JP2004285466A - Method for manufacturing metallic composite sintered body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when a composite sintered article is manufactured by metal powder injection molding (MIM), a joining step is added after the completion of the whole steps of MIM in the case of joining by brazing or welding, which results in the increase in cost and the prolongation of the delivery date in manufacture, and also no practical level of strength can be obtained by the conventional methods of joining where a sintering step of MIM is utilized and joining is performed in the sintering step. <P>SOLUTION: Sintering and joining are simultaneously carried out in MIM to rationalize a joining step. Moreover, when a molded part is placed in a metal mold and further another molded part is injected to carry out bonding, the joining surface of the molded part to be placed is held at an angle of 15 to 45° with respect to the flow direction of a compound and a paste adhesive containing metal powder is applied to the joining surface of the molded part to bond the two molded parts together. By this method, joining strength after sintering can be increased to a practical level. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal composite sintered body by joining molded bodies in metal powder injection molding.
[0002]
2. Description of the Related Art In metal powder injection molding, a compound, which is a kneaded product of metal powder and an organic binder, is injected into a mold to produce a molded product, and the organic binder component is degreased and removed from the molded product. Then, it is a technique of producing a precision metal part having a large degree of freedom in a three-dimensional shape by sintering at a higher temperature.
At present, metal powder injection molding is used for manufacturing precision parts of various metal materials such as stainless steel, magnetic material and tool steel. However, these are products made of a single type of metal material obtained by degreasing and sintering a molded product obtained by one injection molding.
Recently, attempts have been made to manufacture a metal composite sintered body made of a plurality of metal materials by joining in metal powder injection molding. The common manufacturing method involves joining of the sintered body by brazing or welding, but these methods add a brazing and welding step after the completion of all MIM processes up to sintering, so cost is reduced. Upswing and prolonged manufacturing period were inevitable.
Further, another molded body is placed on top of another molded body, or two molded bodies are bonded with an organic paste containing no metal powder, and then joined by degreasing and sintering. However, the adhesion between them is poor, and the bonding strength of the composite sintered body after sintering is much lower than that of a single-material sintered body without bonding.
Further, a molded body produced by injection molding is placed in a part of a mold in advance, another compound is injected into the mold, and the two molded bodies are adhered to each other. In some cases, bonding is performed by doing so. However, since the shape of the joints of the compacts set in the mold in advance is not devised and the adhesion is poor, the joint strength of the composite sintered body after sintering is low and has not reached a practical level.
[0007]
In the conventional method for producing a metal composite sintered body by metal powder injection molding, the method described in (0004) increases costs by adding a step after the step of metal powder injection molding. In addition, the method described in (0005) and (0006) has a problem that the joining strength is low and a practical level of strength cannot be obtained. The present invention is intended to solve the above-mentioned problems of the conventional method. That is, a method of manufacturing a metal composite sintered body having a practical level of bonding strength at low cost and without prolonging the manufacturing period without adding a post-process in metal powder injection molding is realized.
[0008]
Means for Solving the Problems In the conventional joining by brazing or welding, the steps are added after the completion of all the steps of metal powder injection molding, resulting in an increase in cost and a prolonged production period. However, in the present invention, sintering and joining are simultaneously performed in the sintering step of the molded body in the metal powder injection molding process without adding the joining step after the step of metal powder injection molding, thereby reducing cost and manufacturing period. Shorten.
According to a first aspect of the present invention, in order to obtain a high bonding strength in a metal composite sintered body, the shape of a bonding portion of a molded body previously set in a mold is adjusted with respect to the direction of the flow of the compound in the mold. To form a joint surface having an inclination of 15 to 45 degrees. After the molded body is placed in a mold, another kneaded material is injected to bond the two molded bodies through the joint surface. According to this method, high adhesion between the two can be obtained. Thereafter, by sintering, a metal composite sintered body having high bonding strength is obtained.
In the present invention, a paste-like kneaded material (hereinafter, referred to as a paste containing metal powder) composed of a metal powder and an organic binder is applied to a joint surface of the molded bodies to bond the two molded bodies. As a result, a paste intermediate layer containing metal powder having high adhesion between the two is obtained, and thereafter, a metal composite sintered body having high bonding strength is obtained by degreasing and sintering.
According to a third aspect of the present invention, the paste containing the metal powder described in the above paragraph (0010) is applied to the joint surface of the molded body partially degreased to bond the two molded bodies partially degreased. I do. As a result, a paste intermediate layer containing metal powder having high adhesion between the two is obtained, and thereafter, a metal composite sintered body having high bonding strength is obtained by degreasing and sintering.
[0012]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described with reference to examples of the method of claim 1. A compound was prepared by kneading SUS316L or SUS430L stainless steel powder having an average particle size of 10 μm and a plurality of organic polymers. A test piece mold in which this compound is half-closed to the center of the cavity as shown in FIG. 1 with an insert having an end face in contact with the compound having an inclination of 30 degrees with respect to the direction of the flow of the compound in the mold. A flat dumbbell-shaped tensile test specimen was formed by injecting the mixture into the center and only half of the molded product was formed. This compact was placed at the position of the insert, and the same or different stainless steel powder compound was injected again to bond the two compacts together to produce a composite compact as shown in FIG. Thereafter, solvent degreasing and sintering were performed to produce a metal composite sintered body.
In the metal composite sintered body manufactured by this method, a sample obtained by sintering SUS316L at 1350 ° C. shows a tensile strength of 460 MPa, and a sample obtained by sintering SUS430L at 1100 ° C. shows a tensile strength of 360 MPa. The values were 100% and 90% of the strength of the single material without bonding, respectively. Further, a sample obtained by sintering a composite molded product of SUS316L and SUS430L of different stainless steels at 1350 ° C. showed a tensile strength of 320 MPa, which was 70% of the strength of the SUS316L single material without joining. For comparison, in the case of a metal composite sintered body similarly manufactured with an insert piece having a joint end face inclined at an angle of 90 degrees with respect to the direction of compound flow in the mold, SUS316L was heated at 1350 ° C. The sintered sample had a tensile strength of 310 MPa, and the sample obtained by sintering SUS430L at 1100 ° C. had a tensile strength of 260 MPa, and these values were 70% of the strength at an angle of 30 degrees.
Next, an embodiment will be described with reference to an example using the method of claim 3. First, in the same manner as described in (0012), using a compound of SUS316L powder or SUS430L powder, a flat dumbbell tensile test of only one half having an inclination of an angle of 30 degrees with respect to the direction of the flow of the compound in the mold at the joint end surface. A piece was produced. Next, among the organic binder components contained in the compound, PMMA (acrylic resin), PW (paraffin wax), and the like were removed from the molded body in normal hexane vapor except PP (polypropylene). A solution in which SUS316L or SUS430L stainless steel powder and PVA (polyvinyl alcohol) were dissolved in ethanol was mixed and kneaded at a volume ratio of 3: 4 on the joint surface of the molded body from which the binder component was partially degreased and removed. A paste paste containing stainless steel powder was applied and adhered to another similarly degreased half specimen specimen via the paste paste layer as shown in FIG. Thereafter, the remaining PP (polypropylene) of the adhered test piece molded body was subjected to heat degreasing and sintering to produce a metal composite sintered body in which the same or different kinds of metals were joined.
In the metal composite sintered body produced by this method, the SUS316L was bonded with a paste paste containing SUS316L powder and sintered at 1350 ° C. and joined at 400 MPa, and the SUS430L was joined with a paste paste containing SUS430L powder. The samples bonded and sintered at 1100 ° C. and joined exhibited a tensile strength of 320 MPa, these values being 90% and 80% of the strength of the single material without joining, respectively. A sample in which SUS316L / SUS430L dissimilar stainless steels were adhered with SUS316L powder-containing paste and sintered at 1350 ° C. and joined together exhibited 330 MPa, and the SUS430L powder-containing paste showed a tensile strength of 370 MPa.
The metal powder used for the paste containing the metal powder is the same powder as the metal powder contained in the compact, or the same metal powder as one of the two or a mixture of the two metals in the joining of the compacts of different metals. Powder is preferred. The organic binder used for the paste is desirably a liquid, such as an alcohol solution of PVA (polyvinyl alcohol), which is liquid at room temperature, is well kneaded with the metal powder, and has an adhesive force.
[0017]
【The invention's effect】
According to the present invention, a metal composite sintered body having a practical level of bonding strength at a low cost without adding a bonding step such as brazing or welding after the end of the metal powder injection molding step, and without prolonging the manufacturing period is provided. Can be manufactured.
By dividing the molding into a plurality of times, a precision part having a more complicated shape such as a hollow shape can be manufactured without complicating the mold.
Further, by joining molded bodies made of different kinds of metal powders, it is possible to manufacture precision machine parts having a plurality of different functions such as magnetic / non-magnetic and hard / soft in one part.
[Brief description of the drawings]
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a method of bonding a molded article by two injection moldings in (Claim 1), wherein (A) shows a first injection molding and (B) shows a second injection molding.
FIG. 2 is a view showing a molded product of a tensile test piece produced by two injection moldings.
FIG. 3 is a diagram showing a method for producing a tensile test specimen molded body using paste containing metal powder.
[Explanation of symbols]
1 Injection mold 2 Insertion piece 3 Cavity 4 Test piece molded article of only half 5 Tensile test piece molded article 6 Paste paste containing metal powder

