JP2016147278A - Hollow shape material forming extrusion die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow shape material forming extrusion die capable of improving fatigue durability.SOLUTION: An extrusion die 10 includes a male mold 20 for forming an inside shape of a hollow shape material 1 and a female mold 30 for forming an outside shape of the hollow shape material 1. The male mold 20 has a holder 25 formed of a fitting hole 25C and a spider 22 fitted into the fitting hole 25C. The spider 22 is formed of a mandrel 23 corresponding to the inside shape of the hollow shape material 1 and a plurality of bridge parts 24a to 24d protruded outward from the outer circumferential surface of the mandrel 23. An inner circumferential surface 25D of the fitting hole 25C is shrink-fitted to a tip surface 24C of each bridge part 24a to 24d. An interference between the inner circumferential surface 25D of the fitting hole 25C and the tip surface 24C of each bridge part 24a to 24d is 0.4 to 0.6% of an inner diameter of the fitting hole 25C.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an extrusion die for forming a hollow shape for forming a hollow shape.

  The extrusion process of the aluminum alloy has a high degree of freedom in cross-sectional shape, and is excellent for obtaining a hollow shape material to be extruded. In recent years, there has been an increasing demand for hollow shapes made of high-strength aluminum alloys such as so-called 7000 series such as 7075, 7N01, and 7003.

An extrusion die for forming a hollow shape by extruding a billet made of an aluminum alloy from the upstream side to the downstream side, a male die for shaping the inner shape of the hollow shape member, a female die for shaping the outer shape of the hollow shape member, It has.
The male type of the spider-type extrusion die has a holder in which a fitting hole is formed and a spider that is fitted in the fitting hole. The spider is formed with a mandrel corresponding to the inner shape of the hollow shape member and a plurality of bridge portions protruding outward from the outer peripheral surface of the mandrel, and the front end surface of each bridge portion is a fitting hole. It is joined to the inner peripheral surface.

When a billet made of a high-strength aluminum alloy is extruded by the above-described extrusion die, the pushing force of the billet is increased. Therefore, a large pressing force is applied from the billet to the bridge portion during extrusion molding, and the tensile strain of the bridge portion increases.
If the tensile strain of the bridge portion increases during extrusion, the number of times that the bridge portion can be used decreases.
Therefore, as a conventional extrusion die, there is one in which an initial load (compression force) is applied to the bridge portion by shrink fitting the front end surface of each bridge portion and the inner peripheral surface of the fitting hole (for example, , See Patent Document 1). As described above, by causing the bridge portion to have a compressive strain due to shrink fitting, the tensile strain generated in the bridge portion during extrusion molding can be reduced.

JP 2013-059792 A

  In the above-described conventional extrusion die, if the compressive strain of the bridge portion due to shrink fitting is too large, there is a problem in that the durability of the bridge portion when the extrusion molding is repeated decreases.

  This invention makes it a subject to provide the extrusion die for shaping | molding a hollow shape material which can solve an above described problem and can improve fatigue durability.

  In order to solve the above-mentioned problems, the present invention is a hollow shape forming extrusion die for forming a hollow shape shape by extruding a billet made of an aluminum alloy from an upstream side to a downstream side. The extrusion die for forming a hollow shape member includes a male die that shapes the inner shape of the hollow shape member, and a female die that shapes the outer shape of the hollow shape member. The male type has a holder in which a fitting hole is formed and a spider that is fitted into the fitting hole. The spider is formed with a mandrel corresponding to the inner shape of the hollow shape member, and a plurality of bridge portions protruding outward from the outer peripheral surface of the mandrel. The inner peripheral surface of the fitting hole and the front end surface of each bridge portion are shrink-fitted. It is desirable that the tightening margin between the inner peripheral surface of the fitting hole and the front end surface of each bridge portion is set to 0.4% to 0.6% of the inner diameter of the fitting hole.

