US3895968A

US3895968A - Method of making finished steel castings

Info

Publication number: US3895968A
Application number: US431233A
Authority: US
Inventors: Paul L Mcculloch; Burton O Heinrich
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-01-07
Filing date: 1974-01-07
Publication date: 1975-07-22
Anticipated expiration: 1992-07-22
Also published as: BE823773A; ZA746698B; GB1489812A; JPS50101229A; FR2256792B1; CH596918A5; SE418466B; CA1047373A; DE2454979A1; IT1023372B; SE7416169L; FR2256792A1

Abstract

A method of finishing a casting which involves formation of a pattern having laterally extending gates, preparing a mold, pouring molten metal therein and permitting it to cool to form a transitional casting. The transitional casting is reheated to a holding temperature above the critical temperature and then, while the casting is still in the plastic state and near the critical temperature, it is acted upon by a set of dies having cooperating shearing edges located at the lateral surfaces thereof for shearing off the gates and parting line fins and having upper and lower surfaces shaped in accordance with selected surfaces of the finished casting for forming these selected surfaces to desired shape. The casting is then cooled to ambient temperaure at a controlled rate. Forming includes the bending, punching or piercing and coining to size of the casting while it is near the critical temperature. In one of the aspects of the present invention a method is provided for making a finished casting having an at least partially enclosed cavity or without draft and hence difficult and expensive to make by ordinary casting or forging techniques.

Description

United States Patent [1 1 McCulloch et al.

l l METHOD OF MAKING FINISHED STEEL CASTINGS [76] Inventors: Paul L. McCulIoch; Burton 0.

Heinrich, both of 1442 N. Memorial Dr.. Racine. Wis. 53404 [22] Filed: Jan. 7, I974 [Zl] Appl. No.: 431,233

[52] US. Cl 148/2; 148/3 [51] Int. Cl. C2ld 5/00; 822d 31/00 [58] Field of Search l48/3, 2

[56] References Cited UNITED STATES PATENTS 2,352,408 6/1944 Reece et al. 148/3 2.875.109 2/l959 Carter et al 148/3 2,901,384 8/l959 Saivcs 148/3 FOREIGN PATENTS OR APPLICATIONS 649,068 9/1962 Canada 148/3 Primary Examiner-W. Stallard Attorney. Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[ 1 July 22, 1975 [57] ABSTRACT A method of finishing a casting which involves formation of a pattern having laterally extending gates, preparing a mold, pouring molten metal therein and per mitting it to cool to form a transitional casting. The transitional casting is reheated to a holding temperature above the critical temperature and then, while the casting is still in the plastic state and near the critical temperature, it is acted upon by a set of dies having cooperating shearing edges located at the lateral surfaces thereof for shearing off the gates and parting line fins and having upper and lower surfaces shaped in ac cordance with selected surfaces of the finished casting for forming these selected surfaces to desired shape. The casting is then cooled to ambient temperaure at a controlled rate. Forming includes the bending, punch ing or piercing and coining to size of the casting while it is near the critical temperature. In one of the aspects of the present invention a method is provided for making a finished casting having an at least par tially enclosed cavity or without draft and hence difficult and expensive to make by ordinary casting or forging techniques.

12 Claims, 25 Drawing Figures 4 Forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line a I Preparing a mold using the pattern I 6' Pouring molten steel therein I 0 Permitting the casting thus formed to cool to produce a nonhomogeneous dendritic structure austenit ic structure Reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the dendritic ascast structure is converted into a homogeneous Bringing thl divs together to a precisely spurt-d hnttnrnwl t' lnlll t' rl for shearing iff the gates as well as any parting lll'l fins which IT\fl\ have hi-i-n formed in the casting sti-p flush with thr lateral surfaw-s and for formingly engaging lIll upwardly and IIYIWIIWB rlllv faring surfaces li-rmitting the casting to cool to ambient temperature at a controlled r-ate.

PATENTEDJULZE ms 3,895868 sew 1 PATENTEDJUL22 I975 3,895,968

PATENTED JUL 2 2 I975 3.895.968 SHEET 5 Forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line 5 Preparing a mold using the pattern 6' Pouring molten steel therein Permitting the casting thus formed to cool to produce a nonhomogeneous dendritic structure Reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the dendritic as-cast structure is converted into a homogeneous austenitic structure Bringing the dies together to a precisely spaced bottomed condition for shearing off the gates as well as any parting line fins which may have been formed in the casting step flush with the lateral surfaces and for formingly engaging the upwardly and downwardly facing surfaces Permitting the casting to cool to ambient temperature at a controlled rate.

METHOD OF MAKING FINISHED STEEL CASTINGS In the conventional manufacture of steel castings considerable hand work must be done on the rough casting before it is considered a finished product. It is conventional to sever the gates of the sprues and risers, wherever they are located, as well as any parting line fins. by use of a cutting torch or. if the projections are of narrow section. by a chipping hammer. In some cases the projections are knocked off with a sledge. Using such procedures, a considerable amount of finish grinding is required to produce a smooth and flush surface. Since warpage may occur in a casting as it cools. the cold casting may have to be straightened" to bend it back into the desired shape. Such a straightening operation is difficult and time consuming. and imprecise at best, because of the spring back" of the cold metal. Cold straightening may also induce undesirable stresses in the casting. It is. moreover. a difficult matter to form holes of proper size and location in a cold casting.

Also it is found that cold finishing" operations, particularly such gross operations as sledging, can seriously affect the integrity of the piece by reason of breakage and formation of cracks.

As a result. where the shape and dimensions of a piece are critical. and where a high degree of reliability and integrity are required, it has been necessary to resort to forging the piece from a billet in a pair of forging dies and then machining the piece to size or to fabricate the desired final piece by welding or otherwise joining together two or more pieces which may be castings, forgings or pieces cut to size. It is well known that forging followed by machining exceeds the cost of an equiv alent unmachined casting, partly because of the high cost and relatively short life of the forging dies. For pieces of intricate design forging is generally impractical and often impossible. Fabrications, on the other hand. are time consuming and expensive to make.

It is. accordingly. an object of the present invention to provide a method of making a steel casting in which the resultant casting is highly accurate in shape and dimension as well as structurally sound and reliable, while avoiding the high labor cost and other disadvantages normally associated with cold finishing.

It is another object of the present invention to provide a method of making a casting which produces a part which is equal. or superior. to a part produced by forging and which may be manufactured at a lower cost than the latter and which may be produced on a high volume basis.

It is a related object to provide a method of making finished castings which are inherently difficult or uneconomical to make using conventional casting or forging techniques. Examples of such castings include those having a dimensioned internal cavity or those lacking in draft so as to require special coring. Although a piece having a cavity or lack of draft may be produced by forging. it is often necessary to resort to extreme pressure to secure flow of the metal under the forging dies resulting in excessive die wear.

