JPH0313501A - Sintered body and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a sintered body improving magnetic characteristic by adding carbon so as to contain the specific quantity of the carbon in the manufactured sintered body at the time of adding organic binder to metal powder, injection-forming into a formed body, degreasing and sintering. CONSTITUTION:At the time of manufacturing the sintered body by adding the organic binder to the metal or alloy powder, injection-forming, extrusion-forming or compression-forming to make the formed body and degreasing and sintering to this formed body, the carbon powder is added at 0.05-1wt.% together with the organic binder. By this method, the sintered body having 10-1000ppm carbon content and good magnetic characteristic, is obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing sintered metals and sintered alloys having high magnetic properties, and particularly relates to a method for producing sintered metals and sintered alloys having high magnetic properties, and in particular, the present invention relates to a method for producing sintered metals and sintered alloys having high magnetic properties. Add and mix.

The product is kneaded, then injection molded, extrusion molded or compression molded to form a product into the desired shape, and then degreased by a heating method and then sintered to produce a metal having the desired shape and magnetic performance. Or related to alloy products and their manufacturing methods.

[Conventional technology] It has been used as a manufacturing method for metal magnetic materials since ancient times.

Rolling methods, pressing methods, etc. have been used, but in recent years,
A process called "powder compaction" has been attracting attention for the purpose of producing products with more complex or irregular shapes without post-processing or with as little post-processing as possible. This method is.

Add an organic binder to the desired powder and injection mold.

After extrusion molding and compression molding, degreasing and sintering are performed.

You get the product. However, especially when looking at this method from the viewpoint of magnetic materials, the density after sintering is lower than that of conventional methods, and the characteristics as a so-called functional material are insufficient.

Therefore, the technical problem of the present invention is to provide a method for manufacturing metal or alloy products having magnetic performance while fully utilizing the features of the "powder compaction method".

It is an object of the present invention to provide a manufacturing method that can also improve magnetic performance.

[Means for Solving the Problems] According to the present invention, an organic binder is added to metal or alloy powder, a molded body is formed by injection molding, extrusion molding, or compression molding, and the molded body is degreased and sintered to produce the product. A sintered body having magnetic performance characterized by containing 10 to 1000 ppH of carbon is obtained.

According to the present invention, when adding an organic binder to metal or alloy powder, 0.05 to 1 liter of carbon powder is added as an additive.
A method for manufacturing a sintered body characterized by mixing vt% is obtained.

[Structure of the Invention] The present invention provides a metal having magnetic performance obtained by adding an organic binder to a metal and/or alloy powder, forming a molded body by injection molding, extrusion molding, or compression molding, and degreasing and sintering the molded body. or in alloy products.

The product is characterized by containing carbon.

Namely, 1. As a result of intensive studies by the present inventors on a method that can improve the magnetic properties while taking advantage of the characteristics of the "powder compaction method," we found that there are other disadvantages to improving the magnetic properties of the product. The present invention was completed based on the discovery that when a certain amount of carbon exists, the sintered density improves and the magnetic properties improve. Regarding the effect of carbon, during the sintering process, it chemically reacts with the oxygen absorbed from the atmosphere and the oxygen present in the organic binder, cleaning the surface of the metal (alloy) powder, resulting in a more effective than expected effect. It is estimated that this contributed to the improvement of sintered density. Also, from this point of view, it is thought that theoretically it would be most ideal to reduce oxygen and carbon to zero through a reaction, but in reality it is extremely difficult to reduce oxygen and carbon to zero through an equivalent reaction, and the amount of oxygen remaining is not necessarily constant,
It is extremely difficult to determine the amount of carbon based on this, and when oxygen and carbon are present in a sintered product, the presence of oxygen has a greater effect on magnetic properties than carbon. It can be said that it is preferable to carry out the method with excess carbon in order to remove oxygen as much as possible.

If the amount of carbon remaining is too small, the magnetic properties will deteriorate due to the influence of oxygen that is not removed, as described above, and if it is too large, the magnetic properties will also deteriorate because the element is non-magnetic.

Therefore, the effective amount of carbon is 10 to 1000 pp
m is more preferably 30 to 500 ppm+.

Any method for making carbon exist may be used, such as not completely removing the organic binder at the end of degreasing, mixing and dispersing carbon in the compact in advance, or performing sintering in an inert gas atmosphere. but,
The most industrially stable method is to mix carbon into the molded body. In this case, as carbon to be added.

For example, activated carbon powder, graphite powder, graphite powder, etc. can be arbitrarily selected. If the amount added is too small, it will not be effective, and if it is too large, it will inhibit fluidity during injection molding and extrusion molding, making it impossible to obtain a molded product.Also, it will be necessary to increase the amount of binder to obtain a molded product, and the degreasing time will be reduced. extension, large variations in sintering shrinkage, etc.

0.0 for metal or alloy powder as it is industrially disadvantageous.
The amount is 0.05 to 1.0% by weight, preferably 0.1 to 0.5% by weight, but is not particularly limited to this.

[Example] Next, an embodiment of the present invention will be described with reference to the drawings.

Example 1 - A water atomized powder having a composition of 30 vt% Fe-50 vt% Co and an average particle size of 10 μm was used as a raw material powder. The oxygen content of this powder was 5200 ppm.

Next, this powder, the thermoplastic binder shown in Table 1, and the graphite powder (-500l1esh) were kneaded at 130°C for 20 minutes in a pressurized niegu at the distribution ratio shown in Table 2, and then crushed and used for injection molding. A raw material pellet was obtained.

Next, using this raw material pellet, the temperature was 190°C.

With a gauge pressure of 100 kg/cd and an outer diameter of 50 mm.

A molded body having a thickness of 1 mm -5 m+s was produced by injection molding.

