RU2533578C1 - Method of making billets from metal and composite powders - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: powder is arranged in working zone of the mould confined by pot, male die and female die to make both compact said powder. Processing is performed at temperature not higher than powder material recrystallisation temperature, in two steps. At first step, powder is compacted by creation of stress-strain state of 3D compaction and shear strain in planes making the angle 45°≤α≤90° with direction of compaction forces. At second state, compacted billet is calibrated and additionally compacted by male die and female die with end working surfaces perpendicular to direction of compaction forces. Thereafter, the billet is removed from the pot.

EFFECT: better mechanical properties owing to higher density and refined microstructure of material.

4 cl, 5 dwg, 1 ex

Description

The invention relates to the field of powder metallurgy and can be used for the manufacture of blanks for subsequent pressure processing - forging, stamping, pressing, as well as for the manufacture of parts by cutting.

A known method of producing parts from powder by hot isostatic pressing, including filling the container with degassed powder, sealing the container, placing it in an autoclave with pressure and high temperature applied to the container, removing the powder from the container after compacting, control, thermal and mechanical processing of the obtained part [Deformation and material properties for aviation and space technology. Proceedings of the international conference. Houldsworth. 1977. Translation from English. Ed. prof. S.G. Glazunov. Moscow: Metallurgy, 1982. P.302-303].

The disadvantages of this method include the high cost of the parts obtained and the low productivity of the process due to the need to manufacture an individual container for each part.

There is also a method of producing blanks from powder materials, including placing the powder in the working area of the mold, limited by the container, punch and counter-punch, the subsequent application of sealing forces to the punch and counter-punch to consolidate the powder, which is taken as a prototype [Utyashev F.Z. Modern methods of intense plastic deformation: a training manual. Ufa state Aviation tech. un-t Ufa: USATU, 2008. P.246].

The disadvantages of this method include the low density of the resulting workpieces.

The objective of the invention is to improve the physico-mechanical properties of the workpiece by increasing the density of the workpieces and grinding the microstructure of the material.

The specified technical result is achieved by the method of obtaining preforms of powder materials, including placing the powder in the working area of the mold, limited by the container, punch and counter-punch, followed by applying sealing forces to the punch and counter-punch to consolidate the powder, in which, unlike the prototype, processing is carried out at a temperature not above the temperature of recrystallization of the powder material, in two stages, while in the first stage, the powder is consolidated by simultaneously creating of the irradiated workpiece of the stress-strain state diagram of comprehensive bulk compression and shear deformation in planes making an angle of 45 ° <α> 90 ° with the direction of the sealing forces, and at the second stage, the consolidated workpiece located in the container is calibrated and additionally compacted with a punch and counter-punch with workers end surfaces perpendicular to the direction of the sealing forces, after which the workpiece is removed from the container.

According to the invention, at the first stage, the treatment is carried out in several cycles, with each cycle before applying to the punch and counter-punch sealing forces they are rotated relative to the vertical axis by the same angle equal to 5 ... 180 °.

According to the invention, the treatment is carried out with the possibility of extruding part of the volume of the workpiece into the flask.

According to the invention, a medium reducing oxides on the surface of the powder particles, for example, hydrogen, is fed into the working area of the mold with the powder placed in it before consolidation.

The method is illustrated by sketches:

Figure 1 shows the design of the mold and the placement of the powder in its working area;

figure 2 presents a diagram of the consolidation of the powder in the first stage of processing;

figure 3 shows the transitions of the first stage in the case of multi-cycle processing;

figure 4 shows a diagram of calibration and additional sealing of the workpiece in the second stage;

figure 5 presents the supply circuit of the reducing medium. The method is implemented as follows.

To obtain blanks use a mold (figure 1), consisting of a container 1, a punch 2, a counter punch 3. In the working area of the mold is placed powder 4.

The mold is heated to a temperature not higher than the temperature of recrystallization of the powder material and a sealing force P is applied to the punch 3 to consolidate the powder 4 (FIG. 2).

