JPS63111106A - Production of magnetic alloy powder - Google Patents

Abstract

PURPOSE:To produce magnetic alloy powder having excellent resistance to oxidation, wear and corrosion at a low cost by subjecting a molten metal made of a specific compsn. formed by adding a nitride forming element such as Ti to an iron-based magnetic material contg. C and Cr to atomizing with gaseous N2. CONSTITUTION:The molten metal is obtd. by adding >=1 kinds among 0.5-15.0wt% Ti, 0.5-15.0% Zr, 0.5-15.0% Hf, 0.5-10.0% Nb, 0.5-15.0% V, 0.5-15.0% Ta, and 0.5-15.0% Al as the nitride forming elements to the iron- based magnetic material contg. over 0.18 and <=1.0% C, and 12.5-20.0% Cr and melting the mixture. After the molten metal is kept at a prescribed temp., the molten metal is subjected to atomizing by the prescribed gaseous N2 pressure. The above-mentioned material is thereby pulverized and the nitride film of the nitride forming elements is formed on the surface of the powder particles, by which the magnetic alloy powder is obtd. The powder is subjected to a nitriding treatment at need to increase the thickness of the nitride film or the hardness thereof is adjustable by subjecting the powder to a heat treatment at about 900-1,000 deg.C.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing magnetic powder with excellent corrosion resistance, wear resistance, and oxidation resistance. By loading the magnetic powder and magnetizing the magnetic powder, the magnetic attraction force generated between the magnetic powder particles and between the magnetic powder and the transmission member is used to transmit or control rotational force between the transmission members (driving member and driven member). This is the most suitable method for producing magnetic powder for powder clutches and brakes that apply power.

[Conventional technology]

When using magnetic powder as an element of a mechanical structure, it is essential that there is little change in performance or deterioration over a long period of time in terms of reliability as a device.

Particularly when powder is used for the driving body, deterioration of the characteristics of the powder has a large effect on the performance of the device. The magnetic properties of powders are determined by their alloying composition, but during use they are subject to oxidation, corrosion,
Deteriorates due to wear. The most important issue in manufacturing the device is to minimize the deterioration of the magnetic properties of the powder and the properties of the powder.

For example, in electromagnetic clutches, due to magnetic properties.

Sendust could be used, but it is not used because its oxidation resistance is inferior to magnetic stainless steel. As usage conditions become more severe, powders with even better oxidation resistance and wear resistance are required.

[Problem that the invention seeks to solve]

Conventionally, in order to improve the corrosion resistance, abrasion resistance, and oxidation resistance of powder, the surface of powder has been covered with a protective film. That is, there are methods such as coating the powder surface with MoS2 or electroless plating with C01Ni or the like. However, with MoS2, it is difficult to uniformly coat all powder particle surfaces, and the coating peels off during use, resulting in no coating effect.

Furthermore, the electroless plating method limits the metals that can be plated, and does not necessarily improve corrosion resistance, wear resistance, and oxidation resistance. Furthermore, the plating solution is expensive, and the process becomes complicated, increasing costs.

As a wear-resistant and corrosion-resistant film, there is a method of coating various metal materials with a film of carbide or nitride such as TiC or TiN. However, these methods
These methods are called physical vapor deposition (physical vapor deposition) or chemical vapor deposition (CVD), but they are expensive to process powder and are difficult to implement as an industrial method.

The object of the present invention is to solve the above-mentioned problems and to provide a magnetic alloy powder that is inexpensive, has excellent oxidation resistance, wear resistance, and corrosion resistance, and is optimal for powder clutches and brakes.

[Means for solving problems]

In the present invention, 1% by weight of CO is more than 1% and less than 1.0%.

Ti 0.5-15.0%, Zr
0.5-15.0%, Hf 0.5-15.0%, N
b 0.5-10,0%, V 0.5-15,0%.

Ta 0.5-15.0%, A10.5-15.0%
One or more of the following are added to obtain a molten metal, and the molten metal is atomized with N2 gas to form a nitride film composed of the nitride-forming elements on the surface of the powder particles at the same time as powdering. This is a method for producing magnetic alloy powder characterized by the following.

In addition, in the present invention, in order to increase the nitride film thickness,
The powder after the gas atomization may be subjected to a nitriding treatment. Further, the hardness can be adjusted by heat treatment in a temperature range of 950 to 1000°C to obtain a desired hardness.

[Effect]

0.1% C as the iron-based magnetic alloy used in the present invention
The reason why C is limited to less than 1.0% is because if C is less than 0.1%, the hardness of the particles will be low and the nitride layer will peel off during use. Moreover, since the magnetic properties deteriorate significantly when the content exceeds 160%, the content is set at 0.1 to 1.0%.

Further, Cr is an element that narrows the γ loop and stabilizes ferrite. However, if it is less than 12.5%, there is no effect, and if it is added in excess of 20.0%, the effect is not commensurate with the amount added. Therefore, the range is 12.5 to 20
．． It was set to 0%. Note that Si and Mn may be contained as deoxidizing agents in amounts of 0.60% or less, O, and SO%, respectively.

