US2671559A - Process of press forging metal alloys - Google Patents

Description

March 9, 1954 w. ROSENKRANZ PROCESS OF PRESS FORGING METAL ALLOYS Filed Jan. 6. 1950 I aw 51/764776 A/A/E' Coll/65107794770 01 5 INVENTOR VILHELM Rose-11m L BY wiw UNITED STATES PATENT GFFI CE PROCESS OF PRESS FORGING METAL ALLOYS Wilhelm Rosenkranz, Meinerzhagen Kreis Altena, Germany Application January 6, 1950, Serial No. 137,046

Claims priority, application Germany February 3, 1949 6 Claims. 1

The present invention relates to a process for the manufacture of full and hollow sections on a forging press, and more particularly to a process for the manufacture of full and hollow sections on a forging press which is performed at a high pressing speed and at a high starting temperature of the billet and at high temperatures of the tools.

The output of a forging press having a predetermined specific pressure is influenced by three factors, namely, the deformation of the material to be imparted by the press; the flow pressure and the pressing speed. Principally the press :forging allows a high deformation in contradistinction to rolling and drop forging. The flow pressure and the pressing speed are in a well known reciprocal relation to each other. At a low temperature of deformation an unfavorably high flow pressure is combined with a relatively high pressing speed. At a high temperature of deformation conditions are reversed. For reatures of deformation are principally maintained because the output of the forging press is influenced in the first line by the pressing speed owing to the relatively long flow path of the work to be pressed. If the pressing speed is increased the production of full and hollow sections by means of forging presses leads to stresses which may have the effect of producing cracks and fractures in the section.

According to a process for fast pressing which has recently become known, pressing speeds are applied which are considerably higher than the hitherto usual speeds, an increase in temperature of the section extending from the press being prevented by compensating the increased production of heat owing to the higher pressing speed by using intermittently or permanently cooled tools (holder, punch, pressing plunger) and/or by reducing the starting temperature of the billets.

According to another suggestion high pressing speeds are used in combination with high starting temperatures of the billets and high temperatures of the tools in contradistinction to the just mentioned process. The high frictional heat and the heat of deformation is withdrawn immediately at the place of its production, i. e. at the frictional surface of the die, by means of a heat carrier flowing along and in contact with the die. The die used in this process has a duct arranged as a ring at a small distance from the frictional surface of the die which is flown through by the heat carrier, preferably water at an influx temperature of about 10 0., a heat insulation being provided on the wall of the duct opposite to the frictional surface.

It has been discovered in tests by the inventor in which flat rods were pressed from cast billets consisting of an aluminum alloy of the type Al-Cu-Mg with a pressing degree exceeding a starting temperature of the billet amounting to 490 C., and at a pressing speed of 25 m. per minute without any cooling of the pressing tools that the section extruding from the die at a temperature of about 540 C. showed not the least cracks or other surface faults in spite of a socalled hot shortness which had to be expected based on the experience hitherto collected by the persons skilled in the art. This unexpected ,result caused the inventor to work out, as far as he knows, for the first time, the conditions under which cracks and fractures can occur at all in press forgings. The knowledge gained hereby rendered it possible under application of the results of further tests to state the conditions under which the nove1 press forging process according to the present invention can be carried out generally successfully at high extruding temperatures of the sections and at large pressing speeds.

According to the observations of the inventor in press forging metallic materials two kinds of cracks and fractures occur which are denoted hereinafter as violent fractures due to heat and heat fractures proper. The first kind of fractures is observed as having the shape of cracks running under an angle of about 45 with the direction of pressing. The second kind of fractures differs from the first kind in outward appearance in that they mostly penetrate very deeply into the section and run at an angle of not quite 90 to the direction of pressing. A further observation of the microstructure has shown that the fractures or cracks of the first kind are intracrystalline, whereas those of the second kind are intercrystalline, which proves that the two kinds must be caused by different causes. Still, both kinds of fractures are caused by the same stress exerted on the material and which is particular to forging presses. The reason for this is as follows:

