JPS58110602A - Removing method for organic material in sintered magnetic alloy - Google Patents

Abstract

PURPOSE:To remove the org. materials in a sintered alloy effectively and efficiently in an org. material removing treatment in a vacuum by specifying the degree of vacuum. CONSTITUTION:In order to remove org. materials such as wax and the like from the inside of moldings in the stage of molding and sintering powder and producing the magnetic alloy, the moldings are held and treated for a specified time at 20-1X10<-4>Torr degree of vacuum from 400 deg.C up to the sintering temp. of said alloy. Here it is admitted that, if the temp. is below the lower limit, the removal of most of org. materials is impossible. If the degree of vacuum is in excess of the upper limit, the surfaces of the metallic powder are made active at low temp. and stabilize by reacting with the C and O of the decomposed org. materials; therefore, the degree of vacuum is kept lower than the upper limit. If said degree is below the lower limit, the decomposed gases of the org. materials fill the furnace, by which the moldings are contaminated and are sintered defectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing organic matter mixed with or attached to a compact such as alloy powder when producing a sintered magnetic alloy.

Generally, when producing a sintered magnetic alloy, when producing a press-formed body from the powder, organic matter adhering to the alloy powder and the compact, and organic matter (e.g. wax .

It is known to add stearic acid, oleic acid, etc.). If a sintered magnetic alloy is produced from these powders while organic substances are present in the compact, it will interfere with the sintering during firing, making it difficult to obtain a complete sintered body. Furthermore, even if sintering is complete, carbon in the organic matter will remain in the sintered body.

It is known that if there is a large amount of residual carbon at this time, the magnetism of the sintered body will be reduced. One such method is to remove organic matter from a sintered magnetic alloy by heating and reducing it in a hydrogen stream. In this method, when the organic matter inside the molded body is removed, depending on the size of the molded body, the surface portion of the molded body may be sufficiently removed, or the central portion may be insufficiently removed. This phenomenon causes variations in the final properties of the sintered magnetic alloy.

Examples of these include IcA 0-WAX in rare earth magnetic alloys.
(Product name) is added. Table 1 shows residual carbon''
i]t (in the present invention, the presence or absence of removal of organic matter was determined by analyzing the amount of carbon), and Table 2 shows the differences in magnetic properties at that time.

Table 1wt% Table 2 From Table 1, it can be seen that there is a clear difference in the amount of residual carbon between the outer periphery and the center. The amount of carbon in the compact is also shown for reference. Table 2 shows the magnetic properties after heat treatment by cutting and separating the center and outer periphery.
It has a low value of 0 oe and a characteristic of 173 at the outer periphery.

An object of the present invention is to provide a method for effectively and efficiently removing organic matter from a sintered alloy by improving the above-mentioned prior art methods.

In order to achieve the above object, the conventional technology for removing organic substances in a vacuum has been improved, and it has become possible to remove many organic substances. The organic substances here apply to paravin wax-based, stearic acid-based, oleic acid-based, and all other organic substances.

The organic substance removal conditions of the present invention are sintered wet from 400°C and treated by holding for a certain period of time at a vacuum level of 20 Torr to IXI W'Torr, and the lower limit temperature is 40°C.
At temperatures below 400 degrees Celsius (0 degrees Celsius), black ink is observed in which most of the organic matter cannot be removed. The degree of vacuum is 20 Torr to IXI F' Torr. 1 xl llr
If the process is carried out under a high vacuum exceeding 100 Torr, the surface of the violet powder in the compact becomes active at low temperatures and stabilizes by reacting with the carbon and oxygen/element of the decomposed organic matter. In order to prevent this, the vacuum level is 1X1 (1-'Torr).In addition, at a vacuum level of 20'1'Orr to 760Torr, decomposition gas of organic matter will fill up, contaminating the compact and causing poor sintering. The time will depend on the charging capacity, but an example is shown in Figure 1 for reference.