Next, the nitride-forming elements Ti, Al, Nb, Ta
.

V, Zr, and Hf will be explained.

Although there are many elements that form nitrides, Cr nitride reacts with the matrix and decomposes at about 850° C. or higher. Since the temperature during use of powder clutches and brakes is approximately 500°C or higher, it must be more stable than Cr nitride in order to maintain oxidation resistance, corrosion resistance, and wear resistance under these conditions. Must be. Further, from the viewpoint of magnetic properties, it is preferable that the element be a ferrite-forming element. Taking these points into consideration, we investigated various elements and found that Ti, Zr, Hf, Nb-V, and Ta should be added.
, A1 was found to be desirable. The magnetic alloy powder of the present invention is produced by melting a master alloy having the above composition or a material blended to have this alloy composition and atomizing with N2 gas. Nb, Ta
, V, Zr, and Hf were determined depending on the thickness of the nitride film formed by atomization. That is, if it is less than 0.5%, the nitride film thickness will be 500 to 600%.
It is thin and has little film effect. Further, the upper limit of addition was determined depending on the deterioration of magnetic properties. That is, Ti 0.5-15.0%, Zr 0.5 (5.0%,
Hf 0.5-15.0%, Nb 0.5-10.0%,
V 0.5-15.0%, Ta 0.5-15.0%
, A10.5-15.0%.

An alloy having the above composition or a material blended to have this alloy composition is melted. As the melting method, atmospheric melting or vacuum melting can be used as appropriate. After reaching a predetermined temperature, atomization is performed using a predetermined nitrogen gas pressure. Additionally, the atomized powder can be placed in nitrogen gas to increase the nitride coating thickness.

According to the present invention, a nitride coating can be applied inexpensively and in large quantities to the surface of each particle without using high-cost methods such as PVD or CVD, thereby improving the corrosion resistance, abrasion resistance, and acid resistance of the powder. It is possible to improve the chemical properties.

〔Example〕

Example 1 Four types of alloys (■ to ■) shown in Table 1 below were used, and Ti was added as a nitride-forming element in the weight percent shown in Table 2.

Table 1 These were melted in a high frequency melting furnace, then N2 gas pressure 8
Atomization was performed at 0 kgf/d to produce powder.

The TiN film thickness was measured by Auger analysis. The powder properties and magnetic properties are summarized in Table 2.

Next, these powders were subjected to heat treatment in which they were held at 980° C. for 15 minutes and then air cooled. The powder properties and magnetic properties at this time are summarized in Table 3.

Table 4 summarizes the results of using these powders as powder for an electromagnetic powder clutch, which is an example of an application.

The powder properties for this purpose require excellent wear resistance and oxidation resistance. The evaluation was performed using the equipment shown in Figure 1, with a motor rotation speed of 150 rpm and a torque of 10 kg.
The test was carried out at m for 30 minutes.

Table 4 Oxidation resistance was evaluated as an increase in the amount of [○], and wear resistance was evaluated as a change in the average particle size of the powder.

Example 2 Used in Example 1. ■~■ base alloy system includes Al, Z
r, Hf, ■0.5%, 7.0%, 15.0 respectively
A master alloy having a composition in which % was added was melted and atomized at a N7 gas pressure of 80 kgf/a&. Also, Nb, T
Regarding a, the amounts added to the base alloys of ■ to ■ were 0.5%, 5.0%, and 10.0%, respectively. The atomization conditions were a N2 gas pressure of 80 kgf/cJ. Table 5 summarizes the thickness of each nitride film formed on the particle surface. He was about 1.6 to 5.0.

Table 5 Nitriding treatment: 1100℃XIHr, PN, = 0.6a
It was done at tm. The thickness of the film was about 4,000 to 8,000 people. It is clear from the stability of nitride that these nitride films have the same effect as TiN.

〔Effect of the invention〕

As explained above, according to the present invention, corrosion resistance, wear resistance,
It is possible to obtain magnetic alloy powder with excellent oxidation resistance in large quantities and at low cost, which is very useful industrially.

[Brief explanation of the drawing]

Claims (1)

[Claims] Weight%: C over 0.1% and 1.0% or less, Cr12.5
The iron-based magnetic material containing 0.5-15.0% of Ti and 0.5-15.0% of Zr as nitride-forming elements in the iron-based magnetic material containing 0.5-15.0% of Ti and 0.5-15.0% of Zr.
0%, Hf0.5-15.0%, Nb0.5-10.0
%, V0.5-15.0%, Ta0.5-15.0%,
One or more types of Al 0.5 to 15.0% are added to obtain a molten metal, and the molten metal is atomized with N_2 gas to form a powder, and at the same time, the surface of the powder particles is made of the nitride-forming elements. 1. A method for producing magnetic alloy powder, which comprises forming a nitride film.