RU1540153C - Method of manufacturing tungsten powder - Google Patents

Abstract

FIELD: foundry engineering. SUBSTANCE: ammonia paratungstate is discomposed during heat treatment at the temperature of 500-550 C. As a result tungsten trioxide is received. Silico-alkaline and aluminum admixtures are added to tungsten trioxide and reducing is carried out in three stages. The first stage is carried out at the temperature of 500-600 C during 30 minutes. The second stage is carried out at the temperature of 630-700 C during 2-3 hours. The third stage is carried out at the temperature of 800-820 C. Within this method tungsten powder suitable for manufacturing wire with enhanced creeping features is manufactured. EFFECT: enhanced efficiency. 2 cl, 3 tbl

Description

 The invention relates to powder metallurgy, in particular to methods for producing tungsten powder with silica-alkali and aluminum additives for the manufacture of non-sagging tungsten.

 The aim of the invention is to increase the yield and expansion of technological capabilities due to the process in hydrogen furnaces of any type.

EXAMPLE EXAMPLE 1 The starting material take ammonium paratungstate, it is subjected to calcination at 500-550 ^{° C} by thermal decomposition to form tungsten trioxide.

In the resulting trioxide is introduced standard silica-alkali and aluminum additives based on SiO ₂ 0.45; K 0.32; Al ₂ O ₃ 0.03.

 Recovery is carried out in three stages in five-zone two-tube furnaces with separate temperature control in the heating zones and in stationary tube and muffle furnaces.

Additional first reduction is carried out in the stationary tube or muffle furnace at 500, 550 and 600 ^{° C} for 30, 45 and 60 min. The load in the furnace is 300-2250 g, the consumption of hydrogen is 0.6-2 m ³ / h.

The lower tungsten oxides obtained after additional reduction are reduced in a two-tube five-zone furnace according to the following modes: second stage of reduction, temperature in zones, ^о С: 590-650 690-690-650, loading into a boat, 300 g, hydrogen consumption 1.5 m ³ / h , the third stage of recovery is the temperature in zones, ^о С: 700-800-820-820-630, loading into the boat 250 g, hydrogen consumption 2 m ³ / h.

 The recovered tungsten powders are processed according to standard technology to a ⌀1.25 mm tungsten wire, which is tested for creep. The data obtained are given in table. 1.

PRI me R 2. An additional first recovery is carried out in a stationary tubular furnace at 550 ^about C and a duration of 30 minutes, a flow rate of hydrogen of 0.5 m ³ / h and loading into the boat 300 g

The second stage of recovery is carried out in the same furnace at 630-715 ^about C for 3 hours to tungsten dioxide. Loading into the boat 300 g, hydrogen consumption 0.5 m ³ / h.

 The third stage of recovery is carried out in a tubular five-zone furnace under conditions similar to those adopted in example 1.

The results are shown in table. 2. They show that the holding of the second step in the reduction in the stationary oven at 630-700 ^{° C} allows to obtain self supporting tungsten wire.

PRI me R 3. An additional first recovery is carried out in a five-zone multi-tube furnace, and to reduce the duration of the stay of the restored tungsten trioxide in the hot zone, only the second zone of the furnace is included for heating. Recovery mode: temperature 500 and 550 ^о С, loading into a boat 300 g, speed of boat advance 4 or 6 boats per 1 h (≈17 or 25 mm / min), hydrogen consumption 1,5 m ³ / h. The modes of the second and third stages of recovery are similar to those adopted in example 1. The results are shown in table. 3.

PRI me R 4. An additional first recovery, the second and third stage of recovery is carried out in a stationary furnace. Additional recovery mode: temperature 550 ^{° C,} duration 30 minutes, the hydrogen flow rate 0.5 ^m3 / h, loading the boat 300 g, the second temperature reduction step of 690 ^{° C,} duration 2 hours, hydrogen flow rate of 0.5 m ³ / h loading into the boat about 297 g (amount of lower tungsten oxide after an additional reduction step). A third reduction step mode: temperature 850 ^C, the duration of 3 hours, the hydrogen flow rate 0.5 ^m3 / h, weighed, the boat 250, the resulting powder is processed into a wire ⌀1,25 mm by standard regimes wire test gives a result of creep 3 mm.

 The lower tungsten oxide obtained at the additional reduction stage, containing an additive in the form of optimal chemical compounds, can be reduced at subsequent stages without compromising the quality of the manufactured non-sagging tungsten in a wide range of reduction conditions, which contributes to an increase in the yield during reduction under industrial conditions and allows reduction powders for the manufacture of non-sagging tungsten in furnaces of various types, including stationary (without eryvnoy prodvizhki boats) in a laboratory furnace.

Silica-alkali and aluminum additives are found in tungsten trioxide in the form of potassium and aluminum salts of silicic tungsten acid. Experimental research of hydrogen reduction of salts showed that the recovery of hydrogen begins at ⁵⁰⁰ ° C, which gives a lower bound additional reduction stage temperature. Above 600 ^{° C} is changing the nature of the material recovery additive, and this limits the temperature range above. The duration of the additional stage is due to the fact that, with a duration of less than 30 minutes, the process does not proceed completely, with a duration of more than 60 minutes, side effects are observed leading to a deterioration in the quality of non-sagging tungsten.

Carrying out the second stage of reduction in stationary furnaces leads to the fact that non-sagging tungsten can be obtained by reducing lower oxide in an atmosphere of dry hydrogen for 2-3 hours at 630-700 ^o C.

 The conditions of the third stage of recovery have little effect on the quality of non-sagging tungsten, and when it is carried out in stationary furnaces, the conditions of recovery can be selected by analogy with the prototype.

Using the proposed method for producing tungsten powder for the manufacture of non-sagging tungsten provides the following advantages compared to the prototype:
increase in yield upon receipt of a non-sagging tungsten wire of increased heat resistance (having an elongation in the creep test of not more than 4 mm) from 70 to 90%
the possibility of implementing the process in various types of furnaces, including laboratory stationary furnaces, which saves human and material resources.

Claims (2)

1. METHOD FOR PRODUCING TUNGSTEN POWDER, including thermal decomposition of paratungstate with the formation of tungsten trioxide, introduction of silicon-alkali and aluminum additives into the latter and restoration of dry hydrogen in the atmosphere in two stages, characterized in that, in order to increase the yield and expand technological capabilities by carrying out process in hydrogen furnaces of any type, before the first stage of recovery, preliminary reduction is carried out at 500-600 ^o C for 30-60 minutes 2. The method according to p. 1, characterized in that the first stage of recovery is carried out at 630-700 ^o C for 2-3 hours

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