Extruding die for metallic materials

Abstract: An extruding die (1) for metallic materials comprising a male die (2) and a female die (3) is provided with a billet-receiving face (2c) of the male die (2) shaped into convex form. It is possible to reduce breakage frequency of the extruding die (1) by reducing the tensile stress applied on the male die (2) at the time of the extrusion.

Description: This invention relates to an extruding die used for the extrusion of metallic materials. Heretofore, there has been an extruding die which is used for the extrusion of metallic mateials having a structure as shown in Figures 14 to 16 for example. A conventional extruding die 51 shown in the figures is a port-hole die classified into hollow dies and, has a male die 52 and a female die 53. The male die 52 is provided with a mandrel 52a at the top portion thereof and the female die 53 is provided with a die hole 53a in the center portion thereof, and an extruding slit 54 having the shape corresponding to a desired shape of extruded mateial is formed between said mandrel 52a and said die hole 53a. A chamber 55 is formed between the male die 52 and the female die 53, and ports 57 in communication with said chamber 55 are formed at four places between four bridges 52b provided to the male die 52 and an outer peripheral portion 52c of the male die 52 connected with the female die 53 at one end face of the outer peripheral portion 52c. And a container 58 connected to another end face of said outer peripheral portion 52c of the male die 52 is so constructed as to charge a billet 59, a billet-receiving face 52d of the male die 52 sited on the side of the billet 59 is constructed from a flat surface. In performing the extrusion of the billet 59 using the extruding die 51 having a structure of this kind, the billet 59 charged in the container 58 with a dummy block (not shown) placed on the backside of said billet 59 is pressed in the rightward direction in Figure 15 by stem (not shown) . Hereby, the billet 59 is pressed onto the billet-receiving face 52d of the male die 52, and flows in four ports 57 accompanying plastic deformation. Subsequently, the billet 59 is pressed out from the extruding slit 54 after passing through the chamber 55. And hollow extruded material is obtained, which has a desired sectional shape (which is decided against the final shape of the product considering thermal expansion and so on) corresponding to the extruding slit 54 as shown with dotted lines in Figure 14. However, in the conventional extruding die 51 as described above, the billet-receiving face 52d receives heavy pressure in the axial direction when the extrusion of the billet 59 is performed because said billet-receiving face 52d of the male die 52 has a flat surface as described above, and tensile stress is applied on four bridges 52b which hold the mandrel 52a of the male die 52 and form ports 57 at four places, on the side of the chamber 55 (parts shown with letters "T" in Figure 16). Therefore, there is a problem in that a crack in said parts of the bridges 52b on the side of the chamber 55 is apt to develop and sometimes induces breakage of the die. A further extrusion head is known from US 3748885, which discloses an extrusion head having a cone coaxially received in an aperature of a die, the cone being connected to a base portion by webs or bridging portions. The present invention is made in view of the above mentioned problem of the prior art; it is an aim to provide an extruding die for metallic materials possible to decrease breakage frequency of the extruding die by reducing the tensile stress applied on the male die of the extruding die at the time of the extrusion to as low a value as possible in order to prevent a crack, and inhibiting the development of the crack even if the crack occurs. According to the present invention there is provided an extruding die for metallic materials comprising: a female die having a die hole extending therethrough; a male die having a mandrel extending into said die hole with clearance to define an extrusion slit between said mandrel and said die hole; and a plurality of spaced apart bridges connected to said mandrel with end portions engaging said female die and a convex billet-receiving face on a side thereof remote from said female die, characterised in that said bridges each have a decreasing width in the circumferential direction, from said mandrel to said end portion. In the extruding die for metallic materials according to this invention having the aforementioned construction, the billet pressed onto the billet-receiving face shaped into convex form flows foward the extruding slit and is deformed plastically applying pressure to said billet-receiving face in the centripetal direction, and the male die is applied with compression stress, caused by said pressure in the centripetal direction as described above. Consequently, the tensile stress which is produced on the chamber-side on the bridge supporting the mandrel provided to the male die of the extruding die and forming the port in which metallic materials flow is reduced or canceled, and so the occurrence and the development of a crack on the chamber-side of the bridge provided to the male die are inhibited. Embodiments of the invention are described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a front view from the container side illustrating the ring and the male die of the extruding die for metallic materials according to a first comparative embodiment not strictly in accordance with the invention; Figure 2 is a sectional view along section lines A-A shown in Figure 1 ; Figure 3 is a perspective view illustrating the male die shown in Figure 1 ; Figure 4 is a front view from a container side illustrating the ring and the male die of the extruding die for metallic materials