As in the present invention, by setting the tightening margin between the inner peripheral surface of the fitting hole of the holder and the tip surface of each bridge portion of the spider, the bridge portion is caused by the tensile strain and shrinkage that are generated in the bridge portion during extrusion molding. The total strain, which is the value of the difference from the compressive strain generated in, can be made sufficiently small.
That is, in the present invention, the tensile strain generated in the bridge portion of the spider during extrusion molding can be reduced, and the compressive strain of the bridge portion due to shrink fitting can be suppressed.
Thereby, in this invention, since the durable frequency | count of a bridge | bridging part when extrusion molding is repeated can be increased, the fatigue durability of an extrusion die can be improved.

  In the above-described extrusion die for forming a hollow member, the thickness of the hole wall in the radial direction of the fitting hole is set to 60% to 90% of the radius of the fitting hole to sufficiently secure the strength of the holder. By doing so, the fitting hole and each bridge part can be reliably joined by shrink fitting.

  In the extrusion die for forming a hollow shape material described above, a pair of bridge side surfaces parallel to the extrusion direction of the billet are formed on both side surfaces of the bridge portion, and the minimum width between the two bridge side surfaces is By setting it to 30% to 50% of the radius of the fitting hole and sufficiently securing the strength of the bridge portion, the fitting hole and each bridge portion can be reliably joined by shrink fitting.

  According to the extrusion die for forming a hollow shape material of the present invention, the number of times of durability when the extrusion molding is repeated can be increased, and the fatigue durability can be improved, so that the life can be extended.

It is the top view which showed the extrusion die which concerns on embodiment of this invention. It is sectional drawing along the II line | wire of FIG. It is a section perspective view showing a male type and a female type concerning an embodiment of the present invention. It is sectional drawing which showed the state before shrink-fitting the holder and spider which concern on embodiment of this invention. It is sectional drawing which showed the step which inserts a spider in the holder which concerns on embodiment of this invention. It is the top view which showed the spider which concerns on embodiment of this invention. It is a perspective view which shows the spider which concerns on embodiment of this invention. (A) is sectional drawing along the II-II line of FIG. 6, (b) is the figure which looked at the inner side shaping | molding protrusion part of (a) from the downstream. (A) is the longitudinal cross-sectional view along the III-III line of FIG. 6, (b) is the figure which looked at the inner side shaping | molding protrusion part of (a) from the downstream. It is the top view which showed the female type | mold which concerns on embodiment of this invention. It is sectional drawing along the IV-IV line of FIG. It is the top view which showed the spider which concerns on embodiment of this invention, and is the figure which showed the relationship between the minimum width between the both bridge | bridging side surfaces of a bridge part, and the radius of a fitting hole. It is the perspective view which showed the hollow shape shape | molded by the extrusion die which concerns on embodiment of this invention. (A) is a graph showing the relationship between the total strain and shrinkage fit, (b) is a graph showing the relationship between the total strain and the service life.

Embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 2, the extrusion die 10 of this embodiment is used for extrusion molding of a high-strength alloy, particularly a hollow material made of a high-strength aluminum alloy such as a so-called 7000 series.
The extrusion die 10 of this embodiment is a spider die type, and can extrusion-mold the hollow shape material 1 having a cross-sectional shape (ladder shape) as shown in FIG.

  The hollow shape member 1 includes a pair of long side walls 1A and 1A, a pair of short side walls 1B and 1B that connect ends of the long side walls 1A and 1A in the longitudinal direction, and both short side walls 1B and 1B. And two partition walls 1C and 1C arranged at equal intervals. Three spaces 1S, 1S, 1S are formed by two partition walls 1C, 1C inside the hollow shape member 1 of the present embodiment.

As shown in FIG. 2, the extrusion die 10 is configured to extrude a billet B made of an aluminum alloy from the upstream side in the extrusion direction A to the downstream side to form the hollow shape member 1.
The extrusion die 10 includes a male die 20 that molds the inner shape of the hollow shape member 1, a female die 30 that shapes the outer shape of the hollow shape member 1, and a back die 40 that holds the female die 30. . The male mold 20, the female mold 30, and the back die 40 are connected.
In addition, on the upstream side of the male mold 20, a billet extrusion device 60 in which the billet B is accommodated is disposed. Billet B is supplied from the billet extrusion device 60 to the extrusion die 10.

