JPH0480304A - Manufacture of rare earth metal sintered body - Google Patents

Abstract

PURPOSE:To restrain increase of impurities of oxygen, nitrogen, carbon, etc., by inserting a thin plate composed of transition metal at interface between a material to be hot-pressed and a die for hot-pressing and executing the whole press of the hot pressing under reduced pressure or inert gas atmosphere. CONSTITUTION:In the manufacturing method for rare earth metal sintered body, where alloy composed of the rare earth metal and the transion metal under powder state or once pre-formed material is heated and compacted with the hot-pressing, the thin plate composed of the transition metal is inserted at interface between the material to be hot-pressed and the die for hot pressing. This is hot-pressed under reduced pressure or inert gas atmosphere. The inserted thin plate uses metal or alloy composed of one or more kinds of elements selected from Fe, Ti, V, Cr, Mn, Co, Ni, etc., belonging to the transition metal as the raw material. By this method, high purity sintered body composed of the rare earth metal and the transition metal can be easily manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in hot pressing in a method for manufacturing rare earth metal sintered bodies useful as magnets and sputtering targets.

(Prior Art) Powder metallurgy is widely known as a method for manufacturing magnets, sputtering targets, etc., and sintering methods include atmospheric sintering, hot pressing, HIP, etc. However, hot pressing is considered optimal for producing high-density sintered bodies at relatively low cost. This hot press method is a method in which metal powder is heat-molded either in powder form or after it has been preformed, and graphite is generally used for the mold. The obtained sintered body has the advantages of high density, good dimensional accuracy (and requires little machining).

(Problem to be Solved by the Invention) However, when the material to be hot-pressed is a highly active alloy containing rare earth metals, the material of the hot-pressing mold becomes a problem, and oxygen is removed from the graphite mold during hot-pressing.
Gases such as nitrogen or carbon dioxide are released, and this is adsorbed on the surface of the hot pressed material that is in direct contact with the mold.
It diffuses and permeates, reacts with rare earth metals, etc., and produces oxides, nitrides, hydroxides, etc. 1, which act as impurities, resulting in decreased magnetic properties and becoming unsuitable as a target material. Oxygen forms oxides and hydroxides, which increases coercive force,
Nitrogen forms nitrides that reduce magnetic properties.

The present invention aims to solve these disadvantages and shortcomings by improving the hot pressing method, and to provide a sintered body with less impurities.

(Means for Solving the Problems) In order to solve the above-mentioned disadvantages and shortcomings, the present inventors have provided a thin plate made of a transition metal at the interface between the hot-pressed material and the hot-pressing die, and the hot-pressing method By carrying out the process under reduced pressure or an inert gas atmosphere, oxygen, nitrogen,
They discovered that the increase in impurities such as carbon can be suppressed, and after studying the related conditions in detail, they completed the present invention.

That is, the present invention provides a method for producing a rare earth metal sintered body in which an alloy consisting of a rare earth metal and a transition metal is heat-formed in powder form or once preformed by hot pressing. The gist of the present invention is a method for producing a rare earth metal sintered body, which is characterized in that a thin plate made of a transition metal is interposed at the interface with the mold, and hot pressing is carried out under reduced pressure or an inert gas atmosphere.

The present invention will be explained in detail below.

The main feature of the present invention is that the thin plate inserted at the interface between the hot-pressed material and the hot-pressed mold is made of transition metals such as Fe, Ti, V, Cr, Mn,
A thin plate made of a metal or alloy made of one or more elements selected from Co, Ni, etc. Specific examples include iron plates, titanium plates, iron-nickel alloy plates, etc. Hot press material, hot press mold material,
The temperature, pressure, time, atmosphere, and other hot pressing conditions are selected as appropriate. The thickness of the thin plate is 10~
It is sufficient to have a thickness of about 100 μm, and it is press-molded according to the hot press mold (.Furthermore, the hot press conditions are 1.OX 10-' to 0.ITorr under reduced pressure or Ar gas atmosphere The increase in impurities such as oxygen, nitrogen, carbon, etc. can be suppressed by reducing pressure or creating an inert gas atmosphere during the entire hot pressing process.If the degree of reduced pressure exceeds 0.ITorr, degassing in the atmosphere will occur. If insufficient, nitrides, carbides, etc. will be generated.

