US3584487A - Precision forming of titanium alloys and the like by use of induction heating - Google Patents

Abstract

Titanium alloy blanks or the like are successively coated with a high-temperature lubricant; preheated, e.g. in a preheat oven or in the forming machine, to a forming temperature (about 1000 1775* F.); precision formed into a desired shape in a press which includes inductively heated forming tools, serving to maintain the metal at the forming temperature throughout the forming operation; and slowly cooled, e.g. first in a postheat oven down to a lower elevated temperature (e.g. about 600* F.) and then down to ambient temperature under cover of an asbestos blanket or the like. The heat-forming tools include a fixed die, a movable die and a movable clamping pad. The movable tools are mounted for precision movement by leader pins and bushings. Insulation and water jackets are interposed between the heated tools and the leader pins and bushings to prevent harmful heating of the latter. The forming tools comprise water-cooled tubular conductors embedded in insulative material which in turn is embedded in die parts of long life metals on which the forming surfaces are machined or embedded in supporting cores therefor.

Description

Arne H. Carlson 5534 South 119th, Seattle. Wash. 98178 [72] Inventor {2|} Appl.No. 791,553 [22] Filed Jan. 16, I969 [45] Patented June 15, 1971 Continuation-impart of application Ser. No. 702,700, Feb. 2, I968.

[54] PRECISION FORMING OF TITANIUM ALLOYS AND THE LIKE BY USE OF INDUCTION HEATING 26 Claims, I6 Drawing Figs.

Primary Examiner- Lowell A. Larson AuorneyGraybeal, Cole and Barnard ABSTRACT: Titanium alloy blanks or the like are successively coated with a high-temperature lubricant; preheated, e.g. in a preheat oven or in the forming machine, to a forming temperature (about 1000 l775 F.); precision formed into a desired shape in a press which includes inductively heated forming tools, serving to maintain the metal at the forming temperature throughout the forming operation; and slowly [52] US. Cl 72/38, cooled, first in a postheat oven down to a lower elevated 72/342 72/364 72/700 temperature (e.g. about 600 F.) and then down to ambient [51] Int. Cl B2111 37/16 temperature under cover of an asbestos blanket or the i [50] Field of Search 72/342, The h t f i took include a fi d die, a movable die A 56; 148/115 and a movable clamping pad. The movable tools are mounted for precision movement by leader pins and bushings. Insula- [56] References cued tion and water jackets are interposed between the heated tools UNITED STATES PATENTS and the leader pins and bushings to prevent harmful heating of 1,380,250 5/1921 Reymond 72/342 the latter. The forming tools comprise water-cooled tubular 2,247,979 7/1941 Von Tannenberg.. 219/7.5 conductors embedded in insulative material which in turn is 2,372,516 3/1945 Rechton et al 72/342 embedded in die parts oflong life metals on which the forming 2,449,365 9/1948 Bober et al. 219/75 surfaces are machined or embedded in supporting cores 2,890,324 6/1959 l-lavlik 2l9/I49 therefor.

M f" Moi mo r k /52 7 ma 41 1 S\\ VIII/VIII III "1 m, l 4 l PATENTED Jmn 5197i SHEET 3 OF 5 RL 0?, N M Wm mum m A PRECISION FORMING OF TITANIUM ALLOYS AND THE LIKE BY USE OF INDUCTION HEATING CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my copending application Ser. No. 702,700, filed Feb. 2, 1968, and also entitled Precision Forming of Titanium Alloys and the Like By Use of Induction Heating.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for hot pressure forming titanium alloy blanks and the like. It particularly relates to forming equipment comprising movable forming tools which are mounted and guided for precision movement by leader pins and bushings, and to a manner of adequately heating the blanks while in the forming equipment without injuriously heating the leader pins and bushings.

2. Description of the Prior Art Bridwell U.S. Pat. No. 3,015,292 and Haerr U.S. Pat. No. 3,025,905 both discuss the difficulties of pressure-forming titanium alloy blanks. They both explain that such blanks must be heated to a relatively high temperature before they can be formed into a desired shape, and each suggests heating the blanks by means of resistance heaters incorporated in the forming equipment.

Resistance heaters are unsatisfactory for this purpose for several reasons. They experience uneven heat distribution resulting in the occurrence of hot spots and an uneven heating of the forming surfaces, causing them to warp. This results in the production of nonuniform parts which in many instances are inferior and unusable. Furthermore, high-temperature resistance heaters customarily burn out frequently and thus require frequent replacement. Besides being expensive, this frequent replacement of the heaters amounts to a frequent alteration of the forming equipment and is a contributing factor to a shortened life of both the replacement heating elements and the forming tools. This is because the heating element channels become enlarged somewhat during each heating element replacement. As a result, an air space is created about at least a part of the new heater element. Since air is a poor conductor the new heater elements tend to become overheated in use and burn out quickly. Also, the tools are not suitably heated. Replacement of the tools is necessary to correct a reoccurrence of these happenings.

Further examples of known forming machines which utilize resistance heaters are shown by: Shoebridge et al. U.S. Pat. No. 2,956,148; Swain U.S. Pat. No. 3,051,830; Scott U.S. Pat. No. 3,065,331; and Kennedy U.S. Pat. No. 3,080,473. The machines disclosed by these patents are adapted for dimpling and other low order forming operations not involving the use, heating or precision movement of relatively large area forming tools.

Corral U.S. Pat. No. 3,060,564 and Johnson et al. U.S. Pat. No. 3,169,156 are examples of the oven and open flame types of installations for forming titanium alloys which are mentioned in the above discussed Bridwell patent.

Manson U.S. Pat. No. 1,725,465 and Von Tannenberg U.S. Pat. No. 2,247,979 disclose forming presses which utilize inductively heated dies. However, Manson is concerned with drying pulp articles, such as paper pie plates, and Von Tannenberg is concerned with forming magnesium alloy plates at temperatures ofonly about 320i10 C.

SUMMARY OF THE INVENTION Basically, this invention relates to the precision forming of parts from titanium alloy blanks or the like by use of inductively heated forming tools, at least some of which are mounted and guided for precision movement by leader pins and bushings, and to the use of some sort of heat barrier means between the heated components and the leader pins and bushings, to prevent injurious heating of the latter. Other metals to which the invention is applicable, in addition to titanium alloy metals, are Hastoloy, hard to form aluminum alloys, and stainless steel or other steel parts requiring multiple draws.

According to a method aspect of the invention the blanks are first cleaned and are then coated with a high-temperature lubricant capable of withstanding the forming temperature of the particular alloy involved (about 1000 1 755 F. for most titanium alloys, for example). Next the blanks are preheated to the forming temperature, such as in a preheat oven contain ing a noncorrosive atmosphere (e.g. argon for titanium alloys which must be heated in a nitrogen-free atmosphere to avoid surface contamination or corrosion of the metal), for example. The blanks are successively removed from the preheat oven and are then placed in the forming equipment in contact only with the heated forming tools, which are at the forming temperature. Alternatively, the blanks may be preheated in the forming equipment.