The power required for press forging serves on the one hand for overcoming the resistance against the deformation or flowing of the material and on the other hand for overcoming the external frictional forces. The resistance to flow (internal friction) to be overcome, which by the way is dependent on the type of alloy used, has

equal magnitude in the center and marginal zones of the section. Therefore equal forces acting in the pressing direction are required in the central and marginal zones of the section for overcoming this resistance. By an additional power the external frictional resistance at the frictional surface of the die has to be overcome which is transferred to the marginal zones of the section and tends to keep back the marginal zones against the central zone in the direction opposite to the flow of the material. This results in stresses between the marginal zones and the central zone which may lead to a separation of material in the section. This separation occurs at the cracks whichrunmostly in an intracrystalline way and have been noted above as violent fractures due to heat. They are due to the fact that the rigidity of the heterogeneous components present within or on the boundaries of the mixed crystals can no longer meet the 's tresses occurring at increasing pressing speed ornincreasing temperature of the extruding section. The separation can be avoided if the stresses between marginal and central zones are .keptlow by using dies having a frictional surface assmall as possible and if the rigidity of the heterogeneous components is kept high by apiplying relatively low flowing speeds and leaving temperatures of thesection. This method of operation has been used for instance for press forging of alloys of the type Al-Cu-Mg. The inventor has discovered that a second method .for avoiding the violent fractures due to heat consists in that the temperature of the extruding zsectionisincreased from the range below the solubility-line, at which the internal energy is relatively-low, to the homogeneous temperature -range of the mixed crystal, at which the internal energy; is considerably increased.

The phenomena called hereabove heat fractures proper occur at higher temperatures than the violent fractures due to heat and are observed in alloy materials having a limited mislcibility in the solid state. They are caused by ;the softening of those heterogeneous components sof the substance of the grain boundaries which are soluble in the mixed crystal but insoluble in the -basic structure the fusingpoint of which is below-the solidus point of the mixed crystal or g the basic structure which explains that these a fractures .occur along the boundaries of the grains. In the temperature range in which a :softeningor fusing of the components soluble :in the-mixed crystal occurs in the boundaries of :the grains, the mixed crystal has a lower abso- .lute rigidity and in any case an increased elongation which renders the difference between the forces occurring in the marginal and central zones of the section negligibly small, the mixed crystal having an extraordinary increased duetility and internal energy. Therefore for avoiding the heat fractures proper it is required according to the present invention to effect by theeonditions of deformation a spontaneous and practically complete solution of these compolnents of the boundaries of the grains and to prevent their fusing. It has been stated above that these conditions are satisfied for instance in aluminum alloys of the type Al-Cu-Mg if the section leaving the die has a temperature of .lnthepress forging of alloys such as those of thetype Al-Mg with for instance 7% Mg .having asolidus point at 546 C. normally the violent fractures-due to heat are notobserved .ing of the material of the boundaries of the 4 at all, the conditions of the deformation of these alloys being such that the temperature of the section in the aperture of the die is increased to about 440 C. and thus approaches the solidus point so much that the mixed crystal has a high elongation at these temperatures. Above this temperature range, however, is a critical range of transition for the temperature of the leaving section made of these alloys in which intercrystalline heat fractures occur owing to the fusgrains. If however,. conditions of deformation 'are such that the section in the die aperture reaches temperatures above the critical temperature range the intercrystalline heat fractures are avoided.

'In press forging of the technically applied alloys of the type Al-Cu-Mg having solidus temperatures of about 600 C. the temperatures of the extruding section are as a rule about 4 0 C. under the hitherto used conditions of deformation so' that the temperatures lie in the heterogeneous domain of the state diagram. Above these temperatures of the leaving section there is a transitional range giving risetothe intracrystalline violent fractures due to'heat and a transitional range giving rise to-intercrystalline heat fractures, these ranges lying close to each other or merging into each other.

