JP3978916B2 - Method for manufacturing sintered parts - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a metal powder injection molding method, and more particularly to a metal powder injection molding method for manufacturing a part composed of a plurality of metal materials.
[0002]
[Prior art]
Conventionally, this type of metal powder injection molding method is disclosed in Japanese Patent Laid-Open No. 5-59407. In this method, a kneaded body of metal powder and a binder is molded by injection molding to obtain a green body, and a plurality of green bodies are assembled into a desired shape. The assembled green body is degreased and the composite molded body is a mixed gas of hydrogen and an inert gas, and a temperature of 500 ° C. or higher and 750 ° C. or lower is started at a temperature of 750 ° C. or lower in an atmosphere having a dew point of −30 ° C. or lower. After carrying out the heat treatment with the final temperature, sintering is performed.
[0003]
[Problems to be solved by the invention]
However, the above-described method requires a dedicated machine tool for assembling after separately forming a plurality of green bodies. In machine tools, there is an error in forming accuracy for each of the plurality of green bodies. For example, even if it is desired to assemble a plurality of green bodies on a concentric axis, the concentricity of the assembled green bodies can be sufficiently obtained. There may not be.
[0004]
Further, as a method of manufacturing a part in which a plurality of metal materials are integrated by a method other than the metal powder injection molding method, there is one disclosed in Japanese Patent Laid-Open No. 5-237678. This is done by winding a nickel foil around a modified part of a ferromagnetic electromagnetic actuator member and irradiating the part with a laser beam to alloy nickel into the actuator member, which is modified to be nonmagnetic or weakly magnetic. Thus, a component in which the magnetic member and the nonmagnetic member are integrated is obtained.
[0005]
However, in this method, in order to form a non-magnetic or weak magnetic part, the nickel foil is wound around the surface of the ferromagnetic member and modified, so that the surface becomes non-magnetic or weak magnetic inside. Not modified. Further, the boundary surface between the nonmagnetic or weakly magnetic portion and the ferromagnetic portion cannot be clearly controlled by this method, and a desired boundary surface cannot be obtained.
[0006]
Therefore, according to the present invention, in the metal powder injection molding method, a sintered part in which a plurality of metal materials are integrated is manufactured at low cost with high accuracy, and the interface between the ferromagnetic material and the nonmagnetic material is arbitrarily set. The technical problem is to provide a method for manufacturing a sintered part that is possible.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 is provided with a slide mold capable of opening and closing an inlet other than the first inlet into the cavity, and the first kneaded body of the metal powder and the binder is provided in the cavity. After injecting and solidifying from one injection port, the injection port is sequentially opened while moving the slide mold to expand the cavity, and a kneading body made of a material different from the first kneading body is sequentially injected and coagulated. Since a green body made of a metal material is obtained, and the green body is degreased and sintered, it is not necessary to assemble a green body made of a plurality of metal materials, and a green body with good appearance accuracy can be obtained. In addition, since the kneaded bodies are sequentially injected, adhesion to the boundary surface with another kneaded body is promoted by pressurization during injection, so that the kneaded bodies of different materials are not peeled off at the boundary surface. It is.
[0008]
According to the invention of claim 2, after the kneaded body of the first metal powder and the binder is injected and solidified into the cylindrical cavity, the cylindrical slide mold disposed in the cavity is moved. The cavity is expanded to obtain a cylindrical first space, and after the kneaded body of the second metal powder and the binder is injected and solidified in the first space, the slide mold is further moved to expand the cavity. A cylindrical second space is obtained, and a green body made of a three-layer kneaded body obtained by injecting a kneaded body of a third metal powder and a binder into the second space is obtained, and the green body is degreased and baked. As a result, it is possible to obtain an accurate cylindrical green body in which the axes of the respective layers of the metal material are concentrically.
[0009]
Further, according to the invention of claim 3, in the invention of claim 2, since the first metal powder and the third metal powder are the same magnetic material, and the second metal powder is a non-magnetic material, It is possible to obtain a component that can arbitrarily set the boundary surface between the magnetic material and the non-magnetic material.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention of this application will be described with reference to the drawings. FIG. 1 is a sectional view of a metal powder injection molding apparatus according to the present invention. FIG. 2 is a perspective view of a green body and a product molded by the metal powder injection molding apparatus according to the present invention.
[0011]
First, a configuration based on the embodiment will be described.
[0012]
As shown in FIG. 1, the metal powder injection molding apparatus 1 includes a fixed mold 2 in which continuous holes 2 a and 2 b having different diameters forming an outer shape of a green body 10 to be molded are formed, and an opening on the hole 2 a side. , A knockout pin 4 and a cylindrical punch 5 for closing the opening on the hole 2b side.