In addition, if the vapor pressure at the working temperature of the hot-pressed material and the degree of depressurization of the atmosphere are not appropriately selected, components with high vapor pressure will selectively evaporate, and the components of the resulting sintered body will differ from the raw material composition. There may be deviations. For example, Yb, Sm, Tm
, Ho, Dy, etc., it is necessary to consider the amount of evaporation. Furthermore, depending on the molding pressure and sintering temperature, the components of the hot-pressed material and the thin plate made of a transition metal may diffuse and bond with each other. It is preferable to mold at high temperature. For example, the material to be hot pressed is Tb2°Fes. When using alloy powder and a thin iron plate, the liquidus temperature of both is 1 or 2.
It is preferable to form at a sintering temperature of less than 76°C.

The application area of the present invention is an alloy consisting of a rare earth metal and a transition metal, and the rare earth metal includes Y-containing La, Ce,
Pr, Nd, PIII, St, Eu, Gc,
One or more elements selected from Tb, Dy, Ho, Er, Tm, Yb, Lυ, etc., transition metals include Fe, Ti, V, Cr, Mn
An alloy consisting of one or more elements selected from , Co, Ni, etc., specifically, Sm-Go, N
Examples include d-Fe-B, La-Ni, and Tb-Fe, which are useful for permanent magnet alloys, sputtering targets, and the like.

Hereinafter, specific embodiments of the present invention will be explained with reference to Examples, but the present invention is not limited thereto.

(Example 1) SmCos (Sm: 16.7. Co: 83.3 atomic% each) alloy ingot mechanically reduced to 10 μm in N2 atmosphere
The powder was pulverized and used as a material to be hot pressed. An iron-nickel alloy thin plate with a thickness of 80 μm that matched the mold was set in a graphite hot press mold with a die diameter of 60 mm, 135 gr of the alloy powder was charged, and 15 gr of the alloy powder was charged in an Ar gas atmosphere.
0Kg/cm" x 1.050°C and hot pressed. The dimensions of the shaped sintered bodies were 60φ x 5.Stmm in all of Examples 1 to 3. Physical properties of the obtained shaped sintered bodies ° is shown in Table 1.

(Example 2) LaNis (La: 16.7, Ni: 83.3 atomic % each, particle size 300 μm or less) alloy powder was filled into a graphite hot press mold set with a 60 μm thick titanium thin plate,
1. 150Kg/at OX 10-”Torr vacuum degree
cm" x 1. The same process as in Example 1 was carried out except that hot pressing was carried out at 150°C. The physical properties of the obtained shaped sintered body are also listed in Table 1.

(Example 3) TbzoFeso (Tb: 20. Fe: 80 each atomic %
, particle size of 250 μm or less) was filled into a graphite hot press mold set with a thin iron plate with a thickness of 80 μm.
The process was carried out in the same manner as in Example 1 except that hot pressing was carried out at 0 kg/cm"Xi and 150°C. The physical properties of the obtained shaped sintered body are also listed in Table 1.

(Comparative Example 1) Processed in the same manner as in Example 1 except that SmCos (Sm: 16.7, Co: 83.3 atomic %, particle size: 10 μm or less) alloy powder was directly filled into a graphite hot press mold. .

The physical properties of the obtained sintered body are also listed in Table 1.

(Comparative Example 2) Processed in the same manner as in Example 2, except that laNi ([a; 16.7.Ni: 83.3 atomic % of each, particle size 300 μm or less] alloy powder was directly filled into a graphite hot press mold. did.

The physical properties of the obtained sintered body are also listed in Table 1.

(Comparative Example 3) TbaoFeao (Tb: 20. Fe: 80 each atomic %
, particle size of 250 μm or less) was processed in the same manner as in Example 3, except that the alloy powder was directly filled into a graphite hot press mold.

The physical properties of the obtained sintered body are also listed in Table 1.

Table 1 (Effects of the Invention) According to the present invention, by inserting a thin plate made of a transition metal at the interface between the hot-pressed material and the hot-pressing mold, oxygen, nitrogen, carbon, etc. in the sintered body are removed. We were able to suppress the increase in impurities. Furthermore, by eliminating direct contact between the graphite in the hot pressing mold and the material to be hot pressed, the durability of the graphite mold is increased, mold costs are reduced, and high-purity sintered materials made of rare earth metals and transition metals are used. Aggregates can be easily produced.

Claims (1)

[Claims] In a method for producing a rare earth metal sintered body, in which an alloy consisting of a rare earth metal and a transition metal is heat-formed in a powder state or once preformed by hot pressing, the interface between the hot-pressed material and the hot-press mold is A method for producing a rare earth metal sintered body, which comprises hot pressing under reduced pressure or an inert gas atmosphere with a thin plate made of a transition metal interposed therebetween.