At the first stage of processing in the volume of the consolidated workpiece (Fig. 2), a diagram of the stress-strain state of comprehensive compression under the influence of a normal force P _n = Pcosα is created and shear deformation occurs in planes making an angle of 45 ° <α> 90 ° under the influence of a shear force P _τ = Psinα. Shear deformation in the volume of the workpiece under the influence of the force P _τ intensifies the process of consolidation of the powder particles due to their more active movement relative to each other, and also contributes to the grinding of their microstructure. The criterion for choosing the angle α is the resource of technological plasticity of the material of the consolidated workpiece. In subsequent calibration, a smaller value of the angle α corresponds to a greater degree of deformation of the workpiece.

Then, the second processing stage is carried out, where without removing the consolidated workpiece located in the container, it is calibrated and additionally compacted (Fig. 4) with a punch 2 and a counter punch 3 with working end surfaces perpendicular to the axis of the sealing forces P and removed from the container.

To increase the degree of accumulated deformation in the workpiece 5 at the first stage, processing can be carried out in several cycles (Fig. 3), and at each cycle, before applying to the punch 2 and counter-punch 3 sealing forces P they are rotated relative to the axis of the applied forces by the same angle β, equal to 5 ... 180 °. A larger value of the angle of rotation is used for highly plastic materials, for example, copper powder, lower for low-plastic materials, for example, iron powder.

To increase the intensity of movement of the powder particles relative to each other, the treatment is carried out with the possibility of extruding part of the volume of the workpiece 5 into the flask.

In order to increase the density of the obtained preform 5 before consolidating the powder, a medium reducing oxides on the surface of the powder particles, for example, hydrogen, is fed into the working zone of the mold (Fig. 5). Moreover, for supplying a reducing medium and removal of the products of the reducing reaction (vapors), channels 6 are made in the container 1.

An example of a specific implementation.

As the processed material, copper powder M1 with a dispersion of 140-180 μm with a micro grain size of 120-140 nm and a recrystallization temperature of 180 ° C was used. The processing was carried out according to the method of the prototype and according to the proposed method.

In the first case (according to the prototype), a workpiece with a density of 0.85 monolithic material and microhardness H _v = 2150 MPa was obtained.

In the second case, the processing was carried out according to the invention in two stages. At the first stage, the powder was consolidated at the mold temperature t = 140 ° C with the application of a sealing force P to the punch and counter-punch with the action of its components P _n and P _τ at an angle α = 75 ° to the workpiece surface. For this, a punch and a counter punch with inclined end surfaces making an angle α = 75 ° relative to their vertical axes were used (FIG. 2). The processing was carried out in 3 cycles with simultaneous rotation of the punch and counter-punch at an angle β = 45 ° between cycles (figure 3).

At the second stage, the workpiece was calibrated and additionally compacted with a punch and counter punch with end surfaces perpendicular to their vertical axes.

As a result of processing, a workpiece with a density of 0.96 monolithic material and microhardness H _v = 2150 MPa was obtained.

Thus, the proposed invention allows to improve the operational characteristics of the workpiece made of powder material by increasing the density and grinding of the microstructure of the material.

Claims (4)

1. A method of obtaining a blank of powder material, including placing the powder in the working area of the mold, limited by the container, punch and counter-punch, the subsequent application of sealing forces to the punch and counter-punch to consolidate the powder, characterized in that the treatment is carried out at a temperature not higher than the temperature recrystallization of the powder material, in two stages, while at the first stage the powder is consolidated by simultaneously creating a stress-strain circuit with comprehensive compression and shear deformation in planes making an angle of 45 ° ≤α≤90 ° with the direction of the sealing forces, and at the second stage, the consolidated workpiece located in the container is calibrated and additionally compacted with a punch and counter-punch with working end surfaces perpendicular to the direction of the sealing efforts, after which the workpiece is removed from the container. 2. The method according to claim 1, characterized in that at the first stage the processing is carried out in several cycles, with each cycle before applying to the punch and counter-punch sealing forces they are rotated relative to the vertical axis by the same angle equal to 5-180 °. 3. The method according to claim 1, characterized in that the treatment is carried out with the possibility of extruding part of the volume of the workpiece in the flask. 4. The method according to claim 1, characterized in that the medium reducing the oxides on the surface of the powder particles, for example, hydrogen, is supplied to the working area of the mold with the powder placed in it before consolidation.

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