GB1571446A - Forging of wheel shaped workpieces - Google Patents

Description

('4) IMPROVEMENTS IN OR RELATING TO THE FORGING OF WHEEL SHAPED WORKPIECES (71 ) We. HOESCH WERKE AKTIENGESELISCHAFT, of Eberhardstrasse 1'. 4(,()t) Dortmund. Federal Republic of Gerltlanv. a German Companv do hereby declale the invention, for which we prny that a patient may be granted to us. and the method by which it is. be performed. to be particularly described in and bv the following sttement::- The invention relates to a method of forging a wheel shaped orkpiece. prefer bly a workpiece the diameter of which is at least 500 mm. the workpiece having a central thickened hub. a solid middle part and a wheel rim. the method employing staffing Inarkrial comprising a pressed blank of disc form. 'I'he invention also relates to "orkpiece produced by the method and to apparatus for performing it.

Such wheel shaped workpieces are prin- cipally used in large transmissions and as track wheels. The hub preferably has a central opening. The wheel rim can be thinner. equally thick or thicker than the middle part. According to the field of use the outer periphery of the wheel rim may be subsequently fitted with a hoop or tvre. or teeth may be formed therein.

Various production methods are already known for such wheel shaped workpieces. A method frequently emploved is that of cating. In the examples of such wheels produced by casting it is not always possible to achieve the required material strength.

'nwanted inclusions in the starting material lead to increases in the rate of wastage. The subsequent processing of cast wheels results in a high rate of wear of the tools. Moreover such wheels exhibit a high degree of unbalance Such wheels are also produced by the die forging process practised bv the use of hammer forging presses. In this case the production involves the installation of a plurality of presses. One uses a forging press for shaping, a further press for finishing, and another press for forming an opening.

However, the heavy capital cost of dies and machines are regarded as unsatisfactory features in this method, since they render production economical only with large batch working. Furthermore, by the use of this method wheel shaped workpieces having at least 500 mm diameter can be produced only by the use of high power presses.

Accordingly the invention seeks to provide a method for the forging of a wheel shaped workpiece. in particular one having a diameter of at least 500 mm, which will allow economic production whilst utilising smaller press forces than those generally used in die forging. and which moreover will ensure the production of a workpiece with a homogeneous grain structure.

The present invention accordingly provides a method of forging a wheel-shaped workpiece having a central hub joined to a rim portion of an intermediate part, the method employing starting material in the form of a disc-shaped blank and comprising hammer forging carried out in at least two steps using respective die halves for each step and the first step being only on the central portion of the blank and a successive step being only on a successive portion concentric with and immediately radially outwardly of the preceding portion of the blank subjected to a forging step, each such step ending with the achieving of the finished form for the associated portion of the workpiece.

The invention also provides apparatus for carrying out the method defined above and including a first pair of finish form die half elements of circular configuration for working the central portion of a blank and so shapd as to allow free radially outward movement or workpiece material from between these die half elements during use of the same to forge a workpiece and a second pair of finish form die half elements for working an annular portion of the blank radially outwardlv of the said central portion and of which at least one is annular and is so shaped as to inhibit radially inward movement of workpiece material from between the second pair of die half elements during use of the same to forge a workpiece.

This forging method, of so applying the known hammer forging method by the use of finish form dies that the workpiece is forged in at least two working steps beginnine at the centre and proceeding concentricallv outwards. brings with it a series of advantages as compared with the known state of the art, in particular the widely adopted die forging method of the conventional tvpe.

The invention not only substantially sim plifies the forging tools. and brings with it a reduction in the required pressing force in relation to the converted forging surface.

