US20090126449A1 - Roughly shaped material for forging, forged product, apparatus for molding roughly shaped material for forging, and method of molding roughly shaped material for forging - Google Patents

Abstract

A forging stock formed by extrusion such that its cross section perpendicular to the direction of extrusion varies along the direction of extrusion. The forging stock is cut into portions in the direction of extrusion to be forged individually, each cut portion having cross sections varying along the direction of extrusion. Each cut portion includes a pair of first parallel parts at both ends thereof in the direction of extrusion, a second parallel part, which is between the first parallel parts, and which differs in thickness from said first parallel parts, and oblique parts each of which is between the first parallel parts and the second parallel part.

Description

TECHNICAL FIELD
• The present invention relates to a forging stock, a forged product, and an apparatus and a method for forming said forging stock.
BACKGROUND ART
• Forging stocks in simple shape were commonly used in conventional technologies. An example of them which is disclosed in Patent Document 1 is one in cylindrical shape to be forged into a piston of an internal combustion engine. Another example in simple shape is also disclosed in Patent Document 2. Further another example which is shown in Non-Patent Document 1 (FIG. 6) is a cut piece of steel rod as a hot-forging stock for a crankshaft. In hot forging, the steel rod undergoes preforming, finish forming, burr trimming, and coining sequentially.
Patent Document 1:
• Japanese Patent Laid-open No. 2003-53468 (FIG. 5)
Patent Document 2:
• Japanese Patent Laid-open No. 2000-1794000 (FIG. 15)
Non-Patent Document 1:
• Takeuchi Masahiko et al., “Jidousha wo tsukuru tanzou buhin” Sosei to Kako (Nippon Sosei Kako Gakkaishi) [Forged parts for automobiles, Plasticity and Working], Journal of the Society of Plastic Working of Japan], Vol. 39, No. 455, pp. 29-34.
• Conventional forging stocks in simple shape (such as cylinder) are available at comparatively low prices. However, they pose a problem with low yields due to a large amount of burrs resulting from forging.
DISCLOSURE OF THE INVENTION
• The present invention was completed in view of the foregoing. It is an object of the present invention to provide a forging stock that allows forging at low cost in high yields.
• The forging stock according to the present invention is one which is formed by extrusion such that its cross section (perpendicular to the direction of extrusion) varies along the direction of extrusion.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1 is a perspective view showing the forging stock pertaining to Embodiment 1 of the present invention.
• FIG. 2 is a perspective view showing a portion cut from said forging stock.
• FIG. 3 is a front view showing a portion of said forging stock.
• FIG. 4 is a conceptual diagram showing an important part of the apparatus used to form said forging stock and also showing how forming is accomplished, (a) illustrating a fixed die (in perspective view), (b) illustrating a second parallel part being extruded, (c) illustrating an oblique part being extruded, and (d) illustrating a first parallel part being extruded.
• FIG. 5 is a graph showing the relation between the elapsed time of extrusion and the length of each part, which is observed when said forging stock is extruded.
• FIG. 6 illustrates a forged product in front view, plan view, and side view.
• FIG. 7 is a perspective view (likeFIG. 1) showing the forging stock pertaining to another embodiment of the present invention.
• FIG. 8 is a front view showing the forging stock pertaining to another embodiment of the present invention.
• FIG. 9 is a diagram showing the movable die used to extrude the forging stock.
• FIG. 10 is a perspective view (likeFIG. 1) showing the forging stock pertaining to another embodiment of the present invention.
• FIG. 11 is a conceptual diagram showing an important part of the apparatus used to form said forging stock and also showing how forming is accomplished, (a) illustrating a fixed die (in perspective view), (b) illustrating a second parallel part being extruded, (c) illustrating an oblique part being extruded, and (d) illustrating a first parallel part being extruded.
• FIG. 12 is a perspective view showing the forging stock pertaining to Embodiment 2 of the present invention.
• FIG. 13 is a perspective view showing a portion of said forging stock.
• FIG. 14 is a perspective view showing a fixed die and movable dies installed in the apparatus used to form the forging stock.
• FIG. 15 is a diagram showing the process of forming the forging stock, (a) illustrating a first parallel part being extruded, (b) illustrating an oblique part being extruded, (c) illustrating a second parallel part being extruded, (d) illustrating an oppositely oblique part being extruded, (e) illustrating again a first parallel part being extruded.