  The male mold 20 and the female mold 30 are positioned by a knock pin 47 and two positioning pins 46 and 46 (see FIG. 1). The male mold 20, the female mold 30, and the back die 40 are connected by two connecting bolts 45, 45 (see FIG. 1).

  As shown in FIGS. 2 and 3, the male mold 20 includes a holder 25 in which a fitting hole 25C is formed, and a spider 22 that is fitted in the fitting hole 25C. The holder 25 holds the outer periphery of the spider 22.

  As shown in FIG. 1, the holder 25 is formed in a circular shape in plan view. A circular fitting hole 25C is formed in the center of the holder 25 in plan view. As shown in FIG. 2, the fitting hole 25 </ b> C penetrates from the upper end surface 25 </ b> A to the lower end surface 25 </ b> B of the holder 25.

As shown in FIG. 4, the radial thickness L3 of the hole wall portion of the fitting hole 25C of the holder 25 is set between 60% and 90% of the radius L1 / 2 of the fitting hole 25C.
The inner diameter L1 of the fitting hole 25C is the inner diameter of the end portion on the upper end face 25A side of the fitting hole 25C of the holder 25 that is not heated.
Further, the radial thickness L3 of the hole wall portion of the fitting hole 25C is a radial thickness at a substantially intermediate position in the height direction of the holder 25.

  As shown in FIG. 4, the inner peripheral surface 25D of the fitting hole 25C is continuous with the tapered surface portion 25m that gradually increases in diameter from the end portion on the upper end surface 25A side toward the lower end surface 25B side, and the tapered surface portion 25m. Thus, a cylindrical surface portion 24n extending to the lower end surface 25B is formed. The inclination angle α of the tapered surface portion 25m with respect to the axial direction of the fitting hole 25C is set, for example, from 0.5 ° to 1 °.

As shown in FIG. 1, the spider 22 includes a mandrel 23 and a plurality of bridge portions 24 that protrude outward from the side surface of the mandrel 23. As shown in FIG. 2, the mandrel 23 is formed in a shape corresponding to the inner shape of the hollow shape member 1.
Each bridge portion 24 is a portion that supports the mandrel 23. When distinguishing each bridge part 24, as shown in FIG. 1, it calls the 1st bridge part 24a, the 2nd bridge part 24b, the 3rd bridge part 24c, and the 4th bridge part 24d.
Note that the four spaces between the bridge portions 24a to 24d serve as billet B introduction spaces S, respectively.

Each bridge part 24a-24d is arrange | positioned so that it may become a substantially X shape from the side surface of the mandrel 23. FIG.
As shown in FIG. 6, the distance between the outer end portion of the first bridge portion 24a and the outer end portion of the fourth bridge portion 24d, and the outer end portion of the second bridge portion 24b and the outer end portion of the third bridge portion 24c. The distance between the outer end portion of the first bridge portion 24a and the outer end portion of the second bridge portion 24b, and the distance between the outer end portion of the third bridge portion 24c and the outer end portion of the fourth bridge portion 24d. Is formed large.

  Each of the bridge portions 24 a to 24 d extends linearly from the side surface of the mandrel 23 toward the outside. The width of the end portions of the bridge portions 24a to 24d (the circumferential width of the spider 22) gradually increases toward the outside. Therefore, each bridge part 24a-24d is formed so that the width | variety of the front-end | tip part (outer end part) may become the maximum, and the width | variety of the substantially intermediate part of the extension direction may become the minimum in planar view of FIG.

As shown in FIG. 7, a tapered billet guide surface 24 </ b> E that is inclined so as to increase in width from the upper surface 22 </ b> A toward the downstream side is formed at the corner between the upper surface 22 </ b> A and the side surface of the spider 22.
That is, the billet guide surface 24E is formed in the upper part of each bridge part 24a-24d. In each of the bridge portions 24a to 24d, a bridge side surface 24G parallel to the extrusion direction A (see FIG. 2) is formed between the billet guide surface 24E and the downstream end portion.
As shown in FIG. 12, the minimum width L4 between the pair of bridge side surfaces 24G, 24G is set between 30% and 50% of the radius L1 / 2 of the fitting hole 25C.

