RU2668646C1 - Method of hot pressing of difficult-to-form alloys - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the field of metal working with a pressure and can be used in the hot pressing of bars of difficult-to-form alloys, in particular from powdered aluminum, difficult-to-form alloys. Method includes pressing a workpiece from a difficult-to-form alloy disposed in a sheath of plastic material into a matrix. Shell is made in the form of a glass from the detachable shell and the front washer, and the workpiece is immersed in the shell to 70–90 % of its height.

EFFECT: technical result consists in increasing the yield suitable for the account of the absence of a press sag and increasing the length of the used part of the rod.

6 cl, 2 dwg

Description

The invention relates to the field of metallurgy, and in particular to methods of processing metals by pressure, and can be used for hot pressing of rods from hardly deformable alloys.

State of the art

Various methods are known for producing pressed rods from hardly deformable alloys.

A known method of manufacturing continuous bimetallic products consisting of a core and a shell, including joint hot pressing of the prefabricated workpiece into a matrix with the application of force to the rear end and obtaining continuous bimetallic products with the required geometric dimensions of the layers with a minimum number of iterations (patent RU No. 2608119, B22C 23 / 22, priority 07.08.2015). The method is low-tech with a small thickness of the outer layer of the precast.

Known methods:

- semi-continuous hydromechanical pressing of blanks with preliminary application of Bingham plastic in the form of a tight-fitting capsule, feeding one after the other into the container and pressing through successively installed deforming and calibrating matrices with hydrostatic pressure of the working agent (patent RU No. 2440864, B22J 5/04, priority 08.07 .2010);

- the manufacture of rods consisting of cladding material and core material through a combination of deep drawing and impact extrusion processes (application WO No. 2012152235, B21C 23/22, priority 07.05.2011).

The methods require special equipment and therefore not sufficiently technological.

There are also known methods of pressing rods from blanks in a shell in the form of a cover or a tight-fitting capsule of plastic material representing a shell closed at the ends by covers.

In particular, a device is known for pressing rods from composite billets in a shell, the front cover of which is made in the form of a segment of a spherical shell with a concave outer surface (patent RU No. 78706, B21C 23/00, priority 10.07.2008). A sufficiently complex capsule shape reduces the manufacturability of the method. In addition, pulling a more ductile sheath material into the press weights reduces yield.

The closest to the proposed technical solution in its technical essence and the achieved effect is, adopted as a prototype, a method of pressing rods from a durable workpiece placed in a shell made of a material less durable, more plastic than the material of the workpiece, and consisting of a shell with welded flat rear and conical front covers, and the front cover is provided with an insert of material corresponding to the strength properties of the workpiece material (patent RU No. 1605365, B21C 23/22, priority 15.0 5.1994). As in the previous method, the rather complex shape of the shell also reduces the manufacturability of the method, and the pulling of the shell material into the press weights reduces the yield.

Disclosure of invention

The problem to which the invention is directed, is to increase manufacturability and increase yield. The technical result consists in reducing the cost of manufacturing the capsule and increasing the yield by increasing the length of the used part of the bar.

The technical result is achieved by the fact that in the known method of hot pressing into a matrix of a metal billet placed in a shell of plastic material, a shell made in the form of a cup and consisting of a detachable shell and a front washer is used, the billet being immersed in the shell 70-90% of the height blanks.

A feature of the pressing process is the different speed of the material flow over the cross section and the height of the workpiece. Friction on the walls of the container makes it difficult to move metal near the walls. When pressing hard-deformed materials with limited ductility, this leads to surface rupture of the metal on the surface of the bar. An effective way to equalize the flow velocities of the peripheral and central layers of the workpiece and reduce the unevenness of deformation is by pressing in a shell of a material more plastic than the workpiece material.

However, pressing a workpiece in a shell in the form of a capsule or a cover made of ductile metal leads to the retraction of the ductile material of the shell into the press weights, which reduces the yield due to a reduction in the used length of the bar.

The proposed method can improve manufacturability primarily by reducing the cost of manufacturing the shell. The cup-shaped shell consists of a shell rolled, for example, from a sheet with or without a weld, and a front washer cut, for example, from a rod of the desired diameter.