[0013]
In the fixed mold 2, the injection port 2c into which the kneaded body of the metal powder and the binder is injected communicates with the hole 2a having a large diameter, and the injection ports 2d and 2e arranged in parallel in the axial direction communicate with the hole 2b having a small diameter. Is formed. The movable die 3 includes a base 3c that closes the opening on the hole 2a side, a convex portion 3a having a smaller diameter than the hole 2a protruding from the base 3c, and a pin 3b having a smaller diameter than the hole 2b protruding from the convex portion 3a. ing. At the tip side of the pin 3b, a cylindrical punch 5 that can slide between the hole 2b and the pin 3b so as to close the opening on the hole 2b side, a slide that can slide in the punch 5, and a pin A knockout pin 4 having the same diameter as 3b and abutting against the tip surface of the pin 3b is arranged.
[0014]
The cavity 6 includes a wall surface of the hole 2a, a wall surface of the hole 2b, a tip surface of the base 3c of the movable die 3, an outer peripheral surface and a tip surface of the convex portion 3a and the pin 3b, a tip surface of the punch 5, and a knockout pin. 4 tip surfaces. Further, the cavity 6 can be changed in volume by moving the punch 5 and the knockout pin 4.
[0015]
In the embodiment of the present invention, a kneaded body of 18Cr stainless steel powder, which is a magnetic metal powder, and a binder is pressurized and supplied to the injection ports 2c and 2e. The inlet 2d is pressurized and supplied with a kneaded body of 18Cr—Ni stainless steel powder, which is nonmagnetic metal powder, and a binder. As the binder, a thermoplastic resin such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or the like based on a mixture of wax and a low molecular weight additive is used.
[0016]
However, the metal powders contained in the kneaded bodies supplied to the respective inlets 2c, 2d, and 2e may be different. In addition, when the material characteristics of the metal powder do not need to be particularly limited with respect to magnetic or non-magnetic, the metal powder is selected according to other material characteristics, such as stainless steel, titanium (alloy), Fe-Ni alloy, Co You may select from a base alloy, Ni base alloy, high speed steel, etc.
[0017]
The particle shape of the metal powder is preferably spherical and has a particle size of 10 μm or less. In the kneaded body, the metal powder is 45 to 65% by volume with respect to the binder, and the weight ratio accounts for about 90%. It should be adjusted to.
[0018]
Next, the operation based on the embodiment will be described.
[0019]
In the first stage, as shown in FIG. 1A, the punch 5 covers more than half of the pin 3b, opens the injection port 2c, and closes the injection ports 2d and 2e. . At this time, the cavity 6 includes a wall surface of the hole 2a, a wall surface of the hole 2b, a distal end surface of the base 3c of the movable mold 3, an outer peripheral surface of the pin 3b, a distal end surface and an outer peripheral surface of the convex portion 3a, and the punch 5 And a tip end surface of the substrate.
[0020]
The inlet 2c is supplied with a kneaded body of the first metal powder and binder heated to about 150 ° C. to 200 ° C. outside the metal powder injection molding apparatus 1. Next, the kneaded body of the heated first metal powder and binder is heated to about 60 ° C. from the inlet 2c at a plunger speed of 20 to 200 mm / sec under a pressure of about 150 to 1000 kgf / cm ^2. The first green body 10a is formed by being injected into the cavity 6 and solidifying.
[0021]
Next, when the first green body 10a is solidified to some extent in the cavity 6, in the second stage, as shown in FIG. 1B, the punch 5 expands the cavity 6 compared to the first stage. The injection port 2d is opened and the injection port 2e is closed. As the punch 5 moves, the cavity 6 (first space) includes a tip surface of the first green body 10a, a wall surface of the hole 2b, an outer peripheral surface of the pin 3b, a front end surface and an outer peripheral surface of the convex portion 3a. , And the tip surface of the punch 5.
[0022]
A kneaded body of the second metal powder and the binder is supplied to the injection port 2d under the same conditions as in the first stage. The kneaded body of the second metal powder and the binder is injected into the cavity 6 from the injection port 2d, solidifies, and unites with the first green body 10a, thereby forming the second green body 10b.
[0023]
Further, when the second green body 10b is solidified to some extent in the cavity 6, in the third stage, as shown in FIG. 1C, the punch 5 further expands the cavity 6 as compared with the second stage. Move to open the inlet 2e. The knockout pin 4 moves in the same direction together with the punch 5, and the cavity 6 (second space) includes a tip surface of the second green body 10 b, a wall surface of the hole 2 b, a tip surface of the punch 5 and the knockout pin 4, It is formed from the outer peripheral surface and the front end surface of the pin 3b.