In the above mentioned processes which have recently become known for increasing the pressing speed and thus theefiiciency of press forging, the temperature of the extruding section is according to the alloy used either below the critical temperature range for violent fractures due to heat, as for instance for Al-Cu-Mg, or below the critical temperature range for heat fractures, as for instance for Al-Mg. In the process using low starting temperatures of the billet and low temperatures of the tools the section does not reach the lower limit of the critical transltional range even with the additional heat produced byfriction and deformation, so that the violentfractures due to heat and heat fractures mentioned above are avoided. In the other process using higher starting temperatures of the billet and-higher tool temperatures, the temperature of the section in theaperture of the dieis keptlow by an intensive 'coolingof the frictional surface ofthe die sothat the same effect is obtained.

The keeping of the temperature above the critical transitional range ofthe heat fractures throughout the length of the section present in the die is dependent on, or madepossible by, several factorsnamely thespecific pressure of theforgingpress, .thedegree of pressing-the initial temperature of the billet, the'pressing speed maintained during the pressing operation,

and the conicity ofthe frictional surface of the die. In view of the requirement to dissolve prac tically completely during thepressing operation the heterogeneous components of the boundary of the grains soluble in the mixed crystal, an as high as possiblestarting temperature of the billet should involve technical advantages since it favors an equalization of the concentration in the structure which goes as far as possible. The higher the starting temperature of the billet is, the sooner the billet starts flowing at a predetermined pressure of the forging press. By using longer and T more conical frictional .surf aces of the die, more; frictional heat is produced than by using short and non-conical pressing tools. Higher degrees of deformation have the effect of increasing the preliminary pressing time at the predetermined pressure of the forging press; however, they cause production of more frictional heat than lower degrees of deformation. Thus with increasing the degree of deformation the lengths of the frictional surface can be reduced and the angle of inclination to the direction of pressing can be smaller which has a favorable effect in view of the high starting pressure required. High pressing speeds allow high temperatures in the section to be reached in a short time. A relatively high pressure of the forging press renders it possible to keep high degrees of deformation at short preliminary pressing times combined with relatively low starting temperatures of the billet at high pressing speeds.

The above mentioned effects of the pressing conditions are partly known in the art. It is to be kept in mind, however, for the obtaining of a constant temperature above the critical transitional range for the heat fractures proper that the specific pressure of the given forging press is constant and that the degree of deformation and the pressing speed should be as high as possible in order to render the manufacture more economical. Since the heat of friction and deformation is produced to the greatest part in the aperture of the die, a difference in tempera ture always exists between the billet and the section in the die.

In order to avoid a sticking of the section to the die due to fusing the initial temperature of the billet must not be too high. As a rule the initial temperature of the billet is not higher than 20 below that at which the sticking of the cast structure to the die due to fusion starts.

Starting temperatures of the billet which are.

below this upper limit by -20 C. allow on the one hand a fast initial pressing and on the other hand the constant maintaining of high pressing speeds. The heat required for maintaining the temperature difference between the billet and the section is then produced by the heat of friction and deformation the magnitude of which is conditioned by the degree of deformation and the length and conicity of the frictional surface. According to recent discoveries by the inventor the maximal amount of frictional heat is obtained at angles of 2 to 6 between the frictional surface of the die and the direction of pressing. According to the cross sectional area of the section, however, often angles of inclination amounting at least to /2 and going up to 12 are permissible. Corresponding conditions hold for the length of the frictional surface which can amount to 3 mm. at profiled rods with the smallest technically produced cross section and to 200 mm. for the largest cross section.

If the cross section is symmetrical as in cylindrical and square rods the length and conicity of the frictional surface of the die is kept constant over the perimeter of the rod. With fiat rods the length of the frictional surface can be constant but in order to avoid cracks on the smaller sides which are caused by the tendency of the center of the rod to lead, the angle of inclination of the frictional surface must be smaller on the smaller side than on the wider side. The following Table 1 shows the ratios of the angles of inclination preferably to be kept.