It is a further object to provide an improved method of producing a casting in which gates and parting line fins are trimmed and in which the part is given an accurate form and dimension while it is in a hot plastic state at a uniform temperature which is in the region of the critical temperature.

It is a more specific object of the invention to provide a method for producing a steel casting in which the casting is allowed to cool to a temperature at or below solidification and is then reheated to a holding temperature above the upper critical temperature for "homogenization". that is, conversion of the structure from the nonhomogeneous as cast" to the austenitic form and in which the casting is subjected. while still in the region of the homogenizing temperature. to the action of a set of dies having cooperating shearing edges for shearing off gate and riser connections, as well as any parting line fins formed in the casting step. while subjecting the upwardly and downwardly facing surfaces of the casting to a precise forming operation.

It is a still further object of the invention. in one of its aspects, to provide a method and apparatus for trimming of unwanted lateral projections from a workpiece when in a hot plastic state and in which the trimming dies have associated upper and lower die surfaces for engaging and plastically forming to shape and dimension only the most significant ones of the presented upper and lower surfaces of a complex workpiece. a workpiece which it might be considered impractical to make as a forging.

It is a related object to provide a procedure for mak ing a casting which employs a set of dies for action upon the casting in the plastic state incident to holding it at a temperature for homogenizing purposes which is lower than normal forging temperatures and thereby results in substantially less wear and tear upon the dies than is encountered in conventional forging operations with resulting increase in the life of the dies and a sharp lowering of the per unit cost.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is atop view showing a cluster of four castings utilized in the present invention;

FIG. 2 is a fragmentary vertical section looking along the line 2-2 in FIG. 1'.

FIG. 3 is a fragmentary vertical section looking along the line 3-3 in FIG. I;

FIG. 4 is a fragmentary vertical section looking along the line 44 in FIG. 1 and taken through the central sprue;

FIG. 5 is a time-temperature plot showing reheating and holding above the critical temperature for the purpose of bringing about homogenization and showing the region of the finishing step;

FIG. 6 is a phase diagram for carbon steel corresponding to FIG. 5;

FIG. 7 is a vertical section taken through a set of finishing dies utilized in the present invention taken along line 77 in FIG. 8;

FIG. 7a is a schematic diagram showing the press arrangement;

FIG. 8 is a vertical fragmentary section taken along line 88 in FIG. 7;

FIG. 9 is a section corresponding to FIG. 8 with the dies closed;

FIG. 10 is a horizontal fragmentary section taken along line Ill-I0 in FIG. 9'.

FIG. I] is a perspective view of a finished workpiece;

FIG. 12 is a table listing exemplary method steps;

FIG. I3 is a vertical section corresponding to FIG. 8 with the dies modified for punching;

FlG. [4 is a section corresponding to FIG. 13 with the dies closed;

FIG. 15 is a vertical section corresponding to FIG. 8 with the dies modified for coining to size;

FIG. 16 is a section corresponding to FIG. 15 with the dies closed;

FIGS. l7, l8 and 19 are top, front and side views showing a transitional casting utilized in the present in vention;

FIG. 20 is a cross sectional diagram showing the transitional casting interposed between a pair of dies and with a sizing mandrel in position;

FIG. 21 shows the dies in closed position accompa nied by deformation of the casting to final shape; and

FIGS. 22, 23 and 24 are top, front and side views of the finished casting.

While the invention has been described in connection with certain preferred embodiments, it will be understood that we do not intend to be limited to the particular embodiments shown but intend, on the contrary, to cover the various, alternative and equivalent forms of the invention included within the spirit and scope of the appended claims.

Turning now to the drawings and particularly to FIGS. 1 4, there is shown a composite, or cluster", sand casting 10 which includes four individual castings I1, l2, l3 and 14, cast in the same mold. In the casting step molten metal is poured through a sprue IS with the metal dividing and flowing through horizontal runners l6, 17 (FIG. 4]. In the design of the composite casting six risers are utilized as indicated at 21 26, the risers being connected to the castings by gates 21a 26a and 22b, 25b, respectively.

The term gate will be used in this description as meaning both the channel connecting the sprues, run ners or risers to the workpiece through which molten metal flows and the solid metal formation which forms in this channel upon solidification of the molten metal,

FIGSv l l 4 of the drawings serve a double purpose. They illustrate a typical casting cluster utilized in prac ticing the present invention but they also illustrate the pattern which is utilized in making the mold in which the casting is produced. Since the finished workpiece, illustrated in FIG. I], is of hollow construction, it is necessary to use a central core in each of the patterns. The core elements are indicated at 27. The flask which is used in making the casting has not been illustrated. nor is there any need to do so since such flask is entirely conventional. It will, however, be understood that the mold, of which the lower portion M has been shown, has a parting line which has been indicated at PL in FIGS. 2, 3 and 4.

In accordance with the present invention. each of the individual castings ll 14 has lateral surfaces, which lateral surfaces have been indicated by letter subscripts; for example, the casting or workpiece 11 has lateral surfaces Ila I Id. In addition, the castings have upwardly and downwardly facing surfaces, these being indicated by corresponding numerals with subscripts e I (see FIGS 2 and 3).

ln carrying out the present invention, the gates are so located as to extend laterally away from the lateral surfaces of each casting, and, moreover, gates are positioned to lie in the region of the mold parting line PL. Forming a pattern in which the gates extend laterally away from the lateral surfaces of the casting and lie in the region of the mold parting line, and in which the up 4 wardly and downwardly presented surfaces are free of extraneous protuberances in the form of gates or the like, while known per se, constitutes the first element, or step, of our improved method of making castings, which element or stop has been designated as A in FIG. 12.

Following preparation of the pattern. the pattern is used for making a mold, using ordinary molding techniques. and into which molten steel is poured through a central sprue (see 15 in FIG. 4) in accordance with method steps B and C. The molten metal flows into all portions of the mold cavity including the risers 2i 26. The risers serve the conventional purpose of feeding molten metal, through the respective gates, to the workpiece cavities in order to replenish the metal in such cavities and thus compensate for the contraction of the metal which occurs as the molten metal begins to cool.

When it is poured the molten metal may, for example, be on the order of 3,000F. As shown in FIG. 5, the metal is allowed to cool, step D, and the temperature drops on the descending curve, as indicated at 30, to a temperature at which point the metal has solidified to form a casting. At any time after the casting has cooled sufficiently to solidify, it is removed from the mold using conventional techniques, for example, by shaking out. Sand particles adhering to the casting may be removed by shot blasting or the like.

