JPH0481216A - Method for hot-extruding hard-to-work material - Google Patents

Abstract

PURPOSE:To perform sound hot extrusion of hard-to-work material by forming a U-shaped space over both end faces in the axial direction of a core and an outer peripheral surface on a composite billet and keeping a boundary between the core and a sheath material in non-contact. CONSTITUTION:The core 12 made of hard-to-work metallic material is covered with sheath material 3 more excellent in workability than it to make a composite billet 1. This composite billet 1 is heated and hot-extruded. Then, a U-shaped space 4 is formed on the section in the axial direction on the composite billet 1 over both end faces in the axial direction of the core 2 and outer peripheral surface in the axial direction. The boundary between the core 2 and the sheath material 3 is kept in non-contact. In this way, the temperature of the core can be prevented from lowering and heat insulating effect can be maintained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for hot extrusion of difficult-to-process materials, and more specifically, to a core material made of a difficult-to-process metal material, The present invention relates to a method of preparing a composite billet by covering it with a skin material having excellent properties, and heating and hot extruding the composite billet.

(Prior art) Conventionally, when hot extruding a difficult-to-process material, the outside of the difficult-to-process material 5 is covered with a skin material 6 that has better workability than the outer skin material 6 and processed into a composite billet. It is generally known to perform hot extrusion by heating to a certain temperature.

The reason why such a hot extrusion method is adopted for difficult-to-process materials is that if the billet of difficult-to-process materials is directly hot extruded, it will come into contact with the atmosphere, lubricant, extrusion container, etc. from heating to the start of extrusion. The billet surface is cooled and ductility cannot be maintained during extrusion, resulting in billet cracking. On the other hand, when processed into a composite billet, there is a skin material on the surface that cools rapidly, which prevents the difficult-to-process material itself from cooling, and also retains heat during extrusion, allowing smooth extrusion. (Conventional example 1).

(Problem to be Solved by the Invention) However, according to the above-mentioned conventional example 1, the outer skin material is used as a dummy for heat retention, so in the case of hot composite extrusion, there is Since the billet is exposed to a cold atmosphere, the outer skin material needs to have a certain thickness. Therefore, the shape of the core 44 (difficult work) 7I) was inevitably limited, resulting in a poor processing yield.

In view of the problems of the prior art described above, the purpose of the present invention is to provide a method for hot extruding a difficult-to-process material in a sound state using a composite billet that provides a heat-retaining effect.

(Means for Solving the Problems) The present invention creates a composite billet 1 by covering a core material 2 made of a metal material that is difficult to process with an outer skin material 3 having better workability than the core material 2. In the method of heating and hot extruding, the following technical measures are taken to achieve the above-mentioned objective.

That is, in the composite billet 1 of the present invention, a U-shaped space 4 is formed in the axial cross section over both axial end faces and the axial outer peripheral surface of the core material 2, and the core material 2 and the outer skin frA'3 are connected to each other. It is characterized by a non-contact interface.

(Function) The composite billet 1 heated to a predetermined extrusion temperature is heated to a core material 2.
There is a space 4 at the interface between the outer skin material 3 and the outer skin material 3, which provides a heat retention effect.

In addition, the space 4 is U-shaped in the axial cross section and is formed not only on the outer circumferential surface in the axial direction but also on both end faces in the axial direction, so that cracks that are likely to occur on the edges 2R of both end faces in the axial direction of the core material 2 are prevented. Also ensure prevention.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIGS. 1 and 2, a composite billet 1 has a core material 2.
The core material 2 is made of a metal material that is difficult to process, and a fitting protrusion 2A is formed on the end surface of the shaft on the axis thereof. The outer skin material 3 has better workability than the core material 2, and has better workability than the core material 2.
It consists of a cylindrical body 38 that covers the axial outer peripheral surface of the cylindrical body 38, and an end plate 3C that is joined to the cylindrical shaft end face of the cylindrical body 3 by beam welding or the like, and the fitting protrusion 2A is fitted into the end plate 3C. As a result, a U-shaped space 4 is formed in the axial cross section of the composite billet 1 across both axial end faces and the axial outer peripheral surface of the core material 2, and the core material 2 and the outer skin material 3 are The interface between the two is considered to be non-contact.

The composite billet 1 is heated, then placed in a container 5 or the like as shown in FIG. 3, and hot extruded using a pressure stem 6 or the like. Specific examples will be described below.

As the specific dimensions (unit: mm) are shown in Figure 1, the outer diameter is 67 mm.
ITlan, composite billet 1 with length 150mm,
-50 atomic% Ti as core material 2, outer skin material 3
Using SO3316, space 4 is 0.5 cylinder and 31
]=55φ composite billet 1 and as a comparative example, space 0
．． A composite billet with a diameter of 5 mm and no front and rear gaps and a composite billet with no space and the interface between the core material and the outer skin material were in contact (close contact) were heated to 1200° C. and hot extrusion was performed.

In addition, the outer diameter of the core material was unified to 60φmm.

As a result of hot extrusion under the same conditions as above, the core +
The composite billet used in the present invention has a space 4 at the interface between A2 and the outer skin material 3, and has this space 4 not only on the outer peripheral surface in the axial direction but also on both end surfaces in the axial direction. Good results were obtained with no occurrence of cracks or other flaws.

On the other hand, in the case where there was no gap on both end faces in the axial direction, cracking occurred at the end face edge 2B. Further, in the composite billet in which the interface between the core material and the outer skin material was brought into close contact, severe cracking occurred not only on the end face edge 2B but also on the outer periphery of the extruded material.

This means that by providing a space 4 at the interface between the core material 2 and the outer skin material 3, a drop in the temperature of the core material 2 can be prevented, and
This means that extrusion can be carried out at the optimum hot extrusion temperature.

(Effect of the invention) The composite billet 1 used for hot extrusion of the present invention has a core material 2
A U-shaped space 4 is formed in the axial cross section over both axial end faces and the axial outer circumferential surface of the core material 2, and the interface between the core material 2 and the outer skin material 3 is non-contact. It prevents temperature drop and maintains the heat retention effect, making it possible to obtain sound hot-extruded materials even from difficult-to-process materials.

[Brief explanation of the drawing]

FIG. 1 is an axial cross-sectional view of a composite billet used in the present invention;
FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is an explanatory view during extrusion. 1... Composite fillet, 2... Core material, 3... Outer skin material, 4... Space.

Claims (1)

[Claims] (1) A composite billet (1) is created by covering a core material (2) made of a metal material that is difficult to process with a skin material (3) that has better workability than the core material (2), and heats the composite billet (1). In the hot extrusion method, the composite billet (1) has a U-shaped space (
4) is formed so that the interface between the core material (2) and the outer skin material (3) is non-contact.