SU1303261A1 - Method of compacting articles from powder - Google Patents

Abstract

The invention relates to molds for hot pressing of powder products. The aim of the invention is to expand the technological capabilities of the method. In the matrix 1, a rod 5 is installed with spacers 4 and 6 having a diameter greater than the diameter of the rod made of a material, the coefficient of thermal / Ja awoji. 7c (L l / jffejfi / e

Description

whose expansion exceeds the thermal expansion coefficient of the material of the spacers at a ratio of 0, В „р (1 + сА„ рТ) / 1, where 0 „and

В „р - diameters; oioT and cinp are the coefficients of thermal expansion of the material of the alo rods and spacers, respectively, j T is the pressing temperature. At the pressing temperature, the diameter of the rod becomes equal to the diameter of the spacers, the product is lowered.

The invention relates to powder metallurgy, in particular to press molds for hot pressing of articles from powders.

The purpose of the invention is to expand the technological capabilities of the method

FIG. 1 shows a circuit for assisting a rod made with a smaller size than that of a spacer; Fig. 2 is a pressing scheme in a matrix of KTR-regulated material.

In Matrix 1 (Fig. I) with holder 2, the lower punch 3 is installed, the lower spacer 4, on which the rod 5 is mounted, then the upper spacer 6 is placed on the center. from a material whose thermal expansion coefficient exceeds the thermal expansion coefficient of the npoc faBOK material with the ratio

D,

Sip-ii-t-iup-ii

where DCT and VPR are diameters;

c) 1c-gis) 1pr coefficients, thermal expansion of core and spacer materials, respectively;

T is the pressing temperature.

Powder is poured into the mold cavity, the upper punch 7 is installed, and the powder is cold pressed. Hot pressing is performed by staged heating and loading of the punch 7.

303261

sleep on the spacer 4, where its final compaction occurs to the magnitude of the increase in the diameter of the rod during heating. The matrix can be made of a material with a coefficient of thermal expansion equal to the coefficient of thermal expansion of the material of the rod. The method allows to obtain long-length equal-density hollow articles at temperatures up to 2500 ° C. 1 hp f., 2-yl.

W

15

20

25

thirty

35

40

When the rod reaches the pressing temperature, its diameter becomes equal to the diameter of the spacers 4 and 6. Then remove the split lining 8 of the die and move the compact to the spacer 4. Cooling the die is done without relieving the pressure of the punch 7, and the final seal on the spacer 4 increase the diameter of the core51 when heated.

According to the second variant of the method (FIG. 2), the matrix 1 is made of a material with a thermal expansion coefficient equal to the coefficient of thermal expansion of the rod material.

Example. As materials, parts of the molds were used; in the first embodiment, for a rod, MPG-6 grade graphite, for i-matrix spacers, GMZ grade graphite; according to the second option - for spacers - graphite of mark GMZ, for rod and matrix - graphite of mark MPG-6,

In both versions, products of silicon nitride and boron carbide were pressed at 1750 and 2100 C, respectively, 150 in height, 200 in diameter, and with a wall thickness of 8 mm.

The proposed method allows to obtain long-length equal-density hollow articles at temperatures up to.

Claims (1)

Invention Formula 1, Method of pressing products from powders, including installation of a rod into a matrix with piers larger than a rod of diameter made of a material that provides, during heating, a relative change in their transverse dimensions, different from the relative changes in the transverse dimensions of the remaining parts of the mold, filling in the matrix of powder and axial pressing of the powder by hollow punches, accompanied by heating of the mold, characterized in that, with a chain of extension of its technological capabilities, the core is taken from a material, whose coefficient of thermal expansion exceeds the coefficient of thermal expansion of the material of the spacers, in this case the ratio is satisfied D.  Dnali) one where and d ETC di r diameters; - coefficients of thermal expansion of the materials of the rod and spacers, respectively; T is the pressing temperature. 2, a method according to claim 1, characterized in that the matrix is taken from a material with a coefficient of thermal expansion equal to the coefficient of thermal expansion of the rod 20 FI.2 Editor N. Kishtulints Compiled by A. Tumanov Tehred V. Kadar Proofreader A, Zimokosov Order 1246/11 Circulation 741 Subscription VNIIPI USSR State Committee for inventions and discoveries 115035, Moscow, Zh-35, Raushsk nab. D. 4/5 Production and printing company, Uzhgorod, st. Project, 4