a titanium alloy, a nickel-base alloy, a stainless steel alloy, a high-strength low-alloy steel, and an armor steel alloy. In another non-limiting embodiment, the forming temperature range is 0.2 to 0.5 of a melting temperature of the metallic material.

[0010] According to a further aspect of the present disclosure, a method of bending a metallic plate includes placing a metallic plate comprising a metallic material selected from a metal and a metal alloy on a ferrous alloy surface. A lineal region of the ferrous alloy surface in contact with a lineal region of the plate is inductively heated to a predetermined temperature, and a lineal region of the metallic plate is thereby conductively heated to a bending temperature within a bending temperature range. The metallic plate is bent in the lineal region of the metallic plate. In a non-limiting embodiment, the bending temperature range is 0.2 to 0.5 of a melting temperature of the metallic material. In other non-limiting embodiments, the metallic plate comprises a metallic material selected from a titanium alloy, a nickel-base alloy, a stainless steel alloy, a high-strength low-alloy steel, and an armor steel alloy.

[001 1 ] According to yet a further aspect of the present disclosure, a device for indirect localized heating of a metallic article including a material selected from a metal and a metal alloy comprises a support that includes a ferrous alloy surface, and at least one induction heating device. The at least one induction heating device is positioned and adapted to inductively heat a localized region of the ferrous alloy surface. The inductively heated localized region of the ferrous alloy surface is adapted to heat a localized region of a metallic article that is positioned on the ferrous alloy surface to a predetermined temperature.

[0012] According to still another aspect of the present disclosure, a device for direct localized heating of a metallic article including a material selected from a metal and a metal alloy comprises a support including a support surface. At least one induction heating device is positioned and adapted to inductively heat a localized region of the metallic article positioned on the support surface to a predetermined temperature. The support and the support surface comprise a material that is not inductively heated by the at least one induction heating device. [0013] An additional aspect of the present disclosure is directed to a system for bending a metallic article comprising a material selected from a metal and a metal alloy. The system includes a support including a ferrous alloy surface, and at least one induction heating device. The at least one induction heating device is positioned and adapted to inductively heat a predetermined lineal region of the ferrous alloy surface. The inductively heated lineal region of the ferrous alloy surface is adapted to

conductively heat a lineal region of a metallic article positioned on the ferrous alloy surface to a bending temperature in a bending temperature range. The system further includes a metallic material bending apparatus positioned proximate the ferrous alloy surface and adapted to bend the metallic article along the lineal region before the lineal region cools below the bending temperature range.

[0014] Another aspect of the present disclosure is directed to a formed ballistic armor plate comprising a metallic material selected from a titanium alloy, a nickel-base alloy, a stainless steel alloy, a high-strength low-alloy steel, and an armor steel alloy, and wherein the plate has at least one bend region having a bend radius of at least 2t. The formed ballistic plate may be provided as, for example, a monolithic hull, a V- shaped hull, a blast protective vehicle underbelly, or an enclosure.

[0015] A further aspect of the present disclosure is directed to an article of manufacture including a formed ballistic armor plate according to the present disclosure. The formed ballistic plate may be in the form of, for example, a monolithic hull, a V- shaped hull, a blast protective vehicle underbelly, or an enclosure. In certain

embodiments, the formed ballistic plate may include one of a titanium alloy, a nickel- base alloy, a stainless steel alloy, a high-strength low-alloy steel, and an armor steel alloy, and may include at least one bend region having a bend radius of at least 2t. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features and advantages of certain non-limiting embodiments described herein may be better understood by reference to the accompanying drawings in which: [0017] FIG. 1 is a flow diagram of a non-limiting embodiment according to the present disclosure of a method for forming an article comprising a hard-to form metallic material;

[0018] FIG. 2 is a schematic representation of a non-limiting embodiment according to the present disclosure of a method including inductively heating a lineal region of a plate or sheet of a hard-to-form metallic material;

[0019] FIG. 3 is a flow diagram of a non-limiting embodiment according to the present disclosure of a method for bending or otherwise forming a plate, sheet, or other article of a hard-to-form metallic material;

[0020] FIG. 4 is a schematic representation of a non-limiting embodiment according to the present disclosure of a method utilizing indirect induction heating to indirectly heat a lineal or other localized region of a hard-to-form metallic plate, sheet, or other article in order to form the metallic article;

[0021 ] FIG. 5 is a schematic representation of a non-limiting embodiment of a device including a support comprising a ferrous alloy surface, and at least one induction heater. The at least one induction heater is positioned and adapted to inductively heat a localized region of the ferrous alloy surface in a substantially uniform manner to thereby conductively heat a localized region of a metallic article in a substantially uniform manner; [0022] FIG. 6 is a schematic representation of a non-limiting embodiment of a device including a support and at least one induction heater. The at least one induction heater is positioned and adapted to inductively heat a localized region of a metallic article positioned on the surface of the support in a substantially uniform manner. The support comprises material that is not inductively heated by the at least one induction heater;

[0023] FIGS. 7a and 7b depict schematic representations of a non-limiting embodiment of a support for a device for direct and indirect induction heating of a localized region of a metallic article; [0024] FIG. 8 depicts a non-limiting embodiment of a system for forming a metallic article, wherein the device includes an induction heating device adapted to heat a localized region of a metallic article, and a forming apparatus situated near the induction heating device to enable forming of the metallic article before the temperature of the localized region of the metallic article cools below a forming temperature range;

[0025] FIG. 9 is a schematic representation of a non-limiting embodiment according the present disclosure of a formed ballistic armor plate having at least one bend radius of about 2t;

[0026] FIG. 10 is a photograph of a non-limiting embodiment of a heating device according to the present disclosure, in the form of a heating table;

[0027] FIG. 1 1 is a photograph of 1 -inch (2.54 cm) thick ATI 425® titanium alloy (Ti-4AI-2.5V-1 .5Fe-0.25O ₂ (UNS R54250)) plate samples bent to increasing radii of 1 t through 6t using a non-limiting embodiment of a method according to the present disclosure; and [0028] FIG. 12 is a plot of temperatures within a localized region of a titanium alloy inductively heated for 900 seconds and then cooled for 60 seconds as a function of distance from the centerline of the heated localized region.

[0029] The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of certain non-limiting embodiments according to the present disclosure.

DETAILED DESCRIPTION OF CERTAIN NON-LIMITING EMBODIMENTS

[0030] In the present description of non-limiting embodiments, other than in the operating examples or where otherwise indicated, all numbers expressing quantities or characteristics are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, any numerical parameters set forth in the following description are approximations that may vary depending on the desired properties one seeks to obtain by way of the methods according to the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Also, all ranges provided herein are inclusive of the indicated boundaries or limits. For example, a temperature range of "0.2 to 0.5" of a particular temperature is inclusive of the indicated boundaries of 0.2 and 0.5 of the particular temperature.

[0031 ] Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions,

statements, or other disclosure material set forth herein is only incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0032] There is a need for improved methods to bend and otherwise form hard- to-form metallic materials. For example, the present inventors concluded that it would be advantageous to provide a method of forming hard-to-form metallic materials that does not require the use of open torches, large furnaces and associated logistics, or heating of materials to superplastic temperatures. The present inventors believe that such a method may lower the costs of formed components, increase productivity, and/or reduce the thermomechanical processing equipment infrastructure currently required to form many hard-to-form metallic materials. The present inventors also believe that such a method will enable new part design basis, i.e., the production of parts from alloys not previously used for such parts due to limitations of conventional production techniques.

