JPH06200304A - Production of sintered parts having thin and intricate shape - Google Patents

Abstract

PURPOSE:To provide the process for production of sintered parts having thin and intricate shapes without deforming these parts. CONSTITUTION:High-speed steel powder is mixed with an org. binder and the mixture is injection molded to produce an injection molded article. After this injection molded article is degreased, the molded article is sintered by a low temp. (1150 to 1190 deg.C) below the eutectic liquid phase generating temp., by which a presintered body is produced. This presintered body is then subjected to an HIP treatment.

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 thin-walled complex shape sintered part by injection molding using high-speed steel powder, and particularly to a thin-walled complex shape sintered part having a wall thickness of 3 mm or less. Of the manufacturing method of.

In recent years, high-speed steel powder produced by the co-reduction method or the water atomizing method is heated and mixed with a binder,
This is pelletized and injection-molded by an injection molding machine to produce an injection-molded body. The injection-molded body is heated in a non-oxidizing atmosphere such as hydrogen or in a vacuum atmosphere at a temperature of 500 to 700.
Degreasing by holding at ℃, and then sintering in a vacuum atmosphere at a temperature higher than the eutectic liquid phase generation temperature (1200 to 1250 ℃) for thin complex parts such as vanes of rotary compressors and rockers of internal combustion engines. It is known to manufacture arm chips and the like. The particle size of the high-speed steel powder used in the above-mentioned injection molding method is such that the larger the size, the more difficult it becomes to maintain the shape of the injection-molded body after degreasing and the lower the sinterability. It is also known that a powder having a particle size of 30 μm or less is used (Japanese Patent Laid-Open No. 64-35091 and Japanese Patent Laid-Open No. 2-190).
No. 401).

[0003]

The above-mentioned degreased injection-molded article is subjected to a eutectic liquid phase generation temperature or higher (1200 to 1250 ° C.).
The high-speed steel thin-walled complex shape sintered part obtained by the sintering has an increased density and an improved strength. However, in particular, when a thin-walled complex-shaped injection molded body having a wall thickness of 3 mm or less is sintered, there is a problem that a portion which is largely deformed during sintering cannot be shipped as a product.

For example, a web 1 as shown in FIG.
A thin-walled and complex-shaped degreased test piece injection-molded body having a flange 2 only on one side was prepared, and the flange 2 was in contact with the sintering hearth 3 as shown in FIG. When charged in a sintering furnace and sintered at a temperature higher than the eutectic liquid phase generation temperature, the web 1 was deformed as shown in FIG. 2 and could not be shipped as a product.

[0005]

Therefore, the present inventors have
As a result of conducting research to solve such problems, first, the degreased injection-molded body was sintered at a low temperature lower than the eutectic liquid phase generation temperature to prepare a pre-fired body, and then the pre-fired body was hot-pressed. When subjected to hydrostatic pressure (hereinafter referred to as HIP) treatment, the above deformation hardly occurs, and even if the deformation occurs, it is negligibly small, and the density is higher than the conventional eutectic liquid phase generation temperature. It was found that a high-speed high-speed steel complex thin-walled sintered part having a high density of 99.5% or more, which is almost the same as the sintered body, can be obtained.

The present invention has been made on the basis of such findings, and high-speed steel powder is mixed with an organic binder, injection-molded to prepare an injection-molded body, and the injection-molded body is degreased. It is characterized by a method for manufacturing high-speed steel thin-walled complex-shaped sintered parts, in which a pre-fired body is produced by sintering at a temperature lower than the eutectic liquid phase generation temperature, and then the pre-fired body is subjected to HIP treatment. is there.

The high-speed steel powder used in the present invention has a composition specified by JIS, and its particle size is an average particle size of 1 to 30 μm. This is because if the average particle size of the high-speed steel powder exceeds 30 μm, the strength of the injection-molded product after degreasing will be low and it will be difficult to maintain the shape. This is not preferable because it becomes difficult and deformation occurs during preparation of the pre-fired body.

The above-mentioned pre-sintered body has the above-mentioned average particle size:
It is necessary to carry out at a temperature lower than the eutectic liquid phase generation temperature of the high speed steel powder of 1 to 30 μm, and the temperature is 1150 to 150 μm.
It is a predetermined temperature within the range of 1190 ° C. When the sintering temperature of the pre-fired body is less than 1150 ° C, the density of the pre-fired body obtained is 93%
This is because even if the subsequent HIP treatment is performed, sufficient densification does not occur, while the sintering temperature of the pre-fired body is 1
When the temperature exceeds 190 ° C., the density of the obtained pre-fired body exceeds 98% and the density is increased, but deformation during sintering becomes remarkable, which is not preferable.

Further, as the HIP processing, pressure:
It is preferably carried out under the conditions of 500 kg / cm ² or more and temperature: 950 to 1190 ° C.

The production method of the present invention can be applied to the production of thin-walled complex shaped sintered parts of any thickness,
Particularly, it is effective for manufacturing thin-walled sintered parts having a thickness of 3 mm or less. This is because a sintered part having a thickness of more than 3 mm can be manufactured without being deformed even if the conventional sintering method is adopted, not depending on the manufacturing method of the present invention.