In sections having portions of unequal cross sections an adaptation of the length of the frictional surface to the magnitude of the cross section is required, the length of the frictional surfaces of the several cross sections being in the same ratio as the cross sections divided by their perimeters. This is more fully explained by the following example in connection with the appended drawings in which Fig. 1 shows the cross section of an angle profile. Figs. 2-4 illustrate an example of a die, to be more fully described hereinbelow in plan view and sections taken along the lines 3-3, and 4-4, respectively. Figure 5 shows the temperature range for carrying out the process of the present invention.

Referring now to the drawing and first to Fig. 1, an angle profile is represented in cross section the arms of which have both a length of 40 mm. whereas the horizontal arm has a height of 15 mm. and the vertical arm a thickness of 5 mm. In the drawing the horizontal leg is denoted by A, the vertical arm by B, and the portion common to both arms by C.

During the pressing operation with equal length of the frictional surfaces the cross section B would tend to lag behind the cross section A owing to the comparatively larger external friction. In order to prevent that and to avoid the formation of cracks caused thereby in cross section B, the length of the frictional surface has to be reduced for this cross section relatively to that of cross section A. This has to be done ac cording to the following formulae:

aria RB 22 3 9 .92 RA RB QB 4 Here is:

R.4=the length of the frictional surface on cross section A Rs=the length of the frictional surface on cross section B QA=the area of cross section A QB=the area of cross section B UA=the perimeter of cross section A UB=the perimeter of cross section B Yer occur.

ing speed or more correctlythe high flowing speed ofthe cross section through .the aperture of the .die the frictional surface should be made sufficiently long in any case so thatthe dissolution is completed with certainty before the cross section extrudes from .the...aperture. of-the .die.

The temperature ranges which are referredto in the preceding description as those in which complete dissolution of the components of the grain boundariesoccur-are illustrated in Fig. 5. Referring to thisfigura'which shows an equilibrium diagram of a binary alloyin' which the. concentration of a constituent Bin a constituent A is shown by the abscissa and in which the. ordinate indicates temperature; the point ac indicates the concentration of? in a given. alloytwhich is to be worked. The vertical line from the point r on the abscissa is'markedto show temperature ranges a-b, cd and e). The fviolentfractures due to heat occur in the temperature range .2

:at temperatures in the ranges a-b and c--d.

When, however, carrying out ,theinvention the temperatures are maintained in the .range e---;'

which extends below the solidus line but above the temperature ranges within which violent fractures due to heat. and heat. fracturesprop- By keeping the temperature of the material in the range e-f, the components of" the grain boundaries, are :completely dissolved before aperture of the die. parted a 1ow:absolute rigidity and an increased .plete d ssol t Qfth comp n so w eboun ary: of the grains fusing below i the solidus tem perature; of the grains and I being soluble in the mixed crystal.

{In a preferred embodiment of the'presentin- .vention the components of the grain boundaries ofthe-primary crystals of the cast-structure-as well. as the secondary crystals 1 of a block which has been subjected previously to a homogenizing treatment andwhich fuse below the solidus temperature of the grain and are soluble in the mixed crystal are practically dissolved during the pressing-of the section before the latter leaves the Thereby the section is imascertained.

.On principle the process according .to the invention can be applied to all alloys having a temperature range of complete miscibilitylin the solid state and which have components of the grain boundaries fusing below the solidus .temperature of the basic structure whichtare completely dissolved by the mixed crystal. This temperature range (distance between solidus line and separating line) is variable from alloy to alloy in its absoluteheight and'in its'extension. The following Table 2 contains the values for some well known alloys which are technically used. It should be noted that these values may be, of course, subject to slightcorrections-by'more recent measurements; for-the'following discussion, however, this circumstance-is without importance. Table 2 contains also the values of the elongation at 300 C. more fully discussed hereinafter.

Table 2 Temperature Dit- Tempera- "'lemperaierence Elongation Alloy ture of ture of Between of-Pressed Solidus Separating Solidus Rods at Line Line Line and "300 C.