according to the first embodiment of this invention ; Figure 5 is a perspective view illustrating the male die shown in Figure 5 ; Figure 6 is a front view from the container side illustrating the ring and the male die of the extruding die for metallic materials according to the second embodiment of this invention ; Figure 7 is a perspective view illustrating the male die shown in Figure 6 ; Figure 8 is a front view from the container side illustrating the ring and the male die of the extruding die for metallic materials according to the third embodiment of this invention ; Figure 9 is a perspective view illustrating the male die shown in Figure 8 ; Figure 10 is a front view from the container side illustrating the ring and the male die of the extruding die for metallic materials according to the fourth embodiment of this invention ; Figure 11 is a perspective view illustrating the male die shown in Figure 10 ; Figure 12 is a front view from the container side illustrating the ring and the male die of the extruding die for metallic materials according to the fifth embodiment of this invention ; Figure 13 is a perspective view illustrating the male die shown in Figure 12 ; Figure 14 is a front view from the container side illustrating the conventional extruding die for metallic materials ; Figure 15 is a sectional view along section lines C-C shown in Figure 14 ; and Figure 16 is a vertically sectional perspective view illustrating the male die shown in Figure 14. Comparative Embodiment 1 A first comparative embodiment of the extruding die for metallic materials which is not in accordance with the invention (owing to the circumferential width variation of the bridges 2c) is shown in Figure 1 to Figure 3. The extruding die 1 is a hollow die used for manufacturing hollow extruded material, and is provided with a male die 2 and a female die 3 held by a back up (not shown), said male die 2 is provided with a mandrel 2a at top portion thereof and said female die 3 is provided a die hole 3a in the center portion thereof, and an extruding slit 5 having the shape corresponding to a desired shape of extruded material is formed between the meandrel 2a and the die hole 3a at the state in which the male die 2 and the female die 3 are located through a locating pin 4. A chamber 6 is formed between the male die 2 and the female die 3, and ports 9 in communication with said chamber 6 are formed at four places between four bridges 2b provided to the male die 2 and the ring 8 disposed in the outer peripheral side of the male die 2 and connected with the female die 3 at the located state through a location pin 7. A container 11 connected to another end face of said ring 8 is constructed so as to loard a billet 12. Furthermore, the respective bridges 2b are formed into curved surfaces so that a billet-receiving face 2c of the male die 2 on the side of the billet 12 may be shaped into nearly half spherical-convex form on the whole, and the ring 8 is so structured that its inner diameter increases gradually toward the side of the female die 3 from the side of the container 11 by shaping taperingly the inner periphery thereof. In case the extrusion of the billet 12 is performed using the extruding die 1 having aforementioned structure, the billet 12 charged in the container 11 with a dummy block (not shown) placed on the backside thereof is pressed in the rightward direction in Figure 2 by a stem (not shown). Hereby, the billet 12 is pressed against the billet-receiving face 2c of the male die 2, and flows in four ports 9 accompanying plastic deformation, subusequently the billet 12 is pressed out in the forward (directly) from the extruding slit 5 after passing through in the chamber 6. Thus, hollow extruded material having a desired scetional shape corresponding to the extruding slit 5 is obtained. And, during said forward extrusion, the respective bridges 2b are formed into curved forms in order that the billet-receiving face 2c of the male die 2 may have a convex surface protruding toward the billet 12 on the whole, the billet 12 pressed by the stem (not shown) applies pressure on the billet-receiving face 2c of the male die 2 in the centripetal derection, therefore, compression stress is applied to the bridge 2b of the male die 2 on the side of chamber 6, so that the occurrecnce of a crack and its development can be inhibited. And, the inner periphery of the ring 8 is shaped taperingly so that the inner diameter of the ring may become gradually larger toward the side of the female die 3 from the side of the container 11 (i.e. the inner periphery spreads out in the ectruding direction). therefore it is possible to decrease residual metal (billet) remaining in the male die 2 after the extrusion, and so improvement of the yield can be produced. Furthermore, since the male die 2 and the ring 8 are constructed from separate members respectively, it is enough if only the damaged member is exchanged, and it is possible to reduce the renewal cost. And it is possible to decrease the man-hour when the male die 2 having aforementioned structure is manufactured by casting comparing with by machining from block materials, and so it is possible to reduce the cost. Second Embodiment A second embodiment of an extruding die for metallic materials and the first embodiment according to this invention is shown in Figure 4 to Figure 5, in the extruding die 1 of this embodiment, top portion of the billet-receiving face 2c of the male die 2 is formed into a parasol-like shape by combining some triangular planes and the respective bridge 2b is formed into crooked shape having some flat surfaces in order that the billet-receiving face 2c may be shaped into polyhedral-convex form on the whole. And the respective bridge 2b is so formed as to reduce gradually its width in the circumferntial