The cooled casting in the as-cast condition will be found to have a random, non-uniform grain structure characterized by one or more of the following: a dendritic macroscopic structure, a Widmanstatten microscopic structure, and a networlctype, cellular or globular microscopic structure. This nonhomogeneous grain structure is responsible for the poor mechanical properties of the casting (cg, brittleness, internal stresses, poor impact properties, etc.) in the as-cast condition. Accordingly, it has become customary to effect a refinement or homogenization of the grain structure and hence improve the mechanical properties, by heattreating the casting.

Heat-treating processes involve a heating cycle during which the casting is heated to a holding temperature above the critical or transformation temperature at which the casting is maintained for a holding period during which refinement of the grain structure is effected by conversion of the characteristic as-cast structures mentioned above into homogeneous austenite. Heating and holding are followed by controlled cooling during which the austenite is transformed into a uniform structure consisting of one or more of several transformation products which are desired from the standpoint of strength, hardness, or machineability, The characteristics of the product formed on cooling are dependent on the cooling rate. Heat-treatment processes are generally classified according to the manner in which and the rate at which a casting is cooled. If the casting is allowed to cool in still air at a moderate rate the process is called normalizing". A slow rate of controlled cooling such as in a furnace or the like is re ferred to as "anncaling, and a rapid cooling by quenching in air, oil, water, or brine is called hardening" or quenching". It should also be understood that two or more of these heat-treating techniques may be performed sequentially and that the present invention includes the use of sequential hcat'trcating.

The metallurgy of steel castings has given rise to a highly technical vocabulary for communicating fine distinctions in crystalline structure. However, for purposes of this disclosure it is not necessary to explore the metallurgy in much detail or to enumerate all the crystalline structures encountered in different steel alloys at different temperatures. but it is sufficient to understand that given a particular steel alloy and given the desired mechanical properties of the casting one can, through the science of metallurgy. determine values for the heating rate. the holding temperature. the holding period. and the cooling rate; all of which affect the crystalline structure and hence determine the mechanical properties of the casting. Therefore. in the following discussion, in order to simplify the description of the present invention, it will be assumed that the casting consists of carbon steel having a typical carbon content of 0.3% as shown in the phase diagram of FIG. 6. However, phase diagrams similar to that of FIG. 6 exist for all alloy steels so that the present invention is not limited to carbon steel but includes all steel alloys.

In carrying out step E of the present invention, the casting is reheated at the desired rate along a reheat line 32 (FIG. 5) traversing the upper critical" temperature TC at point 33, defined as the lower boundary of the austenite region (see FIG. 6), and proceeding to an elevated holding temperature 34 which may. for example. be 100F. above the upper critical temperature. The piece is held at such temperature for a sufficient length of time to convert the nonhomogeneous, as-cast structure to a uniform austenitic structure (austenite) throughout the piece, the holding time depending upon the size of the piece and which may, for example, be one hour per inch of thickness of the heaviest section. As shown in the phase diagram. FIG. 6, the effect of holding the temperature above the upper critical level is to transform the as-cast structure into austenitic form as shown. for example, at point 35, assuming a carbon content of 0.3%.

In accordance with the present invention. instead of simply allowing the piece to cool slowly in the furnace, cool in still air. or quench in liquid. the casting, while still in a plastic state. and near the holding temperature, is placed between a set of dies having cooperating shearing edges located at the lateral surfaces for shearing off the gates. all of which extend laterally, as well as any parting line fins which may have been formed in the casting step. In the preferred practice of the inven tion, the casting is, at about the same time, acted upon by die surfaces which are distinct from the dies used for trimming. having the desired shape of the casting and which correspond to selected ones of the upper and lower surfaces of the casting for formingly engaging these surfaces so as to insure that these surfaces are in precise position. Although it is preferred, in practicing the invention. to trim and form the casting as part of the same press stroke. these operations may be performed by successive press strokes and in more than one die set in rather quick succession so as to make simultaneous use of the same heat. These two operations, trimming and forming. have been set out in exemplary method steps F and G.

In accordance with one of the further features of the invention, two or more castings. where cast in a cluster. are operated upon simultaneously by corresponding sets of shearing and forming dies. This is illustrated in FIGS. 7 9 where press 40 is indicated (press details wot shown) having die assemblies 41, 42 which act respectively upon castings ll, 12 (FIG. 7). Turning to FIG. 8 which shows die assembly 41 immediately prior to its initial engagement of casting 11, it can be seen that the die assembly 41 is interposed between a vertically. reciprocating head 43 and a bolster 44. As shown schematically in FIG. 7a, the head 43 is reciprocated by a ram 45 acting through spacers 46. lnterposed between the ram and the head are cylinders 47 of the hydraulic or pneumatic type having piston rods 48 extending therefrom and through respective bores 49 in the head. The piston rods are biased to an extended position and each cylinder has a relief valve RV and a check valve A for a reason which will appear below.

To facilitate understanding what happens to the castings I I, 12, the

risers

21, 22, and 23 forming part of the as-cast" assembly are shown in FIG. 7 together with their respective gates 21a, 22a, 22b and 230. which are severed as a result of the operation of the dies.

Focusing attention upon the die assembly 4!, the assembly is made up of an upper die 51 and a lower die 52. The upper die has a generally rectangular mounting plate 53 bolted to the head 43. Bolted to plate 53 are shearing

blades

54, 55, 56, 57 (FIGS. 7 8) having shearing edges 58, 59, 60, M, respectively. which are formed and dimensioned to correspond to lateral surfaces Ila, l lb, I I0. I ld respectively of the casting. The movable body portion 62 having die recess 63, and presenting surfaces which engage corresponding upwardly facing surfaces IIe, l If, 111'. l I] of the workpiece, is slideably mounted between

blades

56, 57 so as to permit vertical motion of the body relative to the shearing blades. The extremes of this vertical motion are shown in FIGS. 8 and 9.

For cooperating with the upper die, the lower die includes a body portion which consists of blocks 77, 78 secured to mounting plate 81 which is in turn bolted to bolster 44. These blocks are mounted so as to form a recess 65 for receiving the workpiece as well as to present upwardly facing surfaces for supporting the workpiece at its downwardly facing surfaces 11k. I ll. Vertical surfaces 79, serve as shearing surfaces for cooperating with the shearing edges 60, 61 of the upper die. Also included in the lower die are sidewalls 67, 68 bolted to blocks 77, 78 and having shearing surfaces 71, 72 which cooperate with the shearing edges 58, 59 of the upper die. These sidewalls also support surfaces 11g and H11.

While the die assembly 41 has been referred to in detail it will be understood that the companion die assembly 42 is similarly constructed. In the drawing (FIG. 7) similar elements have been indicated by corresponding reference numerals with the addition of subscript a.