[0024]
The inlet 2e is supplied with the kneaded body of the first metal powder and binder used in the first stage under the same conditions as in the first stage. The kneaded body of the first metal powder and the binder is injected into the cavity 6 from the injection port 2e, solidifies, and unites with the second green body 10b to form the green body 10.
[0025]
The green body 10 is removed from the metal powder injection molding apparatus 1 by extruding the green body 10 by pulling out the movable body 3 from the fixed mold 2 and opening the hole 2a side to move the knockout pin 4 toward the hole 2a. It is taken out.
[0026]
After the green body 10 is taken out, the green body 10 containing the binder is put in a furnace and gradually heated to a thermal decomposition temperature (within about 600 ° C.) exceeding the melting point of each component constituting the binder. Depending on the thickness of the green body 10, a sufficient time (10 to 72 hours) is taken to decompose the binder into a liquid or gaseous form, and the binder is removed from the green body 10 to obtain the brown body 11. . Regarding the removal of the binder, the green body 10 may be attached to a solvent such as trichlorethylene, and a part of the binder may be dissolved and removed before being put into a furnace.
[0027]
Next, the brown body 11 is heated from 80% or more of the melting point of the metal to a temperature just below the melting point in a hydrogen atmosphere or in a high vacuum, and is sintered into a product 12 as shown in FIG. The product 12 is molded with a shrinkage of 15 to 25% of the brown body 11.
[0028]
In the above-described embodiment, the punch 5 is cylindrical, but it is not always necessary to have this shape. For example, a product having different material characteristics is integrally formed only on a part rather than an annular part. If desired, the plate-shaped punch may be moved so that the inlet to which the kneaded body is supplied can be opened and closed, and the molding can be performed with a substantially rectangular space formed as the punch moves. Further, the front end surface of the punch 5 is formed to be inclined with respect to the axial direction in order to form the end surface of the product 12, but the boundary surface of the kneaded body with different metal powders is adapted to the functional requirements, for example, When it is desired to clearly separate the boundary surface between the magnetic material and the nonmagnetic material in the direction orthogonal to the axial direction of the product 12, the tip surface of the punch 5 may be formed perpendicular to the axial direction.
[0029]
【The invention's effect】
As described above, in the method for manufacturing a sintered part according to the present invention, since a green body made of a plurality of metal materials is integrally formed in the cavity, it is necessary to assemble a green body made of a plurality of metal materials. Thus, a green body with good appearance accuracy can be obtained. In addition, since the kneaded bodies are sequentially injected, adhesion to the boundary surface with another kneaded body is promoted by pressurization during injection, so that the kneaded bodies of different materials are not peeled off at the boundary surface. It is.
[0030]
In addition, since the kneaded body is sequentially supplied into the cylindrical cavity, it is possible to obtain a cylindrical green body with high accuracy in which the axial centers of the respective layers of the metal material are concentrically.
[0031]
Further, the kneaded body of the first metal powder of the magnetic material, the kneaded body of the non-magnetic second metal powder, and the kneaded body of the first metal powder of the magnetic material are supplied sequentially in the cylindrical cavity. Therefore, it is possible to obtain a component that can arbitrarily set the boundary surface between the magnetic material and the non-magnetic material.
[Brief description of the drawings]
FIG. 1 is a sectional view of a metal powder injection molding apparatus according to the present invention.
FIG. 2 is a perspective view of a green body and a product molded by the metal powder injection molding apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal powder injection molding apparatus 2 Fixed mold | type 3 Moving type | mold 4 Knockout pin 5 Punch 6 Cavity 10 Green body 11 Brown body 12 Product

Claims (3)

A slide mold capable of opening and closing an inlet other than the first inlet into the cavity is provided, and after the first kneaded body of the metal powder and the binder is injected from the first inlet into the cavity and solidified, The slide mold is moved to open the inlet sequentially while expanding the cavity, and a kneaded body made of a material different from the first kneaded body is sequentially sprayed and solidified to obtain a green body made of a plurality of metal materials, A method for producing a sintered part, comprising degreasing and sintering the green body. After the kneaded body of the first metal powder and the binder is injected into a cylindrical cavity and solidified, the cylindrical slide mold disposed in the cavity is moved to expand the cavity to form a cylindrical first. After obtaining a space and injecting and solidifying a kneaded body of the second metal powder and the binder into the first space, the slide mold is further moved to expand the cavity to form a cylindrical second space. And obtaining a green body comprising a three-layer kneaded body solidified by injecting a kneaded body of a third metal powder and a binder into the second space, and degreasing and sintering the green body. A method for manufacturing sintered parts. 3. The method of manufacturing a sintered part according to claim 2, wherein the first metal powder and the third metal powder are the same magnetic material, and the second metal powder is a non-magnetic material.

Images