JPH05239503A - Production of high-density stainless steel sintered compact with reduced deformation in sintering - Google Patents

Abstract

PURPOSE:To produce a high-density stainless steel sintered compact which is hardly deformed in sintering by powder metallurgy. CONSTITUTION:An Fe-Sn powder having 2-10mum average grain diameter is added to a water-atomized stainless steel powder having 5-20mum average grain diameter so that the Sn content of the final sintered compact is controlled to 0.5-2wt.%, a binder is further added, and the mixture is compacted, degreased and sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-density stainless steel sintered body having a small shape deformation during sintering by powder metallurgy.

[0002]

2. Description of the Related Art A conventional powder metallurgy method has an average particle size of 60 to 1
Although a powder having a size of about 00 μm is used, the density ratio of the final sintered body is 90% at most, and there is a problem that mechanical properties, magnetic properties and corrosion resistance are inferior to those of the ingot material. In recent years, advances in powder metallurgy have made it possible to use fine powders having an average particle size of 20 μm or less, and achieve a sintered body density ratio of 95% or more. As a molding method, there have been developed an injection molding method in which a thermoplastic resin or the like is mixed as a binder to form a compound, a slip casting method, or a method in which fine powder is granulated and subjected to press molding. However, the method of mixing and molding a binder has a problem that it is difficult to maintain the shape of the sintered body. In the conventional powder metallurgy, powders are entangled and intimately adhered to each other at the stage of compression molding at a high pressure, so that a molded product having a certain strength can be obtained. Even when the molded body is sintered, the sintering is started while maintaining the strength, so that the shape is not likely to collapse. When the fine powder is used, the molded body is shaped by using a binder. In this case, since the binder is removed before the sintering, the strength of the molded body passes through the stage of temporarily weakening.
At that time, the shape of the part may be significantly deformed due to the weight of the molded body. Further, in the case of stainless steel powder, the surface thereof is usually covered with oxides such as Cr, Fe, Mn and Si. After the binder is removed in the heating process, the sintering does not proceed until these oxides are removed at a high temperature, so that the strength of the molded body is further lowered to a high temperature, and the shape deformation becomes significant.

[0003]

DISCLOSURE OF THE INVENTION The present invention improves the strength of a compact in a stainless steel powder after the binder has been removed and the compact before the start of sintering becomes weaker in view of the above-mentioned situation. This is to propose a method for doing so.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted diligent research to improve the strength of the molded body at this stage.
Mixing Fe-Sn powder with stainless steel powder, molding,
It has been discovered that, when sintered, the sintering starts at a relatively low temperature, contributes to the bonding of the powders, and the strength of the compact can be maintained. Therefore, based on this finding, the inventors have made the following inventions. That is, according to the present invention, a stainless steel powder having an average particle size of 5 to 20 μm is added to Fe-S having an average particle size of 2 to 10 μm.
n powder has a Sn content of 0.5 to 2 wt% in the final sintered body.
A high-density stainless steel fired product having a small shape deformation during sintering, which is characterized in that it is mixed and added so that the binder is mixed and molded, and the binder in the molded body is removed, followed by sintering. It is a method for producing a bound body.

[0005]

The function of the present invention will be described below. The average particle size of the stainless steel powder used was 5 to 20 μm, which was 20 μm.
This is because if the density exceeds m, the density of the sintered body will not become sufficiently high, while if it is less than 5 μm, the cost will increase significantly, so the above range was made. The average particle size of the added Fe-Sn powder is set to 2 to 10 µm. When it exceeds 10 µm, the sintering does not proceed rapidly, and therefore the deformation suppressing effect is small.
On the other hand, if the thickness is less than 2 μm, the effect will not change, but the cost will increase significantly. Therefore, it is limited to the above range. Also Fe
The amount of Sn powder to be mixed is specified so that the Sn content in the final sintered body is 0.5 to 2% by weight.
This is because the density of the sintered body is reduced when it exceeds 0.5%, and the effect of promoting the sintering is lost when it is less than 0.5% by weight. Fe-S
The n powder may be a water atomized method or a ground powder.