[0033] FIG. 1 is a flow diagram schematically presenting a non-limiting embodiment according to the present disclosure of a method for elevated temperature forming of a metallic article comprising a hard-to-form metallic material. As used herein, the term "hard-to-form metallic material" refers to metals and metal alloys having high strength and low ductility at a forming temperature, and to metals and metal alloys that flow soften upon deformation. In a non-limiting embodiment, a hard-to-form metallic material has less than a 10% difference in tensile strength and yield strength at a forming temperature. In another non-limiting embodiment, a hard-to-form metallic material is a metal or metal alloy that exhibits a high spring back, such as is the case with titanium alloys, for example. As used herein, hard-to-form metallic materials include, for example, titanium alloys, nickel-base alloys, and specialty steels (e.g., stainless steel, high-strength low-alloy steel (HSLA), and armor steel alloys). Also, as used herein, "metallic" refers to a material or article comprising a metal and/or metal alloy.

[0034] While the embodiment disclosed in FIG. 1 refers to specific hard-to-form metallic materials, the embodiments described herein also may be used in forming high purity metals, commercially pure metals, and other metal alloys that either are or are not considered hard-to-form metallic materials. (Also, in order to reduce repetition in the present discussion, any reference to a "metal alloy" in the succeeding discussion of embodiments according to the present disclosure is inclusive of the unalloyed base metal.) One non-limiting example of a hard-to-form high purity metal that may be processed according to embodiments disclosed herein is high purity zirconium.

[0035] With reference to FIG. 1 , a non-limiting method 10 according to the present disclosure for forming a metallic article, i.e., an article including a hard-to-form metal or metal alloy article, comprises inductively heating 12 a localized region of the metallic article to a forming temperature in a forming temperature range. When the localized region is at the desired forming temperature, the article is bent or otherwise formed 14 in the localized region that has been inductively heated. [0036] In a non-limiting embodiment, the forming temperature is in a forming temperature range of 0.2 to 0.5 of the melting temperature (T _m ) of the metal or metal alloy comprising the metallic article. In another non-limiting embodiment, the forming temperature is in a forming temperature range of 0.24 to 0.3 of a melting temperature of the metal or metal alloy comprising the metallic article. In another non-limiting

embodiment, the forming temperature range is about 0.2 of the melting temperature to a temperature less than the recrystallization temperature of the metal or metal alloy comprising the metallic article. As used herein, the "melting temperature" is defined as being the lowest temperature at which incipient melting of the metal or metal alloy occurs. As used herein, the "recrystallization temperature" is defined as the lowest temperature at which the distorted grain structure of a cold-worked metal or metal alloy is replaced by a new, strain-free grain structure during prolonged heating.

[0037] As used herein, a "titanium alloy" is a metallic alloy including titanium as the predominant element. As used herein, a "nickel base alloy" is a metallic alloy including nickel as the predominant element. As used herein, a "specialty steel" is selected from categories of steel including, but not limited to, electric steels, alloy steels, stainless steels (including, ferritic, martensitic, austenitic, super-austenitic, duplex, and precipitation hardening stainless steels), tool steels, maraging steels, armor steel alloys, high strength low alloy steels, and wear steels.

[0038] Again referring to FIG. 1 , forming 14 the metallic article may comprise, but is not limited to, techniques selected from bending, drawing, punching, stamping, and roll forming. In another non-limiting embodiment, the metallic article comprises a mill product. As used herein, a "mill product" is any metallic (i.e., metal or metal alloy) article that is used as-fabricated or is further fabricated into a finished product. In a non- limiting embodiment according to the present disclosure, the mill product is selected from an ingot, a billet, a bloom, a round bar, a square bar, an extrusion, a tube, a pipe, a slab, a sheet, and a plate. In yet another non-limiting embodiment according to the present disclosure, the metallic article comprises a metallic plate, the localized region of the metallic plate that is inductively heated comprises a lineal region, and forming 14 the metallic plate comprises bending the metallic plate in the lineal region of the metallic plate.

[0039] As used herein, a "localized region" is an area of a metallic article that will be plastically deformed during a forming step. A "localized region" also may include one or more areas immediately adjacent to the area of the metallic article that will be plastically deformed. For example, in certain non-limiting embodiments according to the present disclosure, the localized region may extend up to about 0.5 inch (1 .27 cm), up to about 1 inch (2.54 cm), up to about 2 inches (5.04 cm), up to about 3 inches (7.62 cm), up to about 4 inches (10.16 cm), or a greater distance from the area of the metallic article that will be plastically deformed. For example, it is envisioned that in addition to inductively heating the area that will be plastically deformed, it may be desirable to inductively heat one or more areas immediately adjacent to the area that will be plastically deformed when the method is conducted on thicker metallic articles and/or to better ensure that the area of the metallic article that is plastically deformed is at the forming temperature during the forming step.

[0040] In a non-limiting embodiment of a method according to the present disclosure, a localized region that is inductively heated is a lineal region. As used herein, a "lineal region" is an elongated region that includes the intended bend line (i.e., the centerline of the bend) of a metallic plate or other article. The lineal region also may extend a distance from the intended bend line. For example, the lineal region may extend up to about 0.5 inch ( .27 cm), up to about 1 inch (2.54 cm), up to about 2 inches (5.04 cm), up to about 3 inches (7.62 cm), up to about 4 inches (10.16 cm), or a greater distance from the intended bend line along all or a region of the length of the intended bend line. In certain embodiments, the distance from the intended bend line defining a boundary of the lineal region increases with increasing thickness of the plate or other article to be bent or otherwise formed using the methods herein. [0041 ] In non-limiting embodiments according to the present disclosure, inductively heating a lineal region or other localized region involves utilizing one or more induction heating coils positioned adjacent to the localized region of the plate or other article. FIG. 2 is a schematic representation of a non-limiting embodiment according to the present disclosure of a method of inductively heating 20 a lineal region 22 of a plate 24 of a hard-to-form metal or metal alloy. Lineal region 22 is bounded by lines 22a in FIG. 2. In the non-limiting embodiment represented by FIG. 2, the lineal region 22 is inductively heated by two induction coils 26 positioned adjacent to opposite surfaces 28,29 of the lineal region 22 of the plate 24. While FIG. 2 depicts two induction coils 26 being utilized to heat the lineal region 22 of the plate 24, it is understood that one induction coil 26 or more than two induction coils 26 could be utilized to heat the lineal region 22 of the plate 24. Accordingly, for example, it is within the scope of this disclosure to position one or more induction coils adjacent to one or both opposite surfaces of a lineal region or other localized region of a metallic plate or other article to heat the localized region of the article to a forming temperature. It will be understood that the foregoing discussion concerning the number and positioning of induction coils relative to a localized region of a metallic article applies to any geometry of localized region that may be used in the methods according to the present disclosure.

