JPH06158109A - Method for dewaxing and sintering molded body of metal or ceramic powder - Google Patents

Abstract

PURPOSE:To prevent the deformation of molded bodies at the time of dewaxing and sintering and to obtain sintered compacts excellent in dimensional precision by using a setter having a honeycomb structure as a setter for setting the molded bodies. CONSTITUTION:When molded bodies 2 formed by injection molding or extrusion molding are dewaxed and sintered, a setter 1 having a honeycomb structure is used and the molded bodies 2 are set in many holes arranged in the horizontal direction of the setter 1. It is not necessary to pile up setters, handling is facilitated and production efficiency is enhanced. Sintered compacts excellent in dimensional precision are obtd. without causing warping or waving in the longitudinal direction by imparting a V-shaped groove structure to the bottoms of the holes in the setter 1.

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 sintered product of metal or ceramic powder, and particularly to a degreasing / sintering method which does not cause deformation.

[0002]

2. Description of the Related Art Generally, in a process of manufacturing a metal or ceramics sintered product by a powder metallurgy method, a compact to be sintered is obtained as a green compact by compressing a raw material powder. Since this is a method in which the raw material powder filled in the mold is usually pressed from above and below with a punch, the shape of the obtained molded body is limited to a relatively simple shape, and a product with a more complicated shape is obtained. Therefore, it is necessary to perform post-processes such as cutting and grinding on the product just sintered.

In order to solve such a problem, various techniques for obtaining a molded article having a complicated shape, which cannot be obtained by the conventional method, have been studied, but in the field of ceramic products such as so-called engineering ceramics. Is a method of obtaining a product by adding a binder containing 10 to 20 wt% of an organic polymer compound as a main component to raw material powder, mixing and kneading, and then degreasing and sintering a molded product obtained by injection molding or extrusion molding. Is beginning to take place. Injection molding / extrusion molding has been developed as a plastic molding method, but it is suitable for mass-producing products with high dimensional accuracy without post-processing, so it has the problems described above. There are some noteworthy solutions. And, supported by the recent development of metal powder production technology represented by atomization method and binder blending technology, this production method has been attempted to be applied to sintered products of metal and ceramics.

The difference between the method of using a molded body obtained by injection molding / extrusion molding for sintering and the method of sintering a conventional compression molded body is, of course, that the molding method is different. Since it contains a large amount of binder, it is necessary to perform debinding, that is, degreasing, before sintering.
By the way, in the latter case, the molded body can be directly sintered because it does not contain a binder at all, or even if it does contain a binder, the amount is very small. In this degreasing method, the conventional general method is to gradually heat the molded body to volatilize the binder as the pyrolysis gas. However, if the heating rate at this time is too high, Since the generation is too rapid and causes deformation such as blistering and cracking of the molded product, 5 to 15 ° C / hr
It is necessary to set the degree.

However, the problem here is that when the molded body is placed on the setter and degreased, the surface in contact with the setter has a large diffusion resistance of the decomposed gas of the binder, and the decomposed gas is difficult to escape. However, the expansion and contraction behaviors in the degreasing process are different between the part not in contact with the setter, and there is a drawback in that the molded product is deformed such as warp and undulation. In particular, warping and waviness in the longitudinal direction become large depending on the molded body. Generally, as a countermeasure against this, the molded body is placed on the groove of a setter having a V-shaped groove and degreased / sintered. We have obtained products with excellent straightness and no deformation such as undulations. However, when degreasing is performed using such a setter, stacking the setters makes the setters bulky, resulting in poor production efficiency and is not suitable for mass production.

[0006]

The present invention has been made to solve the problem of deformation that occurs when degreasing and sintering a molded body obtained by injection molding or extrusion molding, and has excellent dimensional accuracy. It is an object of the present invention to provide a method for producing a sintered body with good mass productivity.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a molded product obtained by injection molding or extrusion molding of a mixture obtained by mixing, kneading and pelletizing a metal or ceramic powder and a binder containing an organic polymer as a main component. In the step of degreasing, the one having a honeycomb structure is used as a setter for mounting the molded body, and the setter is inserted and mounted in a large number of holes provided in the horizontal direction of the setter, or This is a method for degreasing and sintering a ceramic powder compact.