• FIG. 16 is a perspective view (likeFIG. 13) showing the forging stock pertaining to another embodiment of the present invention.
• FIG. 17 is a perspective view showing a fixed die and movable dies installed in the apparatus used to form the forging stock.
• FIG. 18 is a perspective view (likeFIG. 13) showing the forging stock pertaining to another embodiment of the present invention.
• FIG. 19 is a perspective view showing a fixed die and movable dies installed in the apparatus used to form the forging stock.
BEST MODE FOR CARRYING OUT THE INVENTION
• The following concerns the best mode for carrying out the invention which is described in detail with reference to the accompanying drawings.
Embodiment 1
• FIG. 1 is a perspective view showing the forging stock pertaining to Embodiment 1 of the present invention. The forging stock10 (thestock10 for short hereinafter) is formed by extrusion in the direction of arrow A.
• Thestock10 is cut into a plurality ofportions11 . . .11. In other words, thestock10 is a continuously formed body consisting ofportions11 . . .11 to undergo forging.FIG. 2 is a perspective view showing aportion11 cut from the stock. Theportion11 shown inFIG. 2 undergoes forging by means of a forging press.
• Theportion11 has a pair of firstparallel parts13 and13, a second parallel part15 (differing in thickness from said firstparallel parts13 and13), and a pair ofoblique parts17 and17. All of these parts are arranged parallel to the direction of extrusion. To be specific, the firstparallel parts13 and13 are at both ends along the direction of extrusion, the secondparallel part15 is between the firstparallel parts13 and13, and theoblique parts17 and17 are between the firstparallel parts13 and13 and the secondparallel part15.
• The firstparallel parts13 and13 and the secondparallel part15 have a uniform thickness along the direction of extrusion, and theoblique parts17 and17 vary in thickness along the direction of extrusion. Theoblique parts17 and17 are formed such that they are as thick as the firstparallel part13 at their ends joining the first parallel parts and also as thick as the secondparallel part15 at their ends joining the second parallel part.
• In this embodiment, the secondparallel part15 is thicker than the firstparallel parts13 and13. Theoblique parts17 and17 and the secondparallel part15 have a hexagonal cross section viewed in the widthwise direction. Incidentally, “thickness” as used herein means the thickness in vertical direction shown inFIG. 3. The distance along the horizontal direction inFIG. 3 is referred to as width in the cross section perpendicular to the direction of extrusion.
• Theportion11 is so formed as to be uniform in width but varied in thickness along the direction of extrusion as mentioned above. In other words, theportion11 has a cross section which continually varies in one direction (or the vertical direction inFIG. 3) perpendicular to the direction of extrusion, or theportion11 has a cross section which changes along the direction of extrusion. The top shown inFIG. 3 is surrounded by edge lines perpendicular to the direction of extrusion, and the edge lines remain unchanged along the direction of extrusion. Likewise, the bottom inFIG. 3 is surrounded by edge lines perpendicular to the direction of extrusion, and the edge lines remain unchanged along the direction of extrusion. Theportion11 is formed such that the edge lines mentioned above move up and down while keeping their configuration in going along the direction of extrusion. The fact that the cross section changes only in one direction (vertical direction) is due to the method of extrusion mentioned later.
• On the other hand, theportion11 has (in any cross section perpendicular to the direction of extrusion)thick parts21 and21,thin part23, andtransitional parts25 and25 which vary in thickness along the widthwise direction. Thethick parts21 and21 are at both ends in the widthwise direction, and between them is thethin part23. Thetransitional parts25 and25 are formed between thethick parts21 and21 and thethin part23 such that the thickness is gradually changes along the widthwise direction. Therefore, the cross section perpendicular to the direction of extrusion consists of thick end parts and a thin intermediate part. In addition, theportion11 is symmetrical about the horizontal axis.
• Thestock10 mentioned above is of light metal. To be specific, the light metal is an aluminum alloy designated as JIS 4000, which includes, for example, alloy No. 4032. This aluminum alloy is one with a high silicon content suitable for swaging. It is more ductile than a cast stock of the same material. Therefore, it easily undergoes deformation processing.
• The following illustrates the formingapparatus30 for thestock10 with reference toFIGS. 4(a) to4(d), which schematically show the important parts thereof. As shown in these figures, the formingapparatus30 has a fixeddie32 and a pair of movable dies34 and34.
