JPH05195017A - Production of high-density iron-base metal powder sintered compact with deformation reduced in sintering - Google Patents

Abstract

PURPOSE:To produce a high-density iron-base metal powder sintered compact with the deformation reduced by removing a binder from the compact of a mixture of the iron-base metal powder having a specified grain diameter and the binder and sintering the compact on a ceramic sheet having high heat conductivity and specific heat. CONSTITUTION:An iron-base metal powder of SUS 316L, etc., having 1-18mum average grain diameter is prepared by the atomization method, etc. About 10% of a binder is added to the powder, and the mixture is compacted. The binder is removed by heating, and then the compact is sintered to obtain a high-density iron-base metal powder sintered compact. In this case, the compact freed of the binder is placed on a ceramic sheet having >=40W/m.K and 27W/m.K heat conductivity respectively at 300 K and 1200 K and having >=1.0kJ /kg.K specific heat at 1200K, the sheet is preferably placed on a graphite sheet, and sintering is carried out. Consequently, the temp. distribution in a sintering furnace is reduced, the reaction of the floor sheet with the sintered compact is prevented, and a sintered compact is obtained with the deformation in sintering reduced.

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 an iron-based metal powder sintered body having a high density and a small change in shape by powder metallurgy.

[0002]

2. Description of the Related Art Conventional powder metallurgy uses iron-based metal powder (hereinafter abbreviated as powder) having an average particle size of 60 to 100 μm, but the density ratio of the final sintered body is 90% at most.
However, there was a problem that mechanical properties, magnetic properties or corrosion resistance were inferior to those of the ingot. With the recent development of technology that uses fine powder with an average particle size of 20 μm or less,
It has become possible to 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 method, or a method in which fine powder is granulated and used for pres molding. However, the method in which the binder is mixed and molded has a problem that the shape of the component is likely to collapse during sintering. In the case of injection molding, since the shape of the molded body is retained by the binder, if the binder is removed before sintering, the parts become temporarily extremely brittle and easily affected by the outside. In this case, the external influences include the weight of the component, the temperature distribution in the furnace, the temperature distribution in the component, the interaction between the component and the floor plate on which the component is placed during sintering, and the like. Especially, the influence of the temperature distribution is great, and the shrinkage rate of the parts at each position in the furnace or the uniformity of the shrinkage rate inside the parts is reduced. Then, due to the non-uniformity of the shrinkage ratio, the shape of the component may be largely deformed, and the final shape of the component may be significantly deformed from the design value. The reason why the temperature distribution is possible is that the temperature of the components inserted into the furnace and the temperature of the floor plate are not uniform, and the specific heat and the thermal conductivity of the floor plate have a great influence. A commonly used floor plate is an alumina plate, but alumina does not have a high thermal conductivity, which has been a factor causing the temperature distribution in the furnace.

[0003]

It is an object of the present invention to use a powder having an average particle size of 1 to 18 μm to achieve high density after sintering and to improve shape retention during sintering. It is to propose a method of manufacturing the body.

[0004]

The present invention has an average particle size of 1
After adding and mixing a binder to an iron-based metal powder having a particle size of up to 18 μm to remove the binder from the molded body, the thermal conductivity at a temperature of 300 K is 40 W / m · K or more and the temperature is 12
At the time of sintering, characterized in that the compact is placed on a ceramic plate having a thermal conductivity of 00 W at 7 W / m · K or more and a specific heat at a temperature of 1200 K of 1.0 kJ / kg · K or more and is sintered. A method for producing a high-density iron-based metal powder sintered body with little shape deformation, by adding and mixing a binder to iron-based metal powder having an average particle size of 1 to 18 μm, and molding to remove the binder in the molded body. After that, a ceramic having a thermal conductivity of 40 W / m · K or more at a temperature of 300 K, a thermal conductivity of 7 W / m · K or more at a temperature of 1200 K, and a specific heat of 1.0 kJ / kg · K or more at a temperature of 1200 K. A method for producing a high-density iron-based metal powder sintered body having a small shape deformation during sintering, which comprises placing the molded body on a plate and placing the plate on a graphite plate for sintering.

