GB2143166A

GB2143166A - Extrusion of metal

Info

Publication number: GB2143166A
Application number: GB08417087A
Authority: GB
Inventors: Norman Reginald Fairey
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1983-07-08
Filing date: 1984-07-04
Publication date: 1985-02-06
Also published as: GB8417087D0

Abstract

A die unit for Conform extrusion apparatus comprises a die 10, a die holder 11 and an annular stress relief member 12 separate from and close to the entry end of the die. Metal must pass through the stress relief member before being extruded through the die where accurately sized wire can be formed. <IMAGE>

Description

SPECIFICATION Extrusion of metal This invention relates to machinery for continuous friction-effected extrusion of metal. More particularly it relates to a machinery of the kind in which a passageway is formed between an arcuate first member and a second member in the form of a wheel having a circumferential groove formed in its peripheral surface into which groove the first member projects, the wheel being rotatable to urge material in the passageway towards one end (the exit end) thereof, an abutment member extending across the passageway at the exit end thereof and at least one die orifice through a part of the arcuate first member adjacent the abutment member.

The abutment member may be large enough to block the end of the passageway completeiy (as described in the specification of UK Patent 1370894) but especially when the material to be extruded is a relatively hard metal, such as copper, we prefer that the abutment member is of substantially smaller cross-section that the passageway and leaves a substantial gap between the abutment member and the groove surface and that the material being extruded is allowed to adhere to the groove surface, whereby a substantial proportion of the metal (as distinct from the inevitable leakage of flash through a working clearance) extends through the clearance and remains as a lining in the groove to re-enter the passageway while the remainder of the metal extrudes through the die orifice(s), as described in our UK Patent No. 2069389B.

Such machinery is commonly known as "Conform" machinery, and will be referred to as such hereinafter.

We have found that the product of Conform extrusion may differ significantly in size from the die which it was produced, and it is the object of this invention to eliminate or at least appreciably reduce this effect.

In accordance with one aspect of the invention a die unit for Conform extrusion apparatus comprises a die, a die holder and an annular stress relief member separate from and close to the entry end of the die through which the metal must pass before being extruded through the die.

It will be understood that the opening of the annular stress relief member will need to be larger than the orifice of the die in most circumstances.

Preferably the stress relief member is flat and lies with one face bounding the front face of the die and the other flush with the wall of the working passageway.

If desired the die unit may include a sleeve extending between the die and the die holder over a substantial part of its length and made of a metal soft compared with the die and the die holder, as described and claim in British application No: 841 7086 filed on the same day as this application claiming priority from British Applications Nos. 8318485 and 8401047. The sleeve may be made of the metal being extruded, but is preferably of another relatively soft metal that does not strongly adhere to the metal being extruded.

For extrusion of copper and most other extrudable metals, mild steel is a suitable metal for the sleeve.

The stress relief member may fit tightly or loosely into the die holder.

The die unit is preferably a separate insert, but, if desired, the die holder could be directly formed in the shoe or the abutment of the machine.

The invention includes also a Conform machine incorporating the die unit described, an extrusion method in which it is used and products of the method.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a cross-section of part of a Conform machine (accordance with our UK Patent No. 2069389B); Figures 2 and 3 are mutually perpendicular views of a die unit forming part of the known apparatus shown in Fig. 1; and Figures 4 and 5 are mutually perpendicular views of a die unit in accordance with the invention.

In the Conform machine shown in Fig. 1, a wheel 1 (the curvature of which is too slight to be visible at this section) is formed with a rectangular groove 2, that forms three walls of the extrusion passageway 3. The fourth wall is formed by an assembly comprising a shoe 4 (a small portion of which is shown), and an abutment 5 projects into the passageway.

A radial extrusion die 6 is formed in a die holder 7 (which is preferably a separate component, though it might be integral with either the abutment or the shoe).

The shoe, abutment and die are of high strength materials and are held in position by heavy-duty support members (not shown), and cooling means is provided.

Figs. 2 and 3 are mutually perpendicular views of a conventional die 6 formed in a die holder 7 and providing a cylindrical orifice 8 (which may be formed integral with the die holder) relieved by a counterbore 9 to provide a clearance around the extruded product.

Figs. 4 and 5 are mutually perpendicular views of a die unit in accordance with the invention, comprising a die insert 10, a die holder 11, and a flat annular stress relief member 1 2 bounding the entry face of the die and flush with the surface of the working passageway.

In a particular example, the die is of a ceramic material and has a nominal bore 2.5 mm in diameter (actual range 2.500 to 2.515), an external diameter of 7.0 mm and a length of 4.0 mm. The stress relief member is of a steel based carbide material and has a bore 3.5 mm in diameter, an external diameter of 7.0 mm and a thickness of 1.5 mm.

When mounted alone, flush with the surface of the holder, as shown in Figs. 2 and 3, the die produced wire with a diameter averaging 2.47 mm (1.1% undersize); when mounted with the stress relief member in accordance with the invention and as shown in Figs. 4 and 5, it produced wire with a mean diameter of 2.49 mm (only 0.3% undersize).

Claims

1. A die unit for Conform extrusion apparatus comprising a die, a die holder and an annular stress relief member separate from and close to the entry end of the die through which the metal must pass before being extruded through the die.

2. A die unit as claimed in Claim 1, wherein the stress relief member is flat and has one face bounding the front face of the die and the other flush with the wall of the working passageway.

3. A die unit as claimed in Claim 1 or Claim 2, wherein there is a sleeve extending between the die and the die holder over a substantial part of its length and made of a metal soft compared with the die and the die holder.

4. A die unit substantially as hereinbefore described and with reference to and as shown in Figs. 4 and 5.

5. A Conform machine incorporating a die unit as claimed in any preceding claim.

6. A method of extrusion using a Conform machine incorporating a die unit as claimed in any preceding claim.

7. An elongate body extruded by the machine claimed in Claim 5 or the method claimed in Claim 6.