KR950014350B1 - Method of manufacturing alloy of w-cu system - Google Patents

Abstract

The tungsten-copper based alloy is manufactured by (a) coating tungsten powder with copper chloride or iron chloride instead of the addition method, (b) reducing the coated W powder with hydrogen gas to make copper or iron coated layer with the fluidized bed reduction method, (c) pressing the copper or iron coated powder and sintering them. The coating process comprises (a) mixing W powder, CuCl2H2O powder and ion exchange water, (b) stirring the mixture with a magnetic bar with heating, (c) drying and evaporating the water.

Description

Manufacturing method of W-Cu alloy

The present invention relates to a method for producing a W-Cu-based alloy, and more particularly to a new method for producing a low concentration C-containing W-Cu-based alloy having a uniform hag density.

W-Cu alloy, which combines W, a strong refractory metal, and Cu with good thermal and electrical conductivity, has been widely used as an electrical contact material because of its high strength and electrical conductivity at the same time. It has been shown to be applicable as an absorbent material. Due to the high melting point of W, the W-Cu alloy is produced by powder metallurgy and is mainly produced by liquid sintering at temperatures above the Cu melting point, or by infiltration by forming a skeleton with W powder and fusing Cu into it. In the conventional method for producing W-Cu alloy by liquid phase sintering, after mixing Cu powder and W powder, the mixed powder is pressurized in a pressure machine and molded, and then sintered and heat-treated at a temperature above the melting point of Cu (> 1083 ° C). do. In some cases, after sintering, re-pressurization may be performed to increase the density and remove residual pores, followed by a resintering process. In addition, the method by the infiltration method forms a pure W powder or a W powder mixed with a small amount of Cu by pressing in a pressure machine. At this time, by adjusting the porosity of the molded body by pressing. After sintering to form a rigid skeleton, Cu lumps are placed on (or below) the skeleton, and then Cu is melted to absorb Cu into the molded body by a mother tube phenomenon. Annealing may be followed.

However, according to the conventional liquid phase sintering method, it is difficult to crack and mix the Cu powder and the W powder, and since Cu and W have little interoperability, it is difficult to manufacture a high density W-Cu alloy by liquid phase sintering alone. In addition, when the liquid phase at the time of sintering has a small sticking angle in the high phase, it is advantageous for densification, and W-Cu has a large sticking angle. On the other hand, according to the infiltration method, the composition of Cu is limited by the porosity of the initially formed W-molded product, which makes it difficult to produce a W-Cu alloy having a low Cu content. In addition, it is impossible to manufacture an alloy in the case of a fine shape. In addition, a method of preparing a W-Cu alloy by adding W into a copper salt solution such as CuCl ₂ , mixing and drying it, and then reducing it with hydrogen is known, but according to this method, a large amount of time is required to perform a reduction operation. In addition, since the reduction operation cannot be carried out continuously, there are defects such as an increase in production cost and difficulty in mass production.

An object of the present invention is to provide a method for producing a high-density W-Cu alloy by eliminating all the problems of the conventional method for producing a W-Cu alloy.

According to the present invention for achieving the above object, the W-Cu alloy combines CuCl ₂ powder and W powder to form agglomerates, pulverizes the agglomerates to form a CuCl ₂ coated W powder, and then flows in a hydrogen atmosphere. Obtained by reduction using Fluidized Bed Reduction.

That is, W powder and CuCI ₂ ㆍ 2H ₂ O powder are measured to a desired composition, mixed with ion exchanged water together, stirred and dried with a magnetic bar while heating and evaporated to remove all ion exchanged water. The lump formed by mixing with the W powder is left.

The mass is further separated into a container and ground to obtain a W powder coated with CuCl ₂ . When through the H ₂ gas charged in this powder back to the fluidized bed reaction, CuCl ₂ + H ₂ → final Cu is uniformly goting by a so-called fluidized-bed reduction CuCl ₂ is being reduced to Cu by reaction of Cu + 2HCl The obtained W powder is obtained.

On the other hand, when preparing a W-Cu-based alloy to prepare a W-Cu-Co-based powder or W-Cu-Fe powder by adding a small amount of Co or Fe to the mixed powder of W and Cu, the adhesion of Cu to the W powder (wettability) is greatly improved. Two methods can be used to produce such powders.

In the first method, CoCl ₂ ㆍ 6H ₂ O powder or FeCl ₃ ㆍ 6H ₂ O powder is weighed to a desired content of Co or Fe in a mixed powder of W powder and CuCl ₂ ㆍ 2H ₂ O powder, and the aforementioned W-Cu Performing the same process as in the preparation of the alloy yields W powder coated with CuCl ₂ and CoCl ₂ or W powder coated with CuCl ₂ and FeCl ₃ as intermediate products and again W-Cu-Co or W by fluid phase reduction. -Cu-Fe powder is finally prepared.