The required pressing force is indeed reduced disproportionately. because the specific pressing force is reduced in consequence of the smaller frictional effect, this being due basically to the use of a smaller forging surface in contrast to die forging methods using the full initial height. Added to this is the fact that the material, due to the design of the tools. can spread substan tally unrestrictedlv outnardlv and thus de mands a smaller pressing force. Moreover, this specific pressing force is dependent upon the ratio of the workpiece height to the forging surface. In the proposed method this ratio is favourable because the strain conversion conditions are improved the greater is the ratio of the workpiece height to the forging surface.For example. an extremely unfavourable ratio results from the pressing of coins. In such a case there is the conversion of a large forging surface at a small height.

The method according to the invention opens up the possibilitv of better utilisation of the capacities of the available presses.

Using the available presses, either it is possible to produce wheel shaped workpieces of greater dimensions whilst exceed inp the output from presses using the previouslv conventional die forging methods, or else presses of a smaller power can be used for producing wheel shaped work pieces of the same size but in a more economical manner than is possible with the known die forging methods.

The invention is further explained below by way of illustration with reference to the accompanying drawings, in which: Fi$loe 1 is a sectional side view of a forging blank in the form of a cvlindrical block having a length greater than its diameter:: Figure 2 is a like view of the blank in a disc shaped form produced by pressing; Figure 3 is a like view of a wheel shaped workpiece produced from the blank of Figure 2 by the performance of a forging step on the central portion thereof; Figure 4 is a like view of a finished wheel-shaped workpiece produced from that of Figure 3; Figure 5 is a like view showing the die halves as well in the working step for producing the workpiece of Figure 3; Figure 6 is a like view showing the die halves as well in the working step for producing the workpiece of Figure 4: Figure 7 is a partial sectional side view of a disc-shaped blank for producing a workpiece of different shape; Figure 8 is a like view of the second wheel-shaped workpiece after a first working step; and Figure 9 is a like view of the second workpiece in the finished state.

In the method illustrated in Figures 1 to 6 of the production of a wheel shaped workpiece, the workpiece 10 (Figure 3) is obtained from the cylindrical block shown in Figure 1. which has a length greater than its diameter, by a preliminary step which converts this blank to a thick disc-shaped blank, shown in Figure 2. The workpiece 10 will be seen to have. after the first working step as shown in Figure 3, a recess 11 formed at the cenre of a hub 12. The hub 12 and the lower region of the solid middle portion 13 have the final form of the workpiece. In the upper region of the workpiece there is provided a groove 14 surrounding and forming the boundary of the hub 12.The die halves (Figure 5) for obtaining the condition of the workpiece shown in Figure 3 comprises a plane base half 16. with a central circular depression 15 having a diameter corresponding to the diameter of the hub 12, and an upper half 19 having a centrally arranged piercing mandrel 17 and a concentric annular projecting crown 18.

The die halves (Figure 6) for forming the second working step to obtain the workpiece configuration shown in Figure 3 comprise a base half 16, corresponding to that of Figure 5, and an upper half 21 of flat circular shape having an annular step 20 of a diameter corresponding to the external diameter of the hub 12. Because of their generally planar formation, both sets of die havles 16, 19 and 16. 20 allow free outward radial flow of the material of the workpiece at the outer circumference of the die. as is desired in accordance with the invention.

However, the step 20 of die half 21 inhibits radially inward flow of the workpiece material.

Also in accordance with the method of the invention. it is possible to forge wheelshaped workpieces having the wheel rim which is thinner or thicker than the solid middle portion as well as of the same thickness as shown in Figure 4, and likewise to produce workpieces having a centrally arranged hub which projects proud of the solid middle portion only at one side thereof. The number of working steps in the forging operation is determined in dependence upon the dimensions of the workpiece, and according to the available power of the press in use.

Steps in the production of a second wheel shaped workpiece having a different shape from thit of Figures 4 and 6 are shown in Figures 7 to 9 of which Figure 7 shows a blank corresponding to that of Figure 2 and Figure s shows the workpiece after a first, central. forging operation.The second \ orkpiece in its final form. after a second forging operation. will be seen from Figure 9 to have a centrally arranged hub 22 with a recess 23. and a solid middle portion 24 cross section of which is thinner than the cross section of a wheel rim 25 forming the outer boundary of the workpiece.