[0042] For purposes herein, induction heating using an arrangement of induction coils such as, for example, induction coils 26 positioned directly adjacent to a metal or metal alloy article such as, for example, plate 24 is referred to herein as "direct" induction heating. In direct induction heating, one or more induction coils or other induction heating devices induce a current in a localized region of a metallic article and thereby cause the temperature of the localized region to increase. Direct induction heating may be contrasted with "indirect" induction heating, wherein a current is induced in and thereby heats a region of a metallic object, and the metallic object heats a localized region of a metallic article through conduction of heat from the inductively heated metallic object to the metallic article. Thus, in direct induction heating, the induction heating device inductively heats the metal or metal alloy article to be bent or otherwise formed without reliance on inductively heating an interposing metal or metal alloy object. [0043] Induction heating is a technique used to heat an electrically conductive object, such as a metal or metal alloy object, by electromagnetic induction, wherein a high frequency alternating current is passed through an electromagnet and induction coil. The induction coil is positioned adjacent to the metallic object, and the current within the coil generates eddy currents within the object. Electrical resistance within the metallic object results in Joule heating of the object. The frequency of alternating current that must be used to inductively heat a particular metal or metal alloy object depends on the object size, the composition of the metal or metal alloy, the particular coupling between the induction coil and the object to be heated, and the depth of penetration of the induced eddy currents. In non-limiting embodiments according to the present disclosure, the induction heating device used to heat the lineal region or other localized region of an article comprising a hard-to-form metallic material employs an alternating current frequency specifically tuned to efficiently and adequately heat the metallic article. Induction heating is known to those having ordinary skill in the art, and further elaboration of the principles of and manner for carrying out the technique is believed to be unnecessary in the present disclosure.

[0044] In certain non-limiting embodiments according to the present disclosure, the forming or bending temperature is within a range of about 0.2 times the melting temperature (0.2T _m ) of the hard-to-form metal or metal alloy, up to about 0.5 times the melting temperature (0.5T _m ) of the hard-to-form metal or metal alloy. Therefore, given the relatively low temperatures utilized, an aspect of non-limiting embodiments according to the present disclosure is that the embodiments may be considered to be "warm forming" methods. It was unexpected and surprising to the present inventors that hard-to-form metallic materials, such as, but not limited to, titanium alloys, nickel- base alloys, and specialty steels, can be bent or otherwise formed at temperatures substantially lower than the materials' melting temperatures without fracturing the material during forming and wherein after forming, the plastically deformed region is completely or substantially free of surface defects such as, for example, linear indications in the form of macro-surface and micro-surface cracking, resulting from the bending or other forming step.

[0045] In a non-limiting embodiment according to the present disclosure wherein the method is performed on a titanium alloy article, the forming or bending temperature range may be in a forming or bending temperature range of 750°F

(398.9°C) to 850°F (454.4°C), or in a forming or bending temperature range of 800°F (426.7°C) to 850°F (454.4°C). According to one non-limiting embodiment, the forming or bending temperature for a titanium alloy article is about 800°F (426.7°C), while in another non-limiting embodiment the forming or bending temperature for a titanium alloy article is about 850°F (454.4°C). According to certain non-limiting embodiments, when the metallic article that is being bent or otherwise plastically deformed consists of or comprises Ti-4AI-2.5V-1 .5Fe-0.25O ₂ alloy (UNS R54250), the forming or bending temperature range may be from 728°F to 874°F (387°C to 468°C). In other non-limiting embodiments according to the present disclosure wherein the metallic article consists of or comprises a titanium alloy, the forming or bending temperature range may be from about 1000°F (555.6°C) below the beta transus temperature (Τ _β ) of the titanium alloy up to about 700°F (388.9°C) below the beta transus temperature of the titanium alloy, i.e., in a temperature range of T _R - 1000°F to Τ _β - 700°F (T _p - 555.6°C to Τ _β - 388.9°C).

[0046] Most conventional processes for forming titanium alloys use

temperatures greater than 1 000°F (537.8°C). At these "hot forming" temperatures, surfaces of the titanium alloys may oxidize, forming an alpha-case. Alpha-case is an oxygen-enriched phase resulting when titanium and its alloys are exposed to heated air or oxygen. Because alpha-case is brittle and tends to cause fatigue cracks in the alloy, it typically is removed in subsequent processing steps. Little or no alpha-case forms at the forming temperatures used in various non-limiting embodiments of the forming methods disclosed herein.

[0047] In addition, above about 1000°F (537.8°C) the mechanical properties of titanium alloys may change. For example, ballistic properties required of titanium alloys for armor applications such as, for example, high toughness, may be lost on thermo- mechanical processing a titanium alloy at hot forming temperatures. In such case, heat treatments subsequent to hot forming may be required to restore desired mechanical properties in the alloys. For some hard-to-form metallic materials, it may not be possible to restore the desired mechanical properties using post-forming heat treatments. The present inventors observed that subjecting titanium alloys and other metal alloys to the relatively low forming temperatures used in non-limiting

embodiments disclosed herein does not significantly affect important mechanical properties of the alloys. As suggested, particularly important mechanical properties may be those required for ballistic armor and/or other applications.

[0048] In certain non-limiting embodiments of the methods according to the present disclosure in which titanium alloys are bent or otherwise formed, as the bending or forming temperature is lowered, both the ability to form or bend to tighter radii and the reproducibility of the method decreases. For example, as the bending or forming temperature is lowered, a higher incidence of "spring back" of the bent or otherwise formed plate or other article occurs. As is known in the art, spring back occurs when, for example, after a plate is bent, the bent plate reverts to a larger bend radius than to which it was bent. Further, as the bending temperature used is lowered, the risk that micro-cracking will occur in the bend line increases. Therefore, in a non-limiting embodiment according to the present disclosure of a method for bending or other forming of titanium alloy articles, a lower limit for the bending or other forming

temperature is about 750°F (398.9°C). In another non-limiting embodiment according to the present disclosure of a method for bending or other forming of titanium alloy articles, a lower limit for the bending or other forming temperature is about 700°F (371 .1 °C). In yet another non-limiting embodiment according to the present disclosure of a method for bending or other forming of titanium alloy articles, a lower limit for the bending or other forming temperature is in a forming temperature range of about 700°F (371 .1 °C) to about 900°F (482.2°C). In general, in various non-limiting embodiments according to the present disclosure of methods for bending and other forming of metals and metal alloys, including hard-to-form metallic materials such as, but not limited to, titanium alloys, nickel-base alloys, and specialty steels {e.g., stainless steel, high-strength low- alloy steel (HSLA), armor steel alloys, and the like), a lower limit of the forming temperature range is about 0.2T _m . Also, in general, in various non-limiting

embodiments according to the present disclosure of methods for bending and other forming of metals and metal alloys, including hard-to-form metallic materials such as, but not limited to, titanium alloys, nickel-base alloys, and specialty steels (e.g., stainless steel, high-strength low-alloy steel (HSLA), armor steel alloys, and the like), a forming temperature range is about 0.2T _m to about 0.5T _m .

