SU1678527A1 - Process for manufacturing hard alloy-based tools - Google Patents

Abstract

The invention relates to powder metallurgy, in particular, to methods for producing carbide products. The purpose of the invention is to increase the strength and uniformity of products. The hard alloy and binder powders, which use solid-phase thermoplastic polymers of the methacrylate class in an amount of 2-3 wt.%, Are vibrated together for 2-3 hours until the polymer cracking is completed, then pressed, the resulting compact is thermo-processed, mechanically processed and baked at 600-700 ° C to remove the binder. 3 tab.

Description

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The invention relates to powder metallurgy, in particular, to methods for producing carbide products.

The purpose of the invention is to increase the strength and equal density of the tool.

The method is carried out as follows.

A joint vibro-processing of powders of a hard alloy and a binder is carried out to evenly distribute the binder over the surface of the hard alloy particles. Solid thermoplastic polymers of the methacrylate class are used as the binder. Chemical Formula

QH3-CH2-C-p

COOR

Then, blanks are pressed, which are thermally processed to increase strength. The moldings are machined to give the desired shape and size. The sintering is carried out stepwise with an exposure at the binder distillation temperature.

PRI me R. Powdery hard alloy grade BK6 and a binder are loaded into an airtight container. The binder is introduced in an amount of 2–3%, so with a lower polymer content, the sp / zz particles are covered with a film only in a small step. When the binder is inserted more than 3%, the polymer decomposes during sintering and forms a gas that accumulates in closed pores leads to the weakening of products. Vibration treatment is carried out within 2–3 hours. With vibration treatment for less than 2 hours, the destruction processes do not proceed and such vibration treatment does not improve the uniformity of distribution of the binder by volume.

Pressing is carried out on a hydraulic press 4 with a pressure of 100-700 MPa. Next, the compacts are subjected to polymerization heating: incubated for

about

VJ C SL Y VJ

2 hours at 120-150 ° C. The heating is carried out in an electric chamber furnace. Then the blanks are machined by cutting. The binder is distilled off at 600-700 ° C in an atmosphere of dissociated ammonia or in a vacuum. Sintering is carried out in an electric vacuum resistance furnace at 1400 ° C with a vacuum depth of 5-1СГ5 mm Hg. within 1 hour. The compressive strength of the compacts is determined on a tensile machine. Density is determined by hydrostatic weighing.

The strength of compacts for various polymers with their different contents, obtained at a pressing pressure of 400 MPa, is shown in Table. one.

As follows from the table. 1 data, the strength of the products obtained by the proposed method, on average, is 2 times higher than the strength of products obtained in the case of use as a bonding polyethylene.

The strength of the resulting compacts allows them to be machined by cutting.

The unevenness in the direction of movement of the punch is a characteristic feature of the extrusion. This is due to the loss of friction force of the powder on the degree of the mold and, consequently, its decrease in the direction of pressing. In order to estimate the decrease in the density of compacts in the direction of extrusion, the following experimental method was chosen. A certain portion of powder is poured into the matrix, smoothed, and then a plate is laid 1 mm thick according to the shape of the matrix. Next, pour the next portion of the powder and again put the plate, and so several times. After pressing with the desired force, the resulting layer cake is disassembled and the density of the obtained tablets is determined.

These experiments are given in table. 2 As follows from the table. 2 data, the introduction of polymers by vibration treatment significantly increases the overall

the density of the compacts (from 8.4 to 10.12 g / cm 3) compared with rubber (8.24 g / cm 3). This is due to the fact that rubber slightly reduces the coefficient of friction of the powder against each other, which makes it difficult for the powder particles to move during pressing and, as a result, the density is low. The carbide powder vibrated in the presence of methacrylates as a result of the graft polymerization is coated with a polymer film, which contributes to a decrease in the coefficient of friction between them and an increase in the overall density of compacts. At the same time, the coefficient of friction of the powder against the walls of the die decreases and, consequently, a more uniform density is achieved in the direction of pressing.

Data on the effect of holding temperature during sintering of compacts on the completeness of binder removal are presented in Table. 3

As follows from the data table. 3, removal of the binder occurs completely at 600-700 ° C. With an increase in the holding temperature above 700 ° C, the increment in the removal of the binder does not occur; therefore, exposure at higher temperatures is impractical and can lead to swelling and distortion of the products.

Claims (1)

The invention The method of manufacturing a carbide tool, including the introduction of a binder into a solid carbide powder, pressing the mixture, thermal and mechanical processing, removing the binder and sintering, characterized in that, in order to increase the strength and equal density of the tool, solid phase thermoplastic polymers of methacrylate class in the amount of 2-3 May. %, then joint processing of the carbide and polymer powders is carried out until the polymer is mechanically cracked, and the binder is removed at 600–700 ° C. Table 1 Note. The pressing pressure is 600 MPa. Continuation of table 1 table 2 Table 3