In carrying out the present invention, castings II, 12 with their associated

risers

21, 22 and 23 intact, are seated in the respective lower dies 52, 52a, with the die assemblies being in the retracted or open" condition (FIGS. 7 8). During operation of the dies. castings I3, l4 may be permitted to hang in an outboard condition, cantilevered on the runners 16, I7 (FIG. 4) or, if desired. the runner may be severed by any desired means prior to placing the piece in the press. Preferably gates, risers and runners are located so as to aid in handling the casting and in accurately positioning the casting in the die. It is one of the features of the present invention that the castings II, I2 are placed in the dies while still at or near the holding temperature at which point the casting is in a plastic state, has a homogeneous refined grain structure, and is of essentially uniform temperature throughout. The fact that the casting is of essentially uniform temperature is significant in respect to die design because the absence of temperature gradients in the casting means that the casting. although of enlarged size due to expansion of the steel. will have experienced the same percentage expansion at all points. Therefore. the desired dimension between lateral surfaces such as 110 and llb, for example. is achieved by spacing shearing edges 58, 59 an incremental distance apart equal to the desired final dimension between I la and 11b increased by the percentage expansion of the particular steel at the holding temperature, which may be on the order of 1%. Hence. when the casting is finally cooled to ambient and experiences the attendant contraction. the lateral surfaces 11a and 1 lb will be accurately spaced the desired distance apart. Similarly, all surfaces and shearing edges of the die assembly are located "oversize" (about 1%) to take into account the uniform contraction of the casting which takes place as it is cooled from the holding temperature.

The desired operating range of finishing temperature is indicated at F in FIG. 5 where it will be noted that the temperature ranges downwardly from the holding temperature TH through the critical temperature TC to a point which may be somewhat below the critical temperature. Although it is preferable to finish the casting while it is at a temperature as close to the holding temperature as possible. in a practical case the lower limit of the finishing temperature may be a temperature which lies within the range of lO to 200 below the critical temperature TC. In any event the casting. or castings. when placed in the press will be in a glowing red plastic state, a state in which the metal may be sheared and bodily formed to desired shape using a relatively light shearing-forming force. a force which is only a fraction of the force which would be required if these finishing steps were carried out with the casting in its cold state.

Focusing attention on FIGS. 8 and 9, the engagement of the casting 11 by the die assembly 41 will be explained. As the press completes its downward stroke but before the casting is engaged by the upper die. the parts occupy the position shown in FIG. 8. In accordance with a preferred method of the present invention in which the casting is first formingly engaged and at the same time held firmly in place by the dies before shearing. the movable die body 62 of the upper die is held in its lowermost position relative to the shearing blades by extended piston rod 48. As the stroke continues the lower surface 64 of the body portion butts against surfaces lIi. llj. The force of this initial engagement may be varied by adjusting the escape of fluid from the cylinder 47 through relief valve RV to offer the desired retarding force to piston rod 48.

After the casting has been engaged by body portion 62 the continued downward motion of the head 43 will cause piston rod 48 to retreat into cylinder 47 thereby allowing downward motion of the upper shearing blades relative to the lower. As the shearing blades 54, 55 and 54a. 55a (FIG. 7) are lowered. the gates 21a, 22a. 22b, 230 are engaged by shearing edges 58, 59, 58a, 590 so that, as the thrust is completed, the risers 2l 23 may fall clear into a suitable receptacle. Similarly. in referring to FIGS. 8 9. it is apparent that as the

shearing blades

56, 57 are lowered. any parting line fins formed at surfaces llc, l Id are engaged by shearing edges 60, 6| and hence are trimmed from the workpiece. In addition, as the head 43 nears the bottom of its downward stroke and after shearing is complete, the lower surface of head 43 butts against the upper surface of movable die body 62 transmitting a final, peak forming force to the workpiece.

Operating on the casting in this sequential manner with only one stroke of the press accomplishes both the removal of extraneous metal from the casting and straightening of horizontal surfaces. Also, since the casting is held firmly in place by piston rod 48 acting through movable die body 62 during shearing. high accuracy is insured in the location of the lateral surfaces.

After the downward stroke is complete the ram is retracted causing the shearing edges to move up and away from the newly sheared edges. However, until the shearing edges are clear of the casting the movable die body 62, by reason of the pressure which continues to be applied to it by piston rod 48, insures that the casting remains seated in the lower die 52. After the shearing blades are clear of the casting the movable die body 62 is retracted and the casting, which is still at or near the holding temperature, is released and may be removed from the lower die by any convenient means. Cooling at the desired rate completes the heat treatment.

While, for the purpose of simple illustration, no provision has been included in FIGS. 7 10 for forming in the way of piercing or coining the casting, it will be understood that such piercing and coining may be brought about by suitable piercing elements on the cooperating dies and suitable coining surfaces included within the inner surfaces 63, 64, 65 of the die sections.

For example, the die assembly, modified so as to per form piercing is shown in FIGS. 13, I4 in which modified die assembly 41m is shown having a piercing element for forming a hole in the surface 111' of the casting II. The elements of the die assembly which have not been modified for the piercing operation are identified by the same numbers used in FIGS. 7 10 (see for example 43, 56, 81) whereas the elements which have been modified are identified in FIGS. l2, 13 by the same number used in FIGS. 7 10 with the addition of the letter m.

For present purposes the term piercing has been used in a generic sense to include both use of (a) a piercing, or drifting tool, which is round-nosed and forces its way through an exiting hole and (b) a punch which is sharp edged and which removes metal in creating or enlarging a hole. The latter has been illustrated.

Turning to FIG. 13 which shows the die assembly 41m just prior to initial engagement of casting 11, the modifications made in the die assembly in order to accomplish piercing will be explained. The ram 43 has piercing element 90 extending from its lower surface and through bore 91 in movable die body 62m. Block 77m in lower die 52m has a cavity 94 having a bore 92 of a diameter equal to the size of the hole to be punched and a larger bore 93 through which the punched metal can pass through and be removed through opening 95.

It is preferred to form an undersized hole in the casting during the casting operation by including a suitable core element in the mold since less resistance will then be encountered by the piercing element and such a hole is indicated at 96 in FIG. 13. However. it should be understood that this is a preferred technique and that punching can be accomplished with or without forming an undersized hole.

In accordance with the preferred method of the present invention the casting 11 is first engaged and held firmly in position by movable die body 61m. As the press stroke continues piston rod 48 retracts allowing downward motion of piercing element 90 relative to movable die body 62m. Piercing element 90 will then engage surface 111' at undersized hole 96 and, as the stroke continues, the piercing element will shear away all metal within the region defined by dotted lines 97 in FIG. 13.