[0049] During development of a "warm forming" method for forming or bending hard-to-form metallic materials, the present inventors observed that an entire plate could be heated in a furnace to a bending temperature as disclosed herein and successfully bent when the plate is transferred from the furnace to a press break before the plate cools outside of the bending temperature range. However, a furnace capable of heating an entire plate must be relatively large, and heating the entire plate to a uniform temperature can take significant time, reducing yield and complicating the handling from the furnace to the forming equipment. [0050] In embodiments according to the present disclosure, localized induction heating of a lineal or other localized region of a metallic article may be accomplished relatively quickly. In certain non-limiting embodiments, inductively heating a lineal or other localized region may be accomplished in, for example, 5 to 10 seconds, no more than 1 minute, no more than 2 minutes, no more than 20 minutes, no more than 30 minutes, or no more than 60 minutes. Other induction heating times possible in certain non-limiting embodiments may be from about 3 minutes to about 20 minutes. Heating times may be extended to better ensure that "cold spots" are not present in the lineal region or other localized region that is heated. As used herein, a "cold spot" is an area within a lineal or other localized region that is cooler than the desired bending or other forming temperature and is outside of the bending or other forming temperature range. Thicker metallic plate and other thicker metallic articles may require longer heating times to reach the desired forming temperature. However, in certain non-limiting embodiments according to the present disclosure, if the one or more induction coils are properly tuned to couple with and heat the metal or metal alloy article that is to be plastically deformed, and the induction coils are positioned properly with respect to the lineal or other localized region of the plate or other article, the localized region can be heated to the desired forming temperature without cold spots in 30 seconds or less. In a non-limiting embodiment, a lineal region of a 1 inch-thick 18 inch X 120 inch titanium alloy plate can be directly inductively heated to a uniform bending temperature of about 850°F (454.4°C) within 1 0 minutes, without cold spots. [0051 ] Referring again to FIG. 1 , after inductively heating the hard-to-form metallic plate or other article, the article is transferred to a forming apparatus. In the non-limiting embodiment depicted in FIG. 2, for example, the lineal region 22 of the plate 24 is rapidly inductively heated by induction coils 26 to a bending temperature within a bending temperature range, and the plate 24 is then bent to a desired bend radius on a forming apparatus (not shown). In a non-limiting embodiment according to the present disclosure, bending or forming is accomplished on a press brake or other forming apparatus. The forming apparatus may be located close to the induction heating device to better ensure that the inductively heated lineal or other localized region of the metallic plate or other article can be bent or otherwise formed before the temperature of the localized region cools to a temperature below the forming

temperature range. [0052] While the non-limiting embodiment schematically illustrated in FIG. 2 involves bending of plate 24 after it is heated to a bending temperature, it will be recognized that other forming processes for plastically deforming the heated article are within the scope of embodiments disclosed herein. For example, such other forming processes include, but are not limited to, drawing, punching, stamping, roll forming, and like forming processes. Also, while certain embodiments discussed herein involve inductively heating a lineal or other localized region and bending the heated article, it will be understood that the present invention is not limited to such arrangements. For example, non-limiting embodiments according to the present disclosure directed to a stamping or coining process may involve directly and/or indirectly inductively heating a localized region of a metallic article that will be plastically deformed in a stamping or coining operation. Other configurations of induction heating of a localized region of a metallic article that are encompassed within the present disclosure may be specific to other forming processes, and one having ordinary skill considering the present disclosure may adapt the methods herein for such applications without undue experimentation.

[0053] Titanium alloys that may be formed using certain non-limiting

embodiments of warm forming according to the present disclosure include, but are not limited to, near-alpha titanium alloys, alpha+beta titanium alloys, and beta titanium alloys, including, for example, near-beta and metastable beta titanium alloys. In certain non limiting embodiments, titanium alloys that can be bent or otherwise formed using warm forming methods according to the present disclosure include, but are not limited to ASTM Grades 5, 6, 12, 19, 20, 21 , 23, 24, 25, 29, 32, 35, 36, and 38 titanium alloys. In certain non-limiting embodiments, a localized region of an article of Grade 38 titanium alloy (UNS R54250) is inductively heated and bent or otherwise formed according to embodiments of the warm forming methods herein. In still another non-limiting embodiment, a localized region of an article of Grade 5 titanium alloy (UNS R56400), which also is referred to as Ti-6-4 alloy and Ti-6AI-4V alloy, is inductively heated and warm bent or otherwise warm formed according to embodiments disclosed herein. In yet another non-limiting embodiment, a localized region of Grade 35 titanium alloy (UNS R56340), which nominally includes, in weight percentages based on total alloy weight, 4.5% aluminum, 2% molybdenum, 1 .6% vanadium, 0.5% iron, 0.3% silicon, and balance titanium and incidental impurities, is inductively heated and warm bent or otherwise warm formed according to embodiments disclosed herein.

[0054] According to a non-limiting aspect of the present disclosure, a warm forming method according to the disclosure includes inductively heating a lineal region or other localized region of a metallic article consisting of a high hard specialty steel to a forming temperature, and bending or otherwise forming the high hard specialty steel article by plastically deforming the lineal or other localized region. According to a non- limiting embodiment of this disclosure, a high hard specialty steel that is a high hard specialty steel armor is processed according to methods herein. According to certain non-limiting embodiments, a high hard specialty steel processed by methods herein is selected from the group consisting of a 400 BHN steel armor, a 500 BHN steel armor alloy, a 600 BHN steel armor alloy, a 700 BHN steel armor, and a high strength low alloy steel. [0055] The armor steel alloys can be generally classified or identified according to their hardness as follows: Rolled Homogeneous Armor ("RHA") alloys with hardness range of 212-388 BHN (Brinell hardness number) under MIL-A-12560H; High Hard Armor ("HHA") alloys with hardness range of 477-535 BHN under MIL-DTL-46100E; and Ultra High Hard Armor ("UHH") alloys with minimum hardness of 570 BHN under MIL-DTL-32332. According to certain non-limiting embodiments, armor steel alloys processed by methods herein include, but are not limited to RHA, HHA, and UHH alloys.

[0056] In a non-limiting embodiment, a localized region of a plate or other article of an armor steel alloy comprising one of an RHA alloy, an HHA alloy, and a UHH alloy is inductively heated and warm bent or otherwise formed according to

embodiments disclosed herein. In another non-limiting embodiment, a localized region of a plat or other article of a 500 BHN steel armor alloy is inductively heated and warm bent or otherwise formed according to embodiments disclosed herein. One non-limiting example of a 500 BHN steel armor alloy that may be processed according to the present disclosure is ATI 500-MIL® high hard specialty steel armor alloy, available from ATI Defense, Washington, PA, an Allegheny Technologies Incorporated market sector team. In still another non-limiting embodiment, a localized region of a plate or other article of a 600 BHN steel armor alloy is inductively heated and warm bent or otherwise formed according to embodiments disclosed herein. A non-limiting example of a 600 BHN steel armor alloy that may be processed according to the present disclosure is ATI 600-MIL® high hard specialty steel armor available from ATI Defense.

[0057] It is recognized that the bending or other forming of metal and metal alloy articles becomes increasingly difficult as the thickness of the articles increase. As discussed above, the present inventors surprisingly discovered that plates of hard-to form metallic materials can be inductively heated in a localized region to a relatively low forming temperature and bent or otherwise formed without resulting in formation of bending surface defects such as micro-cracking. In a non-limiting embodiment, the metal or metal alloy plate or other article processed by methods herein is at least 0.125 inch (3.175 mm) thick. In another non-limiting embodiment, the metal or metal alloy plate or other article processed using the methods herein is at least 0.1 875 inches (4.763 mm) thick. The thickness of plates or other articles capable of being bent or otherwise formed according to non-limiting embodiments disclosed herein is up to about 2 inches (5.08 cm) or, in some cases, up to about 1 inch (2.54 cm), wherein the thickness is in the region that is to be plastically deformed in the method. According to a non-limiting embodiment of a method according to the present disclosure for bending or otherwise forming titanium alloy plate, a brake press or other forming equipment having a capacity of 1 000 tons to 1500 tons (8.896 MN to 13.34 MN) is sufficient to bend a 1 .5 inch (3.81 cm) thick plate. It is believed that the thickness of plate that can be bent or otherwise formed according to embodiments of warm forming methods herein is limited only by the capacity of the brake press or other forming equipment used. It is recognized that the bending or other forming of metal and metal alloy sheet, i.e., product having a thickness less than 0.1875 inches (4.763 mm), is also within the scope of embodiments disclosed herein.