The shell and front washer can be made of one or different materials. The more ductile material of the shell provides a reduction in friction against the walls of the container, makes it possible to equalize the flow rate of the material over the cross section and the height of the workpiece, and prevent tearing of metal on the surface of the bar. The stronger material of the front washer avoids the formation of a section of unsteady flow at the front end of the bar.

The front washer may be structurally flat or conical. In the first case, the pressing of the front washer occurs immediately before extrusion, and the workpiece takes the form of a forming portion of the matrix.

To prevent or reduce the effect of the formation of press-weights and increase the yield allows limiting the immersion of the workpiece in the shell by 70-90% of the height of the workpiece (Fig. 1). With a lower immersion, the ductile metal does not cover the upper part of the side surface of the workpiece. With greater immersion, the ductile metal can be pulled into the press weight. The selection of the ratio of strength and ductility of the material of the shell allows you to ensure the absence of metal breaks on the surface of the bar and to limit the size of the press weight.

The implementation of the invention

Example 1. Pressing a bar of powdered aluminum hardly deformable alloy САС-1-50 with a reduced temperature coefficient of linear expansion

Pressing was performed on a vertical tube press with a capacity of 8 MN (Fig. 1). The blank 1 had a diameter of 95 mm and a height h _W = 160 mm. The shell consisted of a shell 2 with a height of 0.75h _W + h _W and a front washer 3 with a height h _W = 25 mm. Pressing was carried out from a container 4 with a diameter of 100 mm into a matrix 5 fixed in a matrix holder 6, having a conical forming surface with an angle at the apex of the cone of 120 ° and forming a channel with a diameter of 52 mm. The casing 2 was milled from a sheet of AMg 6 with a thickness of 2 mm, the front washer 3 was cut from a bar of alloy AD-31. The blank 1 was degreased, the shell 2 and the front washer 3 were cleaned by chemical etching.

The container 4, the matrix 5, the front washer 3 and the workpiece 1 were heated to a temperature of 480 ° C. The punch 7 was heated by deepening it into a container. Before pressing, the punch 7 was lifted, a die 5, a shell 2, a front washer 3, a workpiece 1 were sequentially installed in the container 4, and the pressing was performed.

At the initial stage of pressing, the front washer is pressed, the sufficient strength of the material of the front washer provides an initial bursting force, which avoids the formation of a section of unsteady flow at the front end of the bar.

The proposed value of immersion of the workpiece in the shell by 70-90% of the height of the workpiece provides coverage of the upper part of the side surface of the workpiece with shell material, reducing friction against the walls of the container, and at the same time does not lead to the retraction of the plastic material of the shell in the press-weight. The press weights in the bar are already missing directly under the cutting punch. Traces of shell material are observed on the surface formed by the cutting punch, but there is no press-tension on the bar adjacent to the cutting punch, and the shell material is not drawn into it (Fig. 2). Thus, the whole bar after trimming goes in good condition.

Example 2. Extrusion rods of aluminum powder alloy difficult-CAC-1-50 as in Example 1. Fan Casing 2 had a height of shell 0,95h _{W W} + h. Press-tension in the bar extends to 50-100 mm from the rear end of the bar, reducing yield.

Example 3. Compression rod powder aluminum alloy hard-CAC-1-50 as in Example 1. Fan Casing 2 had a height of shell 0,6h _{W W} + h. On the lateral surface of the rod at a length of about 1/3 of the length from the rear end, there were surface breaks in the metal.

Thus, the technical result of the proposed solution is to increase manufacturability by reducing the cost of manufacturing the shell and increasing the yield due to the absence of a press weights and increasing the length of the used part of the bar.

Claims (6)

1. The method of hot pressing of hardly deformable alloys into a matrix from a workpiece placed in a shell of plastic material, characterized in that they use a shell made in the form of a glass from a detachable shell and a front washer, while the workpiece is immersed in a shell 70-90% of the height of the workpiece . 2. The method according to p. 1, characterized in that the casing and the front washer are made of the same material. 3. The method according to p. 1, characterized in that the casing and the front washer are made of different materials. 4. The method according to p. 3, characterized in that the front washer is made of a material similar in strength properties to the workpiece material. 5. The method according to any one of claims 1 to 4, characterized in that the front washer is flat. 6. The method according to any one of paragraphs. 1-4, characterized in that the front washer is conical, the cone of which corresponds to the forming surface of the matrix.

Images