JPH01215902A - Manufacture of powder for powder compacting magnetic parts - Google Patents

Abstract

PURPOSE:To enable annealing of magnetic metal powder without any sintering by mixing the high melting point electric insulating powder of alumina cement, etc., at the specific ratio and annealing at the time of annealing the magnetic metal powder as raw material for green compact iron core. CONSTITUTION:In the case of annealing the magnetic metal powder having <=150mum particle size for forming the green compact magnetic core having high magnetic permeability, such as permalloy, sendust, the powder of hydraulic cement having <=150mum the same particle size of alumina cement, etc., having high melting point is mixed at 0.1-10wt.% ratio to the magnetic metal powder and annealed at 700-1200 deg.C. As it can be annealed so that the magnetic metal powder does not become bulky state by sintering because of intervene of alumina cement having high melting point, the magnetic metal powder suiting to the powder compacting magnetic material, such as the green compact magnetic core, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a manufacturing method for manufacturing powder used for powder-molded magnetic parts such as powder magnetic cores.

(Prior art) Powder-molded magnetic parts such as dust cores are produced by mixing magnetic powder made of a magnetic metal with high magnetic permeability with insulating powder made of an insulating material and attaching the insulating powder to the surface of the magnetic powder particles. This mixed powder is then molded into the desired shape. Since the eddy current in magnetic materials increases in proportion to the square of the frequency, powder molding is performed by covering the surface of the magnetic powder particles with insulating powder for interlayer insulation to suppress the generation of eddy current. Manufactures magnetic parts.

Powders made of vitreous materials or resin materials are used as the insulating powder mixed with the magnetic powder to insulate the magnetic powder.

However, if the powder used to manufacture this powder-molded magnetic component is soft and has no internal distortion, it is possible to improve the formability during molding, and in the case of pressure molding, it is possible to increase the molding density. . For this reason, it has been proposed to subject magnetic powder to heat treatment, that is, annealing, prior to molding to remove distortion from the powder and make it soft.

However, when annealing this magnetic powder, heat treatment is performed at a high temperature of about 700 to 1200'C in order to obtain a good annealing effect, that is, to remove distortion from the powder and make it soft. It is desirable to do so. but,
Insulating powder made of glass or resin, which is conventionally mixed with magnetic powder, has a heat resistance temperature lower than the annealing temperature of the magnetic powder, and melts when heated at this temperature.

For this reason, conventionally, only the magnetic powder is annealed at the above-mentioned temperature of 700 to 1200° C. without mixing the insulating powder with the magnetic powder, and thereafter, the magnetic powder is mixed with powders such as E and A.

(Problems to be Solved by the Invention) However, there are the following problems in conventional annealing of powder for powder-molded magnetic parts. That is, when only the magnetic powder is annealed at high temperature, the magnetic powder is sintered and becomes a lump, which cannot be molded as it is.

Therefore, the lump of magnetic powder sintered by annealing is crushed with a crusher to return it to its original powder state.

However, when a lump of magnetic powder is crushed, pressure is applied to the powder, and internal distortion occurs in the crushed magnetic powder. For this reason, the effect of annealing the magnetic powder is reduced, making it impossible to expect an improvement in moldability when molding the magnetic powder. Moreover, a step of pulverizing the powder lump is required after annealing.

The present invention has been made based on the above-mentioned circumstances, and provides a manufacturing method capable of performing high-temperature annealing without sintering, and capable of obtaining powder optimal as material powder for powder-molded magnetic parts. It is.

[Structure of the Invention] (Means and Effects for Solving the Problems) The inventor of the present invention has conducted repeated research on annealing magnetic powder when producing powder for powder-molded magnetic parts. The inventor has focused on mixing magnetic powder with other powders and annealing the magnetic powder as a means to prevent the powder from sintering when annealing the magnetic powder at high temperatures. As the powder used for this purpose, we focused on insulating powder, which is originally mixed with magnetic powder. However, conventional insulating powder made of glass or resin has a low heat resistance temperature, so when this insulating powder is mixed with magnetic powder, annealing must be carried out at a low temperature and almost no annealing effect can be obtained. Therefore, an attempt was made to change the insulating material used for the insulating powder and mix an insulating powder made of an insulating material with a high heat resistance temperature, such as magnesia, with the magnetic powder and perform annealing at the required annealing temperature of 700 to 1200°C. Ta. As a result, the insulating powder did not deteriorate, but the magnetic powder was sintered and a lump was formed as in the conventional case. This revealed that ordinary heat-resistant insulating materials such as shimagnesia do not have the effect of preventing sintering of magnetic powder during annealing.