[0058] Because forming temperatures employed in the methods herein, e.g., forming temperatures in a temperature range of 0.2T _m to 0.5T _m, are relatively low, certain mechanical properties of the lineal or other localized region of the metal or metal alloy article that is inductively heated are not substantially changed after the bending or other forming step. As used herein, a mechanical property does not "substantially change" if the property does not change or changes no greater than 10%, or in some cases no greater than 5%, from the original value.

[0059] It was particularly surprising to the present inventors that hard-to-form metallic materials such as, but not limited to, titanium alloys, nickel-base alloys, and specialty steels {e.g., stainless steel, high-strength low-alloy steel (HSLA), armor steel alloys, and the like) could be locally inductively heated to relatively low temperatures and bent to tight radii according to certain non-limiting embodiments of the present disclosure. For example, according to a non-limiting embodiment herein including inductively heating a lineal region of and bending a metallic article selected from a titanium alloy plate, a nickel-base alloy plate, and a specialty steel plate, the form is bent to a bend radius of at least 6t. As used herein, a "bend radius" is the radius, measured to the inside curvature, to which a plate or other metallic article can be bent without fracturing, forming surface cracks, or significantly degrading the mechanical properties of the metallic article in the bend region. The value of the bend radius is given with respect to the thickness, "t", of the plate or other article. A plate bent to a radius of ^" I t, for example, includes a bend having a radius, measured on the inside of the bend curvature, that is equal to the thickness of the plate. In other non-limiting embodiments including inductively heating a lineal region of and bending a metallic article selected from a titanium alloy plate, a nickel-base alloy plate, and a specialty steel plate, the article is bent to a radius of at least 4t, or at least 2t. In still another non- limiting embodiment including inductively heating a lineal region of and bending a metallic article selected from a titanium alloy plate, a nickel-base alloy plate, and a specialty steel plate, the article is bent to a radius of at least 1t.

[0060] A non-limiting aspect of this disclosure employs indirect induction heating to heat a lineal or other localized region of a metallic plate or other article, and a forming step in order to warm form the metallic article. FIG. 3 is a flow diagram of a non-limiting embodiment according to the present disclosure of a method 30 for bending or otherwise forming a plate or other article of, for example, a hard-to-form metallic material such as a titanium alloy, a nickel-base alloy, or a specialty steel {e.g., stainless steel, high-strength low-alloy steel (HSLA), armor steel, and the like). FIG. 4 is a schematic depiction of an arrangement 40 of materials and equipment used in a non- limiting embodiment according to the present disclosure, wherein indirect induction heating is used to indirectly heat a lineal or other localized region of a metallic plate or other article in order to warm form the metallic article.

[0061 ] Referring to method 30 and arrangement 40 of FIGS. 3 and 4, respectively, a non-limiting embodiment of indirect induction heating for warm forming a metallic article includes placing 32 a metallic article 42 on a ferrous alloy surface 44. In a non-limiting embodiment, the metallic article 42 comprises a hard-to-form metallic material. After placing the metallic article 42 on the ferrous alloy surface 44, a localized region 46 of the ferrous alloy surface 44 that is in contact with a localized region 48 (schematically bounded by lines 48a) of the metallic article 42 is inductively heated 34 to a predetermined temperature. Inductively heating the ferrous alloy surface 44 conductively heats the localized region 48 of the metallic article 42 to a forming temperature within a forming temperature range.

[0062] In a non-limiting embodiment, the predetermined temperature to which the localized region 46 of the ferrous alloy surface 44 is heated is the forming temperature of the metallic article 42. In another non-limiting embodiment, the predetermined temperature to which the localized region 46 of the ferrous alloy surface 44 is heated is a forming temperature in a forming temperature range of the metallic article 42. In yet another non-limiting embodiment, the predetermined temperature to which the localized region 46 of the ferrous alloy surface 44 is heated is higher than the forming temperature of the metallic article 42. Preferably, however, the temperature to which the localized region 48 of the metallic article 42 is conductively heated does not exceed the upper limit of the forming temperature range of the metallic article 42.

[0063] As further illustrated in FIG. 4, in arrangement 40, inductively heating a localized region 46 of the ferrous alloy surface 44 may utilize one or more induction coils 50 positioned on an opposite side 52 of the localized region 46 of the ferrous alloy surface 44 that is to be inductively heated. While FIG. 4 depicts an arrangement in which one induction coil 50 heats the localized region 46 of the ferrous alloy surface 44, it will be understood that more than one induction coil could be utilized to heat the localized region 46 of the ferrous alloy surface 44. It also will be understood that the above discussion concerning the possible number of induction coils and their positions to heat a localized region as depicted in the non-limiting embodiment of FIG. 4, applies equally for other localized region geometries that may be used in the various types of warm forming operations within the scope of this disclosure.

[0064] In a non-limiting embodiment according to the present disclosure utilizing indirect induction heating, when the localized region 48 of the metallic article 42 is conductively heated by the localized region 46 of the ferrous alloy surface 44 to a forming temperature in a forming temperature range, the metallic article 42 is then bent or otherwise formed 14 by plastically deforming the metallic article 42 in the localized region 48 of the metallic article 42.

[0065] In a non-limiting embodiment according to the present disclosure, the indirect induction heating method disclosed herein may be used to bend and otherwise form metallic articles comprising hard-to-form metallic materials, such as, but not limited to, titanium alloys, nickel-base alloys, and specialty steels (e.g., stainless steel, high- strength low-alloy steel (HSLA), armor steels, and the like). Also, in a non-limiting embodiment according to the present disclosure, the indirect induction heating method disclosed herein heats the localized region of the metallic article to a forming

temperature in a forming temperature range of 0.2 to 0.5 of a melting temperature of the metal or metal alloy comprising the metallic article. In another non-limiting embodiment according to the present disclosure, the indirect induction heating method disclosed herein heats the localized region of the metallic article to a forming temperature in a forming temperature range of 0.24 to 0.30 of a melting temperature of the metal or metal alloy comprising the metallic article.

[0066] In certain non-limiting embodiments of the methods disclosed herein, and with particular reference to FIGS. 3 and 4, forming 36 comprises processes such as, but not limited to bending, drawing, punching, stamping, and roll forming. In another non-limiting embodiment, the metallic article 42 consists of or comprises a mill product such as, for example, an ingot, a billet, a bloom, a round bar, a square bar, an extrusion, a tube, a pipe, a slab, a sheet, and a plate. In yet another non-limiting embodiment, the metallic article 42 is a metal alloy plate, the localized region of the metal alloy plate is a lineal region, and forming 36 comprises bending the metal alloy plate in the lineal region of the metal alloy plate. [0067] Again referring to FIG. 4, in a non-limiting embodiment, the localized region 48 of the metallic article 42 includes a region of metallic material immediately adjacent to the metallic material that will be plastically deformed during the forming step 36. In non-limiting embodiments, the localized region 48 includes a region of metallic material that extends up to about 0.5 inch (1 .27 cm), up to about 1 inch (2.54 cm), up to about 2 inches (5.04 cm), up to about 3 inches (7.62 cm), up to about 4 inches (10.16 cm), or a greater distance away from the metallic material of the article 42 that will be plastically deformed during the forming step 36. It is envisioned that in order to form thicker product forms, the area of the localized region may be increased to ensure that the region of the metallic material that undergoes plastic deformation during forming is at the desired bending temperature or other forming temperature.