Separating Line 1. Type .Al-Cu-Mg with about Degrees Degrees 'Degrm Percent 3% Cu 600 470 130 l8 II; Type Al-Ou-Mg Withabout 4 Cu 580 500 -80 13 111. Type Al-Mg with about 5% Mg". .l 573 262 311 65 IV. Type Al-Mg with about 7% Mg v546 301 245 V. Type Al-Mgwith about 9% Mg $523 333 190 55 VIxType Mg-Al with about 9% the material-.extrudes from the exit-opening of ,the .die.

.Thus the present invention relates .to -a process for the manufacture of full and hollow sections particularly of lightmetals on a forging press at high pressing speeds and high starting temperatures of the billet and hi h temperatures of the pressing tools comprising the ,steps of keep ing the 1 temperature of the vsection extruding from the aperture of the die sufficiently highand making the frictional surface-of.,the .,die-s-ufii- .ciently long for eifectingduringpressingiand becourse that generally. valid numerical values for the upper temperature limit of the extruding secfore theleavingofthesectiona.practicallygcomtion. according.to.-the; :preeentginvention. cannot be given. The temperature of the extruding section, however, has to be above, and more particularly sufiiciently above, the separating line in order to ensure that the heterogeneous components of the grain boundaries which are soluble in the rnxied crystal are dissolved before the section leaves the aperture of the die. Therefore numerical values as to the lower temperature of the extruding section cannot be given either.

Since the temperature difference between the solidus line and the separatin line becomes smaller with increasing content of the alloy, with higher percentage alloys a smaller interval for the temperature of the leaving section is available as with smaller percentage alloys. The well known statement as to the greater difiiculties in working higher percentage alloys by means of the known press forging processes (temperature of the section below the critical transition range) is valid per se also for the process according to the invention. It should be pointed out, however, that this circumstance does not prevent the process according to the invention from being carried out for higher percentage alloys but only influences it insofar as the maintaining of the temperature above the critical transition range, and the factors conditioning the deep fractures such as starting temperature of the billet and the pressing degree, can only be changed Within narrower limits.

Essential for the deformation at the high leaving temperatures of the section is doubtless the elongation of the material which is extraordinarily increased at these temperatures. From the elongation of the alloys at 300 C. given in the last column of Table 2 it can be seen that this value at the leaving temperatures of the section according to the invention is higher as to order of magnitude than even at the maximal extruding temperatures of the section which have been applied in the known press forging processes. For instance, for the alloys I-V, etc., the following values according to Table 3 can be chosen:

EXAMPLE Cast billets of 170 mm. diameter and 760 mm. length consisting of an aluminum alloy containing 3.2% Cu, 1.22 Mg, 0.81% Mn, 0.53% Si, 0.59% Fe, remainder Al, were pressed on a forging press with a total pressure of 1500 metric tons at a starting temperature of 485 C. to flat rods of x 80 mm, the pressing degree amounting to 95%. The frictional surface of the die shown in Figs. 2- had a length of 55 mm. and its inclination with respect to the pressing direction amounted to 4 on the broad side of the rod and to 15 on the narrow side of the rod. The temperature of the section pressed at a speed of 25 to 30 meters per minute amounted to 535 C. The temperature of the pressing residue was, at a consecutive pressing of 20 billets, constantly between 460 and 470 C. The rods cooled in air had a largely recrystallized structure. The rods were heated to 490 C. during 1 /2 hours in an air furnace, quenched and. aged for 5 days at room temperature, and then subjected to a 1% cold drawing. The resulting strength values are to be seen from the following Table 4:

Since the rods owing to the spontaneously occurring extensive recrystallization of the structure at the high temperature of deformation did not show the so-called pressing effect which leads to particularly high values of the tensile strength and the yield point in the pressing direction an appreciable reduction of the strength values might have been expected according to experience. As Table 4 shows the pressing effect, which has been extensively obliterated by the spontaneous recrystallization of the deformed structure, is more than compensated owing to the practically complete solution of the hardening components. Thus, the process according to the present invention yields a qualitative improvement of the produced semi-finished material.