• The fixeddie32, which is firmly attached to one end of a billet container (not shown), has a forminghole36 that extends in the direction of extrusion. The forminghole36 is so shaped as to change in cross section in going in the direction of extrusion. That is, the cross section perpendicular to the direction of extrusion has a width which remains constant in direction Y inFIG. 4(a) and a width which gradually increases in direction X inFIG. 4(a).
• The forminghole36 hasguide grooves38 and38 which guide the movable dies34 and34. Theguide grooves38 and38 are arranged at the ends (in direction Y) of the forminghole36. Theguide grooves38 and38 correspond to the movable dies34 and34, respectively. Theguide grooves38 and38 are oblique such that their distance gradually increases in going in the direction of extrusion. Theguide grooves38 and38 each have the same oblique angle (α) to the direction of extrusion.
• There are two movable dies34 and34, which are symmetrically arranged, as shown inFIGS. 4(b) to4(d). Each of the movable dies34 and34 is shaped flat and has the slidingface40 and the formingface42. The movable dies34 and34 are placed in the forminghole36 of the fixed die32 such that they lie at right angles to the direction of extrusion, and they are fitted into theguide grooves38 and38 of the fixeddie32. The movable dies34 and34 face each other in a direction perpendicular to the direction of extrusion, so that they permit thestock10 to be extruded straight. In this state, the slidingface40 of themovable die34 slides on theguide face44 of the forminghole36, and themovable die34 moves along theguide groove38 in a direction oblique to the direction of extrusion. The slidingface40 is oblique to the formingface42, and the oblique angle is equal to that (to the direction of extrusion) of theguide face44. The forming faces42 and42 of the movable dies34 and34 face each other parallel to the direction of extrusion. The gap between the forming faces42 and42 permits the billet to pass through or to be extruded into thestock10.
• The movable dies34 and34 are driven by a drive mechanism (not shown), which is so constructed as to move the movable dies34 and34 simultaneously while keeping them facing each other in the direction perpendicular to the direction of extrusion.
• The formingapparatus30 is operated in the following way to form thestock10. First, the container is charged with a billet of aluminum alloy. The billet is extruded by a stem (not shown) from the container into the forminghole36. The billet is supplied to the forminghole36 from above (FIG. 4(a)) and extruded in the direction of hollow arrow (FIG. 4(b)).
• During extrusion, the movable dies34 and34 are moved (driven) up and down along theguide grooves38 and38. When the movable dies34 and34 are positioned (away from each other) at the downstream end of theguide grooves38 and38, the second parallel part15 (which is thick) is extruded from the forminghole36. As shown inFIG. 4 (c), as the movable dies34 and34 are moved upstream by the drive mechanism while extrusion is going on, the gap between the movable dies34 and34 gradually decreases, with the result that thestock10 being extruded gets thin accordingly. Thus theoblique part17 is formed.
• Then, the movable dies34 and34 are positioned at the upstream end of theguide grooves38 and38 as shown inFIG. 4(d), so that the firstparallel part13 of the stock10 (which is thin and has a uniform thickness) is extruded. The foregoing steps are repeated to extrude thestock10 shown inFIG. 1.
• During extrusion, the stem is moved at a constant rate. Therefore, if the gap between the movable dies34 and34 are held constant, thestock10 is extruded at a constant rate as shown inFIG. 5. Therefore, the length of thestock10 extruded can be calculated from the time of extrusion, and hence the time of extrusion is used to control the timing to start moving the movable dies34 and34. In addition, when the movable dies34 and34 are moved gradually, the amount of movement determines the amount of extrusion. Thus it is possible to calculate the moving rate of the movable dies34 and34 according to the oblique angle of theoblique parts17 and17. This in turn makes it possible to obtain the desired length by controlling the moving rate of the movable dies34 and34. Incidentally, La, Lb, and Lc inFIG. 5 correspond respectively to the length of the secondparallel part15, the length of theoblique parts17 and17, and the length of the firstparallel parts13 and13, measured in the direction of extrusion.
• Thestock10 thus obtained is made by forging into a forgedproduct50 as shown inFIG. 6. This forgedproduct50 has thick discoid parts at both ends and a thin part held between them, which has rib-like parts52. The lengthwise direction of the forgedpart50 is perpendicular to the direction of extrusion. Forging to produce this forgedproduct50 gives rise to only a small amount ofburr54 as shown inFIG. 6.