[0005]

The specific structure of the present invention will be described below. First, the powder particle size is defined to be 1 to 18 μm in order to accelerate sintering and achieve high density. In this case, the powder may be a single atomized powder or a mixed powder. Since the powder to be used has a small particle size, it is difficult to mold the powder alone, and even if the powder is molded, there are problems such as generation of defects such as cracks on the surface of the molded body and damage to the mold. Therefore, the powder is mixed with a binder and molded. Wax, resin or a mixture thereof may be used as the binder.
The molding method may be injection molding, extrusion molding, or press molding, but the amount of the binder mixed depends on the molding method. For example, injection molding requires 10 to 15 wt% binder and press molding 0.5 to 2 wt%.

After molding, heating is performed in a non-oxidizing atmosphere to remove the binder. As the heating temperature and the heating rate, an appropriate pattern is selected depending on the temperature at which the binder decomposes and evaporates. After that, sintering is performed, but in order to reduce the temperature distribution in the sintering furnace as a floor plate on which parts are placed, one having high specific heat and high thermal conductivity is desirable, and the sintering temperature is 1000 to
Although a suitable temperature of 1500 ° C. is selected, a ceramic material that does not react with the sintered body or melt is desirable.
As a result of studying various ceramic-based materials, the inventors have found that the thermal conductivity is 40 W / mK or higher at a temperature of 300 K or higher and the thermal conductivity is 7 W / mK at a temperature of 1200 K.
It was concluded that a plate made of a material having a specific heat of 1.0 kJ / kg · K or more at a temperature of K or higher is suitable.
When the thermal conductivity and the specific heat at each temperature are lower than these values, the temperature of the floorboard itself is hard to rise, which leads to the generation of temperature distribution. These plates may be used alone, but when there is no one of sufficient size, these plates may be placed on a graphite plate, and a compact may be placed on the graphite plate for sintering. As described above, 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 the component is not deformed at the time of sintering.

[0007]

EXAMPLES Examples will be described below. Example 1 A water atomized powder having an average particle size of 13.4 μm adjusted to a SUS316L composition was spray-manufactured. A binder was added to the powder in an amount of 10% by weight and kneaded to produce a raw material compound. This compound was injection molded to produce
Ring (outer diameter 40 mm, inner diameter 31 mm, thickness 3 mm) and cylindrical cup (outer diameter 30 mm, inner diameter 26)
mm, height 30 mm). The binder was removed by heating in a nitrogen atmosphere at 10 ° C./h to a maximum temperature of 650 ° C. Then, after confirming that C and O were proper values, sintering was performed. The test piece is a 2 mm thick, 60 mm square AlN plate (purity 98%, 120 mm X 250 mm).
X 4 mm). Forty AlN plates on which such test pieces were placed were inserted into a sintering furnace and sintered. On the other hand, the same test piece was used for an alumina plate with a density ratio of 90% (purity: 95%, 1
20 mm x 250 mm x 4 mm) and 40 sheets were inserted and sintered in the same manner as described above. With respect to these two batches of sintered bodies, the circularity of the inner diameter of the ring was measured with a circularity meter. The inner diameter of the cylindrical cup was measured in two directions on the lowermost surface and the uppermost surface in contact with the floor plate, and the roundness of the lowermost surface was measured. Furthermore, the density of each sintered body was measured by the Archimedes method, and possible impurities were analyzed.

Table 1 collectively shows the experimental results. The circularity of the ring is improved in the case of using the AlN plate as compared with the case of using the alumina plate. Even in the case of a particularly high cylindrical cup type, there is little deformation of the shape, indicating that the sintering was performed in a good state. Sintered density is 9
5% or more was achieved, and no impurities from the plate were observed as shown in Table 2.

