US2080640A - Method of preparing metal stock - Google Patents

Description

May 18, 1937. R. L. TEMPLINI METHOD OF PREPARING METAL STOCK Filed June 22, 1934 INVENTOR firm/74rd A7207 ///2 ATT RNEY Patented May 18, 1937 UNITED STATES PATENT OFFICE LIETHOD OF PREPARING METAL STOCK Application June 22, 1934, Serial No. 731,876

19 Claims.

The invention relates to metal working and in particular concerns the preparation or improvement of forging stock or of metal stock in genera].

In the metal working arts recognition has been accorded to the beneficial effects of working in relation to grain refinement and improvement in mechanical properties of the metal. Inseparable from the advantages which may be said to result from the working methods commonly employed, as in rolling or drawing, are certain inherent disadvantages. Perhaps one of the most important of these is represented by the phenomenon generally referred to as the production of directional properties in the metal. Thus it is well known that in the case of rolled shapes, for example,

the tensile strength will be greater in the direction of rolling than transversely thereto. Many attempts have been made to avoid or minimize the directional effect of rolling and kindred working operations but, so far as I am aware, none of the methods now known to the art are completely effective; and in some cases they are of doubtful value.

The designs of roll passes and. of forging dies are illustrative of the means commonly adopted to work the metal in such a way as to tend toward refinement of the grain structure and the elimination of directional properties. The improvement obtainable by such expedients is quite limited, however, and is largely dependent upon size and shape of the metal stock which is used, in relation to the size and shape of the product or intermediate product which is to be fabricated.

It is an object of the present invention to provide a. method of preparing metal stock which is characterized by substantial freedom from directional properties and which will show in this respect a far greater improvement than is obtainable by any of the methods which heretofore have been employed. Another object is to provide a method of preparing metal stock characterized by an improvement in mechanical properties and more particularly by an increased fatigue limit.

A more. specific object of my invention is to teach a method of preparing aluminum stock which is characterized by freedom from directional properties and by an attendant improvement in physical properties in all directions with a marked improvement in fatigue limit. I have conducted fatigue tests on specimens cutout of large aluminum alloy forgings such as are made for locomotive connecting rods and have found that the fatigue strength is appreciably below that of wrought metal of similar composition produced in smaller sizes, such as rod or sheet or even small forgings. It is therefore a special object of my invention to provide a method of preparing aluminum forging stock suitable for use in. the fabrication of locomotive connecting rods, airplane propellers and similar articles ,where the amount of working normally performed in the fabricating steps is comparatively small by reason of limitations imposed by the size of ingot or stock available. The method which is described herein will also be found applicable, however, in the production of smaller articles by forging or by other fabricating methods since in every case it will be found possible to start the forming operations with stock more nearly conforming to the size of the article which is to be made; and since the stock which is produced in accordance with the method described is quite free from directional properties, the product will also be comparatively free from directional properties. This, of course, would not be true where forming operations are relied upon for the grain refining effect, in which case there is always a tendency toward production of directional properties. Where cold working must be relied upon for the production of optimum mechanical properties it is likewise possible to start the forming operations with stock more nearly conforming to the size of the article which is to be made.

These are the principal objects of the invention. Others will appear from the following description in which there will be occasion to refer to the appended drawing in which Fig. 1 shows in perspective a metal ingot r billet suitable for processing in accordance with my novel method. Fig. 2 shows the same billet at the end of the first step of the method. Fig. 3 is a perspective view of a blank for a locomotive side rod forging such as would be produced in accordance with my invention following the working or kneading steps indicated in Figs. 1 and 2.

Fig. 4 shows a cast or machined billet such as commonly employed in extruding operations; and

Fig. 5 shows the same body after it has been subjected to the first step of my method which, in the specific embodiment illustrated, has been performed by die expressing or, as more commonly referred to, by extrusion.