• As mentioned above, thestock10 pertaining to Embodiment 1 is formed by extrusion. Extrusion allows efficient and economical production of thestock10 having cross sections (perpendicular to the direction of extrusion) varying along the direction of extrusion. Thestock10 with varying cross sections has a shape resembling the forgedproduct50. Therefore, forging on thestock10 can be accomplished in high yields with a small amount of burr. This leads to efficient production and forging of thestock10 and makes it possible to form thethin part23 at the time of forging.
• Embodiment 1 is intended such that the extrudate is divided intodiscrete parts11, each of which is used as thestock10 for forging. Thus it is possible to produce thestock10 one by one continuously and efficiently. Each of thediscrete parts11 allows efficient forging with a small amount of burr.
• Embodiment 1 is also intended such that the forgedproduct50 has the lengthwise direction parallel to the cross section perpendicular to the direction of extrusion. Thus the forgedproduct50 may vary in thickness in this direction. Thestock10 can be extruded in the direction perpendicular to the lengthwise direction of the forgedproduct50. In this way it is possible to improve the efficiency of extrusion of thestock10 for the forgedproduct50 in elongated thin shape.
• The formingapparatus30 according to Embodiment 1 is designed such that the movable dies34 and34 are moved when thestock10 is formed by extrusion. The resulting extrudate has cross sections (perpendicular to the direction of extrusion) varying along the direction of extrusion. In addition, the formingapparatus30 is designed such that the movable dies34 and34 are moved obliquely with respect to the direction of extrusion. This design does not need sealing unlike conventional movable dies to be moved in the direction perpendicular to the direction of extrusion. Therefore, this design permits the movable dies34 and34 to slide on the fixed die32 with a minimum of wear. The movable dies34 and34, which are arranged in the direction perpendicular to the direction of extrusion, permit thestock10 to be extruded straight, which contributes to the dimensional accuracy of thestock10.
• Although Embodiment 1 is intended to produce an extrudate which is divided intodiscrete parts11 . . .11 (each serving as the stock10), it may be so modified as to extrude a single forging stock.
• According to Embodiment 1, thestock10 is constructed such that the step between each of thethick parts21 and21 and thethin part23 is the same in both the upper part and the lower part. However, this construction may be modified such that the step is different between the upper part and the lower part as shown inFIGS. 7 and 8. To be specific, Embodiment 1 in its original form employs a pair of symmetrical movable dies34 and34 so that the step is the same in both the upper part and the lower part; however, Embodiment 1 in its modified form employs a pair of unsymmetrical dies34 and34 (as shown inFIG. 9) so that the step in thestock10 is different between the upper part and the lower part. The movable dies34 and34 in the latter case differ from each other in the shape (step) of the forming faces42 and42. The same fixed die32 as shown inFIG. 4(a) can be used for the unsymmetrical dies and34.
• Thestock10 in Embodiment 1 in its modified form may be formed such that its upper surface is rugged (as in the case of Embodiment 1 in its original form) but its lower surface is flat, as shown inFIG. 10. To be specific, thestock10 has a pair of the firstparallel parts13 and13, the second part15 (which differs in thickness from the firstparallel parts13 and13), and a pair of theoblique parts17 and17, all of which have the common lower surface which is flat. Thus, the upper surface of thestock10 has the same shape as that of thestock10 in Embodiment 1 in its original form.
• Thestock10 in the above-mentioned shape can be extruded by using the fixeddie32 and the movable dies34 and34 as shown inFIGS. 11(a) to11(d). The fixed die has twoguide grooves38 and38. One of them is constructed in the same way as in Embodiment 1 (in its original form mentioned above) and the other of them is parallel to the direction of extrusion. The paired movable dies34 and34 differ in shape from each other. One of them is identical with that in Embodiment 1 (in its original form mentioned above) and the other of them has the slidingface40 and the formingface42 which are parallel to each other. When the latter fitted into theguide groove38, the slidingface40 and the formingface42 are parallel to the direction of extrusion. The forming face42 (in the latter case), which is flat, forms the lower surface of thestock10. As an alternative, themovable die34 to be fitted into theguide groove38 parallel to the direction of extrusion may be replaced by a die which has the same length as the fixed die32 in the direction of extrusion and which does not move in the direction of extrusion.