The configuration at the completion of the downward stroke is shown in FIG. I4 in which piercing element 90 extends slightly into bore 92 to insure that the metal removed by the piercing element will fall through to the bottom of cavity 94. Retraction of the dies is identical to the sequence described above except that piercing element 90 is retracted along with shearing blade 56 while movable die body 62m through extending piston rod 48 insures that the casting remains firmly seated in lower die 52m.

Similarly. and in accordance with a further aspect of the present invention, coining to size is performed on the casting while it is still at or near the holding temperature. Let it be assumed simply by way of example, that the distance between lateral surfaces llc, l ld (FIG. 8) is not critical and that the critical dimension is the thickness of the wings having surfaces Hi, I lj, l lk. l I], In order to achieve this desired wing thickness the die assembly 41 of FIG. 8 is modified as shown in FIGS. [5, 16 in which modified die assembly 4ln is illustrated. The upper die Sln consists of movable die body 62a, slideably mounted between blocks 56n. 57n and having stop blocks 100, I01 mounted at the lower surface of movable die body and spaced so as to allow for clearance between vertical surfaces Ilc, lid and the stop blocks, Lower die 52n is identical to lower die 52 (FIG. 8) except that blocks 77n. 78n are longer and extend beyond lateral surfaces lie, 1 Id so as to present surface against which stop blocks 100, I01 will abut.

Coining is accomplished at the end of the downward stroke by the final peak force transmitted to movable die body 6211 as the lower surface of head 43 butts against the upper surface of the movable die body. When this coining force is transmitted to the wings: which are of a thickness slightly larger than thickness T of stop blocks [00, I01, there will be a slight displacement of metal into the spaces S until the stop blocks bottom against blocks 77n, 7811, respectively. At this time. and immediately after retraction of the die assembly. the wings will be of thickness T. However, as discussed above. the casting will experience some contraction on subsequent cooling and therefore the thickness T of the stop blocks is slightly larger, on the order of W: or so. than the desired final thickness.

Although for purposes of simple illustration the stop blocks I00. I01 are shown having a relatively limited area for bottoming against the lower die, it will be understood that in a practical case the stop blocks would be designed with an area somewhat larger than the area of the part to be coined to size. However, it should also be understood that often only selected portions need be coined to size. For example. movable die body 62n could be equipped with a localized disc-shaped coining element extending slightly below its lower surface to form a small land area for surrounding a bolt hole in the casting.

It is particularly noteworthy that. because of the plastic state of the metal in the region of the critical temperature, the casting freely adopts the shape of the dies without any tendency toward spring-back, so that a highly accurate form and dimension for the casting is established-even though the casting may. at the time of placing the dies. be in a warped or misshapen condition. No subsequent straightcning' is therefore required, a major problem when a casting is cold fin ishcd".

Although, for simple illustration, the casting I] is shown having planar wings which are formingly engaged by the dies so as to insure that they lie true with respect to a horizontal plane, it would be obvious to one skilled in the art that the upper and lower die assemblies could be modified so as to present corresponding curved surfaces to the casting if it is desired to shape or bend selected surfaces of the casting. For example, if it is desired that the wing" defined by surfaces llk, lll define a curved surface then the mold would be designed so as to form a casting having wings curved to the approximate final desired curvature. It is apparent that the die assembly (FIGS. 8 9) may readily be modified so as to present, to each wing of the casting ll, curved forming surfaces opposed to one another, for example, surfaces 64 in the upper die assembly and the upper supporting surfaces of blocks 77, 78. Hence, after completion of the press stroke, and subse quent cooling of the casting. no cold bending or straightening" of the wings to the desired curvature, with the attendant spring-back problem, would be re quired.

Indeed, it is seen that the operation of the dies incident to heat treatment, and following the holding period, is effective to accomplish automatically all of the steps which formerly required hand operations. That is, the risers and gates, or sprues, are cleanly severed from the castings along accurate dimension lines in the single stroke of the press. together with other irregularities such as any fins which may have been formed along the parting line during the molding step. The shearing cut is sufficiently smooth so that the chipping and grinding usually thought necessary to finish the casting may be completely dispensed with.

While it is preferred to accomplish the plastic forming" using dies which are in the same set as those employed for trimming purposes, it will be apparent to one skilled in the art that the two or more operations may be accomplished in quick succession, that is, using a first set of dies for shearing only, with immediate transfer of the workpiece while still in a hot and plastic state. to a second or further set of dies for forming, including coining, piercing and the like. Thus the term simultaneously" as used herein referring to the trimming and shaping steps has to do with the fact that these two operations are performed sufficiently close together so as to make use of the same heat and same plastic state, and the term is not necessarily limited to a single set of dies.

Regarding the method steps of the present invention. and method step A in particular, it will be understood that the terms latcral. upwardly" and down wardly are used in a relative sense and that the casting cluster depicted in FIGS. 1 4 could also be cast using a pattern which is orientated at so that the parting line is in a vertical plane. In this case the requirements of method step A would be satisfied since a 90 rotation of the pattern would result in the configuration shown in FIGS. 1 4. In addition, although the above description of mold preparation includes reference to a conventional flask, it will be understood that the method of the present invention is suitable for castings produced using the flaskless" mold procedure. Briefly, the flaskless procedure involves forming a series of mold cavities in a horizontal column of sand having a high green strength, advancing the column past a metal pouring station where molten metal is poured into each mold in turn, and removing the sand mold after solidification has occurred. The nature of the flaskless procedure requires a vertically orientated parting line plane and gates which lie in the region of this plane. However, changing reference position by rotating the mold 90 results in a configuration which satisfies method step A. Therefore, the method of the present invention is particularly suitable for practice in conjunction with a flaskless casting operation.

It will also be apparent to one skilled in the art that the present procedure, involving the making of a steel casting, the cooling and subsequent heating of the casting to a holding temperature, with trimming while in the plastic state, brings about a major economy in the making of parts. Compared to forging procedures, a primary difference is that the part which is acted upon by the dies is already in substantially its final shape. After the risers and gates are trimmed off all the dies are required to do is to refine, and make more accurate, the shape which is already present, with the result that the dies are not called upon to forcibly work a billet of metal into the final form of the finished product. This makes it possible, employing the present invention, for a single set of dies to be used to transform the part to final shape and dimension using working forces which are so low as to enable the trimming and shaping steps to be accomplished with substantially reduced wear and tear on the dies. quickly, and using lighter press equipment with only a limited total stroke. The next result is that a piece is produced using the present procedures which has substantially all of the advantages normally associated with a forging, including accurate shape and dimension, plus reliable and consistent characteristics, but at a perunit cost, taking into account a mortized die expense and maintenance, which is su bstantially lower than the cost of the forging.

