JP3214187B2 - Die for hollow product extrusion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow product suitable for use in continuous extrusion of a hollow product such as an aluminum tube, and in particular, a hollow extruded shape having a projection integrally formed on a part of its inner surface. The present invention relates to a product extrusion die.

[0002]

2. Description of the Related Art This type of molding die used for extrusion of a hollow extruded section by a continuous hot extruder generally comprises a die 1 and a mandrel 2 as shown in FIG. Die bearing surface 3 and mandrel
A bearing portion 6 for defining the cross-sectional shape of the hollow extruded profile 5 is constituted by the opposing gap of the bearing surface 4. Die bearing surface 3 that defines the outer shape of hollow extruded profile 5
Is provided on the hole wall surface of the die hole 7 formed in the die 1. The die hole 7 is formed of a tapered hole whose diameter is increased in the extrusion direction (arrow direction) of the hollow extruded profile 5, the entrance shape is equal to the outer shape of the hollow extruded profile 5, and a relief portion (hole) is provided on the exit side.
8 are formed. The relief portion 8 is used to reinforce the die 1 and to form the hollow extruded member 5 formed by the bearing portion 6.
The shape is designed to be similar to the bearing shape, larger than or similar to the bearing shape. On the other hand, the mandrel / bearing surface 4 is formed on the entire outer peripheral surface of the mandrel 2 and defines the inner shape of the hollow extruded section 5.

When extruding the hollow extruded shape member 5, a billet 9 made of aluminum or an aluminum alloy heated to a predetermined temperature is usually loaded into a cylindrical container 10, and the die 1 is installed at one end of the container. The ram (not shown) inserted from the side is moved forward, the billet 9 is pressed by the push plate, and is pushed out from the bearing portion 6.

FIG. 4 shows an example of a hollow extruded member 5 extruded by such a die. The hollow extruded profile 5 has a projection 11 projecting from a part of the inner surface, and the projection 11 is used as a positioning portion or a screw mounting portion of the hollow extruded profile 5.

As shown in FIG. 4, in the extrusion molding of the hollow extruded profile 5 having a projection 11 on a part of the inner surface, a streak, a difference in gloss, a depression, etc. are formed on the surface side corresponding to the projection 11. Surface defects 12 tend to occur, and such surface defects 12 are more remarkable as the thickness of the projections 11 is larger, and there is a problem that the quality of the product is significantly reduced. This is because the flow velocity of the billet 9 flowing along the die bearing surface 3 is different between the portion corresponding to the protrusion 11 and the other bearing portion. That is, when the opposing gap between the die bearing surface 3 and the mandrel bearing surface 4 of the bearing portion corresponding to the protrusion 11 is wider than the other bearing portions, the flow rate of the billet 9 passing through this portion becomes faster at the center of the gap, The billet 9 is formed on the outer side of the bearing portion having a wide opposed gap corresponding to the projecting part 11 because the thickness of the projecting part 11 is small and the facing gap where the projecting part is not formed is narrow. Billet 9 flowing along the die bearing surface of the bearing part
When the flow velocity difference between the bearings is small, a difference in streak and gloss occurs, the wall thickness of the projection 11 increases, and the billet 9 flows outside the bearing portion with a wide opposed gap. When the flow velocity difference with the billet 9 flowing along the die bearing surface of the portion becomes large, the billet 9 flowing outside the wide opposed gap is attracted to the billet 9 flowing in the central portion, thereby causing a depression.

Therefore, as a countermeasure, the flow velocity of the billet 9 passing outside the bearing portion in which the opposed gap between the die bearing surface 3 and the mandrel bearing surface 4 is widened due to the protrusion 11 is increased, and the die bearing surface is increased. 3
Therefore, the present inventors have to increase the amount of billet 9 flowing along the inner surface of the die 1, that is, the billet side surface 1 a near the die hole 7 as shown in FIGS. 5 and 6. A truncated pyramid-shaped projection 14 is provided corresponding to the bearing portion 6a in which the facing gap between the die bearing surface 3 and the mandrel bearing surface 4 is widened to form the projection 11. In a die provided with such a protrusion 14 on the die 1, the inner surface 14a of the protrusion 14 facing the mandrel 2 serves as a guide surface to guide the billet 9 to the bearing portion 6a. It was confirmed that the flow rate of the outer billet 9 flowing into the bearing portion 6a along 3 can be increased, and the occurrence of surface defects can be prevented to some extent.

[0007]

However, since the inner side surface 14a of the projection 14 is inclined, the billet 9 flowing along this surface has a large momentum when it is turned on the billet side surface 1a. Therefore, as the thickness of the projection 11 increases, the amount of the billet 9 flowing along the die / bearing surface 3 decreases because the protrusion 11 enters into the bearing portion more than the central portion of the bearing portion 6a.
The generation of surface defects such as dents could not be completely prevented, and there was still room for improvement.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to extrude a hollow extruded material having a projection on a part of its inner surface. An object of the present invention is to provide a hollow product extrusion die capable of extruding a hollow extruded material without surface defects such as streaks, differences in gloss, and depressions on the surface side.

[0009]

In order to achieve the above object, the present invention provides a hollow product extrusion die for extruding a hollow extruded shape having a die and a mandrel and having a projection on a part of an inner surface thereof. The length of the die bearing surface of the die is set shorter than the mandrel bearing surface of the mandrel, and the protrusion of the hollow extruded material to be extruded is located near the die hole on the billet side surface of the die. A protrusion is provided at a position corresponding to the portion, and the side surface of the protrusion facing the mandrel is substantially perpendicular to the billet side surface, and the height is set to be larger than the distance from the die hole to the protrusion. Is what is being done.