I have found that if an elongated ingot or billet be first upset in one direction and then worked back as by forging or extrusion to substantially its original form, with a number of repetitions of this cycle, a very considerable improvement in mechanical properties is obtained and the forging stock or other stock so produced possesses physical properties which are very simibetween successive working cycles or between lar in all directions. It is particularly to be'obsuccessive steps of a given cycle.

served that in this cyclical process which I have Figs. 4 and 5 are intended to indicate the sucdevised the working-or kneading of the metal is cessive forms of a. billet when processed in acaccomplished without any reference whatsoever cordance with my method when the kneading is 5 to the form or shape of the article which subseto be accomplished by extrusion instead of by quently is to be produced therefrom. Thus it is forging, Fig. 4 representing the billet at the bepossible to carry the process through the reginning and end of the cycle and Fig. 5 representquired number of cycles to produce optimum ing the intermediate form of the billet. when the properties irrespective of the form of the product kneading is to be performed by extrusion I prefer 1 or subsequent methods of fabrication. Hence, the a reduction of at least 50 per cent in the cross secinventionas I have conceived it relates to the tional area of the billet, with a corresponding preparation of stock, and the'method employed is elongation. Thereafter the extruded billet is recharacterized by its cyclical nature and by the turned to substantially its original form by an upfact that the metal is worked back to its original setting or die forging operation. Apparatus by form-or to substantially its original form-"one which the original billet 3 may be extruded to or more times. form the elongated billet 4 is well known in the Throughout the balance of the specification art and need not be here described. One form and in the appended claims the term billet is of app ratu suitable for returning b t t used in a generic sense and will be understood its original form 3 is described in my eopendmg to include, for example, the "ingot" and the app Serial 7 issued February 4. bloom as well as the billet as these terms are 1936. as Patent No. 2, 0. customarily employed. This definition is'necessi- It will be seen that the method described in tated by reason of the fact that the method as. connection with Figs. 4 and 5 is the same as scribed can be performed either by forging or by that described in connection with Figs. 1 and 2, extrusion and the terminology in the two fields the only difference being in the apparatus which is not entirely consistent. The cast body of is utilized in the performance of the method. aluminum, for example, that is used in extruding In each case the billet I or 3 is subjected shapes is generally known as an extrusion billet" to a mechanical worlnng cycle consisting in whereas the cast body of metal used in rolling is deforming it by the application of a working called an ingot. It willbe understood that the pressure and returning the deformed billet (2 body of metal shown in Fig. 1 asthe starting point or 4) to substantially its original form by furof the process may, properly speaking, be neither ther application of a working pressure. In each an ingot nor a billet but a block of metal cut out case this working cycle y be r p a ed a sufof an ingot; This also comes within the purview ficient number of times to produce optimum of my definition of the term bil1et" as used P y a Properties and maximum fatigue herein. sistance. I have found, however, that when The term aluminum as used herein and in the method is performed by the combined steps of the appended claims is intended to comprise both extrusion and die forging two or three cycles are aluminum and alloys in which aluminum forms usually sufficient o produce p m P p r 40 the principal constituent. in aluminum. After the third cycle the alumium The billet I may be cast as an ingot or it may be a y t t d showed greatly mp P p lproduced in any convenient manner from alarger ties and ftu'ther repetitions of the cycle did not body of metal, Assuming that; it is d sired t produce any substantial change. The mechanical make stock for forging, the amount of metal in properties investigated include tensile strength, 5 billet I should be about that which will be reyield strength, elongation and reduction in area. quired to prod 'ce the finished forging. Bill t l i It will of course be understood that some alumiupset as by press or hammer forging, into the num loy m y require a greater number of form shown by the dotted lines 2, the forging p t t s f t cycle th n thers. pressure being applied in the direction indicated As an example whereby the exact nature of by the arrow 11. The upset billet 2 is then turned my invention may be completely understood refup on one of its sides, as shown in Fig. 2, and erence will be made tothe production of side fqrging pressure applied in th direction of t rods for locomotives. For this purpose alumiarrow b. It is then turned between the forging mlm alloy e nss h ve rapidly been increasing dies so that pressure can also be applied in the in favor by reason of their strength and lightdi ect on of the ar ow-6., By-means of forging ess. The weight consideration is particularly pressures b and c the upsetybmetz is important in machine parts having rapid reback again to substantially the form or the ciprocatory motion, from the standpoint of avoiding inertia losses and in the case of locomotive ori 1 ill t I,asindicatedb the otted lines at I l u tile dimension C i: app iximately the side rods the reduction in welght is especially 69 0 important since it reduces the rail hammer Same as the helgm C of the original bmet The caused'by the reciprocating parts. As previously steps of upsetting and returning the indicated, the problem of attaining satisfactor formed billet to substantmny its original form are fatigue limits in large forgings of this sort i then repeated number of times- I Prefer to much more serious than in the case of wrought c5 P the cycle at least three times and in some metal of similar composition produced in smaller cas s it may be desirable that it be repeated sizes, such as rod or sheet or smaller forgings. A six times or more. In the case of aluminum it is 7 x 7 x 15 inch billet was taken from a 20 x 20 x72 Preferable 7 out the Opera-b10118 0f upsetting inch aluminum alloy ingot containing approxiand drawing at an v d temperature mately 45 per cent of copper, 0.8 per cent silicon, 7 tween 500 F. and 840 F. is recommended in the and 0.8 per cent manganese. This billet was upcase of very large forgings. I have in contemplaset to a 9 inch cube, then drawn back again to tion however, the Possibility of kneading the its original dimensions. This cycle was repeated metal at o temperature Where elevated six times and then the billet was reduced 50 peratures are desired reheating may be effected per cent at one end, as at 5 in Fig. 3, and 80 75 ing were carried out between temperatures of 840 F. and 500 F. Specimens taken from a finished forging blank and subjected to a rotating beam fatigue test, showed an average endurance limit in the transverse direction of 13,000 pounds per square inch, based on 500,000,000 cycles, as compared with an average endurance limit in the same direction of 11,000 pounds per square inch for specimens taken from blanks forged in the usual manner. It will be observed that this represents an improvement of about 18 per cent over the results obtainable by the methods known to the prior art. Longitudinal and transverse test specimens showed the following average values for tensile and yield strengths:

. Transverse Transverse Longlmdma] (vertical') (horizontal) Tensile strength (pounds per sq.

in.) 56025 54860 55100 Yield strength (pounds per sq.

As viewed in Fig. 3. It will be seen from these results that. the forgings produced showed very little tendency toward directional properties.

Similar tests were made on specimens taken from 99 per cent aluminum stock prepared in accordance with the specific embodiment of my method described with reference to Figs. 4 and 5 of the drawing. The results of these tests are given in the table:

At the comple- At the completion of 2 cycles tion of 4 cycles Longi- 'Irans- Longi- Transtndinal verse tudinal verse Tensile strength (lbs/sq. in.) 22310 22240 21630 22110 Yield strength (lbsJsq. in.) 19600 20300 18300 21600 Percent elongation 17.5 18.0 18.0 18.0

The foregoing data give a comparison between longitudinal and transverse properties both at the end of the second cycle and at the end of the fourth cycle; that is, in the first case the extrusionand upsetting to the original form is performed twice and in the second case four times. The results clearly show that stock prepared in accordance with the method disclosed herein is characterized by substantial freedom from directional properties.

It will be seen that by my invention I have provided' a method of preparing metal stock which can conveniently be performed with existing equipment; which results in improved mechanical properties-especially as to fatigue limits; and effects a marked decrease in tendency toward directional properties. The method which I have devised also makes possible the production from standard sizes of ingot, of large aluminum alloy forgings characterized by a high fatigue limit.

I claim:

1. Method of preparing metal stock characterbillet, mechanically deforming said billet by the application of a working pressure, and returning the deformed billet tosubstantially its original form by further application of a working pressure.

2. Method of preparing metal stock which comprises providing a metal billet, subjecting said billet to a mechanical working cycle consisting in deforming the billet by the application of a working pressure and returning the deformed billet to substantially its original form by further application of a working pressure, and repeating said mechanical working cycle at least two times.