In the process of reducing to final dimensions by press forging parts consisting of alloys such as the type Al-Zn-Mg, the homogenizing temperatures of which are within the range of the hitherto used temperatures of hot deformation, the section has been quenched in water directly after leaving the die and in this way an operation, namely a renewed heat treatment, has been saved. On principle this operation is also applicable to alloys of the kind Al-Cu-Mg; in doingv so, however, only lower strengths values of the hardened work pieces are obtained. Owing to the high temperature of deformation this very economical process can now be applied to all hardenable alloys, for instance those of the type Al-Cu-Mg without putting up with the reduction of the strength values. Since the mentioned temperatures are high the cooling should be done under particularly effective conditions.

According to further experiments in drop forging of work consisting of a magnesium alloy containing 7% Al, 1% Zn, and 0.12% Mn which has been made from a starting material produced on a forging press according to a process according to the present invention, this material can be drop forged at higher temperatures than hitherto applied without incurring the danger of formation of a coarse recrystallized structure so that higher speeds can be applied.

As to the causes of the difficulties experienced in shaping does not involve cutting it is said in the relevant literature (see Praktische Metalkunde Von G. Sachs, 2. Teil, Berlin 1934) that it is very difiicult to predict whether a novel material can stand a deforming process under heat without heavy damage, for instance, without incurring cracks. With most materials it is z -evmsa 11 said to be necessary to find and define a definite process-of production by experiments, this process havingto be kept more Or less accurately accord ing to the material in question unless heavy damage is to be incurred; It is also'noteclin the literature that the susceptibility of a-material for deformations under heat plays an important part because it is so small in certain criticalranges of temperatures that a cracking occurs. The conditions however for this are said to '-behitherto hardly known.

In pressforging always care has been taken not to choose the starting temperature of the billet too high and to render innocuous the higher heat of friction and deformation which is produced by the increased pressing speed by seeingtoit thatthe material did not reach tem--- peratures during the deformation which are near the solidus point. Since to almost all materials at these temperatures the property of'the socalled hot-shortness was acribed this seemed'to be. justifiable on thebasis of. practical experience.

In this argumentation, however, it was not takeninto regard that the cracks caused by fusingv occur only in the immediate neighborhood of. the mouth ofthe aperture of .the die;

Itwas not appreciatedthat in press forging.

ofl-alloyshaving components of the grain bound.- ary. substance. fusing. belowthe solidus. teme perature of. the basic structure and-completely.

soluble in the mixed crystal, it is only. necessary to eifecta practically complete dissolution of these componentsbefore the section extrudes. from the-.ap.erture..of the die. The-temperature of the sectionreached under.- these conditions. permits the-keepingof high pressing speedsw-ithout being.

given any obligation on the operators part to limit.oneselftolow degrees of deformation. as

in .the initially. mentioned known rapid pressing.

processes.

It'willbe understood thateach of .the elements described-above, r twoor more together, may. alsofihd a,.useful application inother. types of. processes for the manufactureof .full and .hollow.

sections. on a forging. press differing. from the types described above.

While. I have illustrated and. described. the inventionas embodied in processes for the manu= factureoffull.andhollow sections of .light metals.

on.a forging.press, I do notintendtobe limited to.- the-details shown, since .various modifications andstructural. changes may be made without departinginany way fromlthe spirit of-my. in-- vention.