  As shown in FIG. 1, the front end surface 24 </ b> C of each of the bridge portions 24 a to 24 d is in contact with the inner peripheral surface 25 </ b> D of the fitting hole 25 </ b> C of the holder 25. The inner peripheral surface 25D of the fitting hole 25C and the front end surface 24C of each of the bridge portions 24a to 24d are joined by shrink fitting.

The front end surfaces 24C of the bridge portions 24a to 24d are curved along the inner peripheral surface 25D of the fitting hole 25C.
Since the front end surface 24C of each bridge part 24a-24d is the same shape, in the following description, the shape of the front end surface 24C of the 2nd bridge part 24b shown in FIG. 4 is demonstrated, and each other bridge part 24a, 24c. 24d, the shape of the tip surface 24C is omitted.

The distal end surface 24C of the second bridge portion 24b is continuous from the tapered surface portion 24m and the tapered surface portion 24m that is inclined so as to gradually increase outward from the end portion on the upper surface 22A side of the spider 22 toward the downstream side. A cylindrical surface portion 24n extending to the lower surface 22B is formed.
The inclination angle α of the tapered surface portion 24m with respect to the axial direction of the spider 22 is set to 0.5 ° to 1 °, for example.
The tapered surface portion 24m of the second bridge portion 24b is overlapped with the tapered portion 25m of the fitting hole 25C, and the cylindrical surface portion 24n of the second bridge portion 24b is overlapped with the cylindrical surface portion 25n of the fitting hole 25C (see FIG. 2). ).

As described above, the inner peripheral surface 25D of the fitting hole 25C of the holder 25 and the front end surface 24C of each of the bridge portions 24a to 24d of the spider 22 are respectively formed with a tapered surface portion 25m and a tapered surface portion 24m. ing.
Therefore, as shown in FIG. 5, when the spider 22 is inserted into the fitting hole 25C of the holder 25 from the downstream side toward the upstream side, the tapered surface portion 24m of the spider 22 is guided by the tapered surface portion 25m of the holder 25. Therefore, the insertion work is easy.

When the entire inner peripheral surface 25D of the fitting hole 25C and the entire front end surface 24C of each of the bridge portions 24a to 24d are inclined, a force acts on the spider 22 in the direction opposite to the insertion direction. .
Therefore, in the present embodiment, cylindrical surface portions 25n and 24n are provided on the inner peripheral surface 25D of the fitting hole 25C and the distal end surfaces 24C of the bridge portions 24a to 24d, and a frictional force is generated between the cylindrical surface portions 25n and 24n. This prevents the spider 22 from coming out of the holder 25.
In addition, you may form a cylindrical surface part in the whole inner peripheral surface 25D of the fitting hole 25C, and the front end surface 24C of each bridge | bridging part 24a-24d.

  The upper surface 22A of the spider 22 is formed as a flat surface as shown in FIG. In a state in which the spider 22 and the holder 25 are assembled, the upper surface 22A of the spider 22 is disposed at a position downstream of the upper end surface 25A (seal surface) of the holder 25.

Further, the outer end portion of the first bridge portion 24a and the outer end portion of the fourth bridge portion 24d are connected by an arc-shaped bridge lateral shake prevention portion 24D (see FIG. 6).
Similarly, the outer end portion of the second bridge portion 24b and the outer end portion of the third bridge portion 24c are connected by an arcuate bridge lateral shake prevention portion 24D (see FIG. 6).

The bridge lateral shake prevention portion 24D is formed continuously with the cylindrical surface portion 24n of the distal end surface 24C of each of the bridge portions 24a to 24d. That is, the bridge lateral shake prevention portion 24D is formed at the lower end of each of the bridge portions 24a to 24d.
In addition, while connecting the 1st bridge part 24a and the 2nd bridge part 24b with a bridge lateral shake prevention part, you may connect the 3rd bridge part 24c and the 4th bridge part 24d with a bridge lateral shake prevention part.