Table 1 Binder Table 2 Mixture composition (vt%) Margin below Place these molded bodies on an alumina setter.

An atmosphere was created in which H2 gas was flowed at 54 J/sin, and the temperature was raised from room temperature to 600 °C at a rate of 10 °C per hour.
After holding at 0°C for 2 hours, it was cooled to room temperature. Next, it was placed in a hydrogen furnace and heated to 120°C at a heating rate of 200°C per hour from room temperature.
The temperature was raised to 0° C., held for 5 hours, and then cooled in a furnace to obtain a sintered body.

For comparison, injection molded bodies having the same composition ratio except for the graphite powder shown in Table 2 were produced in the same shape, and were subjected to the same degreasing and sintering. The sintered density of the sintered body at this time is shown in Table 3.
90 residual amount is shown in Table 4, and the magnetic properties are shown in Table 5. However, the sintered density is expressed as a relative value (%) to the theoretical density (8.15 g/cc).

Table 3 Sintered density (relative ratio) Table 4 C1 0 remaining amount (ppm) Margin below Table 5 Magnetic properties As a result, the sintered body produced by the above process is.

The results showed that the sintered density was highest when the amount of graphite powder added was in the range of 0.1 to 0.5 νt%, and the magnetic properties were also good.

FIG. 1 shows the magnetic properties of the sintered body with respect to the amount of carbon, and the best magnetic properties were obtained when the amount of carbon added was 0.1 to 0.5 wt%. Also, when looking at the remaining amounts of carbon and oxygen in the sintered bodies (Table 4), the ones with less carbon have more oxygen, and conversely, the ones with more carbon have less oxygen. It was found that both improve the sintered density and improve the magnetic properties, which indicates that there is an optimum amount of carbon added. This optimum range is the above-mentioned 0.1 to 0.5 wt%. Sample Nα10 is a comparative example in which no graphite powder was added, 1.5 wt% of stearic acid was added, and the sample was press-molded at 3 ton/cd. In the case of this sample, the amount of carbon in the sintered body is low, but the amount of oxygen is relatively high and the sintered density is low. This revealed that the addition of carbon is effective in improving the density of the sintered body.

Next, FIG. 2 shows the relationship between the amount of carbon contained in the sintered body and the magnetic properties of the sintered body in which the amount of oxygen was 1 ooopp- or less. It can be seen that when the amount of carbon exceeds 5000 ppm, the characteristics deteriorate significantly. From Figure 2, the amount of carbon is 30 p.
It can be seen that the magnetic properties have a maximum value between pm and 500 ppm.

Example 2 - Carbonyl Fe powder with an average particle size of 5.5 μm was mixed with the binder shown in Table 1 used in Example 1, B, lvt%, and activated carbon powder (-3256) in the amounts shown in Table 6. Add,
The mixture was kneaded using a pressure kneader at 130° C. for 20 minutes, and then crushed using a crusher to obtain raw material pellets for extrusion molding. Further, the O content of the carbonyl Fe powder was 4350 ppt*.

Table 6: Blend composition (wt%) A cylinder was molded. Next, the molded body was cut into rings with a thickness of 5 inches, and this was placed on an alumina setter.
In an atmosphere in which 5 fl of Ar gas was flowed in one layer, the temperature was raised from room temperature to 600°C at a temperature increase rate of 10°C per hour.
After being maintained at 2 hours, the mixture was cooled to room temperature. Next, it was placed in a hydrogen furnace and heated from room temperature to 1200°C at a rate of 200°C per hour, held for 5 hours, and then cooled in the furnace to obtain a sintered body. Table 7 shows the residual oxygen carbon content and magnetic properties of the obtained sintered body.

Table 7 Characteristics of sintered body Next, this raw material pellet was used at a temperature of 160°C, and as a result, an extrusion speed of 1 m was used for a test sample degreased in an argon atmosphere, with an outer diameter of 30 mm and an inner diameter of 20 mm. Similar to 1, the amount of activated carbon powder added is 0.1
It was found that good characteristics can be obtained at ~0.5 vt%.

Example 3 - Fe (!+O) -Co obtained by water atomization method
(50)-V (2) Powder [cemendur] average particle size 10. A pellet for injection molding was obtained in the same manner as in Example 1, except that 10% by volume of the binder shown in Table 8 was added to the powder and no carbon powder was added.

Furthermore, molding was performed in the same manner as in Example 1 using this material. The molded product was degreased under the conditions shown in (Table 8).
The amount of residual carbon was adjusted. These degreased products were sintered for 1200'CX for 5 hours in an argon and hydrogen atmosphere to obtain a sintered body. The magnetic properties and density at this time are shown in Table 8, and it can be seen that there is an optimum range for the magnetic properties depending on the amount of residual carbon.

Margins below [Effects of the Invention] As explained above, according to the present invention, by leaving an optimum amount of carbon, a high sintered density can be obtained and good magnetic properties can also be obtained. As a method for retaining an appropriate amount of carbon as described above, it is industrially most advantageous to increase the total carbon content by using carbon powder before molding, and a great effect has been obtained.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the amount of graphite powder added to an injection molded Fe-50Co body and the magnetic properties of the sintered body. FIG. 2 shows the relationship between the amount of carbon remaining in the sintered body and the magnetic properties of the sintered body. (en) 0019 61

Claims (2)

[Claims] (1) A sintered body produced by adding an organic binder to a metal or alloy powder, forming a molded body by injection molding, extrusion molding, or compression molding, and degreasing and sintering the molded body, containing 10 to 1000 ppm of carbon. A sintered body having magnetic performance characterized by containing. (2) In the method for manufacturing a sintered body according to claim 1, when adding an organic binder to the metal or alloy powder, 0.05 to 1 wt% of carbon powder is mixed as an additive. A method for producing a sintered body.