A further reason that the die costs may be substantially reduced is that the dies may be greatly simplified. Thus, in the case of forging dies, the dies must have surfaces corresponding to each and every surface on the finished product. The present dies, by contrast, may leave certain portions of the workpiece unsupported, that is, unengaged, during the forming step, concentrating upon those surfaces which are dimensionally signifi cant. For example, the upper surface 85 of the cylindrical portion of the workpiece I1 is not engaged by the body portion 62 of the upper die assembly (see FIG. 9).

After the dies shown in FIG. 7 have completed a single cycle, the castings are independent of one another and freed of all extraneous metal and are of accurate shape and dimension. When the dies are open, the finished castings are discharged, using any desired conventional means. Conveniently, the castings will be allowed to cool in still air, thus completing the normal izing of the metal in the castings. Alternatively. the

castings may be annealed by cooling more slowly. Conceivably also, and without departing from the invention, the castings taken from the dies may be quenched, with or without subsequent tempering as these terms are defined in the art. In any event, the requirement of the final step H (FIG. 12) is satisfied.

It is one of the distinguishing characteristics of the present invention that the finishing" of the casting including trimming and shaping is done incident to reheating of the casting for homogenizing, e.g., normalizing purposes. Stated in other words, the invention does not make use of the original casting heat. The reason for this is that we prefer to finish, that is, trim and form, only after the casting has been allowed to cool and is subsequently reheated to a holding temperature, above the upper critical temperature, for a time period long enough to convert the grain to the desired granular, i.e., austenitic, structure, at a time when all of the internal stresses have had opportunity to become equalized, and at a time when substantially all portions of the casting are at the same temperature and degree of plasticity. This is to be contrasted with any procedure utilizing only the original heat of the casting since the casting tends to cool unevenly in the mold so that different portions of the casting would be at a different temperature than other portions with different physical characteristics and ill-defined crystallography, and accompanied by a substantial sacrifice in the result.

In the above discussion the procedure for finishing a casting has involved the making of a pattern which, but for the addition of gates and risers, substantially con forms to the finished workpiece, with the casting resulting from the pattern then being placed in a set of dies for trimming. coining and the like. The invention is not limited thereto and can be utilized to produce a workpiece which includes an at least partially enclosed cav ity and the making of which would normally require use of a core. In this aspect of the invention the original pattern, with its gates and risers, is not made in the shape of the desired finished workpiece. Instead, the pattern is made in the shape of a transitional casting with walls having adequate draft to avoid use of a core. The transitional casting thus formed is then reheated to a plastic state above the upper critical temperature and held there a sufficient length of time for homogenization. Then, while the transitional casting is still in a plastic state and near the holding temperature, the casting is placed in a set of dies for the purpose of shearing off the gates and risers, the set of dies including op posed forming surfaces corresponding to the desired upwardly and downwardly facing surfaces of the finished workpiece. The opposed die surfaces are brought together to act upon the transitional casting so that the walls thereof are deformed inwardly to form an at least partly enclosed cavity. The dies are withdrawn and the casting is permitted to cool at a controlled rate.

By way of example, a piece having a partially enclosed cavity is set forth in transitional form in FIGS. 17 l9 and in final form in FIGS. 22 24. To avoid duplication in the drawings, the illustrations in FIGS. 17 19 may be taken as illustrative, not only of the transitional casting, but of the pattern which is used .to produce it.

The workpiece, indicated at in its transitional form is of channel shape having

side walls

121, 122, which are provided with adequate draft for casting purposes, and which define between them a channelshaped, open-topped cavity 123. The

walls

121, 122 are tapered in the vertical dimension as shown in FIG. 18 and the tip of the piece is spade" shaped as indicated at 124. Secured to the opposite, or thicker, end is a gate 125 having a riser 126.

Using a pattern of the shape illustrated in FIGS. 17 19, a mold is prepared and the casting is molded in the regular way. Since the cavity 123, although bounded by upstanding walls, is open above the parting line PL, no core is required and the casting may be made in the regular way. When the casting thus formed is cooled a nonhomogeneous dendritic grain structure is produced, as previously described. The transitional casting is then reheated to a plastic state above the upper critical temperature and held there until homogenization occurs. While the casting is still in a plastic state and near the holding temperature, it is placed in a set of dies which have a shearing edge 128 (FIG. 18) for trimming off the gate and riser, and at which time shearing surfaces are also applied to trim off any parting line fins as discussed in connection with the previous embodiment. Also, referring to FIG. 20, while the transitional casting is in the plastic state, it is placed between forming dies 130 (only partially shown) including a lower die 131 and an upper die 132. The upper die has a forming surface 133 which differs from the shape of the transitional casting but which corresponds to the shape of the desired finished casting. lnterposed between the dies 131, 132 is a mandrel 135 having a ledge 136. When the dies are brought together, as shown in FIG. 21, the projection 133 on the upper die formingly engages the wall 122 of the transitional casting, causing the plastic material of which the wall is composed to be displaced laterally and to flow into the space defined by the upper surface 133 and the lower ledge surface 136. The upper edges of the walls of the transitional casting are defomred mutually inwardly so that the cavity 123, instead of being open-topped becomes partially enclosed. The result is to produce the workpiece illustrated in FIGS. 22 24 which differs from the shape of the pattern which is used to produce it and which is distinguished by a partially enclosed cavity of a type normally requiring use of a core. In short, the present invention may be employed for economical production of a cast workpiece which cannot be cast in the usual way and which would, because of the partial enclosure, require resort to a core. Moreover, the resulting workpiece is, by reason of its cast nature, and by use of the extremely simple forming dies shown in F168. 20, 21, susceptible of manufacture more cheaply than a forging, and with considerably reduced die expense.

After the dies have completed their stroke, the dies are opened, the mandrel is longitudinally withdrawn, and the casting is removed and allowed to cool at a controlled rate.

We claim as our invention:

1. The method of making a finished steel casting having lateral surfaces as well as upwardly and downwardly facing surfaces, which comprises: forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line, and in which the upwardly and downwardly presented surfaces are free of extraneous protuberances in the form of gates or the like, preparing a mold using the pattern, pouring molten steel therein, permitting the casting thus formed to cool to produce a nonhomogeneous ascast grain structure, reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted into a homogeneous austenitic structure, then, while the casting is still in a plastic state and near the holding temper ature, placing the casting in a set of dies having opposed forming surfaces corresponding to selected ones of the upwardly and downwardly facing surfaces of the casting and having cooperating shearing edges located at the lateral surfaces, bringing the dies together for shearing of the gates as well as any parting line fins which may have been formed in the casting step flush with the lateral surfaces and for formingly engaging the upwardly and downwardly facing surfaces, and finally permitting the casting to cool at a controlled rate.