  As shown in FIG. 1, the space connection hole 26 which connects adjacent introduction space S and S is formed in the lower end part of each bridge | bridging part 24a-24d (refer FIG. 3). Thereby, the billet B (see FIG. 2) that has flowed into each introduction space S is mixed through the space connection hole 26.

As shown in FIG. 8A, an inner molding protrusion 23 </ b> A is formed at the lower end of the mandrel 23. The inner molding protrusion 23A protrudes downstream (the female mold 30 side) from the bridge portions 24a to 24d.
A first inner piece 23B, a second inner piece 23C, and a third inner piece 23D are formed on the inner molding protrusion 23A.

As shown in FIG. 8B, the first inner piece portion 23B, the second inner piece portion 23C, and the third inner piece portion 23D are each formed in a substantially quadrangular prism shape. Each inner piece 23B, 23C, 23D is a part that forms three spaces 1S, 1S, 1S of the hollow shape member 1.
On the outer peripheral surface of each inner piece 23B, 23C, 23D, a protruding frame 23E protrudes over the entire periphery.

As shown in FIG. 6, the mandrel 23 has an introduction space S between the first bridge portion 24a and the fourth bridge portion 24d, and an introduction space S between the second bridge portion 24b and the third bridge portion 24c. Are formed. Two billet guide holes 24F and 24F are formed.
Both billet guide holes 24F, 24F are arranged in parallel in a straight line at intervals in the left-right direction in FIG.
As shown in FIG. 8, the gap between the protruding frame 23E of the first inner piece 23B and the protruding frame 23E of the second inner piece 23C, the protruding frame 23E of the second inner piece 23C and the third inner piece 23D. The gaps with the projection frame 23E communicate with the billet guide holes 24F and 24F, respectively.

As shown in FIG. 10, the female die 30 is a circular member in plan view. On the upper surface (upstream surface) of the female mold, a circular holder receiving surface 30A is formed in plan view.
As shown in FIG. 2, the holder 25 of the male die 20 is held by the female die 30 by the lower end surface 25B of the holder 25 coming into contact with the holder receiving surface 30A.

As shown in FIG. 10, a billet reservoir 30B, which is a circular recess, is formed at the center of the holder receiving surface 30A (see FIG. 11). A rectangular outer molded opening 30C is opened at the center of the billet reservoir 30B.
As shown in FIG. 11, the outer molding opening 30 </ b> C penetrates from the bottom surface of the billet reservoir 30 </ b> B to the downstream surface of the female die 30. The inner peripheral surface of the outer molded opening 30C is a part that forms the outer shape of the hollow shape member 1 (see FIG. 8B).
In addition, an escape portion 30D that is gradually enlarged from the upstream side toward the downstream side is formed on the inner peripheral surface of the outer molding opening 30C.

  As shown in FIG. 2, the inner molding protrusion 23A of the spider 22 of the male mold 20 is inserted into the billet reservoir 30B and the outer molding opening 30C.

As shown in FIG. 8 (b), the gap between the projection frame 23E of each of the inner pieces 23B to 23D and the inner peripheral surface of the outer molding opening 30C is the long side walls 1A and 1A and the short side walls of the hollow profile 1. A shape forming hole 50 for forming the side walls 1B, 1B is formed.
Further, the gap between the projection frame 23E of the first inner piece portion 23B and the projection frame 23E of the second inner piece portion 23C constitutes the shape forming hole 51 for forming the partition wall 1C of the hollow shape member 1. doing.
Further, the gap between the projection frame 23E of the second inner piece 23C and the projection frame 23E of the third inner piece 23D also forms the shape forming hole 51 for forming the partition wall 1C of the hollow shape 1. doing.

Next, a method for forming the hollow profile 1 using the extrusion die 10 will be described.
As shown in FIG. 2, when the billet B is supplied from the billet pushing device 60 to the fitting hole 25C of the holder 25 of the male mold 20, the billet B flows into the four introduction spaces S (see FIG. 1).

  As shown in FIG. 3, the billet guide surface 24 </ b> E formed at the upstream end of the spider 22 is inclined with respect to the billet B extrusion direction (see FIG. 7). Thereby, the billet B flows smoothly and evenly into each introduction space S along the billet guide surface 24E.