[0068] In a non-limiting embodiment according to the present disclosure involving indirect induction heating, a localized region 48 of the metallic article 42 is a lineal region. In certain non-limiting embodiments utilizing indirect induction heating, the lineal region is a region including and surrounding the bend line of a plate or other metallic article that is to be bent, and the lineal region may extend up to about 0.5 inch (1 .27 cm), up to about 1 inch (2.54 cm), up to about 2 inches (5.04 cm), up to about 3 inches (7.62 cm), up to about 4 inches (10.16 cm), or a greater distance on one or both sides of the bend line, along all or a portion of the bend line. It is envisioned that in order to bend thicker plate, the area of the lineal region may also be increased. [0069] In a non-limiting embodiment utilizing indirect induction heating for warm forming a metallic article 42, the metallic article 42 comprises a titanium alloy. In certain non-limiting embodiments, the titanium alloy is selected from ASTM Grades 5, 6, 12, 19, 20, 21 , 23, 24, 25, 29, 32, 35, 36, and 38 titanium alloys.

[0070] In another non-limiting embodiment utilizing indirect induction heating for warm forming a metallic article 42, the metallic article comprises a high hard specialty steel. In a non-limiting embodiment, the metallic article 42 comprises a material selected from a 400 BHN steel armor alloy, a 500 BHN steel armor alloy, a 600 BHN steel armor alloy, a 700 BHN steel armor alloy, a high strength low alloy steel, an RHA alloy, an HHA alloy, and a UHH alloy.

[0071 ] With particular reference to FIG. 4, a non-limiting aspect according to the present disclosure includes using indirect induction heating to bend a metallic article that is in the configuration of a plate 42. In a non-limiting embodiment, the localized region 48 of the plate comprises a lineal region, and forming 36 the plate comprises bending the plate in the lineal region.

[0072] In non-limiting embodiments, the metallic article 42 has a thickness of at least 0.125 inch (3.175 mm). In other non-limiting embodiments, the metallic article 42 has a thickness of at least 0.1875 inches (4.763 mm).

[0073] When the metallic material from which the plate 42 is comprised is Ti-4AI-2.5V-1 .5Fe-0.25O ₂ titanium alloy (UNS 54250), in a non-limiting embodiment the forming temperature range is 728°F to 874°F (387°C to 468°C). In another non-limiting embodiment, when the metallic material is a titanium alloy, the forming temperature range is 700°F to 900°F

[0074] In non-limiting embodiments, localized region 48 of the metallic article 42 may have a bend radius of at least 1 t after forming 36. In other non-limiting embodiments, localized region 48 of the metallic article 42 may have a bend radius of at least 6t, at least 4t, or at least 2t after forming 36.

[0075] In certain non-limiting embodiments, the metallic article is a mill product. In another non-limiting embodiment, the metallic article 42 is one of an ingot, a billet, a bloom, a round bar, a square bar, an extrusion, a tube, a pipe, a slab, a sheet, and a plate.

[0076] A non-limiting aspect of this disclosure is directed to a method for bending a metallic plate using localized indirect induction heating. Because a metallic plate is an embodiment of metallic article, reference is again made to FIGS. 3 and 4. A method 30 and arrangement 40 for bending a metallic plate 42 comprises: placing 32 a metallic plate 42 including a material selected from a metal and a metal alloy on a ferrous alloy surface 44; inductively heating 34 a lineal surface region 46 of the ferrous alloy surface 44 in contact with a lineal region 48 of the metallic plate 42 to a

predetermined temperature and thereby conductively heating the lineal region 48 of the plate 42 to a bending temperature within a bending temperature range; and bending 36 the plate 42 in the lineal region 48.

[0077] Bending is one embodiment of forming. Accordingly, it will be understood that all of the conditions described herein that are useful for localized indirect induction heating for warm forming metallic articles equally apply to non-limiting embodiments of localized indirect induction heating for warm bending metallic plates. In addition, metallic plates may include any of the metallic materials specifically disclosed herein in various non-limiting embodiments and otherwise, and the plates may be processed by the various non-limiting embodiments of localized indirect induction heating discussed herein. [0078] In a non-limiting embodiment, the metallic plate 42 has a thickness of at least 0.125 inch (3.175 mm). In another non-limiting embodiment, the metallic plate has a thickness of at least 0.1875 inches (4.763 mm).

[0079] One non-limiting aspect of this disclosure is directed to a device for indirect localized induction heating of articles comprising a metallic material selected from a metal and a metal alloy. Referring now to FIG. 5, in a non-limiting embodiment, a device 60 comprises a support 62 including a ferrous alloy surface 64, and at least one induction heating device 66. The at least one induction heating device 66 is positioned and adapted to inductively heat a localized region 67 (bounded by lines 67a) of the ferrous alloy surface. While FIG. 5 depicts one induction heating device 66 utilized to heat a localized region 67 of the ferrous alloy surface 64, it will be understood that more than one induction heating device 66 could be utilized to heat a localized region 67 of the ferrous alloy surface 64. Also, while FIG. 5 depicts a device for inductively heating a localized region 67 having a generally lineal configuration, it will be understood that the scope of this disclosure also includes varying the number, shapes, and/or positions of induction coils to inductively heat localized regions having other geometric shapes and/or orientations and which may be useful for various types of forming operations. In a non-limiting embodiment, the inductively heated localized region of the ferrous alloy surface is adapted to conductively heat a localized region of a metallic article including a material selected from a metal and a metal alloy that is positioned on the ferrous alloy surface to a predetermined temperature.

[0080] In a forming operation, such as in bending a metallic plate or other metallic article, for example, the at least one induction heating device 66 is energized to inductively heat the localized region 67 of the ferrous alloy surface 64 to a

predetermined temperature. In a non-limiting embodiment, the predetermined temperature is a bending temperature of a metal or metal alloy plate or other article that is to be bent. The metal or metal alloy article to be bent (not shown) is placed in contact with the ferrous alloy surface 64. A localized region of the metal or metal alloy plate in contact with the inductively heated localized region 67 of the ferrous alloy plate is conductively heated to the predetermined temperature, which, in a non-limiting embodiment, is the temperature at which the metal or metal alloy plate is to be when it is bent.

[0081 ] In a non-limiting embodiment, the ferrous alloy surface 64 and the support 62 comprise the same ferrous alloy. In another non-limiting embodiment, the ferrous alloy surface 64 and the support 62 are one-piece, and the ferrous alloy surface 62 is a surface of the support 62. In one non-limiting embodiment, the support 62 comprises at least one of a ferrous alloy sheet and a ferrous alloy plate. In certain non- limiting embodiments, the ferrous alloy surface comprises a material selected from carbon steel, a steel alloy, and a stainless steel. In other non-limiting embodiments, the ferrous alloy surface 64 is a surface of the support 62, and the surface 64 and support 62 are composed of at least one of a low carbon steel, a steel alloy, and a ferritic stainless steel alloy.