Following the forming operation the formed part is removed from the forming equipment and allowed to slowly cool down to room temperature. By way of typical and therefore nonlimitive example, the parts may be slowly cooled, first in a postheat oven down to the oven temperature which is constantly maintained at a specific level (e.g. 600 F. for some titanium alloys). Then, they are placed on an asbestos pad or the like, are covered by an asbestos blanket or the like, and are allowed to slowly cool down to room temperature. During the short period between the two ovens, and at any other time when the parts are exposed to the corrosive room atmosphere surrounding the equipment, they are adequately protected by the lubricant coating.

Preferably, the forming equipment of this invention comprises a fixed forming tool and two movable forming tools which are supported by common leader pins and their own bushings for precision movement along a path bordering the fixed forming tool. Each blank is individually placed in the equipment with a first portion thereof between the two movable tools and an adjacent second portion in position to contact the fixed forming tool. Then the two movable tools are moved relatively together to clamp and hold between them the first portion of the blank. Next, the two movable tools and the blank are moved together as an assembly relatively toward the fixed forming tool. The rate of movement is controlled so that the heated blank undergoes plastic deformation unattended by appreciable strain hardening. During this operation the lubricant coating functions as a lubricant and permits slippage of the blank laterally of the direction of press movement, within the narrow space which exists between the two movable forming tools. The blanks are permitted only this single degree of movement and are restrained against all other movement by the clamping surface of the two movable tools,

When forming a titanium part, at least, the temperature of the fixed tool (i.e. the forming punch) should be kept below (e.g. 50100 F. lower) the temperature of the two movable tools (i.e. the pressure pad and the die). This is easily accomplished by providing each tool with its own independently controlled energy source, with each control circuit including a temperature sensor adapted to measure the temperature of its tool and send a control signal to means in the energization circuit for making any adjustment which may be necessary to maintain the temperature of the associated tool at its desired temperature level. This differential heating of the tools results in the material which is held by the two movable parts being at a higher temperature, and hence more ductile, than the material which is in contact with the punch. As a result, during forming a greater amount of material flow occurs in the clamped region than in the forming region, i.e. the region in contact with the punch, and thinning of the workpiece in the forming region is thus minimized.

Preferably, each movable formimg tool is a part of an assembly which also includes a plurality of spaced-apart bushing housings containing guide bushings which surroundingly engage the leader pins, and cross frame means rigidly interconnecting said bushing housing. The leader pins are rigid members and are firmly secured to a rigid support. The bushings are precision made so they snugly engage the leader pins and are not free to wobble. The cumulative result of these features is that essentially all parts of the tool assembly always move together and each sequence of movements along the leader pins is essentially identical to each other sequence of movements. This essentially eliminates the occurrence of any nonuniformity amongst the parts as a result of changes in position and/or alignment of the forming surfaces. The bushings and the lubricants used on them cannot withstand the high-forming temperatures. Accordingly, a heat barrier in the form of a body of insulative material and/or a cooling jacket is interposed between the heated components of the tool and the bushings and leader pins. In this manner the bushings and leader pins are maintained relatively cool and are protected from the injurious or destructive effects of the high temperatures existing in the region of the forming tool.

The cross frame which rigidly interconnects the bushing housing supports or carries the forming tool and the heat barrier means. According to one form of the present invention the forming tool comprises an inductively heated core unit and a hard metal die part secured to the core unit, to be conductively heated thereby. The core unit comprises a conduc tor coil (or plural coils), disposed within or encircling a support core. Preferably, the coil(s) are encased in a cast body of insulation which is in turn at least partially encased by the core material (e.g. a ferromagnetic material). In another form of the invention the support core is eliminated, a large piece of the die material is used, and channels for receiving the conductor coils are formed in the die material.

The tubular conductor material, which may be copper tubing, is fashioned into a coil (or multiple coils) which in form closely approximates the shape of the forming surfaces. The core is also formed to closely conform to the shape of the forming surfaces.

Owing to this arrangement of the conductor and the core there is a substantially even distribution of electrical energy throughout the core unit. The conductor is not directly heated by the current it carries as is a resistance heater coil. However, due to its location it is susceptible of being conductively heated by the inductively heated core unit. For this reason the conductor is made tubular in form and a cooling fluid is flowed through it to remove the heat, and preferably it is also encased by insulation. This results in the conductor having relatively low operating temperature, and as a result a relatively long use life. Any uneven heating of the core which might occur is buffered by a dispersion of the generated heat throughout first the core unit, and then the die part to the forming surfaces. This results in a substantially uniform or even heating of the forming surfaces and contributes greatly to the obtainment ofsubstantially uniform parts.

Preferably, the heat barrier means includes a cooling jacket that is integrated into wall portions of the aforementioned cross frame. Preferably also, the entire forming equipment, including the leader pins and the fixed forming tool, is adapted to be placed between and clamped to the platens of a generally conventional forming press.

These and other inherent objects, features, advantages and characteristics of the present invention will be apparent from the following description of typical and therefore nonlimitive embodiments of the invention, as described below in conjunc tion with the accompanying illustrations.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings like element designations refer to like parts, and:

FIG. 1 is a diagrammatic view showing in sequence the four major operations which characterize the preferred method of this invention;

FIG. 2 is a front elevational view of a forming press equipped with draw forming equipment embodying features of the invention;

FIG. 3 is an enlarged scale sectional view, with some parts in side elevation, of the central portion of the forming press shown by FIG. 1, taken substantially along line 3-3 of FIG. 4;

FIG. 4 is another enlarged scale sectional view, with some parts in side elevation, of said central portion of the forming press shown by FIG. I, but taken substantially along line 44 of FIG. I;

FIG. 5 is an isometric view of a part formed by the draw forming equipment of FIGS. 24;

FIG. 6 is an isometric view ofa part formed by the forming equipment of FIGS. 7 and 8;

FIG. 7 is a view similar to FIG. 3, but of a press equipped with wipe-forming equipment;

FIG. 8 is a vertical sectional view taken substantially along line 8-8 of FIG. 7;

FIGS. 9l2 are four operational sequence views of the draw forming equipment of FIGS. 2-5, with FIG. 9 showing the movable forming tools spaced apart and a preheated blank between them in position for forming, with FIG. 10 showing the two movable tools moved together to clamp between them the peripheral portion ofthe blank, with FIG. ll showing the two movable tools and the clamped blank in the process of being moved in unison, as an assembly, toward the stationary tool or punch, and with FIG. 12 showing the movable tools apart, the upper tool raised, and the central knockout element depressed to push out the formed part; and

FIGS. I3l6 are four operational views of the forming equipment of FIGS. 7 and 3, with FIG. 13 showing the movable forming tools spaced apart and a preheated blank between them in position for forming, with FIG. 14 showing the two movable tools moved together to clamp between them a side portion of the blank, with FIG. l5 showing the two movable tools and the blank being moved towards the stationary tool or punch, and with FIG. 16 showing the two tools raised and again spaced apart and the formed part spaced outwardly to one side ofthe forming equipment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a preliminary step in the preferred process of this invention, the titanium alloy blanks 10 are deburred and polished, or are otherwise suitably cleaned. They are then sprayed or otherwise coated with a suitable high-temperature lubricant (i.e. a lubricant capable of withstanding the forming temperature), such as Everlube T-SO, a graphite base lubricant manufactured by Everlube Corporation of America having a place ofbusiness at North Hollywood, California.

