JPS58133355A - Method for processing tungsten material - Google Patents

Abstract

PURPOSE:To obtain a processed product comprising a W-material free from deterioration in sag property, by a method wherein light impact processing and recrystallizing treatment are applied to the W-material so as to bring the same to the range of a predetermined cross area reduction ratio and the treated W- material is subjected to secondary processing. CONSTITUTION:For example, a W-ingot obtained by sintering a W-powder doped with K2O, SiO2 and Al2O3 is prepared. To this ingot, light impact processing is applied at 1,300-1,500 deg.C so as to adjust a cross area reduction ratio to 60- 90% and recrystallizing treatment is applied. In the next step, the W-ingot after recrystallizing treatment is subjected to secondary processing, for example, wire drawing processing at 800-1,000 deg.C by using a die having a cartridge heater mounted therein shown by Japanese Patent Application No.55-11819 to prepare a 170MG wire material. The resulting obtained wire material is good in sag property, low in a cracking ratio and size irregularity and the yield of the ingot material is enhanced.

Description

[Detailed description of the invention] The present invention relates to a method for processing tungsten material.

In general, this type of processing method is used to manufacture tungsten filaments and the like by rolling an ingot provided as a tungsten material and then subjecting it to wire drawing and the like.

Conventionally, this processing method involves rolling the tungsten material before wire drawing to reduce the area reduction rate.

In other words, a method has been proposed in which [1-(+ii area at the start of pulling/ingot cross-sectional area]) x 100 (a) is processed so that it becomes 90 to 97 inches (Japanese Patent Publication No. 53-7
No. 26).

It has been pointed out that according to this method, the sagging properties of products such as filaments can be improved and no cracks are observed.

Here, in this method, as stated in Japanese Patent Publication No. 53-15449, it is desirable that no or only one recrystallization treatment be performed during the rolling process. In this way, if the recrystallization treatment is kept to a minimum, there is a risk that two cracks will occur during the rolling process. In order to prevent this cracking, it has been proposed in Japanese Patent Publication No. 15449/1983 to reduce the rate of rolling per round (ie, the rate of area reduction). However, it is very difficult to reduce the rolling rate per round to achieve an overall area reduction rate of 90 to 97% due to the mechanism of the rolling machine. Also,
The number of rolling operations must be increased, which also increases costs.

An object of the present invention is to provide a method for processing tungsten material in which deterioration of sagging properties is not observed even if the area reduction rate is reduced.

In the present invention, it has been found that if the grain size of the crystals is controlled during the recrystallization treatment performed during the rolling process, good results can be obtained with a cross-sectional reduction rate in the range of 60 to 90 inches. . In addition, we were able to improve the sag resistance during wire drawing.

Although only tungsten will be described below, the present invention is also applicable to tungsten alloys.

First, a large number of tungsten ingots obtained by sintering tungsten powder doped with *K2O* 5102+ and At203 are prepared, and these ingots are subjected to rolling processing at 1300 to 1500 °C,
After recrystallization treatment 1. A wire with a grain size of 200 to 170 MG was prepared by drawing using a die. Note that the drawing temperature was 800 to 1000°C.

The characteristics of the material obtained by the present invention will be explained below while comparing them with the materials obtained by conventional processing methods.

(1) Sag property At203,5i02. A 170MG wire rod is obtained by varying the rolling processing rate from doped tungsten to which 20% is added. FIG. 1 is a diagram showing the deformation rate on the vertical axis and the rolling processing rate on the horizontal axis. As is clear from this figure, it can be seen that when the rolling processing rate is 60 to 89 inches, the deformation rate is small and the sagging property is good. Further, those with a rolling processing rate of 90% or more have a decreased sagging property.

(2) Yield of material 170 MG wire is obtained in the same manner as the sag property. FIG. 2 shows the cracking rate on the vertical axis and the rolling rate on the horizontal axis, and FIG. 3 shows the size deviation on the vertical axis and the rolling rate on the horizontal axis. As is clear from these figures, when drawing was carried out at a rolling rate of less than 90 inches, the variation in crack rate size was small and the yield of material was improved.

This is the effect of reducing the rolling rate and developing the fiber structure through strong drawing.

(3) During the secondary recrystallization, a 200 mm long line was cut out and the tensile strength at room temperature and the recrystallization temperature were determined using a microscope. The results of this determination are shown in FIG. 4, where the vertical axis represents the recrystallization temperature and the horizontal axis represents the rolling rate. As is clear from this figure, the smaller the rolling rate, the higher the recrystallization temperature. When the rolling rate is 90 inches or more, the recrystallization temperature drops significantly.

Next, the filament obtained by the processing method of the present invention was applied to a Halodan light bulb, and a practical test was carried out to produce a Nologon light bulb with a design life of 100 hours, as shown in this presentation.

Table 1 As shown in Table 1, those having a cross-sectional area reduction rate of 60% to 89% at the start of linearization using the processing method of the present invention have good sag resistance and service life.

As detailed above, the tungsten material processed by the processing method of the present invention has excellent properties.

[Brief explanation of drawings]

Figures 1, 2, 3 and 4 are diagrams showing various properties of tungsten material manufactured using the processing method of the present invention. The figure shows the material yield, and FIG. 4 shows the secondary recrystallization. Rolling and rolling process (o/□) Rolling and processing rate ('/,)

Claims (1)

[Claims] 1. A tungsten material processing method in which the tungsten material is rolled and recrystallized and then subjected to secondary processing, in which the cross-section reduction rate before the secondary processing is from 60 inches to 90 inches.
, a method for processing a tungsten material, characterized in that the tungsten material is subjected to a rolling process such that the tungsten material does not exceed .