[0011]

[Example] As a raw material powder, Cr: 4%, Mo: 5%,
W: 6%, V: 2%, C: 1%, balance: Fe and component composition consisting of unavoidable impurities (above, weight%, this component composition corresponds to JIS standard SKH51)
The water atomized high speed steel powder having the average particle diameter shown in Table 1 was prepared.

EVA (ethylene vinyl acetate copolymer): 3% by weight and paraffin wax:
Adding 45% by volume of a commercial binder containing 3% by weight,
Kneading is performed using a pressure kneader under the conditions of temperature: 135 ° C. and holding for 3 hours, and then using an injection molding machine, injection pressure:
While having a pressure of 500 kgf / cm ² , it has a shape having five flanges 2 on one side of the web 1 shown in FIG.
Test piece injection molded bodies having the wall thickness shown in Table 1 were prepared. Distance L between the flange 2 and the flange 2 of the test piece injection molded body
₀ was 5 mm in all cases.

This test piece injection molded article was degreased in a hydrogen atmosphere at a temperature of 700 ° C. for 5 hours, and the degreased test piece injection molded article was sintered in a vacuum atmosphere of 1 × 10 ^-2 Torr. As shown in FIG. 2, the flange 2 has a sintering hearth 3
Place it in contact with and sinter under the conditions shown in Table 1,
A pre-fired body was prepared.

These pre-fired bodies were subjected to HIP treatment under the conditions shown in Table 1 in an argon atmosphere, and the method 1 to 8 of the present invention was performed.
And the thin-walled complex shape test piece was produced by the comparative methods 1-4.

The density of the obtained thin-walled complex-shape test piece and the amount of deformation shown in FIG. 2: H ₁ , H ₂ , H ₃ , H ₄ and their average value H ₀ {= (H ₁ + H ₂ + H ₃ + H ₄ ). / 4} was obtained and shown in Table 2.

Further, for comparison, the same test piece injection molded article as the degreased test piece injection molded article used in Method 1 of the present invention was used, and the temperature was above the conventional eutectic liquid phase generation temperature.
Fig. 2 shows a sintering furnace in a vacuum atmosphere of 00 ° C and 1 × 10 ^-2 Torr.
As shown in (1), the sample was placed and sintered, and a thin-walled complex shape test piece was prepared by the conventional method without HIP treatment. The density, H ₁ , H ₂ , H ₃ , H _4, and H ₀ values of the thin-walled and complex-shaped test pieces produced by the above-mentioned conventional method were measured,
The measurement results are shown in Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

From the results shown in Tables 1 and 2, the density of the thin-walled complex shape test piece produced by the method 1 of the present invention was found to be the same as that of the thin-walled complex shape produced by the conventional method using the same test piece injection molded article. Although the density is almost the same as that of the shape test piece, the deformation amount (H ₁ , H
₂ , H ₃ , H ₄ and H ₀ ) are extremely smaller than the deformation amounts (H ₁ , H ₂ , H ₃ , H ₄ and H ₀ ) of the thin-walled complex shape test pieces produced by the conventional method, and Invention Method 2-8
Deformation amount (H ₁ ,
It can be seen that H ₂ , H ₃ , H ₄ and H ₀ ) are also small enough to be ignored.

However, as seen in Comparative Method 1, when the sintering temperature is lower than 1150 ° C., even if the HIP treatment is applied, the density of the thin-walled complex shape test piece does not increase and a large local deformation occurs, so that the firing is performed. Comparative method 2 when the binding temperature is higher than 1190 ° C
Is not preferable because the amount of deformation increases as in the conventional method.

Further, as seen in Comparative Example 4, when the thickness of the test piece injection-molded body exceeds 3 mm, the amount of deformation at the time of sintering becomes small, and the amount of deformation even at the conventional sintering temperature. It turns out that becomes smaller.

As described above, according to the manufacturing method of the present invention, it is possible to finish a thin-walled sintered part having a thickness of 3 mm or less with a high density without deformation, and it is excellent in reducing the weight of mechanical parts. Is played.

[Brief description of drawings]

FIG. 1 is a perspective view of a test piece injection-molded body.

FIG. 2 is an elevational view showing a state where a test piece injection-molded body is placed on a sintering hearth.

[Explanation of symbols]

 1 Web 2 Flange 3 Sintered hearth

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 29, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a perspective view of a test piece injection-molded body.

[Explanation of symbols] 1 Web 2 Flange 3 Sintered hearth

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (3)

[Claims] 1. A high-speed steel powder is mixed with an organic binder, injection-molded to prepare an injection-molded body, the injection-molded body is degreased, and the temperature is lower than the eutectic liquid phase generation temperature of the high-speed steel powder. A method for manufacturing a thin-walled complex-shaped sintered part, which comprises sintering at low temperature to prepare a pre-fired body, and then subjecting the pre-fired body to hot isostatic pressing. 2. The thin-walled complex shape sintering according to claim 1, wherein the low temperature of the high-speed steel powder, which is lower than the eutectic liquid phase generation temperature, is a predetermined temperature within a range of 1150 to 1190 ° C. Manufacturing method of parts. 3. The wall thickness of the thin-walled complex-shaped sintered part is 3 mm.
The method for manufacturing a thin-walled complex-shaped component according to claim 1 or 2, wherein: