JPH01127605A - Production of pure cr or high-cr alloy wire rod - Google Patents

Abstract

PURPOSE:To produce a pure Cr wire rod which has no defects such as cracks with high productivity by packing pure Cr powder into a capsule and subjecting the capsule to vacuum sealing, HIP, hot swaging, surface conditioning, capsule coating, and hot swaging successively under specific conditions. CONSTITUTION:The pure Cr powder or high-Cr alloy powder is packed into the capsule and is vacuum sealed under 10<-3>mmHg. This capsule is then subjected to hot isostatic press molding for >=30 minutes at >=1000 deg.C and under >=500kgf/cm<2> pressure. The molding is heated to 850-1300 deg.C and is subjected to the hot swaging down to about the wire diameter at which the defects such as cracks are not generated; thereafter, the surface characteristics are conditioned by removing the oxide layer on the outside peripheral face of the work by centerless grinding. The work is further coated with the capsule to retard the cooling of the work interior and is heated to 850-1300 deg.C, following which the work is hot swaged down to the desired wire diameter. The capsule is removed by centerless grinding or etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing pure Cr or high Cr alloy wire by powder metallurgy.

[Conventional technology]

Pure Cr or high Cr alloys are used as coatings on glass for mirrors, as thermal insulators, and as wear-resistant protection materials.

It is widely used as switching materials, various electrode materials, and in the semiconductor industry.

Conventionally, methods for manufacturing high-density pure Cr or high Cr alloys include Japanese Patent Publication No. 60-58289 and Japanese Patent Application Laid-open No. 62-17.
The one disclosed in No. 4373 is known. These methods apply a powder metallurgy method, and generally include (a) vacuum-sealing a raw material powder having a desired composition into a metal container (referred to as a capsule in the present specification) under heating;

(b) Sintering under pressure using a hot isostatic press (hereinafter referred to as HIP), (c) Hot working at a predetermined temperature and processing rate, (d) Removing the metal container by grinding or other means. This manufacturing method consists of a series of steps, and is mainly applied to manufacturing sputtering targets.

This manufacturing method is a useful method because it can manufacture members with high density and no internal defects with high productivity.

[Problem that the invention seeks to solve]

The manufacturing method described in Japanese Patent Publication No. 60-58289 is aimed at manufacturing a sputtering target as described above, and is mainly applied to manufacturing a plate-shaped article in its final form.

The applications of pure Cr or high Cr alloys are as mentioned above, but depending on the application, such as electrode materials and switching materials, there is a demand for small diameter wires and rods (herein simply referred to as wires). .

The present inventors conducted experiments and studies to manufacture a wire rod using the above manufacturing method, specifically, the HIP-rolling method.

A 100φ capsule made of 5US304 steel was filled with pure Cr powder and sealed by vacuuming at 10°5μl1g. Next, this capsule was heated to a temperature of 1180°C and 100100O.
HIP treatment was performed for 2 hours under the conditions of /aJ. The outer diameter of the capsule after HIP was 80φ. This temperature range is 950 ~
Hot rolling was performed at 1150°C to a diameter of 30φ. The cross section after rolling is shown in FIG. 1, and the capsule had wrinkles that could cause material defects. Furthermore, when rolling was carried out to 7.0 φ, the capsule was removed, and the appearance was checked, cracks had occurred over the entire length.

As is clear from the above experimental and study results.

(a) When attempting to produce a hot-rolled wire rod after hot heating after HIP, wrinkles in the capsule are more undesirable.

Therefore, it is necessary to process the capsule and the inside at the same time when processing the wire. (b) As the diameter of the workpiece becomes smaller, the temperature drop increases and material defects such as cracks are more likely to occur.

There is a problem.

An object of the present invention is to provide a method for manufacturing pure Cr or high Cr alloy wire that eliminates the above problems.

[Means for solving problems]

As a result of various studies, the present inventor found that among the above problems, the generation of wrinkles in the capsule can be solved by adopting swaging processing instead of rolling after HIP processing, and
We discovered that to reduce the temperature drop due to the reduction in the diameter of the workpiece, it is sufficient to coat the workpiece with a capsule thick enough to prevent the temperature drop when the diameter of the workpiece is reduced, and process the workpiece in a large diameter state as a whole. .

That is, the present invention is a method of manufacturing a wire rod using pure Cr or high Cr alloy powder, comprising: (a) filling a capsule with pure Cr or high Cr alloy powder;
Step of vacuum sealing at 10-3IIllH or less, (b) i
A step of hot isostatic pressing at ooo℃ or higher and a pressure of 500kgf/aJ or higher for 30 minutes or more; (c) heating to a temperature of 850 to 1300℃ to a wire diameter that does not cause defects such as cracks; (iv) a step of removing the surface oxidation layer and adjusting the surface texture;

(e) A step of re-covering the heated wire with a capsule so that it is difficult to cool down during the hot swaging process, (f) heating to a temperature of 850-1300°C and hot swaging to the desired wire diameter. A method for manufacturing a pure Cr or high Cr alloy wire, comprising the following steps:

Each of the steps (a) to (f) above will be explained below.