  As shown in FIG. 9A, the billet B is guided from each introduction space S as indicated by an arrow m, and is pushed downstream from the shape forming hole 50. The long side walls 1A and 1A and the short side walls 1B and 1B of the hollow shape 1 are formed by the billet B pushed out from the shape forming hole 50 (see FIG. 9B).

  Further, as shown in FIG. 8A, the billet B flows into the billet guide hole 24F from the introduction space S, is guided as indicated by the arrow n in the billet guide hole 24F, and is formed into the shape forming hole 51. Extruded downstream. Then, the partition wall 1C of the hollow shape member 1 is formed by the billet B pushed out from the shape member forming hole 51 (see FIG. 8B).

  The hollow profile 1 extruded from the profile forming holes 50 and 51 is not shown in FIG. 2 after being fed from the outer molding opening 30C to the profile feed hole 40A of the back die 40. It is held by a holding mechanism and carried into a predetermined stock yard or the like.

  In addition, since the escape portion 30D that is gradually enlarged from the upstream side toward the downstream side is formed on the inner peripheral surface of the outer molding opening 30C, the hollow extruded from the shape forming holes 50 and 51 is formed. The profile 1 is sent downstream without coming into contact with the outer peripheral opening 30C and the inner peripheral surface of the profile delivery hole 40A.

  Next, shrink fitting between each bridge portion 24a to 24d of the spider 22 and the fitting hole 25C of the holder 25 in the extrusion die 10 of the present embodiment will be described.

  When the holder 25 is heated, the holder 25 is thermally expanded to expand the fitting hole 25C, and the spider 22 can be inserted into the fitting hole 25C. Then, as shown in FIG. 4, the spider 22 is inserted into the fitting hole 25 </ b> C of the heated holder 25 from the downstream side toward the upstream side.

  When inserting the spider 22 into the fitting hole 25C, as shown in FIG. 5, for example, the holder 25 can be placed on the shrink-fitting work table 90. In this case, the spider 22 and the holder 25 can be positioned in the thickness direction by abutting the lower surface 22B of the spider 22 against the upper end surface 90A of the shrink-fitting work table 90.

Further, when the spider 22 is inserted into the fitting hole 25C, the spider 22 is pushed into the fitting hole 25C while being rotated.
At this time, as shown in FIG. 7, the spider 22 of the present embodiment has a space between the first bridge portion 24a and the fourth bridge portion 24d and a space between the second bridge portion 24b and the third bridge portion 24c, respectively. Since the bridge lateral shake prevention portions 24D and 24D are provided, the deformation of the bridge portions 24a to 24d can be prevented.

  Here, among the bridge portions 24a to 24d, the one having a larger distance between adjacent bridge portions tends to be deformed, that is, tends to be narrowed. Therefore, in the present embodiment, the bridge sideways between the first bridge portion 24a and the fourth bridge portion 24d, and between the second bridge portion 24b and the third bridge portion 24c, which have a large distance between adjacent bridge portions, respectively. Shake prevention units 24D and 24D are provided.

Thereafter, as shown in FIG. 2, when the spider 22 is positioned in the fitting hole 25C of the holder 25 and the holder 25 is cooled, the holder 25 contracts and the fitting hole 25C is reduced in diameter.
Thereby, the inner peripheral surface 25D of the fitting hole 25C is fastened to the distal end surface 24C of each bridge portion 24a to 24d, and the spider 22 is firmly fixed to the holder 25.

  Next, the fastening allowance between the inner peripheral surface 25D of the fitting hole 25C of the holder 25 and the distal end surface 24C of each of the bridge portions 24a to 24d of the spider 22 will be described.

  FIG. 4 shows the outer diameter L2 of the distal end surface 24C of each of the bridge portions 24a to 24d (see FIG. 1) of the spider 22. In the present embodiment, the outer diameter L2 of the distal end surface 24C of each of the bridge portions 24a to 24d is a diameter of a circle in which the end portion on the upper surface 22A side of the distal end surface 24C of each of the bridge portions 24a to 24d is inscribed.