[0082] In a non-limiting embodiment according to the present disclosure, one or more of the induction heating devices 66 comprises one or more induction coils. In another non-limiting embodiment, the one or more induction heating devices 66 are tuned to a frequency that couples with the specific material of the ferrous alloy surface. For example, the ferrous alloy surface 64 may be composed of a steel alloy and the frequency of the alternating magnetic field of the induction coil is adjusted to optimally heat the steel alloy. The tuning of induction coils to heat specific materials is known to a person skilled in the art and need not be elaborated upon further here. In another non- limiting embodiment, the at least one induction heating device is positioned opposite the ferrous alloy surface 64 and is adapted to inductively heat a lineal region of the ferrous alloy surface 64.

[0083] In certain non-limiting embodiments, the device 60 may be in the form of an induction heating table comprising legs 68. In addition, optionally, the device may include insulation 69 in areas away from the localized region 67 to better contain the heat within the localized region 69 and to insulate the water cooled induction coils 66.

[0084] One non-limiting aspect of this disclosure is directed to a device for direct induction heating of a localized region of a metallic plate or other metallic article. Referring to FIG. 6, in a non-limiting embodiment, a device 70 comprises a support 71 including a support surface 72, and at least one induction heating device 73. The support 71 and support surface 72 are constructed from one or more materials that are not inductively heated by the at least one induction heating device 73. For example, the support 71 and support surface 72 may be constructed from one or more materials that are not electrically conductive and, therefore, cannot be heated using induction. In a non-limiting embodiment, the support 71 and the support surface 72 comprise a refractory material. As used herein, the term "refractory material" refers to non-metallic materials having chemical and physical properties that allow them to withstand high temperature such as, for example, temperatures greater than 1 ,000°F (538°C).

Refractory materials that may be used in fabricating the support 71 and support surface 72 include, but are not limited to, aluminum oxide, silicon oxide, aluminosilicates, magnesium oxide, zirconium oxide, calcium oxide, silicon carbide, fire clay, fire brick, magnesite ore, dolomite ore, chrome ore, and mixtures thereof. In a non-limiting embodiment, the support 71 and support surface 72 comprise the same refractory material. However, it will be understood that the support 71 and support surface 72 may comprise different refractory materials, or other suitable materials [0085] The at least one induction heating device 73 is positioned and adapted to inductively heat a localized region 74 (bounded by lines 74a) of a metallic article 75 that is positioned on the support surface 72 of the support 71 . It is understood that the metallic article 75 is not an element of the device 70, and is included in FIG. 6 to better illustrate the function of the device 70. While FIG. 6 depicts one induction heating device 73 to heat a localized region 74 of a metallic article 75 disposed on the support surface 72, it will be understood that more than one induction heating device 73 could be utilized to heat a localized region 74 of metallic article 75 positioned on the support surface 72. In addition, while the non-limiting embodiment of FIG. 6 depicts an induction coil 73 positioned under the support 71 , in another non-limiting embodiment at least one induction coil or other induction heating device 73 may be embedded in the support. Also, while FIG. 6 depicts a device for direct inductive heating of a localized region 74 having a generally lineal configuration, it will be understood that the scope of this disclosure also includes varying the number, shapes, and/or positions of induction coils to directly inductively heat localized regions having other geometric shapes and/or orientations and which may be useful in various types of forming operations.

[0086] In a forming operation, such as bending a metallic plate or other metallic article, for example, the at least one induction heating device 73 of device 70 is energized to directly inductively heat the localized region 74 of the metallic article 75 to a predetermined temperature. In a non-limiting embodiment wherein the metallic article 75 is a metallic plate and the forming operation is a bending operation, the

predetermined temperature is a bending temperature of the metal plate 75 within a bending temperature range.

[0087] In certain non-limiting embodiments wherein the induction heating device 73 is one or more water-cooled induction coils, the device 70 may be in the form of an induction heating table comprising legs 76. In addition, optionally, the device may include thermal insulation 77 to better contain the heat within the localized region 74 and to insulate the water cooled induction coils 73.

[0088] With regard to various non-limiting embodiments of direct and indirect localized induction heating according to the present disclosure, it will be appreciated that the positioning of induction coils with respect to the localized region to be heated affects the temperature distribution in the localized region being heated. FIGS. 7a and 7b are schematic representations of non-limiting embodiments of a support 62,71 for direct induction heating device 70 and an indirect induction heating device 60 for heating a localized region of a metallic article. The support 62,71 includes a surface 64,72 and an opposing surface 80. In non-limiting embodiments of a device 60,70, at least one induction coil 66,73 may be positioned adjacent to the opposing surface. The non-limiting embodiment of FIGS. 7a and 7b depict portions of six induction coils 66, 73, wherein the ends of each coil 66,73 are connected to the electromagnet power supply. However, the depiction of FIGS. 7a and 7b can also be interpreted to represent a non- limiting embodiment including one induction coil that is positioned adjacent to the opposing surface and has a serpentine shape, and wherein only the outermost sections of the coil 66,73 are connected to the electromagnet power supply. The bend sections of the serpentine induction coil connecting the portions of the coils that are shown in FIGS. 7a and 7b are not shown in those figures.

[0089] In FIGS. 7a and 7b, a distance of the at least one induction coil 66,73 from the opposing surface is represented by arrow A. In a non-limiting embodiment, the distance A is about 0.5 inches (1 .27 cm). The distance between the coils or section of the at least one coil 66,73 is represented by the arrows B. In a non-limiting

embodiment, the distance B is about 3 inches (7.62 cm). The thickness of a support 62,71 is represented by arrow C. In a non-limiting embodiment, the distance C is about 1 inch (2.54 cm).

[0090] In a non-limiting embodiment of a device 60,70, the frequency and power of the electromagnet power supply are selected to effectively heat the localized region 67 of the ferrous alloy surface 64 in the indirect induction heating device 60, or the localized region 74 of the specific metallic article 75 in the direct induction heating device 70. In a non-limiting embodiment of a direct induction heating device for heating of titanium and titanium alloys, an electromagnet power supply may be operated at 150 KW and 1 KHz at about 6 KA. [0091 ] Referring now to FIG. 8, another non-limiting aspect of this disclosure is directed to a system for bending or otherwise forming a metallic plate or other metallic article including a material selected from a metal and a metal alloy. In a non-limiting embodiment, the system comprises a heating device 60,70, as discussed in, for example, various non-limiting embodiments herein, and a bending apparatus 80 or other forming apparatus positioned proximate or adjacent to the heating device and adapted to bend or otherwise form the metallic article along (i.e., in) a lineal or other localized region before a temperature of the lineal or other localized region cools below a desired temperature range. In non-limiting embodiments, the heating device 60,70 heats a lineal or localized region to a bending temperature or other forming temperature in a bending temperature or other forming temperature range. In a non-limiting embodiment the bending or forming apparatus is positioned proximate to the heating device and adapted to bend or otherwise form the metallic article along (i.e., in) a lineal or other localized region before a temperature of the lineal or other localized region cools below the bending or other forming temperature range.