[0010]

According to the present invention, the die bearing surface is formed to be shorter than the mandrel bearing surface, so that the resistance is small and the flow velocity of the billet flowing along the die bearing surface is increased. Since the side surface of the projection facing the mandrel is substantially perpendicular to the side surface of the die on the billet side, unlike the case of the inclined surface, the billet is less likely to move toward the center of the die. Therefore, in the bearing portion where the opposed gap between the die bearing surface and the mandrel bearing surface is widened due to the formation of the protrusion, the amount of billet entering the bearing portion along the die bearing surface is increased.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a die for extruding a hollow product according to the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a hollow product extrusion die according to the present invention, and FIG. 2 is a view taken in the direction of arrow B in FIG. In addition, in FIG.
Components having the same components as those shown in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. In these figures, in this embodiment, a trapezoidal projection 20 is provided near the die hole 7 on the billet side surface 1a of the die 1 and a projection 11 is provided on the inner surface of the hollow extruded profile 5 (FIG. 6). Therefore, the protrusion is provided corresponding to the bearing portion 6a in which the facing gap between the die bearing surface 3 and the mandrel bearing surface 4 is increased. The length L1 of the die bearing surface 3 is set shorter than the length L2 of the mandrel bearing surface 4.
The mandrel 2 is inserted into the die hole 7 such that the tip of the mandrel bearing surface 4 substantially coincides with the exit opening end of the die hole 7. The inclination angle α of the die bearing surface 3 is 2
It is about 3 °. The upper surface 20a of the projection 20 is a flat surface, and the side surface 20b facing the mandrel 2 is a vertical surface parallel to the die axis, in other words, a vertical surface substantially orthogonal to the billet side surface 1a of the die 1, and the remaining three side surfaces 20c to 20c. 20e is a slope. However, these three side surfaces 20c to 20e
Is not necessarily a slope. The height H of the projection 20 is about 1.5 to 2 mm, and is set to be larger than the distance D from the die hole 7 to the projection 20. Distance D is 1.5mm
Degree.

Thus, in a die having such a configuration, the resistance of the die bearing surface 3 to the billet 9 is smaller than that of the mandrel bearing surface 4 because of L1 <L2, and therefore, the billet 9 flowing along the die bearing surface 3 is not formed. The flow is not hindered, and can be faster than the billet 9 flowing along the mandrel bearing surface 4. Further, since the side surface 20b of the protrusion 20 facing the mandrel 2 is substantially orthogonal to the billet side surface 1a, the billet 9 flowing along the mandrel side surface 20b hits the billet side surface 1a and changes its direction toward the center of the die. In this case, the momentum is weaker than in the case of the truncated pyramid-shaped projection 14 shown in FIG. 5, and flows into the bearing portion 6a along the die bearing surface 3. As a result, the amount of the billet 9 flowing along the die bearing surface 3 of the bearing portion 6a does not decrease, the flow velocity does not decrease, and the die bearing of the bearing portion 6a having a narrow opposed gap where no protrusion is formed. A difference in flow velocity between the billet 9 flowing along the surface and the billet 9 hardly occurs, so that it is possible to reliably prevent surface defects such as streaks, differences in gloss, and dents on the surface side of the hollow extruded profile 5.

If the distance D from the protrusion 20 to the die hole 7 is too large, the billet 9 flowing along the mandrel side surface 20b of the protrusion 20 hits the billet side surface 1a of the die 1 and the center of the die. After being turned in the direction, the amount flowing into the die hole 7 along the die bearing surface 3 decreases, which is not preferable.

A projection 11 projecting from a part of the inner surface of the hollow extruded section 5 has a trapezoidal shape as shown in FIGS.
FIG. 4 shows trapezoidal and C-shaped ones. However, the present invention is not limited to this, and can be applied to projections of various shapes such as rectangular and columnar as it is. is there.

[0015]

As described above, according to the die for extruding hollow products according to the present invention, when extruding a hollow extruded shape having a projection on a part of the inner surface, a strip or luster, which has been conventionally unavoidable, is conventionally required. The occurrence of surface defects such as differences and dents can be reliably prevented, and the product quality can be improved.
Further, since it is only necessary to provide the protrusions on the die, the structure is simple, and even if the existing die is formed by forming the protrusions by building up, it can be used as it is, and the economic effect is large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a hollow product extrusion die according to the present invention.

FIG. 2 is a view on arrow B of FIG. 1;

FIG. 3 is a sectional view showing a conventional example of a hollow product extrusion die.

FIG. 4 is a perspective view of a main part of a hollow extruded profile having a projection on an inner surface.

FIG. 5 is a cross-sectional view of a hollow product extrusion die that can be considered to prevent the occurrence of surface defects.

6 is a view as viewed in the direction of the arrow A in FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 die 1a die billet side surface 2 die mandrel 3 die bearing surface 4 mandrel bearing surface 5 hollow extruded material 6 bearing portion 6a bearing portion for forming protrusion 7 die hole 8 relief portion 9 billet 10 container 11 protrusion 12 Surface Defect 20 Projection 20b Side of Mandrel Side of Projection

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B21C 25/00

Claims (1)

(57) [Claims] 1. A hollow product extrusion die for extruding a hollow extruded material having a die and a mandrel and having a projection on a part of an inner surface thereof, wherein a length of a die bearing surface of the die is set to a length of the mandrel. While setting it shorter than the mandrel bearing surface,
In the vicinity of the die hole on the billet side surface of the die, a projection is provided at a position corresponding to the projection of the hollow extruded shape to be extruded, and the side of the projection facing the mandrel A die for extruding a hollow product, wherein the height is set to be substantially perpendicular to the billet side surface and the height is set to be larger than the distance from the die hole to the projection.