Since the powder to be used has a small particle size, it is difficult to mold the powder alone, and there are problems that defects such as cracks occur on the surface of the molded body and the mold is damaged. Therefore, the powder is mixed with a binder to be molded. Wax, resin or a mixture thereof may be used as the binder.
The molding method may be any of injection molding, extrusion molding and press molding, but the binder is added in an appropriate amount depending on the molding method. For example, injection molding requires 10 to 15% by weight of binder and press molding requires about 0.5 to 2% by weight. After the molding, the binder is removed. As the method, an appropriate method such as a heating method or a method of removing in a solvent is selected. After that, sintering is performed. The optimum sintering pattern is selected for each composition system. According to the method of the present invention as described above, it is possible to manufacture a high-density sintered body in which the shape of a component during sintering is small.

[0007]

EXAMPLES Hereinafter, examples will be described. (Example 1) SUS316L composition, average particle size 5.3,
11.2, 15.4, 18.7, and 22.3 μm high-pressure water atomized powders were prepared. Fe-20% Sn water atomized powder having an average particle size of 7.5 μm was added to these powders as Sn.
The mixture was added and mixed so that the content was 1.5% by weight. Fe
Two systems were prepared, one with and without the addition of -20% Sn powder, and 10% by weight of binder was added to these powders,
A raw material compound was manufactured by kneading. This compound is injection molded to a length of 60 mm, a width of 10 mm and a thickness of 6
mm rectangular parallelepiped test pieces were manufactured. The binder was removed by heating at a maximum temperature of 550 ° C. at 10 ° C./h in a nitrogen atmosphere. Then, sintering was carried out after confirming that the carbon and oxygen contents of the molded body were appropriate. At the time of sintering, the test pieces were installed in a beam shape on an alumina block placed at intervals of 50 mm, and the amount of downward deformation of the center of the test piece was measured. Sintering is performed at a temperature rising rate of 10 ° C./min in vacuum at 1250 ° C. for 2 hours.
Hold for h. The experimental results are summarized in Table 1. It can be seen that, in the case where the Fe-20% Sn powder is added, the deformation during sintering is obviously suppressed as compared with the case where the Fe-20% Sn powder is not added. The average particle size of the high-pressure water atomized powder is 2
In the case of 2.3 μm, the density of the sintered body remains low.

[0008]

[Table 1]

Example 2 Here, the grain size of Fe-20% Sn powder was examined. Fe-20% with an average particle size of 2.2, 7.5, 9.0 and 11.8 μm in water atomized powder of SUS316L composition with an average particle size of 11.2 μm.
Sn water atomized powder was added and mixed so that the Sn content was 1.5% by weight. Example 1 using these powders
The same experiment was performed. Table 2 shows the experimental results. Fe
When the -20% Sn powder has a particle size of 11.8 μm, the deformation suppressing effect is not exhibited.

[0010]

[Table 2]

(Embodiment 3) Here, Fe-20% Sn
The amount of powder added was examined. Fe-20% Sn water atomized powder having a SUS316L composition and an average particle size of 11.2 μm and Fe-20% Sn water atomized powder having an average particle size of 7.5 μm and having Sn contents of 0.3, 0.8, 1.5, 1. 9, 2.5
The mixture was added and mixed so as to have a weight percentage. The same experiment as in Example 1 was conducted using these powders. Table 3 shows the experimental results. When the content of the sintered body Sn is 0.3% by weight, the effect of suppressing the sintering deformation is small. On the other hand, with 2.5% by weight, the density of the sintered body does not increase.

[0012]

[Table 3]

[0013]

As described above, according to the present invention, it is possible to produce a high density stainless steel sintered body while suppressing deformation during sintering. Highly useful.

Claims (1)

[Claims] 1. A Fe—Sn powder having an average particle size of 2 to 10 μm is added to a stainless steel powder having an average particle size of 5 to 20 μm so that the Sn content in the final sintered body is 0.5 to 2% by weight. Manufacture of a high-density stainless steel sintered body with little shape deformation during sintering, characterized by mixing and adding, mixing and shaping the binder, removing the binder in the molded body, and then sintering Method.