Generally, as a method of using a setter having a honeycomb structure, the holes are installed in the vertical direction,
The molded body is placed on top of it, but in the present invention, the molded body is inserted and placed in the holes arranged in the horizontal direction of the setter having the honeycomb structure. By degreasing and sintering by this method, stacking of setters is not required as in the case of using flat plate setters, it is easy to handle because it is not bulky and production efficiency can be improved, which is very useful for mass production. An excellent manufacturing method is provided.
Further, since the bottom of the holes provided in the setter has a V-shaped groove structure, the molded body is supported in the groove as in the case of using the flat plate type setter having the V-shaped groove.
It is possible to obtain a sintered body with excellent straightness accuracy in which warpage and undulation do not occur in the longitudinal direction.

[0009]

[Function] When a mixture obtained by mixing, kneading, and pelletizing a metal or ceramic powder and a binder is injection-molded or extrusion-molded, the setter used when degreasing and sintering a honeycomb structure has a honeycomb structure. Since the molded body can be placed in each of the many through holes formed in the, it is possible to process a large number of molded bodies at one time without stacking the setters as in the case of the flat plate type setter like the conventional one. Since the production efficiency is good and the bottom of the horizontal through-hole has a V-shaped groove structure, warp, undulation, etc. in the longitudinal direction do not occur, and a sintered body with excellent straightness accuracy can be obtained.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

[0011]

[Embodiment 1] FIG. 1 is a partial perspective view showing a state where a molded body 2 is placed on a setter 1 having a honeycomb structure according to Embodiment 1 of the present invention.

The raw material for molding is N having an average particle size of 0.5 μm.
To 91% by weight of i-Zn ferrite calcined powder, 5% by weight of ethylene-vinyl acetate copolymer having a vinyl acetate content of 20% by weight as a binder, 3% by weight of paraffin wax having a melting point of 60 ° C., and 1% by weight of dioctyl phthalate were used by a pressure kneader. After kneading at ℃ for 30 minutes, length is about 4m
It was obtained by pelletizing to m. A cylindrical molded body 2 having a cross section of φ3 mm was produced from this raw material by an extrusion molding machine (screw diameter: 30 mm, L / D: 22). The barrel temperature of the extruder was set to 130 ° C by a band heater. When the molded body 2 is degreased, it is cut into 50 mm in the longitudinal direction and, as shown in FIG. 1, a setter 1 having a honeycomb structure made of alumina having pores with a lattice shape (3.5 mm × 3.5 mm) in cross section. It was inserted and placed in the hole. This was placed in a degreasing furnace, heated in the atmosphere at a temperature rising rate of 5 ° C./hr, held at 300 ° C. for 1 hour, and then cooled in the furnace to degrease the product. In addition, 1
Sintering was performed at 100 ° C. for 3 hours. As a result, Ni-Z with a cross-sectional diameter of 2.65 mm, a length of 45 mm, and a density of 5.20 g / milliliter that does not cause warping or waviness in the longitudinal direction
A sintered body of n-ferrite was obtained.

[0013]

[Embodiment 2] FIG. 2 is a partial front view showing a state in which a molded body 21 is placed on a setter 11 having a honeycomb structure according to Embodiment 2 of the present invention.

Fe 50 wt% -C as a raw material for molding
An alloy with a composition of 50 wt% was melted by high frequency heating in an argon gas atmosphere, and averaged 1 by the water atomizing method.
The powder prepared to 0 μm was used, and polybutyl methacrylate 5 wt%, paraffin wax 5 wt% with a melting point of 60 ° C. and dioctyl phthalate 2 wt% were used as the binder in 88 wt% of the powder, and the raw material pellets were prepared in the same manner as in Example 1. Was produced. An injection molding machine was used to form a molded body 21 having a cross section of 1.0 mm × 3.0 mm and a length of 70 mm. The molded body 21 was placed in the pores of the setter 11 having a honeycomb structure made of zirconia and having lattice-shaped pores having a cross section of 4.0 mm × 4.0 mm. This was placed in a degreasing furnace and heated at a temperature rising rate of 5 ° C / hr in an argon gas atmosphere to 400 ° C.
Degreasing was carried out by holding for 3 hours and then cooling. Further, this was sintered at 1200 ° C. for 2 hours. As a result, there is no warpage or undulation in the longitudinal direction, and the cross-sectional shape is 0.
85mm x 2.55mm, length 59.5mm, density 7.9
Fe50wt% -Co50wt which becomes 0g / milliliter
% Sintered alloy was obtained.