[0092] Referring to FIG. 9, still another aspect of the present disclosure is directed to a formed ballistic armor plate 90. In a non-limiting embodiment, a formed ballistic armor plate 90 according to this disclosure has a thickness of "t" designated by arrows 92a and 92b, and includes at least one bend region 94 having a bend radius of about 2t, as depicted by arrow 96. In non-limiting embodiments according to this disclosure, the ballistic armor plate 90 has a thickness "t" of at least 0.125 inches (3.175 mm), or at least 0.1875 inches (4.763 mm). While FIG. 9 depicts a formed ballistic armor plate 90 having two bend regions 94 with a bend radius 96 of about 2t, other non-limiting embodiments of a formed ballistic armor plate 90 according to this disclosure have at least one bend region 94 with a bend radius 96 of at least 1 t, at least 2t, at least 4t, or at least 6t. In another embodiment, the formed ballistic armor plate comprises one of a titanium alloy, a nickel-base alloy, and a specialty steel (e.g., a stainless steel, a high-strength low-alloy steel (HSLA), an armor steel, and the like). In another non-limiting embodiment according to this disclosure, the bend region 94 of a ballistic armor plate 90 is free of surface defects, linear indications, and cracks. [0093] Another aspect of this disclosure is directed to an article of manufacture that comprises an embodiment of the formed ballistic armor plate 90 of this disclosure. According to certain non-limiting embodiments, the article of manufacture consists of or comprises a formed ballistic armor plate 90 in the form of one of a monolithic hull, a V- shaped hull, a blast protective vehicle underbelly (for protection from mines and other explosive devices), and an enclosure for blast protection.

[0094] Several examples illustrating certain non-limiting embodiments according to the present disclosure follow.

EXAMPLE 1

[0095] An induction heating device was constructed in the form of an induction heating table. A photograph of the heating table is provided in FIG. 10. A steel alloy plate having a thickness of 0.5 inch (1 .27 cm) was used as the support and the ferrous alloy surface. Legs were welded to the steel plate to support the plate. A copper induction coil was positioned on the underside of the steel alloy plate and adapted to heat a lineal region of the steel alloy plate and thereby heat the ferrous alloy surface of the steel alloy plate. The induction coil was energized with an RF power transformer using a frequency suitable for heating of ferrous alloys such as the steel alloy of the steel alloy plate. The induction heating device may be used to conductively heat localized regions of metallic plates and other articles including hard-to-form metallic materials and other metallic materials. The conductively heated forms may then be bent or otherwise formed, for example, as discussed in connection with various embodiments herein.

EXAMPLE 2

[0096] A plate of ATI 425® titanium alloy (Ti-4AI-2.5V-1 .5Fe-0.25O ₂ alloy, UNS R54250) having a thickness of 1 inch (2.54 cm) was obtained from ATI Wah Chang, Albany OR, an Allegheny Technologies Incorporated company. The plate was hot rolled via conventional mill practices and was received in mill-annealed condition. The plate was sawed into 12 inch by 30 inch samples. The induction heating table described in Example 1 was configured so that a localized lineal region of the ferrous alloy surface was inductively heated to a temperature of 800°F (428°C). The titanium alloy plate samples were sequentially positioned on the induction table so that an intended bend line of each sample was positioned over the heated localized region of the induction heating table, and a localized region of each sample was thereby conductively heated. More specifically, a lineal region of each sample, including an intended bend line and an immediately adjacent region, was conductively heated to 800°F (428°C) in about 12 minutes through contact with the ferrous alloy surface.

Before any significant cooling could occur, the samples were bent along the heated bend line on a brake press located near the induction heating table. The samples were bent to increasing radii of 1 t through 6t. The bent sample are shown in the photograph of FIG. 1 1 .

[0097] The bent samples were examined to assess the condition of the bend region of each sample. No surface defects, linear indications, or cracks were observed in the bend regions. EXAMPLE 3

[0098] An ATI 425® titanium alloy plate having a thickness of 1 inch (2.54 cm), in the same mill-annealed condition as used in Example 2, was obtained from ATI Wah Chang. The length and width of the plate were 100 inches (2.54 m) by 80 inches (2.032 m). The plate was positioned on the induction heating table described in Example 1 , and a lineal region of the plate including an intended bend line and an adjacent region was conductively heated to 800°F (426°C) in about 20 minutes. The plate was transferred to a brake press before the heated lineal region of the plate experienced any significant cooling, and the plate was bent to a radius of 2t along the bend line. The plate was positioned back on the induction heating table and arranged so that a different lineal region including another intended bend line was conductively heated to 850°F (454.4°C). The plate was then transferred to a brake press and bent along the bend line to a radius of 2t before any significant cooling of the lineal region occurred. This process was repeated until the plate was bent to a 2t radius at six different locations. No surface defects or cracking were observed in the six bend regions. EXAMPLE 4

[0099] A plate is formed using the process generally described in Example 3 to include one or more bends. The plate may be comprised of, for example, Ti-4AI-2.5V- 1 .5Fe-0.25O ₂ alloy, another titanium alloy, or an armor alloy such as, for example, a 500 BHN steel armor alloy, a 600 BHN steel armor alloy, a 700 BHN steel armor alloy, a high strength low alloy steel, an RHA alloy, an HHA alloy, or a UHH alloy. The formed plate is welded to the chassis of an armored or other vehicle. The formed plate serves as a ballistic armor plate underbelly for the vehicle. The shape, orientation, and/or composition of the formed plate is adapted to dissipate blast energy generated by explosive devices detonated under the vehicle.

EXAMPLE 5

[0100] A localized region of an 85-inch(215.9 cm) long, 1 -inch (2.54 cm) thick ATI 425® titanium alloy plate was directly inductively heated using a non-limiting embodiment of a direct localized induction heating device as disclosed herein and as depicted in FIG. 6. The induction heating device included a serpentine-shaped induction coil having six sections spaced in a plane about 3 inches (7.62 cm) apart and positioned about 0.5 inches (1 .27 cm) from the refractory support, as depicted in FIG. 7. The thickness of the refractory support was about 1 inch (2.54 cm). The induction coil was energized at 150 KW, 1 KHz, and 1 A for 900 seconds. The power to the induction coil was then shut off, and the plate was allowed to air cool. The temperature of the top and bottom of the plate was measured after 900 seconds of localized induction heating and after 60 seconds of air cooling as a function of the distance from the center line of the heated zone. FIG. 12 contains a plot of the measured temperatures of the top and bottom of the plate after heating and after cooling for 60 seconds. The temperature of the top and bottom of the plate in the center region of the heated zone ranged from about 1200°F (648.9°C) to about 900°F (482°C) after 900 seconds of induction heating, and the heated zone extended about 1 1 inches (27.94 cm) on each side of the center line of the plate region that was to be bent. After cooling in ambient air for about 60 seconds, the temperature in the center region of the heated zone was in a range of about 900°F (482°C) to about 1000°F (537.8°C), which is in the temperature range at which the plate could be bent or otherwise formed.

[0101 ] It will be understood that the present description illustrates those aspects of the invention relevant to a clear understanding of the invention. Certain aspects that would be apparent to those of ordinary skill in the art and that, therefore, would not facilitate a better understanding of the invention have not been presented in order to simplify the present description. Although only a limited number of

embodiments of the present invention are necessarily described herein, one of ordinary skill in the art will, upon considering the foregoing description, recognize that many modifications and variations of the invention may be employed. All such variations and modifications of the invention are intended to be covered by the foregoing description and the following claims.