Therefore, the inventor focused on using a heat-resistant insulating powder that has a high heat resistance temperature and has the effect of preventing sintering of the magnetic powder during annealing as an insulating powder to be mixed with the magnetic powder, and as a result of various experiments. We have discovered that hydraulic cement such as alumina cement, alumina powder, etc. have both of the above properties as insulating materials that have the above properties.

In other words, it is better to use a powder that is a mixture of insulating powder made of these heat-resistant insulating materials with magnetic powder, and to prevent sintering of the magnetic powder and annealing it at the required high temperature to ensure sufficient annealing. I found out that it can be effective. Moreover, in this method, there is no need to specifically mix other materials with the magnetic powder to prevent sintering of the magnetic powder, so the process is simple and material costs can be saved.

The present invention is based on such knowledge.

That is, the method for producing powder for powder-molded magnetic parts of the present invention is characterized by mixing magnetic powder made of a magnetic metal and magnetic powder made of a heat-resistant insulating material and annealing the mixture.

The manufacturing method of the present invention will be explained.

First, magnetic powder made of magnetic metal is prepared.

Examples of the magnetic metal include magnetic metals with high magnetic permeability, such as pure iron, permalloy, and sendust.

Permalloy is about 80% N1-Fe%Ni by weight
A composition such as 45-50 Chi Fe is suitable. Also,
About 80% Ni - Mo to improve the electrical resistance value of Fe
, Cr, Cu, etc. may be added.

For example, there is a type of dust consisting of 9.5% Si, 5.4% At, and the balance Fe.

Insulating powder made of heat-resistant insulating material is mixed with magnetic powder. The heat-resistant insulating powder is an insulating material that has a heat resistance temperature of 120 t)°C or higher, which is the annealing temperature of the magnetic powder, and has the function of preventing sintering of the magnetic powder during annealing. Specific examples include hydraulic cement such as alumina cement, alumina powder, and the like. Among these, alumina cement is suitable as a heat-resistant insulating material. What is the effect of preventing sintering of magnetic powder in these heat-resistant insulating materials?
This is an action that prevents the powder particles of magnetic powder from adhering to each other when the magnetic powder is heated.

The amount of this insulating powder added is 0.1% by weight of the entire mixed powder.
-10% range. That is, if the amount added is less than 0.14, some sintering of the magnetic powder is observed, and if the amount added is less than 0.14,
Exceeding this will adversely affect the magnetic properties of magnetic metals.

Further, the particle size of the magnetic powder and the insulating powder is 150 mm or less.

In this way, the magnetic powder and the insulating powder are sufficiently mixed to form a mixed powder, and this mixed powder is annealed. The temperature of this annealing is 700 to 1200°C. By this annealing, internal strain is removed from the s-type powder, making it soft and providing a good annealing effect. Further, during this annealing, the insulating powder prevents the powder particles of the magnetic powder from coming into contact with each other, thereby preventing sintering of the magnetic powder. Therefore, even if the magnetic powder is annealed at a high temperature, it will not sinter.

The mixed powder produced in this way has no internal distortion and is of good quality, making it optimal as a material powder for molding powder-molded magnetic parts.

Then, this mixed powder is molded into a predetermined shape by pressure molding using a press or injection molding.

In this case, since the mixed powder has no distortion and is soft, it has good moldability and can be molded into a high-quality powder compact. In particular, in the case of pressure molding using a press, a molded body with a high molding density can be obtained.

"Effects of the Invention" As described above, according to the method for producing powder for powder-molded magnetic parts of the present invention, the magnetic powder is sintered by mixing the magnetic powder and the insulating powder made of a heat-resistant insulating material and heat-treating the mixture. By heat-treating the magnetic powder at the required high temperature without causing any damage, the properties can be improved to make it suitable for powder compaction.Moreover, the magnetic powder does not sinter during this heat treatment, so there is no need for the troublesome process of crushing the powder. This is not necessary and does not cause internal distortion in the magnetic powder due to this crushing step. The process of adding special powder to prevent sintering of the magnetic powder due to heat treatment and separating this powder after heat treatment is also unnecessary. In particular, by using hydraulic cement such as alumina cement as an insulating powder mixed with magnetic powder, high annealing temperature (7
00 to 1200°C), which is highly effective in preventing sintering of the magnetic powder during annealing.

Claims (4)

[Claims] (1) A method for producing powder for powder-molded magnetic parts, which comprises mixing and heat-treating a magnetic powder made of a magnetic metal and an insulating powder made of a heat-resistant insulating material. (2) The method for producing powder for powder-molded magnetic parts according to claim 1, wherein the insulating powder is hydraulic cement. (3) The method for producing powder for powder molded magnetic parts according to claim 2, wherein the hydraulic cement is alumina cement. (4) Claim 1 wherein the heat treatment temperature is 700 to 1200°C.
, 2 or 3. A method for producing a powder for powder molded magnetic parts according to .