WIIAI WE CLAIM IS: 1. A method of forging a wheel-shaped 'vorkpiece ha\-in a central hub joined to a rim portion by an intermediate part. the method employing starting material in the form of a disc-shaped blank and comprising hammer forging carried out in at least two steps using respective die halves for each step and the first step being only on the central portion of the blank and a successive step being only on a successive portion concentric with and immediatelv radically outwardly of the preceding portion of the blank subjected to a forging step. each such step ending with the achieving of the finished form for the associated portion of the workpiece.

2 .A method according to Claim I wherein the workpiece has a finished exter nal diameter of at least 500mm.

3. A method of forging a wheel-shaped workpiece substantially as herein described with reference to Figures 1 to 6 or Figures 7 to 9 of the accompanying drawings.

4. A wheel-shaped workpiece forged by a method of claim 1. 2 or 3.

5. Apparatus for carrying out a method of forging a wheel-shaped workpiece according to any one of claims 1 to 3 including a first pair of finish form die half elements of circular configuration for work ing the central portion of a blank and so shaped as to allow free radially outward movement of workpiece material from be tween these die half elements during use of the same to forge a workpiece and a second pair of finish form die half elements for working an annular portion of the blank radially outwardly of the said central por tion and of which at least one is annular and is so shaped as to inhibit radially inward movement of workpiece material from between the second pair of die half elements during use of the same to forge a workpiece.

6. Appultus fol foryilly a wheel shaped workpiece substantially as herein described with reference to Figures 5 and 6 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. which is thinner or thicker than the solid middle portion as well as of the same thickness as shown in Figure 4, and likewise to produce workpieces having a centrally arranged hub which projects proud of the solid middle portion only at one side thereof. The number of working steps in the forging operation is determined in dependence upon the dimensions of the workpiece, and according to the available power of the press in use. Steps in the production of a second wheel shaped workpiece having a different shape from thit of Figures 4 and 6 are shown in Figures 7 to 9 of which Figure 7 shows a blank corresponding to that of Figure 2 and Figure s shows the workpiece after a first, central. forging operation.The second \ orkpiece in its final form. after a second forging operation. will be seen from Figure 9 to have a centrally arranged hub 22 with a recess 23. and a solid middle portion 24 cross section of which is thinner than the cross section of a wheel rim 25 forming the outer boundary of the workpiece. WIIAI WE CLAIM IS:

1. A method of forging a wheel-shaped 'vorkpiece ha\-in a central hub joined to a rim portion by an intermediate part. the method employing starting material in the form of a disc-shaped blank and comprising hammer forging carried out in at least two steps using respective die halves for each step and the first step being only on the central portion of the blank and a successive step being only on a successive portion concentric with and immediatelv radically outwardly of the preceding portion of the blank subjected to a forging step. each such step ending with the achieving of the finished form for the associated portion of the workpiece.

2 .A method according to Claim I wherein the workpiece has a finished exter nal diameter of at least 500mm.

3. A method of forging a wheel-shaped workpiece substantially as herein described with reference to Figures 1 to 6 or Figures 7 to 9 of the accompanying drawings.

4. A wheel-shaped workpiece forged by a method of claim 1. 2 or 3.

5. Apparatus for carrying out a method of forging a wheel-shaped workpiece according to any one of claims 1 to 3 including a first pair of finish form die half elements of circular configuration for work ing the central portion of a blank and so shaped as to allow free radially outward movement of workpiece material from be tween these die half elements during use of the same to forge a workpiece and a second pair of finish form die half elements for working an annular portion of the blank radially outwardly of the said central por tion and of which at least one is annular and is so shaped as to inhibit radially inward movement of workpiece material from between the second pair of die half elements during use of the same to forge a workpiece.

6. Appultus fol foryilly a wheel shaped workpiece substantially as herein described with reference to Figures 5 and 6 of the accompanying drawings.