• Incidentally, the secondmovable die34 may have its formingface42 formed in stepped shape as in Embodiment 1 in its original form, so that the resultingstock10 has thehollow part46 at the center (in the widthwise direction) on its lower surface, as indicated by a dotted line inFIG. 10. Thehollow part46 extends continuously with a constant depth in the direction of extrusion.
Embodiment 2
• FIG. 12 is a perspective view showing thestock10 pertaining to embodiment 2. Thestock10 differs from that in Embodiment 1. It is formed by extrusion in such a way that the direction of extrusion coincides with the lengthwise direction of the forgedproduct50. In the following about thestock10, constituents common in Embodiments 1 and 2 are named alike without repetition of their description.
• Thestock10 pertaining to Embodiment 2 is cut into a plurality ofportions11 . . .11, which subsequently undergo forging individually. One of thecut portions11 . . .11 is illustrated inFIG. 13. It has a pair of firstparallel parts13 and13, a second parallel part15 (differing in thickness from said firstparallel parts13 and13), and a pair ofoblique parts17 and17. The firstparallel parts13 and13 are at both ends in the direction of extrusion, the secondparallel part15 is between the firstparallel parts13 and13, and theoblique parts17 and17 are between the firstparallel parts13 and13 and the secondparallel part15.
• The firstparallel parts13 and13 and the secondparallel part15 have a uniform thickness along the direction of extrusion, and the latter is thinner than the former. The firstparallel parts13 and13, the secondparallel part15, and theoblique parts17 and17 all have an octagonal cross section perpendicular to the direction of extrusion.
• Thestock10 is of light metal. To be specific, the light metal is an aluminum alloy designated as JIS 4000, which includes, for example, alloy No. 4032. This aluminum alloy is one with a high silicon content suitable for swaging. It is more ductile than a cast stock of the same material. Therefore, it easily undergoes deformation processing.
• FIG. 14 shows theapparatus30 used to form by extrusion thestock10 pertaining to Embodiment 2. Theapparatus30 has a fixeddie32 and a pair of movable dies34 and34. The fixed die32 has a forminghole36 which gradually widens along the direction of extrusion. The forminghole36 has a pair ofguide grooves38 and38, which are inclined an angle of β equally to the direction of extrusion. Into theguide grooves38 and38 are fitted the movable dies34 and34, so that the former permit the latter to move along them. As the movable dies34 and34 move, their slidingfaces40 and40 slide on the guide faces44 and44 of the forminghole36, so that the billet passes through the opening between the forming faces42 and42 to give the extrudedstock10. The movable dies34 and34 are shaped symmetrically.
• During extrusion, the movable dies34 and34 move as shown inFIG. 15(a) to15(e). The movable dies34 and34 positioned at the downstream end of the forminghole36 as shown inFIG. 15(a) form the firstparallel part13 which is uniformly thick. Having moved upstream as shown inFIG. 15(b), the movable dies34 and34 form theoblique part17. The resultingstock10 has a cross section symmetrical to its axis because theguide grooves38 and38 are equally inclined an angle of β. With their position remaining at the upstream end as shown inFIG. 15(c), the movable dies34 and34 form the secondparallel part15 which is uniformly thick. Having moved downstream as shown inFIG. 15(d), the movable dies34 and34 form theoblique part17. Having returned to the downstream end as shown in FIG.15(e), the movable dies34 and34 form the firstparallel parts13 and13. Extrusion with the foregoing steps repeated gives rise to thestock10.
• Thestock10 thus obtained can be forged into a forgedproduct50 shown inFIG. 6. Forging in this case is carried out (unlike forging in Embodiment 1) in such a way that the lengthwise direction of thestock10 coincides with that of the forgedproduct50.
• The fact that the direction of extrusion coincides with the lengthwise direction of the forgedproduct50 is the advantage of Embodiment 2 that the directionality of the stock contributes to the lengthwise characteristics of the forgedproduct50.
• Incidentally, Embodiment 2 is intended to produce thestock10 which is symmetrical with respect to its axis. However, thestock10 may also be shaped such that theoblique parts17 and17 are inclined differently in the thickness direction (or the vertical direction) as shown inFIG. 16. Thestock10 shaped in this manner is obtained by using the fixed die32 whose forminghole36 has theguide grooves38 and38 differing in oblique angle as shown inFIG. 17. Into theguide grooves38 and38 are fitted the paired movable dies34 and34 whose sliding faces40 and40 have different oblique angles indicated by β and γ. The movable dies34 and34 are driven in the same way as that of the embodiment 2.