Without further analysis, .thezforegoing will sofully reveal the gistofmy invention that others. can by applying. current knowledge readily adapt it for. various applications withoutomitting'features that, from the standpoint of prior art,

fairly constituteessential characteristics of the.

generic .or specific aspects of this-invention'and,

therefore, such adaptations should and. are .in-.-

tended tobe comprehendedwithin the. meaning and range -.of equivalence of the followingclaims. What- Iclaim as new and desire to secure by Letters Patent is:

1. Aprocess of. press forgingmetal alloys, comprising. thestepsof passing a metalalloy at high. speed at a temperature between the temperature of complete miscibility in the solidstateofithe components of said alloy and the solidus temperature of said alloy through a die channel having a frictional surface and sufficient length to: effect during passage of said metal alloy through the channel at said temperature com- 12 plate dissolution of the components ofsaidalloy in each other; andextruding at theend of the die channel said'metal alloy atsaid temperature through an apertureso as to form an extruded" an apertureand-quenchingthe' same so as to form:an extruded metal alloy piece free of heat fractures:

3; A process of press forging metal alloys, comprising-the" steps of' passing a metal alloy at' high speedat a" temperature Ill-20 C. below thesolidus'temperature of said'alloy through a die channel having a frictional surface and sufficient-lengthxto effect duringpassage' of said metal alloy through-thechannel at said temperature' complete dissolution of the components ofsaia alloy-in each:- other; and" extruding at the end of the die channel said metal alloy at said-temperature through an aperture so as to form an extrudedmetal alloy piece free'of heat fractures:

43 A process of press-forging metal alloys, comprisingthe steps of'passing an aluminum alloy ath'igh speed at a temperature between the temperature of complete miscibility in the solid state of the components of said alloy and the solidus temperature of said'alloy through a die channel having africtional surface and sufficient length.to effect during passage. ofsaid aluminum alloy throughthe. channel at said temperature complete dissolution of'the components of said .alloy in each other; and extruding at the end of the die channel said aluminum alloy at said temperature through an aperture so as to form an extruded aluminum alloy piece free of heat fractures;

5. A process of: press forging metal alloys, comprising'thesteps of passing an aluminum alloy. at high speed at a temperature 10-20 C. below the, solidus temperature of said alloy through a die channel having a frictional surface andsufficientlength to effect during passage of saidlaluminumalloy through the channel at said temperature complete dissolution of the components of said alloyineach other; and extruding at the end -of the die channel said aluminum alloy at said temperature through an aperture so' asto form'an' extruded aluminum alloy piece free of heat fractures.

6. A process of press forging metal alloys, comprising the: steps of. passing a metal alloy at highspeedfat'a temperature between the temperature of" complete miscibility in the solid state of'the components of said alloy and the solidus temperature'ofsaidalloy through a die channel of'3-200 mm. length sufficient to effect during passageof saidmetal alloy through the channel at said temperature complete dissolution of,v the components of said alloy in each nel said metal alloy at said temperature through 2,671,559 13 24 an aperture so as to form an extruded metal alloy FOREIGN PATENTS piece free of heat fractures. Number Country Date WILHELM ROSENKRANZ. 672,342 Great Britain May 21, 1952 OTHER REFERENCES Grain Control in Industrial 1\eta11urgy-American Society for Metals, Cleveland, Ohio, 1949.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,290,684 Graham July 21, 1942 10 2,559,523 Templin July 3, 1951

Claims (1)

1. A PROCESS OF PRESS FORGING METAL ALLOYS, COMPRISING THE STEPS OF PASSING A METAL ALLOY AT HIGH SPEED AT A TEMPERATURE BETWEEN THE TEMPERATURE OF COMPLETE MISCIBILITY IN THE SOLID STATE OF THE COMPONENTS OF SAID ALLOY AND THE SOLIDUS TEMPERATURE OF SAID ALLOY THROUGH A DIE CHANNEL HAVING A FRICTIONAL SURFACE AND SUFFICIENT LENGTH TO EFFECT DURING PASSAGE OF SAID METAL ALLOY THROUGH THE CHANNEL AT SAID TEMPERATURE COMPLETE DISSOLUTION OF THE COMPONENTS OF SAID ALLOY IN EACH OTHER; AND EXTRUDING AT THE END OF THE DIE CHANNEL SAID METAL ALLOY AT SAID TEMPERATURE THROUGH AN APERTURE SO AS TO FORM AN EXTRUDED METAL ALLOY PIECE FREE OF HEAT FRACTURES.

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