JPH02302013A - Manufacture of anisotropic rare-earth magnet powder - Google Patents

Abstract

PURPOSE:To sutlice with one hot-pressing operation and to shorten a production cycle by a method wherein a powder which has pulverized a quenched thin belt of an R-Fe-B- based alloy (where R represents one or more kinds of rare earths containing Y and composed mainly of Nd) is heated and held in an inert gas atmosphere, it is pressurized and deformed in a uniaxial direction and it is then pulverized. CONSTITUTION:Prescribed amounts of, e.g. electrolytic iron, a ferroboron and an Nd metal as starting raw materials are weighed; they are fed to a high-frequency melting furnace; its temperature is raised up to 1100 deg.C; a molten body having a composi tion of Nd: 30%, Fe: 69% and B: 1% in terms of a weight percentage is formed. This molten body is injected onto a roll, made of copper, which is moved at a speed of 30m/sec from a high-frequency furnace crucible; it is quenched down to room tempera ture at a cooling speed of 10 deg.C/sec or faster; an amorphous thin belt with a thickness of about 30mum is obtained. This thin belt is pulverized to form a powder whose average particle diameter is 20mum. Then, this powder is filled into a container made of Cu; it is heated at a prescribed temperature; it is pressurized and deformed in a uniaxial direction by using an impact press of a high-air pressure system. An anisotropic magnet which has been obtained is pulverized to obtain an average particle diameter of 30mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing anisotropic rare earth magnet powder useful as a plastic magnet.

(Prior technology) Anisotropic rare earth plastic magnets have higher magnetic properties than isotropic magnets, do not crack or chip like sintered magnets, and have the advantage of being able to be molded in one piece. It has become widely used in equipment. However, Nd-based anisotropic rare earth plastic magnets have the following problems in their manufacturing process, making it difficult to mass-produce them.

That is, the manufacturing method of Nd-based anisotropic rare-earth magnet powder, which is the raw material for Nd-based anisotropic rare-earth plastic magnets, includes a) hot deformation of a quenched ribbon (also referred to as die-up setting method) and b)
There is a method of crushing sintered magnets. The former requires hot pressing twice, so the cycle time is long (there are drawbacks such as poor productivity, high equipment costs, and complicated processes).
Not suitable for mass production. The latter has drawbacks such as the coercive force is significantly reduced by pulverizing the sintered magnet, and the powder is easily oxidized and ignited when pulverized.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks and difficulties by changing the two hot pressing steps of the die-up setting method to anisotropy in one step using another new method. The main challenge was to eliminate the pulverization step in the powder sintering method.

(Means for Solving the Problems) In order to solve the above problems, the present inventors fundamentally reviewed the manufacturing method of Nd-based anisotropic rare earth magnet powder, examined the manufacturing conditions of each step, and omitted the steps. As a result, the present invention was achieved.

The gist of this is that a powder obtained by pulverizing a quenched ribbon of an R-Fe-B alloy (where R is one or more rare earth elements containing Y and mainly Nd) is heated in an inert gas atmosphere. A method for producing an anisotropic rare earth magnet powder, which is characterized in that after being held, the powder is pressurized and deformed in a uniaxial direction by impact pressure, and then pulverized.

The present invention will be explained in detail below.

The magnet composition to which the manufacturing method of the present invention is applied is R-Fe
-B-based magnet alloy, where R is composed of one or more rare earth elements containing Y and mainly Nd; rare earth elements other than the above include Pr, Tb, Dy, Ho, Er
, La, Ce, Sm, etc. In addition, the alloys used in the present invention include Co, Al, Bi, Cu, G
a, Zr, Hf, V, W, Mo, Mn, Cr
, Ta, Sb, Ge, Nb, Ni, Ti, Sn, SL,
One or more of Pb, Zn, etc. may be added. The alloy composition is Nd+ <, +Fe
ao, 7 B 4. Q, Nd13 Ding Fea
o, +B 11. ? A10.5+ Nd+s, o
Examples include Fey++ 8cos, s B5, and A1°4.

In order to understand the present invention, first, the apparatus and manufacturing conditions used in the conventional hot press method will be explained in the order of steps A to D.

Step A: Production of isotropic rare earth magnet powder.

The melt of the R-Fe-B alloy is rapidly cooled to form an amorphous ribbon, which is then ground to about 250 μm.

Step B: Manufacture of bicyclic bulk magnet.

Use a hot press.

a) The atmosphere is vacuum or inert gas.

b) Heating the amorphous powder to 700°C.

C) Pressure (20±10Kpsi)
(seconds). This is preferably a semi-static, hydraulic or mechanical press.

d) Cool down to room temperature.

Step C: Production of anisotropic bulk magnet.

Use a hot press.

a) The atmosphere is vacuum or inert gas.

b) Heat the molded body in step B to 700°C.

c) Press for several seconds at a pressure of 20 Kps LX in the same manner as in step B.

d) Cool down to room temperature.

D. Production of anisotropic magnet powder.

Pulverize the bulk magnet in step C. High coercivity anisotropic magnet powder is obtained.

A drawback of the conventional manufacturing process described above is that it takes a long time to raise and lower the temperature during resistance heating.

Next, the present invention will be compared with the conventional method.

Step A: Production of bipartite rare earth magnet powder.