direction toward the end part outwardly. Thus, it is possible to inhibite the occurrence of a crack and its development because compression stress is applied to the bridge 2b of the male die 2 on the side of the chamber 6 even when the billet-receiving face 2c is shaped into polyhedral-convex form as a whole by combining polyganal planes (triangular planes and square planes). And because the width in the circumferential direction of the bridge 2b becomes gradually narrower toward the end part of the bridge 2b outwardly and the volume of the respective port 9 is large as compared with that of the first embodiment, the billet flows in the port 9 more smoothly at the time of the extrusion. In addition to above, it is possible to reduce the cost of the die and to facilitete the handling of the die because the male die 2 has a small volume as compared with that of the first embodiment and the weight of the die decreases. Third Embodiment A third embodiment of an extruding die for metallic materials and the second embodiment according to this invention is shown in Figure 6 and Figure 7 in the extruding die 1 of this embodiment, four bridges 2b provided for the male die 2 of the extruding die 1 of the first embodiment shown in Figure 1 to Figure 3 are so structured that the widths in the circumferential direction of the bridges 2b become gradually narrower toward the end parts thereof outwardly. Also in this embodiment, compression stress is applied to the bridge 2b of the male die 2 on the side of the chamber 6 in case of the extrusion, therefore, it is possible to inhibit the occurrence of a crack and its development at this position. And because the width in the circumferential direction of the bridge 2b becomes gradually narrower toward the end part outwardly and the volume of the respective port 9 is large as compared with that of the first embodiment, the billet flows in the port 9 more smoothly at the time of the extrusion. And it is possible to reduce the cost of the die and to facilitate the handling of the die because the male die 2 has a small volume as compared with the case of the first embodiment and the weight of the die decreases. Fourth Embodiment A fourth embodiment of an extruding die for metallic materials and the third embodiment according to this invention is shown in Figure 8 and Figure 9, the extruding die 1 of this embodiment is provided with two bridges 2b to the male die 2, the respective bridges 2b are formed into curved form so that the billet-receiving face 2c may be shaped into nearly arched-convex form as a whole, and the respective bridge 2b in formed so as to reduce the width in the circumferential direction thereof toward the end part outwardly and is provided with a flange 2d along the ci cumferential direction on the both sides of said end part thereof. In case the extrusion of the billet is performed using the extruding die 1 having afore-mentioned structure, the billet pressed by the stem (not shown) is pressed against the billet-receiving face 2c of the male die 2 and flows in two ports 9 accompanying plastic deformation, subsequently the billet is pressed out from the extruding slit after passing through in the chamber 6. In this manner, hollow extruded material having a desired section corresponding to the shape of the extruding slit is obtained. And also in this embodiment, because compression stress is applied to the bridge 2b of the male die 2 on the side of the chamber 6, it is possible to inhibit the occurrence of a crack and its development at this position. As the male die 2 has two bridges 2b and is so formed that the width in the circumferential direction of said bridge 2b becomes gradually narrower toward the end part, the volume of two ports 9 is fully large as compared with the case of the first embodiment and the billet flows in these ports 9 more smoothly of the time of the extrusion. And it is possible to reduce the cost of the die and to facilitate the handling of the die because the male die 2 has a small volume and the weight decreases. Furthermore, if the billet goes into the die hole unevenly at the time of the extrusion, the mandrel 2a of the male die 2 receives the force in the vertical direction in Figure 8. However, the bridge 2b can support said mandrel 2a stably though its width is narrowed down, because said bridge 2b is provided with the flange 2d to the end part of the bridge 2b. In addition to above, it is possible to obtain the sufficient interconnecting strength if the male die 2 and the female die 3 are connected each other by screwing bolts passed through the female die 3 into said flanges 2d. And the respective flanges 2d provided to the end parts of the two bridges 2b are not always necessary to be provided protrudingly on the both sides from the end parts of the bridges 2b, they may be provided respectively on the either sides which are rotational-symmetric with each other from the end parts of the two bridges 2b. Fifth Embodiment A fifth embodiment of an extruding die for metallic materials and the fourth embodiment according to this invention is shown in Figure 10 and Figure 11, the extruding die 1 of this embodiment is provided with the bridges 2b brovided to the male die 2 of the extruding die 1 of the 13th embodiment shown in Figure 8 and Figure 9 at three places on the male die 2, and disposed with respective bridges 2b at almost equal interval so as to shape the billet-receiving face 2c into half spherical-convex form on the whole. Also in this embodiment, it is possible to inhibite the occurrence of a crack and its development because compression stress is applied to the bridge 2b of the male die 2 on the side of the chamber 6. As the male die 2 has three bridges 2b and is so formed that the width in the circumferential direction of said bridge 2b becomes gradually narrower toward