Title:
METHOD OF DIE-FORMING PARTS WITH IMPROVED GRAIN STRUCTURE
United States Patent 3791188
Abstract:
A method of die-forming parts so that, in their final shape, they have a substantially continuous grain structure, whereby a cylindrical blank is shaped into a spherical part by drawing the grain line ends together in two polar areas, and the spherical part is reshaped into a ring of final dimensions without breaking any of the grain lines.
Application Number:
05/192289
Publication Date:
02/12/1974
Other Classes:
72/360, 72/377
International Classes:
B21J5/02; B21K1/02; B21K1/76; B21J5/00; B21K1/00; (IPC1-7): B21J5/02
Field of Search:
72/356,360,377 29
Primary Examiner:
Larson, Lowell A.
Attorney, Agent or Firm:
Geiger, Joseph A.
Claims:
I claim
1. A method of die-forming parts so that, in their final shape, they have a substantially continuous grain structure, comprising the steps of:
2. A die-forming method as defined in claim 1, further comprising the steps of:
3. A die-forming method as defined in claim 2, wherein;
4. A die-forming method as defined in claim 1, further comprising the steps of:
5. A die-forming method as defined in claim 4, wherein;
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of die-forming metal parts and in particular to a method of die-forming metal parts in such a way that the grain lines in the final part remain uninterrupted, the part being shaped in a non-cutting cold-forming method to final dimensions without requiring any subsequent machining on a lathe, planer, or mill, and without requiring any subsequent heat treatment.
2. Description of the Prior Art
Normally, machine parts which receive their form through forging or through material-removing machining operations have a grain structure which is interrupted in many places. Such an interrupted grain structure can represent major problems in some cases of machine parts, the interruptions leading to hardening cracks, fatigue fractures and the like. It would be possible to avoid such shortcomings if a solution can be found to produce these machine parts in such a way that their grain lines remain unbroken. Of course, a prerequisite for such a condition is that the blank piece, too, has an unbroken fiber structure.
The only shape which can be produced with a substantially unbroken grain structure is a sphere. It is known to obtain such a structure in the production of spheres, by inserting a cylindrical blank into the forging dye in such a manner that the grain direction of the blank extends in the direction of compression. However, due to the fact that the grain lines in the end faces of the blank are broken, the forged sphere will also have broken grain lines in one of its axes and because the blank is usually of a somewhat greater volume than the volume of the fully closed forging die, the finished sphere will have a small so-called "equator" which has to be removed by grinding. Such a grinding operation, however, results in an interruption of the grain structure, leading to situations where, under heavy shock load conditions, the balls chip on their surface, or split into two halves.
SUMMARY OF THE INVENTION
It is a primary objective of the present invention to suggest a method of die-forming machine parts where the grain structure remains unbroken and where the method is easy to perform and requires no additional work operations.
In order to attain this objective, the invention proposes a method where the blank is initially formed to a spherical shape with substantially uninterrupted grain lines, whereupon the spherical intermediate part is reshaped into the desired end shape without interrupting the substantially continuous grain structure. It should be understood that the spherical intermediate part can also be used as an end product, in cases where it is desired that the end product is a sphere. The purpose of the method of the invention is in each case to obtain parts whose improved grain structure gives them superior resistance characteristics over similar parts whose grain structure is broken.
In a further development of the invention, it is suggested that the blank used to produce the spherical intermediate part has the same volume as the sphere into which it is to be shaped, and that the grain orientation of the blank is perpendicular to the direction of compression. Using these particular dimensions for the blank and observing the perpendicular grain orientation, one obtains a spherical part which has a practically unbroken fiber structure, rendering it superior to other spherical parts. In this forming method, the grain line ends are virtually drawn together in a single point, or at least into a very small area, so that the resistance of the sphere is not impaired. The spheres obtained with this new forming method are definitely superior to those where a grinding operation is necessary to produce the final form as in the case mentioned further above.
A further suggestion of the invention provides that the spherical intermediate part is inserted into a forging die which has a recessed forging punch and where the sphere is reshaped into a sleeve or a ring or any similar final shape. Again, the grain structure remains unbroken after this reshaping operation, so that the sleeve or ring obtained has exceptional resistance characteristics and therefore is not subject to prematrue aging or fatigue failure.
BRIEF DESCRIPTION OF THE DRAWINGS
Further special features and advantages of the invention will become apparent from the description following below, when taken together with the accompanying drawings which illustrate, by way of examples, several steps embodying the method of the invention, represented in the various figures as follows:
FIG. 1 shows the forging die with a blank inserted therein;
FIG. 2 shows a spherical part as obtained by using the tool shown in FIG. 1;
FIG. 3 shows an opened forging die in which an intermediate spherical part is to be reshaped into a sleeve;
FIG. 4 shows a sleeve such as may be obtained by using the tool of FIG. 3;
FIG. 5 shows an open ring as an alternate end product obtainable by using the tool of FIG. 3;
FIG. 6 shows another opened forging die where an intermediate spherical part is to be reshaped into a ring of different cross-section; and
FIG. 7 shows the tool of FIG. 6 in its closed position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order to produce the sphere 1 of FIG. 2, a cylindrical blank 2 is inserted into the forming die of FIG. 1 and so oriented between the die parts 4 and 5 that the grain lines 3 of the blank are oriented perpendicularly to the direction of compression. The volume of the blank is the same as the volume of the space contained between the closed die parts 4 and 5. The sphere 1 (FIG. 2) obtained in the first forming operation has no "equator" and the grain lines 3 are drawn together into very small areas 6 and 7 at opposite poles of the sphere 1 so as to produce a body of substantially continuous grain structure.
As is shown in FIG. 3, the sphere 1 can be reshaped in a forging die 8 by means of a punch 9 which squeezes the intermediate sphere into the final shape of either a cap sleeve 10 with a closed end portion 11 (FIG. 4) or a ring 12 (FIG. 5). The lines 3 in FIGS. 4 and 5 indicate the preserved continuity of the grain structure of the final parts.
In FIGS. 6 and 7 are shown the different methods and steps for reshaping the intermediate sphere 1 into a ring 19, by using a forging die consisting of two die parts 13 and 14 which carry in opposite alignment two pressure spheres 15 and 16. The intermediate sphere 1 itself is held in position between two brackets 17 and 18 which, as the die deforms the sphere 1 by closing, are retracted outside the die stroke. The sphere 1 is so oriented in the forging die of FIG. 6 that the two poles 6 and 7 on which the grain lines 3 meet are aligned with the compression axis of the die. As can be seen in FIG. 7, the reshaped part has its previous poles 6 and 7 compressed into a narrow web 20 between the pressure spheres 15 and 16 so that, for all practical purposes, all the grain lines inside the reshaped part 19 are continuous and unbroken. This ring is subsequently reshaped into its final form in a further forging operation, the latter not being a part of this invention.
It should be understood that, whenever it is desired that the sleeve 10 or the rings 12 have final dimensions as required by the drawing, it is a necessary prerequisite that the intermediate spherical part have exactly the same volume as the final part. Following the forging operation described above no additional machining is necessary, except for possible surface grinding or polishing operations. Furthermore, no subsequent heat treatment is necessary, as the required degree of hardness is obtainable by using this constant-volume forming method.