Referring now to FIG. 1, following their lubrication the blanks are slowly heated, such as in a preheat oven 12, up to the forming temperature, which temperature is in the range of about lOO0l775 F. for titanium alloys. If heated to temperatures of this order in an air atmosphere (without being covered by a highly efficient coating), the titanium metal would attract nitrogen and other contaminants from the air which would chemically combine with the metal and contaminate or corrode its outer surfaces. Therefore, a noncorro sive or nitrogen free atmosphere is provided and maintained in the oven during the heating. Argon is an example ofa suitable gas for use in the oven 12 to provide such an atmosphere.

The preheated blanks 10 are successively removed from the preheat oven 12 and set into the forming equipment, such as by a workman using tongs and asbestos gloves, and are then pressure formed, in a manner to be hereinafter described in more detail. The blanks 10 are then slowly cooled to prevent severe (i.e. untolerable surface checking or cracking.

At least with relatively thick parts, the cooling is preferably conducted in two stages. Firstly, the formed parts 10' are placed into a postheat oven 16 which is maintained at a specific elevated temperature between ambient temperature and the forming temperature (e.g. about 600700 F. for

titanium alloys) and also contains a noncorrosive atmosphere, such as argon, and are allowed to slowly and naturally cool in such oven 16 down to the oven temperature. The formed parts are then removed from the postheat oven 16, are placed on an asbestos board or pad 18, and then are quickly covered by an asbestos blanket 20. So covered, they are allowed to slowly and naturally cool down to ambient temperature. This two stage cooling amounts to a simplified manner of slowing down the cooling process of the parts from the high-forming temperature toambient temperature. to avoid the aforementioned surface cracking which would result if rapid cooling were permitted. With thinner parts the cooling can be done under the asbestos blanket alone.

During the intervals that the heated blanks 10 are between the preheat and postheat ovens l2, l6 and the heated parts 10' are between the postheat oven 16 and the asbestos board 18, (or in the situation where such ovens are not used) and such blanks 10 or parts 10' are exposed to air, the lubricant serves as a protective coating and protects the metal against contamination.

After cooling, the parts are cleaned and trimmed and are otherwise machined to desired final form.

Referring now to FIG. 2, the forming press 14 is shown to comprise a rigid-main frame 22 including a set of corner columns 24 rigidly interconnected at the top by upper crossmembers 26 and at the bottom by lower crossmembers 28. Husky intermediate crossmembers 30 are interconnected between intermediate portions of the columns 24 and function as a support table or platform for the fixed platen 32 of the press 14. A second set of intermediate crossmembers 34 are located above the movable platen 36 and serve to lend rigidity to the main frame 22 at such location.

The lower end portions of a plurality of parallel, husky guide pins 38 are firmly anchored in outer portions of the fixed platen 32. The movable platen 36 carries a set of guide bushings 40 which surroundingly engage the guide pins 38.

A primary hydraulic ram 40 is suspended from a central location on the upper end portion of the frame 22 with the piston rod 42 thereof directed downwardly. The lower end of the piston rod 42 is secured to the movable platen36. The primary ram 40 is employed to raise and lower the movable platen 36, with the guide pins 38 and the bushings 40 serving to maintain proper alignment of the movable platen 36 during its movement.

A secondary hydraulic ram 44 is supported below the intermediate support table 30 substantially in line with the upper ram 40. lts piston rod 46 is directed upwardly and carries at its upper end a support pad 48 of substantial area. The secondary ram 44 serves to apply a controlled biasing force on a floating portion of the forming equipment, hereinafter to be described. A support shelf 50 is bracketed out from the main frame 22 on each of its two sides and at its rear, to each support one of three transformers 52 powered by generator-driven induction heat stations, which are conventional per se and not shown. In FIG. 2, which is a view looking toward the front of the machine, only the two side transformers 52 are shown. The third transformer 52 and its support shelf 50 are located to the rear of the press 14 and are thus hidden from view. The lower support table which carries the lowermounting 54 for the secondary ram 44 may also serve to mount components of the hydraulic system, such as the hydraulic pump 56 and an'electric motor 58 for driving the pump 56. Alternatively, these accessories and others may be located in a console or the like which is apart from the press 14.

The precision forming equipment of the present invention will now be described. The particular forming equipment shown by FIGS. 3 and 4 is of the draw-forming type while the forming equipment shown by FlGS. 7 and 8 is of the wipe"- forming type. However, as will be evident as the description of these two types of equipment progress, both tubes are basically similar.

Referring now to FIGS. 3 and 4, the forming equipment is shown to comprise a die set composed of a lower or fixed bolster plate 60, an upper or movable bolster plate 62, and a pair of leader pins 64. The two bolster plates 60, 62 may be fabricated from aluminum alloy and the leader pin 64 may be fabricated from stainless steel. A pair of sockets are formed in outer edge portions of the lower bolster plate 60 to receive the lower end portions of the leader pins 64. The lower end portions of the leader pins 64 are tightly received in such sockets so that the leader pins 64 are firmly held in parallelism. Bearing, sleeves or housings 66, carried by the movable bolster plate 62, house bronze bushings 68 or the like, which snugly surroundingly engage the leader pins 64.

The upper bolster plate 62 is in some manner removably secured to the movable platen 36 and the lower bolster plate 60 is in a like manner secured to the fixed platen 32. By way of typical and therefore nonlimitive example, the bolster plates may be secured to the platens by clamp assemblies C which are carried by the latter and include clamping plates 70 shown in FIGS. 24 to overlap border portions of the bolster plates 60, 62. The die set, i.e. the two bolster plates 60, 62 and the leader pins 64, constitute the support portion of the forming equipment, making such equipment structurally self-contained. This feature, plus the use of the clamps for removably securing the bolster plates tothe platens of the press, makes it easy to selectively use a number of different forming equipment assemblies, each possessing similar bolster plates, within a single press.

The draw-forming equipment of FIGS. 3 and 4 comprises two movable tools and one fixed tool, each of which is inductively heated as will hereinafter be explained in detail, and may include a knockout punch 72. One of the movable forming tools is a cavity die and is mounted on or supported by the upper bolster plate 62. The second movable forming tool is a part of a floating" assembly mounted between the two bolster plates 60, 62 for precision movement along the leader pins 64. The fixed forming member is in the nature of a forming punch and is mounted on a central portion of the lower bolster plate 60.