2. The method as claimed in claim 1 in which (a) the forming surfaces on the dies are engaged with the corresponding surfaces on the casting, (b) the shearing edges are shearingly engaged with the casting, (c) the forming surfaces on the dies are pressed with peak force on the casting, (d) the shearing edges are fully withdrawn from the casting, and (e) the forming surfaces are fully withdrawn following which the finished casting is removed and permitted to cool at a controlled rate.

3. The method as claimed in claim 1 in which the pattern has a plurality of connected units and the resulting mold has a plurality of casting cavities defining a plurality of unit castings having interconnecting gates and runners, and in which corresponding sets of shearing and forming dies are operated simultaneously whereby said unit castings are individually severed from the gates and runners which connect them.

4. The method as claimed in claim 1 in which the shearing edges are spaced laterally apart from one another an incremental amount taking into account the expanded condition of the casting at the holding temperature whereby upon subsequent contraction of the casting due to cooling the lateral surfaces of the casting will be accurately spaced with respect to one another.

5. The method of making a finished steel casting having lateral surfaces as well as upwardly and downwardly facing surfaces, which comprises: forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line and in which the upwardly and downwardly presented surfaces are free of extraneous protuberances in the form of gates or the like, preparing a mold using the pattern, pouring molten steel therein, permitting the casting thus formed to cool to produce a nonhomogeneous ascast grain structure, reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted into a homogeneous austenitic structure, then, while the casting is still in a plastic state and near the holding temperature, placing the casting in a set of dies having cooperating shearing edges located at the lateral surfaces, and then bringing the dies together for shearing off the gates as well as any parting line fins which may have been formed in the casting step flush with the lateral surfaces. and finally permitting the casting to cool at a controlled rate.

6. The method as claimed in claim 5 further comprising: placing the casting, while it is in a plastic state and near the holding temperature, in a set of dies having forming surfaces opposite sections of the casting having a critical thickness dimension, and then bringing the dies together to a precisely spaced bottomed condition to establish the thickness dimension simultaneously with the shearing off of the gates and fins.

7. The method as claimed in claim 5 further comprising: placing the casting, while it is in a plastic state and near the holding temperature, in a set of dies having opposed piercing elements and then bringing the dies together to pierce the casting simultaneously with the shearing off of the gates and fins.

8. The method as claimed in claim 5 further comprising: placing the casting, while it is in a plastic state and near the holding temperature, in a set of dies having opposed coining surfaces arranged opposite selected surfaces of the casting, limiting the travel of one coining surface with respect to the other as the dies come to gether so as to bottom said coining surfaces at a predetermined spacing equal to the desired final separation of the selected surfaces of the casting increased by an incremental amount taking into account the expanded condition of the casting at the holding temperature, whereby upon subsequent contraction of the casting due to cooling the selected surfaces will be accurately spaced with respect to one another.

9. The method of making a finished steel casting having lateral surfaces as well as upwardly and downwardly facing surfaces, which comprises: forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line, and in which the upwardly and downwardly presented surfaces are free of extraneous protuberances in the form of gates or the like, preparing a mold using the patten, pouring molten steel therein, permitting the casting thus formed to cool to produce a nonhomogeneous ascast grain structure, reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted into a homogeneous austenitic structure, then, while the casting is still in a plastic state and near the holding temperature, placing the casting between a set of dies having forming surfaces corresponding to selected ones of the upwardly and downwardly facing surfaces of the workpiece and having cooperating shearing edges located at the lateral surfaces, advancing the forming surfaces into firm engagement with the casting for holding the latter securely in position, separately advancing the cooperating shearing edges for shearing from the lateral surfaces the gates as well as any parting line fins which may have been formed in the casting step flush with the lateral surfaces, and then advancing the forming surfaces incrementally to a final precisely spaced bottomed condition accompanied by generation of a peak pressure at the forming surfaces adequate to plastically form the surfaces into desired shape and thickness dimension, and then permitting the casting to cool at a controlled rate.

10. The method of making a finished steel casting having lateral surfaces and upward and downwardly facing surfaces and including an at least partially enclosed cavity having a desired internal dimension which comprises: fonning a pattern of open topped channel shape providing draft and in which the gate extends laterally away from the lateral surfaces in the region of the mold parting line, preparing a mold using the pattern, pouring steel therein to form a transitional casting, permitting the casting thus formed to cool to produce a nonhomogeneous as-cast grain structure, reheating the transitional casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted to a homogeneous austenitic structure, then while it is still in a plastic state and near the holding temperature shearing the gate and placing the transitional casting in a set of dies having opposed forming surfaces corresponding to the desired upwardly and downwardly facing surfaces of the finished casting, bringing the dies together to a precisely spaced bottomed condition with a mandrel of the desired internal dimension in the root of the channel for deforming the walls of the channel inwardly upon the mandrel to finish the casting and to form the enclosed cavity, withdrawing the dies and mandrel, and finally permitting the casting to cool at a controlled rate.

11. The method of making a finished steel casting having lateral surfaces and upwardly and downwardly facing surfaces including an at least partially enclosed cavity and the making of which would normally require use of a core, which comprises: forming a pattern dif fering substantially from the desired shape of the finished casting and in which the cavity is open sided and bounded by upstanding walls having sufficient draft as to enable a core to be dispensed with and in which a gate extends laterally away from the lateral surfaces in the region of the mold parting line, preparing a mold using the pattern, pouring molten steel therein to form a transitional casting in the shape of the pattern, permitting the casting thus formed to cool to produce a nonhomogeneous as-cast grain structure, reheating the transitional casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the ascast grain structure is converted to a homogeneous austenitic structure, then while it is still in a plastic state and near the holding temperature, placing the transitional casting in a set of dies having cooperating shearing edges for shearing off the gate and having opposed forming surfaces corresponding to the desired upwardly and downwardly facing surfaces of the finished casting, bringing the dies together to shear the gate and to a precisely spaced bottomed condition for deforming the walls inwardly thereby to form the enclosed cavity, withdrawing the dies, and finally permitting the casting to cool at a controlled ratev 12. The method as claimed in claim 10 in which a set of dies includes two pair of dies the first pair having cooperating shearing edges and the second pair having the opposed forming surfaces.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,895 ,968 Dated July 25 1975 Paul L. McCulloch et a1. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

-- [73] Assignee: Evans Products Company Signed and Scalcd this Attest:

RUTH C. MASON C. IAISIIALI. DAMN Arresting Officer Commission" a] Paula and Trademarks