As in the conventional method, the melt of the R-Fe-B alloy is rapidly cooled to form an amorphous ribbon, which is then ground to about 250 μm.

Step B: Manufacture of bicyclic bulk magnet. ...Unnecessary.

Step C, manufacturing anisotropic bulk magnet.

Anisotropy can be achieved in a short time by rapid heating and impact pressing.

a) Create an inert gas atmosphere only in the pressurized section. Examples of the inert gas include N*, Ar, and He.

b) Filling the amorphous powder of step A into a Cu container,
Heat to 600-950°C and hold for 10 seconds to 5 minutes.

C) Impact pressing at a pressure of 0.2 to 4 ton/cm2. The time during which the impact pressure is applied is 1 second or less. Pneumatic impact cylinders are preferred.

d) Cool down to room temperature.

D step: Production of anisotropic magnet powder.

Pulverize the bulk magnet in step C to obtain an average particle size of 10 to 40 μm.
High coercive force anisotropic magnet powder. For pulverization, conventionally known pulverizers such as a Brown mill, a Shaw crusher, a jet mill, and a ball mill are used.

An advantage of the above process of the present invention is that a vacuum container is not required because simple atmosphere control is required.

As a heating method using an inert gas atmosphere, a high frequency heating method and a pulse current heating method can be applied, and are effective in shortening the temperature rising time. Examples include. Resistance heating can also be used, but it takes a long time to raise the temperature. Using the anisotropic magnet powder obtained in step D as a raw material, an anisotropic plastic Nd-based magnet is manufactured by a conventionally known method, that is, by mixing anisotropic magnet powder and plastic and using a press method or an injection molding method. As mentioned above, according to the rapid heating/impact pressing method of the present invention, hot pressing can be performed only once. This is because densification does not occur when the temperature is less than 600°C, and coercive force decreases significantly when the temperature exceeds 950°C.In addition, densification does not occur when the holding time is less than 10 seconds, and densification does not occur when the holding time is less than 10 seconds. This is because if the impact pressure exceeds 0.2 ton/cm2, the coercive force will decrease.Furthermore, if the impact bracing pressure is less than 0.2 ton/cm2, densification and anisotropy will not occur, and if it exceeds 4 ton/am2, the sample will break. Yes, as a pre-treatment condition for impact presses, only the pressurizing section needs to be in an inert gas atmosphere, so the volume of gas replacement is small (reducing replacement time and amount of replacement gas).

The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

(Example) As starting materials, predetermined amounts of electrolytic iron, ferroboron, and Nd metal were weighed and charged into a high-frequency melting furnace, heated to 1100°C, and the weight percentages were Nd: 30%, Fe+69%, B:
The melt had a composition of 1%. This melt is injected from a high frequency furnace crucible onto a copper roll moving at a speed of 30 m/sec, and rapidly cooled to room temperature at a cooling rate of 104 ° C./sec or more to form an amorphous ribbon with a thickness of about 30 μm,
This ribbon was pulverized into powder with an average particle size of 20 μm.

Next, this powder was filled into a Cu container and heated to a predetermined temperature shown in Table 1 using a high-pressure air shock bath.
- Pressure deformation occurred in the axial direction. This pressure deformation condition is such that the air in the pressurizing part of the impact press is sufficiently replaced with Ar gas, and then high-frequency heating is performed to produce an instantaneous (10-20m5e) of 650~b0.2~4 ton/c.
c) Shock cylinder 1 Table Changes in magnet properties due to heating temperature Cylinder 2 Table Changes in magnet properties due to constant temperature time [Note]
Heating temperature is constant at 850℃.

A press was added and the temperature was lowered to room temperature. The obtained anisotropic magnet was crushed to have an average particle size of 30 μm.

Tables 1 and 2 show the effects of impact press temperature and constant temperature time on magnet properties.

(Effects of the Invention) The present invention provides powder obtained by pulverizing a quenched ribbon of an R-Fe-B alloy (herein, R is one or more rare earth elements including Y and mainly Nd). A method for producing Nd-based anisotropic rare earth magnet powder, which is characterized by heating and holding in a gas atmosphere, deforming it in a uniaxial direction by impact pressure, and pulverizing it. The production cycle can be shortened, and since the pressing method is an impact press, the cycle is further shortened, and a vacuum container is no longer required, which improves productivity and reduces costs. It is extremely useful for industry.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an impact press according to the present invention. 1: Impact breath 2: Impact piston 3: Pneumatic piston 4: Air pressure adjustment valve 5; Pressure adjustment tank
6: Combretcer 7: Inert gas inlet/outlet 8: High frequency heating copper coil 9; Raw material magnet powder 10: Copper container Fig. 1

Claims (2)

[Claims] 1. A powder obtained by pulverizing a quenched ribbon of an R-Fe-B alloy (where R is one or more rare earth elements mainly containing Y and Nd) is heated and held in an inert gas atmosphere, and then uniaxially heated by impact pressure. A method for producing anisotropic rare earth magnet powder, characterized by deforming it under pressure in a direction and then pulverizing it. 2. Heating and holding conditions are 600-950℃ for 10 seconds or more5
The method for producing an anisotropic rare earth magnet powder according to claim 1, wherein the anisotropic rare earth magnet powder is deformed under impact pressure of 0.2 to 4 ton/cm^2 in less than 1 minute.