For the purpose of better describing the forming equipment in a manner showing the similarities which exist between the various components, the equipment will be described as being made up of three major components consisting of two movable tool assemblies and a fixed tool assembly. The bushing housings 66, the bushings 68 therein, the structural portions of the bolster plate 62 which rigidly interconnect the bushing housings 66, and the various components of the cavity die tool, including some yet to be described heating and heat barrier means associated'therewith, together constitute the first movable tool assembly. The second movable tool assembly is the floating" assembly. It comprises a pair of bushing sleeves 74 containing bronze bushings 76 which snugly surroundingly engage the leader pins 64, a rigid structural portion or cross frame which spans between the leader pins 64 and rigidly interconnects the bushing housings 74, the forming tool tself, and the heat barrier means associated therewith. The three forming tools will now be specifically described in detail.

Each illustrated forming tool comprises an inductively heated core unit. The core units of the two movable tools are basically alike and will be described together. Each comprises a ferromagnetic core 82 of annular channel form, and an electrical conductor coil embedded in a body 78 of cast insulation which fills the channel. An annular plate 84 spans across and covers the open side of the channel 82.

The core unit of the fixed forming tool comprises a block or body 86 which includes a girth channel for receiving a conductor coil 88 and a body 90 of cast insulative material in which such coil 88 is embedded. Hard metal die parts 92, 94, 96 are secured to the ferromagnetic cores to be at least primarily conductively heated thereby. It is necessary that these parts be made of a metal capable of maintaining a hard wear surface at elevated temperatures. Examples of such metals are Hastoloy X, Inconel 750, lnconel 820, and Esco 58, each of which is a nonmagnetic metal.

The lower surface of die part 92 and the upper surface of die part 94 are parallel and function as clamping or gripping surfaces. The surfaces of the die part 92 which immediately border and define the central opening in such part, and the upper and side surfaces of the die part 96 are of complementary design and function to form or give shape to the blanks 10.

Each one of the transformers 52 is associated with, and its output is connected to, a particular one of the three conductor coils 80,80,138. The coils 80, 80, 88 and the associated magnetic cores 82, 82, 86 are fashioned to closely approximate in form the shape of the finished part. The electrical energy conducted to the conductor coils 80, 80, 88 by the transformers does not directly heat such coils, as in the case of resistance heater elements, but rather inductively heats the magnetic cores 82, 82, 86. Since the conductors 110, 80, 88 are closely adjacent the conductively heated cores 82, 82, 86, they are susceptible to being heated by the conduction of heat back from such cores. The conductors 80, 80, 88 are protected from such heating to some extent by the insulative material in which they are embedded. However, the conductors 110, 80, 88 are also made of tubular form and a cooling liquid, c.g. water, courses through them for removing the heat which does reach the conductors 80, 80, 88.

As will be evident, the generated heat will be dispersed by conduction throughout the four cores 82, 82, 86 before being transferred by conduction or otherwise to the die parts 92, 94, 96, contributing to an even or uniform heating of such parts and the forming surfaces they carry.

As earlier explained, the bushings 68, 76 which are key elements to the obtainment of a large number of uniform parts throughout a long operational life of the forming equipment must be operated at relatively low temperatures. Otherwise the lubricant they employ, and the bushing material itself, will suffer injurious or destructive effects. According to the present invention, a heat barrier is provided to substantially surround the heated zone, so as to isolate such zone and localize the heat only where it is desired, while protecting the surrounding parts of the forming equipment, especially in the re gion ofthe bushings, from being excessively heated.

in the preferred embodiment the heat barrier means for each tool assembly comprises both a thickness of insulative material and a coolant jacket containing passageways through which a cooling fluid is flowed. As best shown by FIG. 3, each movable tool assembly may comprise a boxlike structure formed by four sidewalls and a top and bottom wall, each drilled to include a plurality of passageways for receiving the flowing cooling fluid. The boxlike water jacket of the floating tool assembly is the rigid cross frame which rigidly interconnects or integrates the two bushing housings 74. lt comprises a bottom plate or wall 98 and four sideplates or walls, two of which are shown and are designated 100, 102, respectively. By way ofexample, plurality of parallel, vertical passageways 104 are drilled in sideplate 100. Short grooves 106 are formed in the upper surface of the bottom plate 98 in position to interconnect the lower ends of the first and second passageways 100, the third and fourth passageways, and so on. A barshaped cap member 108 is secured to the upper edge of plate 100. It is formed to include short grooves 110 in its lower surface which interconnect the upper ends of the second and third passageways 100, the fourth and fifth passageways. and so on. This basic construction, including the use of cap members where needed, is found throughout the cooling jackets of both movable tool assemblies. Copper or rubber tubing conduits 112, or the like, may be connected to corner portions of the cross plates, or to corner portions of the cap members, as shown by HO. 4, to serve as supply and discharge conduits for the cooling fluid.

A wall or plank ofinsulation 114 is situated immediately inwardly of each sidewall ofthe boxlike cross frame, and a centrally apertured wall 116 is interposed between the plate 84 and the bottom wall 98. These walls 114, 116 may be fashioned from a board-type insulation, such as the ceramic fiber of alumina and silica board made by the Carborundum Company and sold under the name Fiberfrax, for example.

The water jacket of the upper movable forming tool is also shown to be of boxlike form and to include four side walls, two of which are designated 118, 120, in FIG. 3, and a top wall 122. A wall or plank ofinsulation 124 is provided immediately inwardly of each sidewall, and a centrally apertured plank 126 is provided immediately inwardly ofthe top plate 122.

The upper bolster plate 62 is shown to include a downwardly opening central recess in which the water jacket plate 122 and an upper portion of the sideplates of the water jacket are snugly received. Preferably, as in the ease of the floating tool assembly, the sidewalls and the top wall forming the waterjacket are rigidly secured together to form a boxlike cross frame which rigidly interconnects the bearing housings 66. The bearing housings 66 may include side mounting portions 128, 130 which are apertured to receive bolts 132, 134 used for securing the housing or sleeve 66 to the sidewalls (cg. wall 118 in FlG. 4).

Referring again to FIG. 3, the lower bolster plate 60 may also include a central recess 136 shaped to snugly receive the lower portion of the floating tool assembly when it is in its lowermost position. A metallic baseplate 138 is shown secured to the central portion of the bolster plate 60, and a grooved plate 140 is shown positioned on the plate 138. The plates 138, 140 together form a cooling jacket for the fixed forming tool assembly. lnlet and outlet means (not shown) are provided for delivering a cooling fluid (e.g. water) through the passageways 142. A plank 146 of an insulative material is interposed between the plate 140 and the core 86, Anchor bolts 144 are provided for securing together the coolant jacket plates 138, 140, the insulation 146 and the core 86. Enlarged wells are formed in the plates 138, 140 around the headed portions of the bolts 144, and a castable insulation, such as a castable form of the aforementioned Fiberfrax, for example, is introduced in such recesses to surround the headed portions ofthe bolts to form insulation plugs 148. Washers may be provided immediately inwardly of the bolt heads to better anchor the bolts in the plugs 148. The insulation plugs 148 prevent, or at least minimize, heat conduction from the core 86 into the bolster plate 60.