Claims

1. THE METHOD OF MAKING A FINISHED SEEL CASTING HAVING LATRAL SURFACS AS WELL AS UPWARDLY AND DOWNWARDLY FACING SURFACES, WHICH COMPRISES, FORMING A PATTERN IN WHICH GATES EXTEND LATERALLY AWAY FROM THE LATERAL SURFACES AND LIE IN THE REGION OF THE MOLD PARTING LINE, AND IN WHICH THE UPWARDLY AND DOWNWARDLY PRESENTED SURFACES ARE FREE OF EXTRANEOUS PROUTUBERANCES IN THE FORM OF GATES OR THE LIKE, PREPARING A MOLD USING THE PATTERN, POURING MOLTEN STEEL THEREIN, PERMITTING THE CASTING THUS FORMED TO COOL TO PRODUCE A NONHOMGENEOUS AS-CAST GRAIN STRUCTURE, REHEATING THE CASTING TO A PLASTIC STATE ABOVE THE UPPER CRITICAL TEMPERATURE AND HOLDING IT THERE A SUFFICIENT LENGTH OF TIME FOR HOMOGENEOUS AUSTENITIC GRAIN STRUCTURE IS CONVERTED INTO A HOMOGENEOUS AUSTENITIC STRUCTURE, THEN WHILE THE CASTING IS STILL A PLASTIC STATE AND NEAR THE HOLDING TEMPERATURE, PLACING THE CASTING IN A SET OF DIES HAVING OPPOSED FORMING SURFACES CORRESPONDING TO SELECTED ONES OF THE UPWARDLY AND DOWNWARDLY FACING SURFACES OF THE CASTING AND HAVING COOPERATING SHEARING EDGES LOCATED AT THE LATERAL SURFACES, BRINGING THE DIES TOGETHER FOR SHRING OF THE GATES AS WELL AS ANY PARTING LINE FINS WHICH MAY HAVE BEEN FORMED IN THE CASTING STEP FLUSH WITH THE LATERAL SURFACES AND FOR FORMINGLY ENGAGINGLY ENGAGING THE UPWARDLY AND DOWNWARDLY

5. The method of making a finished steel casting having lateral surfaces as well as upwardly and downwardly facing surfaces, which comprises: forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line and in which the upwardly and downwardly presented surfaces are free of extraneous protuberances in the form of gates or the like, preparing a mold using the pattern, pouring molten steel therein, permitting the casting thus formed to cool to produce a nonhomogeneous as-cast grain structure, reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted into a homogeneous austenitic structure, then, while the casting is still in a plastic state and near the holding temperature, placing the casting in a set of dies having cooperating shearing edges located at the lateral surfaces, and then bringing the dies together for shearing off the gates as well as any parting line fins which may have been formed in the casting step flush with the lateral surfaces, and finally permitting the casting to cool at a controlled rate.

8. The method as claimed in claim 5 further comprising: placing the casting, while it is in a plastic state and near the holding temperature, in a set of dies having opposed coining surfaces arranged opposite selected surfaces of the casting, limiting the travel of one coining surface with respect to the other as the dies come together so as to bottom said coining surfaces at a predetermined spacing equal to the desired final separation of the selected surfaces of the casting increased by an incremental amount taking into account the expanded condition of the casting at the holding temperature, whereby upon subsequent contraction of the casting due to cooling the selected surfaces will be accurately spaced with respect to one another.

9. The method of making a finished steel casting having lateral surfaces as well as upwardly and downwardly facing surfaces, which comprises: forming a pattern in which gates extend laterally away from the lateral surfaces and lie in the region of the mold parting line, and in which the upwardly and downwardly presented surfaces are free of extraneous protuberances in the form of gates or the like, preparing a mold using the patten, pouring molten steel therein, permitting the casting thus formed to cool to produce a nonhomogeneous as-cast grain structure, reheating the casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted into a homogeneous austenitic structure, then, while the casting is still in a plastic state and near the holding temperature, placing the casting between a set of dies having forming surfaces corresponding to selected ones of the upwardly and downwardly facing surfaces of the workpiece and having cooperating shearing edges located at the lateral surfaces, advancing the forming surfaces into firm engagement with the casting for holding the latter securely in position, separately advancing the cooperating shearing edges for shearing from the lateral surfaces the gates as well as any parting line fins which may have been formed in the casting step flush with the lateral surfaces, and then advancing the forming surfaces incrementally to a final precisely spaced bottomed condition accompanied by generation of a peak pressure at the forming surfaces adequate to plastically form the surfaces into desired shape and thickness dimension, and then permitting the casting to cool at a controlled rate.

10. The method of making a finished steel casting having lateral surfaces and upward and downwardly facing surfaces and including an at least partially enclosed cavity having a desired internal dimension which comprises: forming a pattern of open topped channel shape providing draft and in which the gate extends laterally away from the lateral surfaces in the region of the mold parting line, preparing a mold using the pattern, pouring steel therein to form a transitional casting, permitting the casting thus formed to cool to produce a nonhomogeneous as-cast grain structure, reheating the transitional casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted to a homogeneous austenitic structure, then while it is still in a plastic state and near the holding temperature shearing the gate and placing the transitional casting in a set of dies having opposed forming surfaces corresponding to the desired upwardly and downwardly facing surfaces of the finished casting, bringing the dies together to a precisely spaced bottomed condition with a mandrel of the desired internal dimension in the root of the channel for deforming the walls of the channel inwardLy upon the mandrel to finish the casting and to form the enclosed cavity, withdrawing the dies and mandrel, and finally permitting the casting to cool at a controlled rate.

11. The method of making a finished steel casting having lateral surfaces and upwardly and downwardly facing surfaces including an at least partially enclosed cavity and the making of which would normally require use of a core, which comprises: forming a pattern differing substantially from the desired shape of the finished casting and in which the cavity is open sided and bounded by upstanding walls having sufficient draft as to enable a core to be dispensed with and in which a gate extends laterally away from the lateral surfaces in the region of the mold parting line, preparing a mold using the pattern, pouring molten steel therein to form a transitional casting in the shape of the pattern, permitting the casting thus formed to cool to produce a nonhomogeneous as-cast grain structure, reheating the transitional casting to a plastic state above the upper critical temperature and holding it there a sufficient length of time for homogenization so that the as-cast grain structure is converted to a homogeneous austenitic structure, then while it is still in a plastic state and near the holding temperature, placing the transitional casting in a set of dies having cooperating shearing edges for shearing off the gate and having opposed forming surfaces corresponding to the desired upwardly and downwardly facing surfaces of the finished casting, bringing the dies together to shear the gate and to a precisely spaced bottomed condition for deforming the walls inwardly thereby to form the enclosed cavity, withdrawing the dies, and finally permitting the casting to cool at a controlled rate.

12. The method as claimed in claim 10 in which a set of dies includes two pair of dies the first pair having cooperating shearing edges and the second pair having the opposed forming surfaces.