JPH0417726B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a mandrel bar used for mandrel extrusion of aluminum, and particularly to a mandrel bar with excellent wear resistance.

Conventional Technology and Problems Conventionally, the above-mentioned mandrel bar has been formed from a single piece such as die steel, but due to repeated use, the bearing part in particular receives a large frictional force, which causes premature wear of the bearing part. However, there were drawbacks such as deterioration of the inner surface quality of the extruded tube and poor durability. Of course, the above drawbacks could be overcome by forming the entire mandrel bar from high-speed steel, which has better wear resistance than die steel, but this would result in higher costs.

On the other hand, as shown in FIG. 3, a cylindrical body 21 made of high-speed steel is attached to a tool base 2 made of die steel.
2, and drive a bolt 24 to prevent the cylindrical body 21 from coming off on the tip end surface of the core.
The cylindrical body 21 is used only for the bearing part where wear is a problem.
A mandrel bar 20 constructed with the following is also used. However, with this mandrel bar, the heart 2
Since the coefficient of thermal expansion of the die steel of the three parts is larger than that of the high-speed steel that forms the cylindrical body 21, the cylindrical body 21 is damaged by internal pressure due to thermal expansion of the core 23 during extrusion processing, resulting in decreased durability. I was unable to improve my performance. Furthermore, if the fit between the core portion 23 and the cylindrical body 21 is loosened in order to prevent damage, a disadvantage arises in that misalignment occurs. Also, the heart part 2
There was also the problem that when the bolt 3 became thinner, it became difficult to process the bolt 24.

This invention was made in view of this technical background, and improves the wear resistance of the processing section corresponding to the bearing section of the mandrel bar for aluminum extrusion, that is, the section that directly controls the processing of the extruded material. At the same time, the purpose is to prevent damage to the processed portion and to provide excellent durability.

Means for Solving the Problems In order to achieve the above object, the mandrel bar with excellent wear resistance according to the present invention has a mandrel bar with excellent wear resistance than the base body 2, which extends from the tip surface of the base body 2. The machined part 3 made of high speed steel is integrally joined by friction welding.

Effect By constructing the machined part corresponding to the bearing part from high-speed steel, which has better wear resistance than at least the base body, wear of the machined part is reduced compared to when the whole body is made of the same material as the base body. Ru. In addition, since this machined part is integrally joined to the tip of the base body in a concentrically extending state by friction welding, the integrity of the base body and the machined part is firmly maintained, and damage to the machined part and misalignment can be avoided. is prevented. Furthermore, since high-speed steel has poor affinity with aluminum, the aluminum pipe extruded using the mandrel bar has excellent inner surface precision.

Embodiments Next, the configuration of the present invention will be explained based on illustrated embodiments.

In FIGS. 1 and 2, 1 is a mandrel bar, and the mandrel bar 1 is machined into a rod-shaped base 2 with a circular cross-section and a rod-shaped base 2 with a circular cross-section, which is joined and integrated in a concentrically extending state at the tip surface of the base. It consists of part 3. The base body 2 is made of die steel such as SKD61, while the processed portion 3 is made of high-speed steel (SKH), which has better wear resistance than the base body 2.

The base body 2 and the processed portion 3 are integrally joined by friction welding. That is, the base 2
The joint surfaces 5 of the and processed part 3 are brought into contact and subjected to relative rotational motion, and the friction heat generated on the contact surfaces is used to soften the butt surfaces and the vicinity thereof and press them together to form a joint. It is finished by cutting to the same outer diameter by removing the unevenness. Note that the base body 2
The shapes of the processed portion 3 and the processed portion 3 are not necessarily limited to the illustrated shapes, and the base body 2 may have a reduced diameter shape, or the processed portion 3 may be formed to have a small diameter.

When extruding aluminum, the mandrel bar 1 is used as a die 10 as shown in FIG.
The distal end of the processed portion 3 is arranged to face the extrusion hole 11 . The outer peripheral surface of the processed part 3 facing the bearing part 12 of the die is made into a bearing part 4,
A molding gap 13 is formed between both bearing parts 12 and 4 through which extruded material 15 passes. In addition, in FIG. 2, 14 is a container, and A is an aluminum extrusion material. When the extruded material 15 passes through the forming gap 13, the processed portion 3 of the mandrel bar is subjected to a large frictional force, but since the processed portion is made of high-speed steel with excellent wear resistance, its wear is reduced. can be suppressed. Furthermore, since high-speed steel has poor affinity with aluminum, the inner surface precision of the extruded aluminum pipe is improved.

Effects of the Invention As described above, the present invention has a working part made of high-speed steel, which has at least better wear resistance than the base body, which is integrally joined to the front end face of the base body in an extended state by friction welding. It is something that has been done. Therefore, the excellent wear resistance of high-speed steel can reduce the wear of processed parts during aluminum extrusion, and improve the wear resistance and durability of the mandrel bar. Also,
By using high-speed steel with excellent wear resistance only in necessary parts, it is possible to improve wear resistance while suppressing material costs. Furthermore, friction welding allows the joint end surfaces of the processed part and the base body to be fully joined and integrated over the entire surface, so there is no risk of separation or damage between the two at the joint surface, and there is no risk of separation or damage. The mandrel bar can be used stably for a long period of time without the risk of slippage, and can be made into a highly durable mandrel bar. Furthermore, since high-speed steel has poor affinity with aluminum, the inner surface precision of extruded aluminum pipes can be improved compared to traditional die steel mandrel bars, and the inner surface precision is generally required. It can be made suitable for extrusion of aluminum pipes. By the way, when we extruded an aluminum pipe under the same conditions except that we used the mandrel bar according to the present invention and a conventional mandrel bar made entirely of die steel, and examined the internal accuracy, we found that the conventional mandrel bar was not used. In contrast, the mandrel bar according to the present invention had an Rz of 3 to 4 μm.
It was hot.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a mandrel bar according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a state during extrusion processing using the mandrel bar of FIG. 1, and FIG.
The figure is a vertical cross-sectional view of a main part of a conventional mandrel bar. 1... Mandrel bar, 2... Base body, 3... Processing part,
4...Bearing part.

Claims (1)

[Claims] 1 A processed portion 3 made of high-speed steel that has better wear resistance than the base body 2 and extends from the tip surface of the base body 2.
A mandrel bar for aluminum extrusion with excellent wear resistance, characterized by being integrally joined by friction welding.