The knockout punch or tool 72 is shown to comprise a head 150 and a shank 152. Openings for the shank are provided through the waterjacket plate 122 and the upper bolster plate 62. A cross pin 154, or the like, may be provided for limiting the extend of downward movement of the shank 152, and hence the knockout tool '72 itself. The upper platen 36 of the press 14 is shown to be composed of a top plate 156 spaced above a lower plate 158 by spacer blocks or plates 160 arranged to provide a central recess 162 in the upper platen 136 about the upper end of the shank 152. A side tunnel is pro vided so that a hand tool may be inserted into the recess 162 and used to depress and operate the knockout tool.

Two or more sets of bores are provided through the lower bolster plate 60 and the lower platen 32, in parallelism with the guide or leader pins 64, to each receive a support pin 164 which rests at its upper end against the lower surface of the floating tool assembly and at its lower end against the upper surface of the support pad 48. It is through the intermediacies of the support pins 164 that the secondary ram 44 exerts a biasing force on the floating tool assembly. A wear plate 166 of stainless steel or some other hard and durable metal may be provided on the underside of the floating tool assembly to be the part thereofthat is immediately contacted by the pins 164.

As should be apparent by now, the isolation of the generated heat by the insulation 114, 116, 124, 126, 146 into the central region of the forming equipment, and the removal ofsuch heat from such central region by means of the coolant jackets 93,100,102,118, 122, 124, 140, is what makes possible the use of the leader pins 64 and the bushings 68, 76 for accurately guiding the two movable forming tools. A further advantageous result ofthe use and particular placement of the insulation is that it reduces the amount of exposed surface on each of the cores. and thus reduces the amount of oxidation that takes place on the cores during heating.

In operation, the lubricated and possibly preheated blank 10 is placed in the forming equipment between the two movable forming tools (FIG. 9), and if not already preheated is preheated in the forming equipment. Hydraulic fluid is then 99 to the secondary ram 44 to cause it, through the intermediacy of the support pins 164, to raise the floating tool assembly. Fluid is also delivered into the main ram 40 to cause a lowering of the upper platen 36, and the upper forming tool carried thereby. A larger force is intentionally developed by the main ram 40 so that it will override the secondary ram 44, causing the two movable forming tools and the blank 10 clamped between them to be moved downwardly the the punch. The force differential is regulated so that a sufficient holding pressure is maintained between the holding surfaces of the plates 92, 94 and the portion of the blank 10 sandwiched between them. Preferably, the two rams 40, 44 are conjunctively operated by maintaining a constant fluid pressure in the cylinder of the upper ram 40 above the piston therein, while slowly bleeding fluid from below such piston. At the same time, a constant pressure is maintained in the cylinder of the lower ram 44, below the piston therein, while the space above such piston is vented. The force differential which causes downward movement of the movable tools and the blank is regulated by such bleeding of fluid from below the upper piston. This arrangement results in a substantially jerk-free downward movement of the blank 10. The pressure developed between the holding surfaces of the plates 92, 94 is sufficient to prevent wrinkling, but insufficient to prevent the blank aided by the lubricant coating from sliding sideways of the press as the part is being formed. Downward movement of the blank (i.e. the bleeding rate) is carefully controlled so that plastic deformation of the blank 10 occurs unattended by any appreciable strain hardening thereof.

If for any reason it becomes necessary to look at the part being formed prior to completion thereof, bleeding of fluid from the upper cylinder is ceased and the upper ram 40 is reversed to lift the upper platen 36 and the die assembly carried thereby. Then, when it is desired to resume the forming process, fluid flow to the upper ram 40 is again reversed to cause a lowering of the platen 36 and the die assembly. Once the die assembly is back in mating engagement with the partially formed part, bleeding of fluid from below the upper piston is once again started and continued until the part is fully formed (FIG. 11).

Following forming of the part 10 the two movable tools are raised until the support pad is in the position shown by FIG. 12, and the upper platen and the die assembly carried thereby are by themselves raised an additional amount. Next, the knockout tool 72 is depressed, such as by means ofa hand tool introduced through the side tunnel into the recess 162, as earlier explained. The part is then ready to be grasped by means of a pair of tongs or the like and moved to a cooling station, e.g. the postheat oven 16, as earlier explained.

In FIGS. 9-12 the insulation blankets have been omitted and the coolant jackets have not been detailed, for simplicity of illustration.

FIGS. 7 and 8 relate to a modified form of forming equipment which is adapted for forming a part 10 of the type shown by FIG. 6. Such equipment includes a lower fixed bolster plate 166, a pair ofleader pins 168 extending upwardly therefrom, and an upper movable bolster plate 170. The upper bolster plate 170 carries a movable forming tool or die 172, shown to comprise a metallic cross frame which also serves as a coolant jacket. Such cross frame is shown to include a rear wall 174, a top wall 176, and end walls 178, 180. The walls 172, 178, 180 are formed to include a plurality or relatively closely spaced vertical passageways 188, and the top panel 176 is formed to include a plurality of closely spaced horizontal passageways 190. As in the earlier embodiment, cap member 182, 184, 186 are provided to border the longitudinal edges of the plates 174, 176. The corner cap member 182 may be provided with intersecting bores 192, 194 which together form a right-angled passageway for interconnecting the upper ends of passageways 188 with the adjacent ends of passageways 190. Cap member 184 includes a plurality of short grooves 196 which serve to interconnect the opposite ends of the passageways 190 in a pattern of pairs. Similarly, cap member 186 includes a plurality of short grooves 198 which serve to interconnect the lower ends of the passageways 188 in groups of pairs. An inlet 200 may be provided in end wall 178 and an outlet 202 in end wall 180, to complete with the various passageways and grooves a continuous flow path for the coolant (e.g. water) through the coolant jacket.

In this embodiment the bolster plate is shown to include integrally formed bushing housings 204, 206 which include bushings 208, 210 serving to mount the bolster plate 170 and the forming tool carried thereby for precision movement up and down along the leader pins 168. Thus, in this embodiment it is the bolster plate 170 itself which constitutes the cross frame means which rigidly interconnects the bushing housings 204,206.

A plank of board insulation 212 is situated immediately below the top plate 176, and a smaller board of insulation 214 is positioned immediately inwardly of the portion of plate 176 which extends below the lower surface of plank 212. Similarly, planks 216, 218 of insulation are provided at the two ends of the assembly immediately inwardly of the end walls 178, 180.

The forming tool 220 itself is located within a generally square cornered nook bounded on top by the insulation plank 212, at the rear by insulation plank 214 and at the ends by insulation planks 216, 218. Such tool is shown to comprise a core assembly composed of main body 222 about which has been formed a girth channel, and a rear plate 224 positioned between the body 222 and the insulation 214. The girth channel is filled with insulative material, which is preferably cast in place. A coil 228 of copper tubing or some other suitable tubular conductor material is embedded within the insulation 226. A hard metal die part 230 is secured to the body 222 and the plate 224.