(b) Process capsule sealing should be 10-3■Hg or less because if it is higher than this, gases, moisture, etc. adhering to the raw material powder will not be removed sufficiently, leading to difficulty in sintering. This is because internal defects may occur.

Note that the capsule is not particularly limited as long as it can withstand HIP and hot swaging.

(b) Process This is a process of consolidating and sintering pure Cr powder or high Cr alloy powder.
Processing for 30 minutes or more is required at a pressure of 500 kgf/cm2 or more.

(c) Process By using swaging processing instead of rolling as in the main step, the generation of wrinkles in the capsule can be prevented.

If the heating temperature is less than 850°C, material defects such as cracks and scratches will occur, and if it exceeds 1300°C, oxidation will be severe and swaging will be difficult.

The temperature shall be 850°C or higher and 1300°C or lower.

(d) After the process swaging process, the outer peripheral surface of the workpiece has an uneven shape. Such shape defects make it impossible to obtain a good capsule covering (bonding) state in the next process.

This poses a problem in the subsequent swaging process.

Therefore, the surface texture is adjusted in this process. This can be easily carried out by centerless grinding.

On the other hand, after the swaging process, the surface of the workpiece is oxidized, and this process also serves to remove the oxidation method, which not only prevents shape defects but also hinders good capsule coverage.

(e) Process This process is performed when the diameter of the workpiece is reduced during the subsequent swaging process.
In order to prevent the temperature of the r-alloy from decreasing, the diameter of the workpiece is apparently increased to maintain the temperature.

The capsule to be coated may have a wall thickness that can prevent a temperature drop as a result, and a thick walled capsule may be used as a single layer, or a thin walled capsule may be used as two or more layers. It's okay.

In addition, in order to obtain a good coating condition, HI
It is desirable to apply P.

(f) Process This is the process of processing the wire to the final desired diameter.

The processing temperature is set at 850-1300° C. for the same reason as in step (c) above.

After completing the above steps (a) to (f), the capsules can be removed by mechanical processing such as centerless grinding, or by etching with hydrochloric acid, aqua regia, etc. It is okay if some capsules remain. in case of.

It goes without saying that it is not necessary to remove all the capsules.

〔Example〕

The present invention will be explained below based on examples.

(Example) Made of SUS304 steel, outer diameter 27mφ, inner diameter 23.7■φ,
Pure Cr powder (purity 99.6%') in a 450mQ capsule
) and sealed by vacuum suction at 10' mHg.

This capsule was subjected to HIP treatment at 1180° C. and 1000 atm for 2 hours. After HIP was completed (capsule dimensions were outer diameter 25-φ x 400 mm), the capsule was heated to 1200° C. and swaged until the outer diameter became 10.6 φ. After swaging, centerless grinding is performed to obtain an outer diameter of 9
．． The capsule was removed by grinding until it had a diameter of 8 mm, but no defects such as scratches or cracks could be found.

Next, the pure Cr sintered body with an outer diameter of 9.8-φ was placed into the pure Cr sintered body with an outer diameter of 13.
Insert into a capsule made of 5US304 steel of 8a*φ.

Further, the capsule was inserted into a capsule made of 5US304 steel with an outer diameter of 17.3 φ (double capsule), vacuum degassed and sealed, and HIPIP treatment was performed again. The HIP treatment conditions were a temperature of 1180° C., a pressure of 1000 atm, and a time of 2 hours.

The outer diameter after HIP is 16.5 mφ, which is
It was heated to 200°C and the swaging process was repeated until the outer diameter became 4.7-φ. After the swaging process was completed, the capsule was ground to 2.8 diameter by centerless grinding and the capsule was removed, but there were very few defects and the condition was satisfactory.

(Comparative example) Filling of pure Cr powder into capsules, sealing, )
The dimensions are the same as in the example, with an outer diameter of 25 mm x 400 mm.

Next, the capsule was heated to 1200° C., swaged to an outer diameter of 7.0 φ, and then the capsule was removed by centerless grinding. When we checked the exterior, we found that cracks had formed along the entire length. this is.

This is thought to be due to the fact that the temperature of the material decreases significantly when the diameter is as small as about 7.0 pusφ.

〔Effect of the invention〕

As explained above, it is possible to manufacture pure Cr or high Cr alloy wire rods without defects and with good productivity, which has been considered difficult in the past, and is very effective industrially.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross section of a capsule filled with pure Cr powder, hot rolled after HIP. 1: Cr molded body, 2: Capsule Figure 1

Claims (1)

[Claims] A method for producing pure Cr or high Cr alloy wire rod by powder metallurgy, comprising: (a) filling a capsule with pure Cr powder or high Cr alloy powder and vacuuming at 10^-^3 mmHg or less; (b) Hot isostatic pressing at a temperature of 1000°C or higher and a pressure of 500kgf/cm^2 or more for 30 minutes or more; (c) Heating to a temperature of 850 to 1300°C to eliminate defects such as cracks. (d) removing the surface oxidation layer and adjusting the surface properties; (e) hot swaging to a wire diameter that does not cause Pure Cr characterized by comprising the following steps: (f) covering the material with a capsule so that the inside of the material is difficult to cool down; (f) heating to a temperature of 850 to 1300°C and hot swaging to a desired wire diameter. Or a method for producing a high Cr alloy wire.