the end part, the volume of the ports 9 becomes large and the billet flows in these parts 9 more smoothly at the time of the extrusion, and it is possible to reduce the cost of the die and to facilitate the handling of the die because the volume of the male die 2 becomes small and the weight dereases. Furthermore, because three bridges 2b are provided with the flanges 2d to the end parts thereof respectively, said brings 2b can support the mandrel 2a stably through its width is narrowed down, and it is possible to obtain the sufficient interconnecting strength if the male die 2 and the female die 3 are connected each other by screwing bolts passed through the female die 3 into the flanges 2d. Sixth Embodiment A sixth embodiment of an extruding die for metallic materials and the fifth embodiment according to this invention is shown in Figure 12 and Figure 13, in the extrusion die 1 of this embodiment, the respective end parts of four bridges 2b provided to the male die 2 of the extruding die 1 of the third embodiment shown in Figure 6 and Figure 7 are conneted with a ringshaped flange 2e. Also in this embodiment, because compression stress in applied to the bridge 2b of the male die on the side of the chamber 6, it is possible to inhibit the occurrence of a crack and its development at this position. Although the extruding die 1 of this embodiment is inferior to that of the third embodiment in the cost and the handling facility of the die because the end parts of the bridges 2b are connected with the ringshaped flange 2e, it is possible to support the mandrel 2a under more stable condition. In addition to above, if the male die 2 and the female die 3 are connected each other by screwing bolts passed through the female die 3 into said ringshaped flange 2e, it is possible to connect the both dies firmly. And though the male dies 2 having two to four bridges 2b were shown in aforementioned respective embodiment, the male die used in this invention is not limited to such a type, the male die having bridges more than four may be also used for this invention. Furthermore, the sectional shape of the bridge 2b of the male die used in this invention is not limited to the shape as shown in the respective embodiments. As mentioned above, the extruding die for metallic materials according to this invention has an extruding slit in which a billet pressed onto a billet-receiving face of a male die passes through accompanying plastic deformation between a mandrel provided to said male die and a die hole povided to a female die, and said billet-receiving face of the male die is shaped into convex form. Therefore an excellent effect is obtained that it is possible to inhibite the occurrence of a crack and its development and to contribute to the improvement of productivity by decreasing the breakage frequency of the die because the extruding die is prevented from the applying of tensile stress at the extrusion, and especially. Tensile stress produced at the bridge on the side of chamber is reduced or canceled. Furthermore, in the extruding die according to this invention, it is possible to improve the strength of the die considerably as compared with the conventional extruding die when the distance from the mandrel of the male die to the billet-receiving face is the same as that of the conventional one, and so it is possible to reduce the volume of the die when the strength of the extruding die according to this invention is coordinated with that of the conventional one. Accordingly, another excellent effect is obtained that it is possible to minuture the male die and to facilitate the handling of the die.

Claims: An extruding die (1) for metallic materials comprising: a female die (3) having a die hole (3a) extending therethrough; a male die (2) having a mandrel (2a) extending into said die hole (3a) with clearance to define an extrusion slit between said mandrel (2a) and said die hole (3a); and a plurality of spaced apart bridges (2b) connected to said mandrel (2a) with end portions engaging said female die and a convex billet-receiving face (2c) on a side thereof remote from said female die, characterised in that said bridges (2b) each have a decreasing width in the circumferential direction, from said mandrel (2a) to said end portion. An extruding die for metallic materials as set forth in claim 1, wherein said billet-receiving face (2c) of the male die (2) is shaped into convex form at every bridge (2b) provided on said male die (2). An extruding die for metallic materials as set forth in claim 1, wherein said billet-receiving face (2c) of the male die (2) is shaped into nearly half spherical-convex form. An extruding die for metallic materials as set forth in claim 1, wherein said billet-receiving face (2c) of the male die (2) is shaped into polyhedral-convex form. An extruding die for metallic materials as set forth in claim 1, wherein said male die (2) is provided with four bridges (2b). An extruding die for metallic materials as set forth in claim 1, wherein said male die (2) is provided with three bridges (2b). An extruding die for metallic materials as set forth in claim 1, wherein said male die (2) is provided with two bridges (2b). An extruding die for metallic materials as set forth in claim 1, wherein said bridges (2b) of the male die (2) are provided with flanges (2d) on the end portions respectively. An extruding die for metallic materials as set forth in claim 1, wherein said male die (2) is provided with a ringshaped flange (2e) connecting the end portions of said bridges (2b).

Inventors: OKI YOSHINARI, TANAKA TAKESHI, TUNO RYOJI, YOSHIDA YOSHIHIRO, OKI, YOSHINARI, TANAKA, TAKESHI, TUNO, RYOJI, YOSHIDA, YOSHIHIRO
Applicants: SANKYO ALU IND, SANKYO ALUMINIUM INDUSTRY COMPANY LIMITED
Application year: 1989
Main classification: B21C25
IPC codes: B21C25