The second or floating movable tool assembly is basically similar to the just-described tool assembly. Hence, it will not be described in as great detail. It comprises a coolant jacket composed of a rear wall 232, a lower wall 234, end walls 236, 238, and edge caps 240, 242, 244. In such assembly, the bearing housings or sleeves 246, 248 (FIG. 7) are secured to the end walls 236, 238, and the coolant jacket serves as a crossframe which structurally interconnects the two housings 246, 248. In FIG. 7, the bushing 250 in housing 246 is shown in section, whereas the bushing 252 in the opposite housing 248 merely has its position indicated by broken or hidden lines.

The insulation jacket of the floating tool assembly comprises a rear plank 254, a lower plank 256, and end planks 258, 260. The tool itself includes a body 262 formed to include a girth channel, a member 264 interposed between plank 254 and body 262, and a die part 266. The girth channel is filled with insulation 268 in which is embedded a conductor coil 270.

A hard metal wear plate 272 may be provided below coolant jacket member 234 to serve as a contact plate for the support pins 164.

In FIG. 8 a guide bracket 274 is shown positioned to the rear of the path of movement of the two movable tool assemblies. It is shown to include a wear plate 276 of a hard metal which in use is contacted by a similar plate 278 provided to the rear of coolant jacket member 174 of the upper movable tool assembly.

The equipment also comprises a fixed forming tool or die 280 which is similar in basic construction to the two movable tools. It includes a coolant jacket formed by a bottom plate 282, a front plate 284, end plates 286, 288, and cap members 290, 292, 294. Passageways are provided in the parts 282, 284,286, 288 and grooves in the parts 290, 292 to all together form a continuous passageway for a flowing coolant. Such assembly also includes an insulation jacket composed of a front plank 296, a lower plank 298, and two end planks 300, 302. The tool itself comprises a body 304 which like the bodies llll 222, 262 includes a girth channel for receiving insulative material 306 in which is embedded a coil 308 ofcopper tubing or some other suitable tubular conductor. A plate 310 is interposed between the body 304 and the insulation plank 296, and a hard metal die part 312 is secured to the top of body 304.

Die parts 230, 312 carry complementary forming surfaces. Locator pins 314 are carried by die part 312. Die part 266 serves primarily as a holding member.

In operation of the forming equipment shown by FIGS. 7 and 8, the blanks 10 are successively placed on the upper surface of die part 266 and in contact with the locating pins 314 (see FlG. 13). The two rams 40, 44 of the press 14 are operated as in the operation of the first embodiment to first cause a clamping of the blank 10 between the clamping surfaces of the die parts 230, 266, and then a downward movement of the two movable tool assemblies relative to the fixed tool assembly. As before, care is taken to see that the heated blank (cg. to temperature of l,OO0l.775 F.) is slowly moved relative to the fixed forming tool. The action desired is a wiping" action in which the metal is slowly moved and reformed to cause a plastic deformation unattended by any appreciable strain hardening.

A heel block 316 is positioned forwardly ofthe fixed tool assembly and serves to support and prevent a forward movement of the fixed tool assembly during the forming operation. At the rear of the equipment, the tight engagement made between the wear plates 276,278 braces the two movable tool assemblies against an unwanted turning movement as a result of the forces imposed on them during the forming operation.

In either type of forming apparatus each forming tool is independently heated by one ofthe transformers 52 and is independently controlled as to temperature The control circuitry (not shown) for each conductor coil includes a temperature sensor or measuring device (e.g. a thermocouple) which measures the temperature of the die part with which such coil is associated. When forming titanium, at least, the fixed tool is operated at a lower temperature (e.g. about 50l00 F. lower) than the temperature of the two movable tools which are maintained together at about the same temperature. This differential heating results in the portion of the titanium (or other metal) blank which is held or clamped between the two higher temperature movable parts being heated a greater amount so as to be more ductile than the portion ofsuch blank which is in contact with the punch or fixed tool. As a con sequence, during forming there is a greater tendency for metal flow to occur in the clamped region than in the region contoured by the punch, resulting in a minimization of thinning in the region of the finished part which is contacted by the punch. For most titanium alloy forming the punch may be heated to a temperature within the range of l300- l400 F. and the two movable tools heated to a temperature within the range of 14001500 Alpha-Beta titanium can be hardened by first forming the part at a higher temperature followed by water or like quenching. To effect such heating the punch may be heated to a temperature within the range of l725 1 750 F., and the two movable tools to a temperature within the range of l750l775 F. A coated part is first drawn and then held in the press for about 15-2O seconds to assure even heating at this level. Next, the press is opened and the part is removed and quickly quenched, as in water at room temperature. The part is then aged in a furnace at about 1000 F., containing an inert, e.g. argon, atmosphere for about 4 hours. lNstead of forming at the 1700 F. level the forming may be done at a lower temperature and then be followed by a heating of the formed part in the press or in an oven up to a temperature above the temperature required for hardening.

While various forms of forming equipment embodying principles of the invention and a preferred method have been described, it is to be understood that changes in construction and technique may be made without departing from the principles of the invention. Accordingly. the scope of the invention is to be determined solely by the scope and proper interpretation ofthe following claims.

What 1 claim is:

1. A method of forming a part from a sheet metal blank in a forming press which includes a fixed forming tool and two movable forming tools, supported by leader pins and bushings for precision movement along a path bordering the fixed forming tool, in which each said tool includes a mass which is capable of being heated by induction, comprising:

placing a first portion ofthe blank between the two movable forming tools and an adjacent second portion ofthe blank in position to contact the fixed forming tool; moving the two movable forming tools relatively together to firmly clamp the first portion of said blank between them;

using induction heating coils which surround portions of said tool masses to inductively heat each of said forming tools to a temperature sufficient to cause them to in turn conductively heat the blank and maintain it at forming temperature, while maintaining said leader pins and bushings relatively cool, so that they can function properly throughout a long life ofrepetitious use; and

moving the two movable forming tools and the blank clamped between them, as an assembly, relatively towards the fixed forming tool, and the blank against such tool, at a rate causing plastic deformation of the blank attended by no appreciable strain hardening.

2. The method of claim 1, including circulating a cooling fluid through at least a portion of the region containing the inductively heated forming tools and the guide pins and bushings, to remove heat from such region which, if not removed, would tend to harmfully heat such guide pins and bushings.

3. The method of claim 1, further comprising preheating the blank to about its forming temperature before placing it in the forming press.

4. The method of claim 1, further comprising preheating the blank to about its forming temperature in a substantially airfree atmosphere before placing it in the forming press.

5. The method of claim 1, further comprising coating the blank with a high temperature lubricant before placing it in the forming press, said lubricant serving to facilitate some slippage ofthc clamped portion of the blank during its forming.

