JPH05171217A - Manufacture of sintered compact of alloy of rare earth element - Google Patents

Abstract

PURPOSE:To manufacture a sintered compact of an alloy of rare earth elements free from deformation and crack, not contaminated by impurities, especially by carbon and utilized for the heater of an electric furnace, etc., by sintering a compact of powder of the alloy in a vessel made of a metal such as Ti, Zr, Ta or Nb. CONSTITUTION:When a compact of powder of an alloy of rare earth elements is put in a vessel made of a metal acting as a carbon getter and the compact in the vessel is sintered in a sintering furnace to produce a sintered compact of the alloy, Ti, Zr, Ta or Nb are used as the metal acting as a carbon getter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered body by molding and sintering a rare earth alloy powder useful as a heater material for an electric furnace.

[0002]

2. Description of the Related Art The heating method of a commonly used sintering furnace for powder metallurgy is electric heating, and Ni is used as a heater material.
-Cr, SiC, W, Mo, Ta, C, etc., but rare earth alloys
Many of them have a high melting point of 1,000 ° C or higher, and carbon (C) that can stably heat up to a high temperature range is suitable as a heater material. However, when carbon is used as a heater, even if the atmosphere inside the sintering furnace is evacuated or vacuumed, a trace amount of carbon reacts with the carbon due to the oxygen remaining in the furnace material, etc., generating CO, CO _2, etc. . Further, carbon fine powder is scattered and reacts with the rare earth alloy to form a carbide, which causes deformation and cracks. Even if the fine carbon powder can be prevented from entering even if the lid is put in an alumina crucible or the like, C
Since gases such as O and CO ₂ enter, there is a drawback that the formation of carbides is unavoidable. The carbide is generated so as to cover the surface of the rare earth alloy molded body, impedes heat conduction to the molded body, and causes deformation and cracks.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and to provide a method for producing a sintered body of a rare earth alloy which is free from deformation and cracks and is not contaminated with impurities, especially carbon. It is a thing.

[0004]

In order to solve the above problems, the present inventor has found that as a method for treating fine carbon powder as a pollution source, metals such as Ti, Zr, Ta and Nb, preferably Ti is effective as a gettering agent for carbon. Therefore, paying attention to the fact that carbon contamination can be prevented by sintering a molded body of rare earth alloy powder in a container made of these metals, the shape of the container, the type of metal and the sintering conditions are examined in detail. The present invention has been completed. The gist of the invention is a method for producing a rare earth alloy sintered body, which comprises sintering a compact formed by compression molding of rare earth alloy powder in a sintering furnace in a metal container that serves as a getter agent for carbon. is there.

The present invention will be described in detail below. The most characteristic feature of the present invention is carbon gettering agents such as Ti, Zr, Ta,
A metal such as Nb, preferably Ti is suitable. These metals are selected from the standard free energies of the reaction for forming carbides, are more likely to form carbides than rare earth elements, and are effective as gettering agents for carbon. Zr is the most preferable from the order of free energy (Zr <Ti <Ta <Nb),
Judging from the availability, price, workability, etc., Ti is preferable. The present invention prevents carbonization of the compact due to the fine carbon powder scattered in the sintering furnace by sintering the compact in a metal sintering container that serves as a gettering agent for these carbons. This sintering container may be formed in a box shape having a slightly large capacity in consideration of the shape and size of the molded body, and the plate material may be welded. The lid is processed to have a sufficient side wall length to prevent the infiltration of fine carbon powder. FIG. 1 is a vertical cross-sectional view of a sintering container in which a molded body 1 is placed on a floor plate 2 and placed in a sintering container 3 for sintering. In FIG. 2, since the molded body 1 is placed on the floor plate 2 by the usual method and placed in the sintering furnace as it is for sintering, contamination by impurities cannot be avoided.