3. Method of preparing metal stock characterized by substantial freedom from directional properties which comprises providing a metal extrusion billet, reducing the cross sectional area of said billet by extrusion through a die, and' returning the extruded billet to substantially its original form by an upsetting operation.

4. Method of preparing metal stock characterized by substantial freedom from directional properties which comprises providing a metal extrusion billet, reducing the cross sectional area of said billet by extrusion through a die, and returning the extruded billet to substantially its original form by a die forging operation.

5.-Method of preparing metal stock which comprises providing a metal billet, subjecting said billet to a mechanical working cycle consisting in reducing the cross sectional area of said billet by extrusion through a die and returning the extruded billet to substantially its original form by an upsetting operation, and repeating said mechanical working cycle at least two times.

6. Method of preparing metal stock which comterized by substantial freedom from directional properties which comprises providing a. metal billet, upsetting said billet by applying a forging pressure in the direction of its longest dimension, and returning said upset billet to substantially its original form by drawing out through forging dies. v

8; Method of preparing metal stock characterized by substantial freedom from directional properties which comprises providing a metal billet, upsetting said billet by applying a forging pressure in the direction of its longest dimension, and returning said upset billet to substantially its original form by the further application of forging pressure in directions normal to the initial forging pressure.

9. Method of preparing metal stock which comprises providing a metal billet, subjecting said billet .to a mechanical working cycle consisting in upsetting said billet by applying a forging pressure in the direction of its longest dimension and returning said upset billet to substantially its original form by drawlngout through forging dies, and repeating said mechanical working cycle at least two times.

10. Method of preparing metal stock which comprises providing a metal billet, subjecting said billet to a mechanical working cycle consisting in upsetting said billet by applying a forging pressure in the direction of its longest turning the extruded billet dimension and returning said upset billet to sub-' stantially its original form bythe further application of forging pressure in directions normal to the initial forging pressure, and repeating said mechanical working cycle at least two times.

' 11. Method of preparing aluminum stock characterized by substantial freedom from directional properties which comprises providing an aluminum billet, mechanically deforming said billet by the application of a working pressure, and returning the deformed billet to substantially its original form by further application of a working pressure. I 12. Methodof preparing aluminum stock which comprises providing an aluminum billet, subjecting said billet to a mechanical working cycle consisting in deforming the billet by the application of a working pressure and returning the deformed billet to substantially its original form by further application of a working pressure, and repeating said mechanical working cycle at least two times.

13. Method of preparing aluminum stock characterized by substantial freedom from directional properties which comprises casting an aluminum extrusion billet, reducing the cross sectional area,

of said billet by extrusion through a die, and reto substantially its original form by an upsetting operation.

14. Method of preparing aluminum stock which comprises providing an aluminum extrusion billet,

subjecting said billet to a mechanical working cycle consisting in reducing the cross sectional area of said billet by extrusion through a die and returning the extruded billet to substantially its original form by an upsetting operation, and repeating said mechanical working cycle at least two times.

15. Method of preparing aluminum stock characterized by substantial freedom from directional properties which comprises providing an aluminum extrusion billet, reducing the cross sectional area of said billet by extrusion through a die, and returning the extruded billet to substantially its original form by a die forging operation.

16. Method of preparing aluminum stock char acterized by substantial freedom from directional properties which comprises providingan aluminum billet, upsetting said billet by applying a forging pressure dimension, and returning said upset billet to substantially its original form by drawing out through forging dies.

17. Method of preparins aluminum stock characterized by substantial freedom from directional dimension and returning said upset billet to substantially its original form by drawing out through forging dies, and repeating said mechanical working cycle at least two times.

19., Method of preparing aluminum stock. which comprises providing an aluminum billet, subjecting said billet to a mechanical working cycle consisting in upsetting said billet by applying a forging pressure in the direction of its longest dimension and returning said upset billet to substantially its original form by the further application of forging pressure in directions normal to the initial forging pressure, and repeating in the direction of its longest said mechanical working cycle at least two times.

RICHARD L. TEM'PLIN.

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