6. The method of claim 5, further comprising preheating the coated blank in a substantially nitrogen-free atmosphere.

7. The method of claim 1, comprising slowing cooling the formed part to prevent severe surface cracking.

The method of claim 7 comprising slowly cooling the formed part in a substantially air-free atmosphere.

9. The method of claim 7 comprising cooling the formed part by first placing it in a heated confined zone the temperature ofwhich is below the forming temperature but above ambient temperature, allowing it to slowly and naturally cool in said zone down to the temperature of the zone, and then placing such part in a nonheated zone and allowing it to slowly and naturally cool in said zone down to ambient temperature.

10. The method of claim 1, applied to a titanium metal containing blank and wherein the forming tools are inductively heated to a temperature enabling them to conductively heat the blank to about l00O- 1 775 F.

11. A method of forming a part from a sheet metal blank in a forming press which includes a fixed forming tool and two movable forming tools supported for movement along a path bordering the fixed forming tool, comprising:

placing a first portion ofthe blank between the two movable forming tools and an adjacent second portion ofthe blank in position to contact the fixed forming tool; moving the two movable forming tools relatively together to firmly hold the first portion of said blank between them;

inductively heating each of said forming tools to a temperature sufficient to cause them to in turn conductively heat the blank and maintain it at forming temperature, including heating the two movable tools, and hence the held portion of the blank, to a higher temperature than the fixed forming tool and the unheld portion of the blank which is heated thereby; and

moving the two movable forming tools and the blank held between them, as an assembly, relatively towards the fixed forming tool, and the blank against such tool, at a rate causing plastic deformation of the blank attended by no appreciable strain hardening, with the greater heating of the held portion causing more material flow to occur in such portion than in the lower temperature unheld portion of the blank, resulting in a minimization of thinning in the contoured region ofthe finished part.

12. The method of claim 11, wherein a titanium alloy blank is used and the forming tools are inductively heated to a temperature enabling them to conductively heat the blank to about l000l775 F., and a -200 F. temperature differential is maintained between the portions of the blank heated by the movable and fixed tools.

13. The method of claim 12, wherein the titanium alloy is temperable and said method includes heating the formed part to a suitable temperature for hardening and then while still hot quenching it in water of the like.

14. The method of claim 11, further comprising coating the blank with a high-temperature lubricant and preheating it to about its forming temperature, said lubricant serving both as a protective coating, to protect the metal against corrosion, and as a lubricant to facilitate some slippage of the held portion of the blank during forming.

15. Sheet metal forming equipment comprising:

a first bolster plate;

a plurality of spaced-apart leader pins, each of which is firmly secured at one of its ends to said first bolster plate and extends away from said plate, in parallelism with each other leader pin;

a first forming tool assembly secured to said bolster plate on the same side thereofas said leader pins, said assembly including an inductively heatable mass, an induction heating coil surrounding a portion of said mass, a die part on said mass, and heat barrier means interconnected between said mass and said bolster plate, and

a second bolster plate including bushing means mounting it for precision movement along said leader pins;

a second-forming tool assembly secured to said second bolster plate, on the side thereof facing the first forming tool assembly, and comprising an inductively heatable mass, and induction heating coil surrounding a portion of said mass, a die part on said mass, and heat barrier means interconnected between said heated mass and said bolster plate, said heat barrier means extending between said mass and said bushing means for protecting the bushing means against overheating, with the die part of the second forming tool assembly cooperating with the die part of the first forming tool assembly when the bolster plates are moved relatively together to impress a shape into a sheet metal blank inserted between them.

16. The sheet metal forming equipment of claim 15, wherein each said induction heating coil comprises electrical conductors of tubular form, so that a cooling fluid can be circulated through them.

17. The sheet metal forming equipment of claim 15, wherein said equipment further comprises a third forming tool assembly interposed between said first and second bolster plates and including:

a bushing housing for each leader pin, said housings containing guide bushings which surroundingly engage said leader pins;

support means rigidly interconnecting said bushing housings; and

a third forming tool assembly secured to said support means, on the side thereof forming the second forming tool assembly, and comprising an inductively heatable mass, a die part on said mass, and an induction heating coil surrounding a portion of said mass, with said leader pins, guide bushings, the second bolster plate and said support means serving to mount the second and third forming tool assemblies for precision movement along a 8path bordering the first forming assembly. 1 The sheet metal formmg equipment of claim 17, further comprising first, second and third independently controllable means for supplying electrical energy to the induction heating coils of said first, second and third forming tool assemblies, enabling the second and third assemblies to be control heated at a higher temperature than the first assembly.

19. The sheet metal forming equipment of claim 15, wherein each said heat barrier means includes a coolantjacket containing passageways through which a cooling fluid may be flowed.

20. The sheet metal equipment of claim 15, wherein each said forming tool assembly comprises sidewall means, and said heat barrier means comprises insulative material interposed between said sidewall means and the forming tool.

21. The sheet metal equipment of claim 20, wherein said bushing means comprise sleeve members situated outwardly of, and rigidly secured to, the sidewall means of said second forming tool assembly.

22. The sheet metal forming equipment ofclaim 15, in combination with a forming press including a fixed platen, a movable platen, and means for removably securing one of said bolster plates to one of said platens and the other bolster plate to the other platen.

23. The sheet metal forming equipment of claim 17, wherein said first bolster plate includes at least one support pin opening extending through it in parallelism with said leader pins, and said equipment further includes:

a support pin extending through said opening, and at one end containing the support means of said third forming tool assembly;

a first piston-cylinder motor connected to said second bolster plate, for moving it towards and away from said first bolster member; and

a second piston-cylinder motor for moving said third forming tool assembly through the intermediary of said support pin.

24. Sheet metal forming equipment comprising:

a fixed forming tool and two movable forming tools supported for movement with a clamped portion of a sheet metal blank between them along a path bordering the fixed forming tool, with each said forming tool comprising a die member and an induction heating coil associated with said member; and

first, second and third independently controllable means for supplying electrical energy to the induction heating coils of said fixed and said two movable forming tools, enabling the two movable die members to be control heated at a higher temperature than the fixed die member.

25. Sheet metal forming equipment according to claim 24, wherein each die member comprises an inductively heatable mass, and wherein each induction heating coil surrounds a portion of said mass, with said induction heating coils in use inductively heating said masses, and with said die members conductively heating material to be formed which is in contact with said members.

26. Sheet metal forming equipment according to claim 24, wherein each induction heating coil comprises electrical conductors of tubular form, so that a cooling fluid can be flowed through them, and wherein said equipment further comprises means for delivering a cooling fluid into said conductors.

