Tungsten based sintered compact and method for production thereof

Abstract

The present invention is directed to provide a tungsten-based sintered body having a relative density of 99.5% or more (a porosity of 0.5 volume % or less) and a uniform and isotropic structure, which has not been able to be achieved by conventional techniques. In particular, the tungsten-based sintered body is intended for use as a discharge lamp electrode, a sputtering target, a crucible, a radiation shielding member or a resistance welding electrode. The intended tungsten-based sintered body is produced by subjecting a tungsten-based powder to a CIP process at a pressure of 350 MPa or more to form a powder compact, sintering the powder compact in a hydrogen gas atmosphere at a sintering temperature of 1600° C. or more for a holding time of 5 hours or more to form a sintered compact, and subjecting the sintered compact to a HIP process in an argon gas atmosphere under conditions of 150 MPa or more and 1900° C. or more. The tungsten-based sintered body of the present invention is suitably used, for example, as a discharge lamp electrode, a sputtering target, a crucible, a radiation shielding member, an electric discharge machining electrode, a semiconductor element mounting substrate and a structural member.

Description

TECHNICAL FIELD [0001] The present invention relates to a tungsten-based sintered body and a production method therefor. [0002] The present invention also relates to a product of the tungsten-based sintered body, such as a discharge lamp electrode, a sputtering target, a crucible, a radiation shielding member, a resistance welding electrode, a semiconductor element mounting substrate, a structural member, a switch contact, a member for semiconductor manufacturing equipment, a member for an ion-implantation apparatus or an internal member for a nuclear fusion reactor. BACKGROUND ART [0003] Typically, a tungsten-based sintered body has been produced by use of a “electric current-aided sintering process” which is designed to apply a high-voltage pulsed current to a rod-shaped tungsten-based powder compact through a pair of electrodes attached, respectively, to opposite ends of the powder compact, so as to sinter the powder compact. [0004] The electric current-aided sintering process ha...

AI Technical Summary

Benefits of technology

[0084] As above, the tungsten-based sintered body of the present invention is a high-density homogeneous tungsten-based sintered body which has a small volume or number of pores, a high recrystallization temperature, an isotropic characteristic in hardness, thermal conductivity or thermal expansion coefficient, and a significantly small difference in hardness, thermal conductivity or thermal expansion coefficient between a surface portion and an inside portion thereof.

[0085] By taking advantage of these characteristics, the

Problems solved by technology

The first disadvantage is that the sintered body has an extremely poor flexibility in shape due to the need for sintering the rod-shaped powder compact in a given gas atmosphere while applying a pulsed current to the powder compact through the electrodes connected to the respective ends thereof.

This leads to a considerable increase in production cost.

The second disadvantage is that a sufficient density cannot be obtained without an additional process after the sintering.

While the sintered compact may be subjected to a forging process, such as a swaging process, to provide enhanced density, the restriction in shape will become more severe.

Further, if it is attempted to obtain a relatively large sintered body with a sufficient density through a plastic working process, such as a forging process, it is necessary to allow the sintered compact before the forging process to have a larger size causing the need for a single-purpose facility requiring a

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