[0009]

[Table 1]

[0010]

[Table 2]

Example 2 Here, materials other than alumina and AlN were examined. SiC, BeO, MgO, C shown in Table 3
aO, stabilized ZrO ₂ , BN, mullite (3Al ₂ O ₃ 2Si
A plate of O ₂ ) was used. The specific heat and thermal conductivity at 300K and 1200K of each plate are shown in Table 3. The same experiment as in Example 1 was conducted using these plates. The experimental results are shown in Table 4,
5 shows.

[0012]

[Table 3]

[0013]

[Table 4]

As shown in Table 4, SiC, BeO, Mg
Those using O, also showed good results in comparison with the results of Example 1. On the other hand, CaO and stabilized ZrO
_{The result} of using ₂ is larger than that of alumina. Further, as shown in Table 5, BN reacted with the sintered body and melted. In the case of using ZrO ₂ or mullite, Si was remarkably increased in the sintered body and the sintered density was lowered.

[0015]

[Table 5]

Example 3 Here, the influence of the particle size of the powder used is shown. SUS31
The composition was adjusted to a 6 L composition and the average particle diameters were 2.3 and 5.
6, 8.9, 13.4, 19.5, 22.8 μm powders were spray produced by water atomization. Rings and cylindrical cups were produced by injection molding using this powder in the same manner as in Example 1, and degreasing was performed in the same manner. Then, the floor plate was sintered using the same AlN and alumina plate as in Example 1. The experimental results are shown in Table 6. Sintering densities of 95% or more were obtained for powders with particle diameters of 2.3, 5.6, 8.9 and 13.4 μm, and AlN had good results in terms of shape deformation. showed that. However, for the two with particle sizes of 19.5 and 22.8 μm,
The density is low, and the effect due to the difference in floor plate is also small.

[0017]

[Table 6]

Example 4 Here, the effect of using a graphite plate will be described. S
50mm made of iC, AlN, BeO, MgO
A thin plate having a thickness of X 50 mm and a thickness of 1.5 mm was used. The test piece was molded and degreased in the same manner as in Example 1. This test piece is placed on the above-mentioned thin plate, and this plate is 175 mm.
Sintering was performed on a graphite plate of 124 mm X and 4 mm thickness. The sintering conditions are the same as in Example 1. The experimental results are shown in Table 7. A good sintered body with little change in shape was obtained using any of the plates.

[0019]

[Table 7]

[0020]

As described above, according to the present invention, since it is possible to obtain a high-density sintered body by suppressing the shape deformation during sintering, it is possible to manufacture a sintered part by powder metallurgy. Highly useful.

[Brief description of drawings]

FIG. 1 is a plan view showing the shape of a ring test piece.

FIG. 2 is a cross-sectional view showing the shape of a cylindrical cup test piece.

Claims (2)

[Claims] 1. A binder is added to an iron-based metal powder having an average particle diameter of 1 to 18 μm, and the mixture is molded, and after removing the binder in the molded body, the thermal conductivity at a temperature of 300 K is 40 W / m.
・ K and above, and thermal conductivity at temperature 1200K is 7
High density with little shape deformation during sintering, characterized by placing the compact on a ceramic plate having a specific heat of 1.0 kJ / kg · K or more at a temperature of 1200 K or more and W / m · K or more and sintering. A method for producing an iron-based metal powder sintered body. 2. An iron-based metal powder having an average particle size of 1 to 18 μm is mixed with a binder and molded, and after removing the binder in the molded body, the thermal conductivity at a temperature of 300 K is 40 W / m.
・ K and above, and thermal conductivity at temperature 1200K is 7
The molded body is placed on a ceramic plate having a specific heat of W / m · K or higher and a specific heat at a temperature of 1200 K of 1.0 kJ / kg · K or higher, and the plate is placed on a graphite plate and sintered. A method for producing a high-density iron-based metal powder sintered body, which has little shape deformation during sintering.