SU1632629A1 - Mould for powder compaction - Google Patents

Abstract

The invention relates to powder metallurgy. The goal is to obtain blanks with a porosity of less than 1%. The pressed powder is loaded into the cavity bounded by the bottom of the punch 3, and on the sides with inserts 4 and 5 and an elastic sheath 6. Then the upper punch is inserted and the billet is molded. The gap between the outer surface of the punches and the inner surface of the inserts is 0.05-0.1 mm, which allows air to be removed from the compression mold and prevent the powder from flowing into the specified gap. As a result of pressing, pressed blanks with a porosity of less than 1% are obtained. 2 Il.

Description

FIG. one

The invention relates to powder metallurgy, in particular to molds for pressing powder blanks.

The aim of the invention is to obtain blanks with a porosity of less than 1%.

Fig. 1 is a diagram of the mold prior to the start of pressing; Fig. 2 is the same at the time of pressing.

The powder pressing mold consists of a die 1, symmetrical punches 2 and 3, inserts 4 and 5, and an elastic sheath 6.

The mold works as follows.

When the upper punch 2 is removed, the pressed powder is loaded into the cavity bounded below by the punch 3, and on the sides by inserts 4 and 5 and the elastic sheath 6. Then the upper punch is inserted, the mold is placed under the press and the billet is formed. The gap between the punches and the inner surface of the inserts is 0.05-0.1 mm, which allows the air between the powder particles to continuously pass outwards, helping to close the pores and obtain dense preforms. The external and internal diameters of the inserts located in the cavity of the die channel coincide with the same dimensions of the elastic shell.

During the pressing process, the elastic casing, over its entire length, perceives a part of the pressure, which is transmitted through the end parts of the pressed workpiece and maintains in the zone limited by its length, equal density of the briquette and uniform distribution of pressure in it. The elastic casing absorbs most of the pressing force. Since the working length of the punches is equal to the length of the inserts, their pressing plane at the end of the molding process reaches the edge of the elastic sheath, thereby ensuring the transfer of the full pressing force to it through the edge of the pressed billet.

The mold is disassembled in the following order. The puller nuts (not shown) are screwed onto the threaded ends of the inserts, and the inserts together with the punches are removed from the mold, then the workpiece is pushed out of the die along with the elastic sheath. Shell removed

one of the known methods (cutting, melting, etc.) The resulting billet has a porosity of less than 1 micron. Example. Formed subjected

basalt powder of the following particle size distribution: (1500 + 1000) μm 55%, (200 + 100) μm 30%, (40 + 0) μm 15% Amount of powder 14.04 g.

Internal diameter of a matrix is 20 mm,

height of the channel is 50 mm, internal diameter of inserts and lead sheath is 17 mm. the diameter of the punches is 16.93 mm, the height of the workpiece and lead sheath is 20 mm, the working length of the punches and the length of the inserts is 30 mm. An effort

The compaction was 2.7 tons. For comparison, the same powder was compacted in a known mold under similar conditions. Samples of a height of 20.05 mm (the proposed mold) and

21.8 mm (known mold), the porosity of which is 0.5 and 4%, respectively.

The use of gaps smaller than 0.05 mm in the proposed mold can lead to seizure of the punches in the insertion channels, since at pressures of the order of 10 kbar the maximum increase in the diameter of the punch is of the order of 0.05 mm. The use of gaps in excess of 0.1 mm can lead to the extrusion of powder particles into the gap and the setting of the punches in the insertion channels, which causes an increase in pressing forces and an increase in the porosity of the pressed blanks.

Thus, the use of the proposed mold allows to obtain blanks from powders, mainly natural minerals with a porosity of less than 1%.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A mold for pressing powder blanks containing a matrix, punches and an elastic sleeve, characterized in that, in order to obtain blanks with a porosity of less than 1%, it is provided with inserts whose length is equal to the length of the working part of the punches, and located on either side of the sleeve, their 0, the inner diameter is equal to the inner diameter of the sleeve and exceeds the diameter of the working part of the punches by 0.05-0.1 mm. fig ..