  Further, the inner diameter L1 of the fitting hole 25C of the holder 25 is the inner diameter of the end portion on the upper end face 25A side of the fitting hole 25C of the holder 25 that is not heated.

  And the inner diameter L1 of the fitting hole 25C of the holder 25 is formed slightly smaller than the outer diameter L2 of the front end surface 24C of each bridge part 24a-24d.

The interference allowance δ of the present embodiment is a difference (L2−L1) between the inner diameter L1 of the inner peripheral surface 25D of the fitting hole 25C and the outer shape L2 of the distal end surface 24C of each bridge portion 24a to 24d. The tightening allowance δ is set between 0.4% and 0.6% of the inner diameter L1 of the fitting hole 25C. That is, it is obtained by the following formula 1.
δ = (0.004 to 0.006) · L1 (Formula 1)
Thus, in the present embodiment, the shrink fit amount δ / L1 in the shrink fit between the holder 25 and the spider 22 is set from 0.4% to 0.6%.
In addition, when the holder 25 and the spider 22 are shrink-fitted, if the holder 25 is heated and thermally expanded, the inner diameter L1 of the fitting hole 25C is larger than the outer diameter L2 of the distal end surface 24C of each bridge portion 24a to 24d. And the spider 22 can be inserted into the fitting hole 25C.

The larger the tightening allowance between the outer diameter L2 of the end face 24C of each bridge portion 24a to 24d and the inner diameter L1 of the fitting hole 25C, the tighter the inner peripheral surface 25D of the fitting hole 25C with respect to the spider 22 during shrink fitting. Increased power.
And the initial load (compressive force) which arises in each bridge | bridging part 24a-24d by shrink fitting becomes large, so that the interference margin of inner peripheral surface 25D of fitting hole 25C and the front end surface 24C of each bridge | bridging part 24a-24d is large. The compressive strain generated in each of the bridge portions 24a to 24d increases.

The graph shown in FIG. 14A shows the relationship between the shrinkage amount and the total strain of each of the bridge portions 24a to 24d (see FIG. 1).
The total strain Δε of each bridge portion 24a to 24d is the maximum value of the main tensile strain ε1 generated at the base end portion (base portion) of each bridge portion 24a to 24d during extrusion molding and to each bridge portion 24a to 24d by shrink fitting. This is a value of a difference from the minimum value of the compression main strain ε2 that occurs, and is obtained by the following equation 2.
Δε = ε1-ε2 (Formula 2)

  The tensile main strain ε1 and the compression main strain ε2 are main strains at the same portion (base end portions of the bridge portions 24a to 24d) in a state where the holder 25 and the spider 22 are heated at the time of extrusion molding. The tensile principal strain ε1 and the compression principal strain ε2 are obtained by simulation by a finite element method (FEM).

As shown in the graph of FIG. 14B, the greater the total strain of each of the bridge portions 24a to 24d, the smaller the number of times each bridge portion 24a to 24d can be used when the extrusion molding is repeated.
In other words, not only when the tensile main strain ε1 generated in each bridge portion 24a-24d is large, but also when the compression main strain ε2 of each bridge portion 24a-24d due to shrink fitting is too large, the durability of each bridge portion 24a-24d. The number of times decreases.

In the line segment shown in the graph of FIG. 14A, the total strain Δε is small in the region where the shrinkage fit amount δ / L1 is 0.4% to 0.6%.
In the present embodiment, the total strain Δε of each of the bridge portions 24a to 24d (see FIG. 1) is reduced by setting the shrinkage fit amount δ / L1 from 0.4% to 0.6%.

As described above, in the extrusion die 10 of the present embodiment, as shown in FIG. 4, the inner peripheral surface 25 </ b> D of the fitting hole 25 </ b> C of the holder 25 and the bridge portions 24 a to 24 d (see FIG. 1) of the spider 22. The tightening margin with the front end surface 24C is set to 0.4% to 0.6% of the inner diameter L1 of the fitting hole 25C.
In this way, when the tightening margin is set, the total strain of each of the bridge portions 24a to 24d at the time of extrusion molding can be sufficiently reduced (see FIG. 14A).
Thereby, in the extrusion die 10, the durability of the extrusion die 10 can be increased when the extrusion molding is repeated, and the fatigue durability of the extrusion die 10 can be improved. Life can be extended.