Claims (25)

1. 2. The method of claim 1, including circulating a cooling fluid through at least a portion of the region containing the inductively heated forming tools and the guide pins and bushings, to remove heat from such region which, if not removed, would tend to harmfully heat such guide pins and bushings.
2. 3. The method of claim 1, further comprising preheating the blank to about its forming temperature before placing it in the forming press.
3. 4. The method of claim 1, further comprising preheating the blank to about its forming temperature in a substantially air-free atmosphere before placing it in the forming press.
4. 5. The method of claim 1, further comprising coating the blank with a high temperature lubricant before placing it in the forming press, said lubricant serving to facilitate some slippage of the clamped portion of the blank during its forming.
5. 6. The method of claim 5, further comprising preheating the coated blank in a substantially nitrogen-free atmosphere.
6. 7. The method of claim 1, comprising slowing cooling the formed part to prevent severe surface cracking.
7. 8. The method of claim 7, comprising slowly cooling the formed part in a substantially air-free atmosphere.
8. 9. The method of claim 7, comprising cooling the formed part by first placing it in a heated confined zone the temperature of which is below the forming temperature but above ambient temperature, allowing it to slowly and naturally cool in said zone down to the temperature of the zone, and then placing such part in a nonheated zone and allowing it to slowly and naturally cool in said zone down to ambient temperature.
9. 10. The method of claim 1, applied to a titanium metal containing blank and wherein the forming tools are inductively heated to a temperature enabling them to conductively heat the blank to about 1000*-1775* F.
10. 11. A method of forming a part from a sheet metal blank in a forming press which includes a fixed forming tool and two movable forming tools supported for movement along a path bordering the fixed forming tool, comprising: placing a first portion of the blank between the two movable forming tools and an adjacent second portion of the blank in position tO contact the fixed forming tool; moving the two movable forming tools relatively together to firmly hold the first portion of said blank between them; inductively heating each of said forming tools to a temperature sufficient to cause them to in turn conductively heat the blank and maintain it at forming temperature, including heating the two movable tools, and hence the held portion of the blank, to a higher temperature than the fixed forming tool and the unheld portion of the blank which is heated thereby; and moving the two movable forming tools and the blank held between them, as an assembly, relatively towards the fixed forming tool, and the blank against such tool, at a rate causing plastic deformation of the blank attended by no appreciable strain hardening, with the greater heating of the held portion causing more material flow to occur in such portion than in the lower temperature unheld portion of the blank, resulting in a minimization of thinning in the contoured region of the finished part.
11. 12. The method of claim 11, wherein a titanium alloy blank is used and the forming tools are inductively heated to a temperature enabling them to conductively heat the blank to about 1000*-1775* F., and a 25*-200* F. temperature differential is maintained between the portions of the blank heated by the movable and fixed tools.
12. 13. The method of claim 12, wherein the titanium alloy is temperable and said method includes heating the formed part to a suitable temperature for hardening and then while still hot quenching it in water of the like.
13. 14. The method of claim 11, further comprising coating the blank with a high-temperature lubricant and preheating it to about its forming temperature, said lubricant serving both as a protective coating, to protect the metal against corrosion, and as a lubricant to facilitate some slippage of the held portion of the blank during forming.
14. 15. Sheet metal forming equipment comprising: a first bolster plate; a plurality of spaced-apart leader pins, each of which is firmly secured at one of its ends to said first bolster plate and extends away from said plate, in parallelism with each other leader pin; a first forming tool assembly secured to said bolster plate on the same side thereof as said leader pins, said assembly including an inductively heatable mass, an induction heating coil surrounding a portion of said mass, a die part on said mass, and heat barrier means interconnected between said mass and said bolster plate; and a second bolster plate including bushing means mounting it for precision movement along said leader pins; a second-forming tool assembly secured to said second bolster plate, on the side thereof facing the first forming tool assembly, and comprising an inductively heatable mass, and induction heating coil surrounding a portion of said mass, a die part on said mass, and heat barrier means interconnected between said heated mass and said bolster plate, said heat barrier means extending between said mass and said bushing means for protecting the bushing means against overheating, with the die part of the second forming tool assembly cooperating with the die part of the first forming tool assembly when the bolster plates are moved relatively together to impress a shape into a sheet metal blank inserted between them.
15. 16. The sheet metal forming equipment of claim 15, wherein each said induction heating coil comprises electrical conductors of tubular form, so that a cooling fluid can be circulated through them.
16. 17. The sheet metal forming equipment of claim 15, wherein said equipment further comprises a third forming tool assembly interposed between said first and second bolster plates and including: a bushing housing for each leader pin, said housings containing guide bushings which surroundingly engage said leader pins; support means rigidly interconnecting said bushing housings; and a third forming tool assembly secured to said support means, on the side thereof forming the second forming tool assembly, and comprising an inductively heatable mass, a die part on said mass, and an induction heating coil surrounding a portion of said mass, with said leader pins, guide bushings, the second bolster plate and said support means serving to mount the second and third forming tool assemblies for precision movement along a path bordering the first-forming assembly.
17. 18. The sheet metal forming equipment of claim 17, further comprising first, second and third independently controllable means for supplying electrical energy to the induction heating coils of said first, second and third forming tool assemblies, enabling the second and third assemblies to be control heated at a higher temperature than the first assembly.
18. 19. The sheet metal forming equipment of claim 15, wherein each said heat barrier means includes a coolant jacket containing passageways through which a cooling fluid may be flowed.
19. 20. The sheet metal equipment of claim 15, wherein each said forming tool assembly comprises sidewall means, and said heat barrier means comprises insulative material interposed between said sidewall means and the forming tool.
20. 21. The sheet metal equipment of claim 20, wherein said bushing means comprise sleeve members situated outwardly of, and rigidly secured to, the sidewall means of said second forming tool assembly.
21. 22. The sheet metal forming equipment of claim 15, in combination with a forming press including a fixed platen, a movable platen, and means for removably securing one of said bolster plates to one of said platens and the other bolster plate to the other platen.
22. 23. The sheet metal forming equipment of claim 17, wherein said first bolster plate includes at least one support pin opening extending through it in parallelism with said leader pins, and said equipment further includes: a support pin extending through said opening, and at one end containing the support means of said third forming tool assembly; a first piston-cylinder motor connected to said second bolster plate, for moving it towards and away from said first bolster member; and a second piston-cylinder motor for moving said third forming tool assembly through the intermediary of said support pin.
23. 24. Sheet metal forming equipment comprising: a fixed forming tool and two movable forming tools supported for movement with a clamped portion of a sheet metal blank between them along a path bordering the fixed forming tool, with each said forming tool comprising a die member and an induction heating coil associated with said member; and first, second and third independently controllable means for supplying electrical energy to the induction heating coils of said fixed and said two movable forming tools, enabling the two movable die members to be control heated at a higher temperature than the fixed die member.
24. 25. Sheet metal forming equipment according to claim 24, wherein each die member comprises an inductively heatable mass, and wherein each induction heating coil surrounds a portion of said mass, with said induction heating coils in use inductively heating said masses, and with said die members conductively heating material to be formed which is in contact with said members.
25. 26. Sheet metal forming equipment according to claim 24, wherein each induction heating coil comprises electrical conductors of tubular form, so that a cooling fluid can be flowed through them, and wherein said equipment further comprises means for delivering a cooling fluid into said conductors.

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