• Theoblique parts17 and17 may be shaped such that one side is oblique to the axis and the other side is not oblique, as shown inFIG. 18. Thestock10 in such a modified shape may be formed by using the fixed die32 as shown inFIG. 19. The fixed die32 has theguide grooves38 and38, one of which is parallel to the direction of extrusion and the other of which is oblique at an angle of β to the direction of extrusion. The fixed die32 also has the guide faces44 and44 along which the sliding faces40 and40 of the movable dies34 and34 move. In this case, themovable die34 fitting into theguide groove38 parallel to the direction of extrusion may be replaced by a stationary die which is as long as the fixed die32 in the direction of extrusion. The fixed die32 modified in this manner has only oneguide groove38 at the right side. Embodiment 2 is identical with Embodiment 1 in structure, functions, and effects whose description is omitted.
SUMMARY OF THE INVENTION
• The present invention is summarized as follows.
• (1) The present invention permits a forging stock to be formed by extrusion economically and efficiently. The resulting forging stock varies in cross section perpendicular to the direction of extrusion. The forging stock with varied cross sections closely resembles the forged product in shape, and hence it can be forged in high yields with a minimum amount of burr. This contributes to efficient stock production and efficient forging. Thus, the present invention provides forging stocks capable of economical and efficient forging.
  (2) The forging stock mentioned above should preferably be cut into portions (in the direction of extrusion) to be forged individually. Each cut portion should preferably have cross sections varying along the direction of extrusion.
• In this way the forging stocks can be produced continuously and efficiently by extrusion. Each forging stock can be forged in high yields with a minimum of burr.
• (3) Each cut fraction mentioned above may have a pair of parallel parts at both ends thereof in the direction of extrusion, a second parallel part which is between said first parallel parts and which differs in thickness from said first parallel parts, and oblique parts each of which is between said first parallel parts and said second parallel part.
  (4) The forging stock mentioned above may be formed in such a way that the width remains constant along the direction of extrusion and the thickness varies along the direction of extrusion for the thick part, thin part, and transitional part between them.
• The forging stock formed in this manner may be forged in such a way that the direction along the cross section coincides with the lengthwise direction of the forged product. The resulting forged product varies in thickness along the lengthwise direction. Forging in this manner causes the stock to be extruded in the direction perpendicular to the lengthwise direction of the forged product. Thus the forging stock for a forged product in thin long shape can be produced efficiently by extrusion.
• (5) The forging stock mentioned above may be of light metal.
  (6) The present invention covers a forged product obtained by forging from the forging stock mentioned above.
  (7) The present invention covers an apparatus for forming the forging stock mentioned above. The apparatus consists of a fixed die, movable dies, and a drive mechanism. The fixed die has a forming hole provided with guide grooves extending obliquely to the direction of extrusion. The movable dies are arranged in the forming hole, and each of them has a forming face. The drive mechanism moves the movable dies along the guide grooves.
• The forming apparatus according to the present invention works in such a way that the movable dies move while the forging stock is being extruded, so that the forging stock varies in cross section (perpendicular to the direction of extrusion) along the direction of extrusion. In addition, the movable dies move obliquely to the direction of extrusion. This structure obviates the necessity of applying sealing force to the movable dies unlike the conventional structure in which the movable dies move in the direction perpendicular to the direction of extrusion. This protects the movable dies sliding on the fixed die from wearing.
• (8) The present invention covers a method for forming the forging stock mentioned above. The method employs a fixed die and movable dies. The fixed die has a forming hole having guide grooves extending in the direction oblique to the direction of extrusion. The movable dies, each having a forming face, are arranged in the forming hole. During extrusion, the movable dies move along the guide grooves. Extrusion in this manner gives the forging stock (mentioned above) whose cross section perpendicular to the direction of extrusion varies along the direction of extrusion.
EXPLOITATION IN INDUSTRY
• The present invention is useful in the field of forging.