Further, in the extrusion die 10, as shown in FIG. 1, the inner peripheral surface 25 </ b> D of the holder 25 and the tip surfaces 24 </ b> C of the bridge portions 24 a to 24 d of the spider 22 are firmly joined by shrink fitting.
Further, in the present embodiment, as shown in FIG. 4, the radial thickness L3 of the hole wall portion of the fitting hole 25C is set to 60% to 90% of the radius L1 / 2 of the fitting hole 25C. Thus, the strength of the holder 25 is sufficiently secured.
In the present embodiment, as shown in FIG. 12, the minimum width L4 between the bridge side surfaces 24G and 24G of the bridge portions 24a to 24d is set to 30% to 50% of the radius L1 / 2 of the fitting hole 25C. By setting to, the strength of each of the bridge portions 24a to 24d is sufficiently ensured.
Therefore, the fitting hole 25C and the bridge portions 24a to 24d can be securely joined by shrink fitting, and the pushing force at the time of extrusion molding is distributed to the spider 22 and the holder 25. The stress concentration on 24d can be relaxed. Thereby, as shown in FIG. 2, even when the billet B made of a high-strength aluminum alloy having a large pushing force is extruded, the billet B can be extruded at a high speed.

As mentioned above, although this embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning, it can change suitably.
As shown in FIG. 8B, the extrusion die 10 of the present embodiment is configured to extrude the hollow shape 1 having a cross-sectional shape, but the shape of the hollow shape is limited. It is not a thing. Then, the shapes of the outer molding opening 30C of the female die 30 and the inner molding protrusion 23A of the spider 22 are formed corresponding to the shape of the hollow shape material to be molded.

DESCRIPTION OF SYMBOLS 1 Hollow profile 10 Extrusion die 20 Male type 22 Spider 23 Mandrel 23A Inner shaping | molding projection part 23B 1st inner piece part 23C 2nd inner piece part 23D 3rd inner piece part 23E Projection frame 24 Bridge part 24C Front end surface 24D Bridge lateral runout Prevention part 24E Billet guide surface 24F Billet guide hole 24G Bridge side surface 24a First bridge part 24b Second bridge part 24c Third bridge part 24d Fourth bridge part 25 Holder 25C Fitting hole 25D Inner peripheral surface 25E Hole wall part 26 Spatial connection Hole 30 Female type 30A Holder receiving surface 30B Billet pool part 30C Outer molding opening 30D Escape part 50 Profile forming hole 51 Profile forming hole 60 Billet extrusion device B Billet S Introduction space

Claims (3)

A hollow shape forming extrusion die for forming a hollow shape by extruding a billet made of an aluminum alloy from an upstream side to a downstream side,
A male mold for molding the inner shape of the hollow profile, and a female mold for molding the outer profile of the hollow profile,
The male type has a holder in which a fitting hole is formed, and a spider that is fitted in the fitting hole,
The spider is formed with a mandrel corresponding to the inner shape of the hollow shape member, and a plurality of bridge portions protruding outward from the outer peripheral surface of the mandrel,
The inner peripheral surface of the fitting hole and the front end surface of each bridge portion are shrink-fitted,
The fastening allowance between the inner peripheral surface of the fitting hole and the front end surface of each bridge portion is 0.4% to 0.6% of the inner diameter of the fitting hole. Extrusion die.   2. The extrusion die for forming a hollow shape member according to claim 1, wherein a thickness in a radial direction of a hole wall portion of the fitting hole is 60% to 90% of a radius of the fitting hole. On both side surfaces of the bridge part, a pair of bridge side surfaces parallel to the extrusion direction of the billet are formed,
The extrusion die for hollow profile molding according to claim 1 or 2, wherein a minimum width between the side surfaces of both bridges is 30% to 50% of a radius of the fitting hole.

Images