[0015]

[Embodiment 3] FIG. 3 is a partial front view showing a state in which a molded body 22 is placed on a setter 12 having a honeycomb structure according to Embodiment 3 of the present invention.

The raw material for molding has an average particle size of 0.1 μm.
Lead titanate-lead zirconate (PZT) calcined powder 92wt
%, Butyl methacrylate as a binder 2.
Using 5 wt%, vinyl acetate-containing 14 wt% ethylene-piniacetate copolymer 2.5 wt%, paraffin wax 2 wt% with a melting point of 60 ° C., and dioctyl phthalate 1 wt%, raw material pellets were prepared in the same manner as in Example 1. did.
This raw material was molded by the same extruder as that used in Example 1 to form a triangular prism 22 having a cross-sectional shape of an isosceles right triangle having two sides of 2 mm. When the molded body 22 is degreased, it is cut into 20 mm in the longitudinal direction and inserted into the pores of the setter 12 having a honeycomb structure made of alumina and having lattice-shaped pores having a cross-sectional shape of 2.5 mm × 2.5 mm. Placed. This is installed in the degreasing furnace, and the
Degreasing was performed by heating at a temperature rising rate of ° C / hr, holding at 550 ° C for 3 hours, and then cooling in a furnace. In addition, 1
Sintering was performed at 200 ° C. for 2 hours. As a result, a PZT sintered body having a length of 17.4 mm and a density of 7.8 g / milliliter, which has a right-angled isosceles triangular cross-section with two sides of 1.75 mm and does not cause warpage or undulation in the longitudinal direction, is obtained. It was

[0017]

As described in detail above, according to the degreasing / sintering method of the present invention, there is no deformation in the production of a sintered product of a metal or ceramic powder compact molded by injection molding or extrusion molding. Sintered products with good dimensional accuracy can be efficiently produced, which is very useful in industry. In the present invention, as the raw material powder for molding, Ni-Zn ferrite, Mn-Zn ferrite, barium titanate, etc. in ceramics, iron, Fe in metals, etc.
-Co alloy, Fe-Si alloy, sendust, etc. can be used, but not limited thereto. Further, in the present invention, various polyolefins, copolymers, waxes and the like can be used as the binder mixed with the raw material powder, and they are appropriately selected in consideration of the particle size and surface property of the raw material powder. Further, as the material of the setter to be used, alumina, zirconia or the like can be used, but the material is not limited to these.

[Brief description of drawings]

FIG. 1 is a perspective view showing a mounted state of a molded body on a setter having a honeycomb structure according to a first embodiment of the present invention.

[Fig. 2] Fig. 2 is a partial front sectional view showing a placement body of a molded body on a setter having a honeycomb structure according to a second embodiment of the present invention.

[Fig. 3] Fig. 3 is a partial front sectional view showing a placement body of a molded body on a setter having a honeycomb structure according to a third embodiment of the present invention.

[Explanation of symbols]

 1,11,12 setter 2,21,22 molded body

Claims (2)

[Claims] 1. A step of degreasing and sintering a molded body formed by injection molding or extrusion molding of a mixture obtained by mixing and kneading metal or ceramic powder and a binder containing an organic polymer as a main component and pelletizing the mixture. , The molded body,
A degreasing / sintering method of a metal or ceramic powder compact, which is characterized in that the metal or ceramic powder compact is placed in the pores of a setter having a substantially honeycomb structure having a large number of pores in the horizontal direction. 2. A method for degreasing and sintering a metal or ceramic powder compact, wherein the bottom surface of the holes of the setter forms a V-shaped groove.