Claims (3)

A molded body produced by injection molding a kneaded product of a metal powder and an organic binder is placed in a part of a mold in advance, and a kneaded product of the same or different kind of a metal powder and an organic binder is further placed in the mold. In the production of a metal composite sintered body, which is performed by bonding the two compacts by degreasing and sintering them after injection, the shape of the joints of the compacts previously set in the mold is determined. A method for producing a metal composite sintered body in which same or different kinds of metals are joined by taking a joining surface having an inclination of 15 to 45 degrees with respect to the direction of flow of the kneaded material in the mold. . A paste-like kneaded product composed of a metal powder and an organic binder is applied to a part of the surface of a molded body produced by injection-molding a kneaded material of a metal powder and an organic binder, and this part is used as an adhesive surface to form another molded body and a paste. A method for producing a metal composite sintered body in which the same or different types of metals are joined by performing degreasing and sintering after bonding via a kneaded material layer. After degreased some organic binder components from the molded body produced by injection molding the kneaded product consisting of metal powder and organic binder, a paste-like kneaded product consisting of metal powder and organic binder was applied to a part of the surface of the molded body Then, this portion is used as an adhesive surface and adhered to another similarly degreased molded body via a layer of the paste-like kneaded material. Thereafter, a method of producing a metal composite sintered body in which the same or different types of metals are joined by performing degreasing and sintering.

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