Figure 1 shows KAO-WAX (product name) used in a rare earth magnetic alloy at a temperature of 700°C and a vacuum of 20 Torr.
This is a diagram showing the relationship between the amount of residual carbon and time in ~1eTorr treatment. 1 in the figure is 2o'3x1sz (unit -
2 is the change in the amount of residual carbon in a molded body (approximately 25F) with a shape of 50X50X30 (approximately 4001
), and 3 shows the amount of change in the case of processing a large amount (approximately 3 cars). According to this, it can be seen that the amount of residual carbon is saturated not only in a small amount of treatment but also in a large amount of treatment after about 2 hours of treatment.

Examples of the present invention will be described below.

Example 1 When manufacturing a rare earth magnetic alloy by sintering, KAO-WAX is added after pulverizing the alloy powder, and after press molding (carbon content analysis value α21 wt'Ir) vacuum degree is 20 Tor r~
I Ir4Torr temperature 700℃, hour 1'l! 1i60
Wax removal treatment is performed for 1 minute, and then main sintering is performed at 1200℃.
I went there. The samples were then heat treated and the amount of residual carbon and magnetic properties were investigated. Table 4 shows the results.

Table 4 As is clear from Table 4, when the wax was evaporated, the carbon'Xtht decreased, and at the same time, sufficient density and magnetic properties were obtained. Here, the one without the dewaxing process has a higher carbon content than the one after the dewaxing process, so the magnetic property Hc 5500°e-(BH)max 160MQ-o
It is clear that the value is low.

Example 2 When producing a rare earth magnetic alloy by sintering, the alloy powder was crushed, calcium stearate was added, and after press molding (carbon analysis value was 0.15 wt%), the degree of vacuum was 20 Torr~
Calcium stearate removal treatment was performed at 10' Torr, temperature 500°C, and time 60 minutes, and then 1200° C.
Main sintering was performed at ℃. The samples were then heat treated and the amount of residual carbon and magnetic properties were investigated. Table 5 shows the results.

Table 5 As is clear from Table 5, when calcium stearate was removed, the amount of carbon decreased, and at the same time, sufficient values for density and magnetic properties were obtained. Here, the material without the calcium stearate process has a higher carbon content than the material with the calcium stearate process, and thus has lower magnetic properties. On the other hand, the case with the destearinization step showed both characteristics, Hc6200 oe, (131()max
Obtained at 22.6 MQ, oe 'f.

Example 3 When manufacturing an alnico magnet by sintering, use powder of alnico alloy components, add calcium stearate, press mold (carbon content analysis value: Ll 2wt%), vacuum degree 20
Torr-10'Torr, temperature 900'C 1 hour 6
Calcium stearate removal treatment was performed for 0 minutes, and main sintering was performed at 1300°C. The samples were then heat treated and the amount of residual carbon and magnetic properties were investigated. Table 7 shows the results.

Table 7 As is clear from Table 7, in the case without detreatment, a large amount of carbon cap was contained and the magnetic properties were decreased. On the other hand, the temperature is 900℃
, after IHr detreatment, the carbon cap was reduced to 0.04”t%.
and the magnetic temporal Hc shows a high value of 550.

As explained above, this method shows the method of removing organic substances by vacuum according to Honfumei, and by holding and processing at a temperature of 400°C to sintering temperature and a vacuum degree of 20'l'orr to 10 Torr for a certain period of time, This method was able to remove organic substances more effectively than hydrogen treatment and conventional vacuum treatment methods, and a great industrial effect can be obtained.

[Brief explanation of drawings]

Claims (1)

[Claims] In the production of a magnetic alloy produced by molding and sintering powder, the temperature is from 400°C to the sintering temperature of the alloy, and the vacuum level is 20 Torr to IXl ff' Torr.
A method for removing organic matter from a sintered magnetic alloy, which involves holding and treating it for a certain period of time while maintaining the temperature.