JPH0116305B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a high-melting point metal wire, and more specifically, it suppresses the occurrence of defects such as surface cracks during electrolytic polishing, and thereby increases the yield of non-defective wire rods. The present invention relates to a method for manufacturing a high melting point metal wire with increased .

[Technical background of the invention and its problems]

High melting point metal wire, such as tungsten W wire,
Tungsten-rhenium (W-Re) alloy wire and the like are generally manufactured as follows.

First, a sintered body of a high-melting point metal produced by a known powder metallurgy method is hot rolled several times to make its structure denser and to stretch the equiaxed crystals into a fibrous shape. The wires are then arranged to make a wire rod with toughness.

The wire is then heat treated as necessary to remove internal distortion caused by the rolling process, and then passed through a number of dies with hole diameters that gradually change from large to small, either hot or warm, to form the wire. The wire is drawn to become even thinner. In this process, graphite suspension is usually used as a lubricant, so
A black surface adhesion layer made of graphite and an oxide such as W is formed on the surface of the wire after the wire drawing process is completed.

Although these wires are sometimes used in this state, they are sometimes further subjected to electrolytic polishing treatment to remove the surface adhesion layer and make the surface white and glossy.

However, during this electrolytic polishing process, cracks, cracks, etc. often occur on the surface of the wire rod, which may increase the defective rate of the product. In the case of wire rods with a small diameter, the occurrence of surface defects is relatively low, but in the case of relatively thick wire rods with a wire diameter of 0.2 mmφ or more after wire drawing, the incidence of surface defects is relatively low. becomes extremely high.

[Purpose of the invention]

The present invention aims to provide a method for suppressing the occurrence of surface defects during the subsequent electrolytic polishing of relatively thick wire rods having a wire diameter of 1.2 mmφ or more after wire drawing, thereby increasing the yield of good wire rods. purpose.

[Summary of the invention]

As a result of intensive research into the causes of surface defects during electrolytic polishing of thick wires, the inventors of the present invention have discovered that these surface defects are caused by the process of drawing process that remains on the surface and inside of the wire due to the thick wire. They discovered that distortion is caused by imbalance, and in order to eliminate this imbalance, they came up with the idea of heat treatment and annealing before electrolytic polishing, and developed the method of the present invention.

That is, the method of the present invention is a method for manufacturing a high-melting point metal wire, in which a sintered slag of a high-melting point metal is subjected to a rolling process, then a wire is drawn to form a wire rod, and then the wire rod is electrolytically polished. , a method for producing a high melting point metal wire, characterized in that a heat treatment is performed to uniformize the processing strain existing in the wire between the wire drawing process and the electrolytic polishing process.

The high melting point metal here refers to alloys such as W and W-Re, molybdenum (Mo), and alloys such as Mo-W alloy.

In the method of the present invention, first, a sintered body is manufactured from the above-mentioned metal by a commonly used powder metallurgy method. Next, this sintered body is rolled through a plurality of rolling machines, and the wire diameter is successively reduced to form a round bar with a predetermined diameter. Before passing through the next stage rolling machine, heat treatment is performed as necessary to remove distortion accumulated in the previous stage rolling process.

In the wire drawing process, the transferred wire is passed through a plurality of dies to gradually reduce its diameter. In the present invention, the wire diameter of the wire after drawing is 0.2 mm.
The effect is greater when the diameter is larger than 3mmφ.
Significant to a certain degree. It is particularly effective when the wire diameter is 1 to 1.8 mmφ.

In wire drawing, a graphite suspension is applied to the wire to provide lubricity, and the wire is passed through a die. The wire rod pulled out from the die is subjected to heat treatment, and then subjected to the above-described treatment again and passed through the next stage die. By repeating this process multiple times, a wire rod having the desired wire diameter is finally obtained.

Next, electropolishing is performed to remove the black adhesion layer on the surface of the wire. Electrolytic polishing is usually carried out using a caustic soda solution as an electrolyte and using direct current or alternating current.

Note that the above-mentioned drawing process is performed continuously,
Further, efficiency is increased if the wire rod that has completed this wire drawing process is directly passed to the next electrolytic polishing process.

The method of the present invention is characterized in that a heat treatment is performed to uniformize the processing strain existing in the wire during the transition from the end of wire drawing to electrolytic polishing. The heat treatment may be performed at a temperature of 900 to 1000°C, preferably 920 to 980°C, as long as the surface and internal condition of the wire is uniform.
It is appropriate to heat and anneal at a temperature of °C.

Specifically, for example, an annealing furnace is placed between the wire drawing process and the electrolytic polishing process, and the wire rod that comes out of the wire drawing process is allowed to run as it is through the annealing furnace, where it is annealed. It is introduced into the electrolytic polishing process.

A practical temperature range during annealing is 900 to 1000°C. If this temperature is too low, the unbalance of residual strain on the surface and inside of the wire during wire drawing will not be effectively resolved, and if it is too high, problems such as loss due to oxidation and recrystallization embrittlement may occur. may occur.

The atmosphere during annealing is not particularly limited and may be either an oxidizing atmosphere or a non-oxidizing atmosphere. When carried out in a non-oxidizing atmosphere, there is less oxidation loss. Furthermore, the annealing time is not particularly limited.

[Embodiments of the invention]

W slag was manufactured using a powder metallurgy method. This slag was subjected to a rolling process to obtain a wire rod with a wire diameter of 2.5 mmφ.
Next, this wire is passed through a six-stage die to determine the wire diameter.
The wire rod had a diameter of 1.55 mm. The surface was black. The obtained wire rod was heated in an air atmosphere at 950℃ and about 50cm in length.
The wire was passed through an annealing furnace at a running speed of approximately 10 m/min, and then electrolytically polished in a 25% caustic soda solution to a wire diameter of 1.5 mmφ.
A wire rod was obtained. When we observed defects on the surface of the wire after electrolytic polishing, no defects were observed per kilometer of wire length.

For comparison, we performed electrolytic polishing directly after wire drawing under the same conditions as above without passing it through an annealing furnace, and observed defects on the wire surface. Cracks occurred from half of the wire length to the entire subsequent length.

〔Effect of the invention〕

As is clear from the above explanation, according to the method of the present invention, defects such as cracks that occur on the wire surface are significantly reduced even after electrolytic polishing, and as a result, the yield of the product is increased and its industrial value is increased. big.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a high-melting point metal wire, which comprises subjecting a sintered body of a high-melting point metal to a rolling process, then performing a wire drawing process to obtain a wire rod, and then electrolytically polishing the wire rod. ,
A method for manufacturing a high-melting point metal wire, which comprises performing a heat treatment to uniformize processing strain existing in the wire between the wire drawing process and the electrolytic polishing process. 2. The method according to claim 1, wherein the high melting point metal wire is a tungsten wire or a tungsten alloy wire. 3. The method according to claim 1, wherein the wire diameter is 0.2 mmφ or more. 4. The method according to claim 1, wherein the heat treatment is performed at 900 to 1000°C.