The rare earth metal to which the present invention is applicable includes
La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb including Y
And an alloy of one or more rare earth metals selected from Lu and one or more metals selected from the groups 4A to 2B as transition metals, specifically Y-Ni, Er- N
Examples include i, La-Ni, Ce-Ni and the like.

The method of manufacturing a sintered body will be described in order of steps. First, a rare earth alloy powder having an average particle size of 4 to 20 μm is filled in a predetermined die and compression-molded, and the obtained molded body is specified by the present invention. Put in a metal container, put a lid made of the same metal in a sintering furnace with a carbon heater, 1,000 ~ 1,400 ℃, 1 ~ 10
Sintering for a period of time, under vacuum or in an atmosphere of an inert gas such as argon. According to this method, a metal as a gettering agent of carbon is used as a container for sintering a molded body, so that impurities scattered in the sintering furnace, particularly fine carbon powder, are blocked, and the container itself adsorbs carbon to cause metal carbide. To generate. Therefore, it is possible to prevent carbonization of the molded body of rare earth metal and alloy in the container, and it is possible to manufacture a high-quality sintered body without deformation and cracks.

[0008]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Example 1) Y-Ni (25: 75% by weight) alloy powder (average particle diameter D ₅₀ = 7.0 μm) was 100 mmφ × 100 mmL by die molding.
After forming into a molded body of 120mmφ × 120mmL Ti plate container
A Mo plate was put in as a floor plate, and a Ti plate lid was put on. Place this in a sintering furnace equipped with a carbon heater at 1,300 ° C for 1 hour at 10 ^-4
Sintered in torr vacuum. The obtained sintered body had a relative density TD of 95.0% and was free from deformation and cracks.
As a result of analysis, carbon as an impurity was 0.01% by weight.

(Example 2) Er-Fe (25: 75% by weight) alloy powder (average particle diameter D ₅₀ = 7.0 μm) was molded by die molding to give 150
After forming a molded body of mmW × 150 mmL × 5 mmT, 170 mmW × 17
Put a Mo plate as a floorboard in a 0 mmL × 15 mmH Ta plate container,
A lid made of Ta plate was put on. This was sintered in a sintering furnace equipped with a carbon heater at 1,300 ° C. for 1 hour in a vacuum of 10 ⁻⁴ Torr. The obtained sintered body is deformed at a relative density TD = 95.0%,
A crack-free product was obtained. As a result of analysis, carbon as an impurity was 0.01% by weight.

Comparative Example 1 Sintering was carried out under the same composition and conditions as in Example 1 except that the molded body was placed on a Mo floor plate and placed in a sintering furnace as it was. Deformation was observed in the obtained sintered body at a relative density TD = 85.5%. As a result of analysis, carbon as an impurity was 0.69% by weight.

(Comparative Example 2) A compact was placed on a Mo floor plate, placed in an alumina crucible, and sintered under the same composition and conditions as in Example 2 except that the lid was closed. The obtained sintered body has a relative density TD =
Deformation was observed in 80.0%. As a result of analysis, carbon as an impurity was 0.53% by weight.

[0012]

[Effects of the Invention] Molded bodies of rare earth alloy powders are manufactured using Ti, Zr, Ta,
By sintering in a metal container that serves as a gettering agent for carbon such as Nb, it is possible to produce a sintered body of a rare earth metal and its alloy that is free from deformation and cracks and is not contaminated by impurities mainly composed of carbon. Its industrial utility value is extremely high.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an example of a comparative example.

[Explanation of symbols]

 1 molded body 2 floor plate 3 sintering container

Claims (2)

[Claims] 1. A method for producing a rare earth alloy sintered body, which comprises sintering a compact obtained by compression molding rare earth alloy powder in a sintering furnace in a state of being placed in a metal container serving as a getter agent for carbon. .. 2. A metal as a gettering agent for carbon is Ti or Z.
The method for producing a rare earth alloy sintered body according to claim 1, wherein the sintered body is r, Ta, or Nb.