The second method is the same method as coating Cu on W powder. First, Co or Fe is surface-coated on W powder to obtain W powder coated with Co or Fe, and then the same method is used again to coat Cu. Finally, W-Cu-Co or W-Cu-Fe powders are obtained. Reduction temperature at the time of reduction by the fluidized bed reduction method is thermodynamically, the reduction reaction may occur by hydrogen at CuCl ₂ above room temperature, CoCl ₂ above 600 ° C, and FeCl ₃ above 300 ° C. In practice, however, the reduction of CuCl ₂ occurred at temperatures above 20 ° C and the reduction reactions of FeCl ₂ and CoCl ₂ occurred at thermodynamically expected temperatures. Therefore, the W-Cu powder may be prepared at 200 ° C. or higher and the W-Cu-Co powder at 600 ° C. or higher, and the W-Cu-Fe powder may be prepared at 300 ° C. or higher.

The W-Cu, W-Cu-Co or W-Cu-Fe powders obtained as described above are press-molded in predetermined dies to solid-sinter at or below the melting point (1083 ° C) of Cu. Liquid phase sintering at gives a sintered body of high density W-Cu, W-Cu-Co or W-Cu-Fe alloy. The sintered body may be repressurized to remove residual pores or deformed to desired dimensions, or may be resintered as necessary.

Example 1

Preparation of 75% W-25% Cu sintered body, where% is% by weight and all the same below

12.01 g of W powder and 10.73 g of CuCl ₂ · 2H ₂ O powder were taken, followed by mixing in 30 ml of water and a glass bottle. The mixture was kept at 110 ° C. and stirred for about 120 minutes to completely remove moisture, and the obtained mass was pulverized and then fed using a 325 mesh sieve. The powder thus obtained is charged into a vertical quartz tube and passed through about 20 ml / min of hydrogen to form a hydrogen atmosphere. When the furnace temperature reaches 300 ° C., the powder flows while passing through 20 ml / min of hydrogen. The chloride was reduced for about 40 minutes. The reduced powder is put in a cylindrical pressurization mold and pressurized at 200 MPa to form a molded body. The molding agent was heated to 1200 ° C. in a hydrogen atmosphere to obtain a sintered body, and the characteristics thereof are shown in Table 1.

Example 2

Preparation of 75% W-24.5%, Cu-0.5% Co Sintered Body

W powder 12.0 lg, CuCl ₂ .2H ₂ O 10.52 g, CoCl ₂ .6H ₂ o 0.32 g. A W-Cu-Co sintered body was obtained in the same manner as in Example 1 except that the furnace temperature at reduction was 700 ° C., and the properties thereof are shown in Table 1 below.

Example 3

Preparation of 75% W-24.5%, Cu-0 5% Fe Sintered Body

W-Cu in the same manner as in Example 1 except that 12.01 g of W powder, 10.5% of CuCl ₂ · 2H ₂ O, 039 g of FeCl 3 · 6H ₂ O, and the furnace temperature at the time of reduction were kept at 400 ° C. A -Fe sintered body was obtained and its properties are shown in Table 1.

According to the present invention as described above by the addition of Cu by the coating by the fluidized phase reduction method to the fine W powder of 1μm or less, it is possible to manufacture a finer and more uniform W-Cu powder and by sintering it, A high density W-Cu sintered body can be prepared, and a small amount of Co or Fe can be added thereto to improve adhesion of the Cu liquid phase, thereby producing a W-Cu alloy having a higher density at a faster time.

Table 1 shows the volume shrinkage rule when sintered at each sintering temperature for 0 hours. In the case of sintered body in which 0.5% of Co (or Fe) was added to W-Cu, the relative density was about 96% at 1200 ° C. In the case of -Cu sintered body, it can be seen that the sintered density exceeds 70%.

TABLE 1

Volume Shrinkage Rate of Sintered Body According to Sintering Temperature

Such experimental results according to the present invention are superior to 60% relative density and 70% W-30% Cu composition suggested by JSLEE et al. (Modern Development in P / M, 1985, 15, PP. 489-506). It is superior to that reported by Fujii et al. (ISIJ. 1990, 76 (5) .PP 743-750) with a relative density of 90% or less even after 1 hour of sintering at 1150 ° C.

Its high strength and high conductivity make it suitable for many applications, including electrical contact materials and heatsinks for IC chips. In addition, according to the present invention, it is possible to manufacture a fine-shaped W-Cu alloy parts and may be easily used for the production of W-Cu alloys requiring low concentration of Cu.

Claims (2)

By reduction with a coating of CuCl ₂ in the W powder and then through the H ₂ gas to a powder A method of after preparing the W-Cu based alloy by sintering the press-molding it to form a Cu coating layer, the CoCl ₂ in the W powder A method for producing a W-Cu alloy, characterized in that Co is added as a trace element by further coating. The method of claim 1, wherein Fe is added as a trace element by further coating FeCl ₃ on the W powder.