Claims (8)

1. A forging stock which is formed by extrusion such that its cross section perpendicular to the direction of extrusion varies along the direction of extrusion.

2. The forging stock defined inclaim 1 which is cut into portions in the direction of extrusion to be forged individually, each cut portion having cross sections varying along the direction of extrusion.

3. The forging stock as defined inclaim 2, wherein each cut portion has a pair of first parallel parts at both ends thereof in the direction of extrusion, a second parallel part which is between said first parallel parts and which differs in thickness from said first parallel parts, and oblique parts each of which is between said first parallel parts and said second parallel part.

4. The forging stock as defined inclaim 1, which is formed in such a way that the width remains constant along the direction of extrusion and that thick parts, a thin part, and transitional parts between said thick parts and said thin part are formed in any cross section perpendicular to the direction of extrusion.

5. The forging stock as defined inclaim 1, which is of light metal.

6. A forged product which is obtained by forging from the forging stock defined inclaim 1.

7. An apparatus for forming the forging stock defined inclaim 1, said apparatus comprising a fixed die, movable dies, and a drive mechanism, said fixed die having a forming hole provided with guide grooves extending obliquely to the direction of extrusion, said movable dies being arranged in the forming hole, and each of them having a forming face, said drive mechanism moves the movable dies along the guide grooves.

8. A method for forming the forging stock defined inclaim 1, said method employing a fixed die and movable dies, said fixed die having a forming hole with guide grooves extending in the direction oblique to the direction of extrusion, said movable dies, each having a forming face, being arranged in the forming hole, such that during extrusion, said movable dies move along said guide grooves and extrusion gives the forging stock whose cross section perpendicular to the direction of extrusion varies along the direction of extrusion.

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