JPH0499807A - Manufacture of powder sintered product - Google Patents

Abstract

PURPOSE:To obtain a powder sintered product, only the necessary part of which is made porous and which fits for the heavy load by preparing two kinds of materials changed with mixing ratio of an organic binder to the powder for compacting and arranging the material having large shrinkage ratio to the part desired to be porous. CONSTITUTION:Two kinds of the materials having different shrinkage ratio at the time of sintering are prepared by changing the mixing ratio of the powder for compacting (e.g. SKH51 powder having 12mum average particle diameter) and the organic binder added to this and the material having large shrinkage ratio is set to the part desired to be porous at the time of compacting. Successively, this part desired to be porous, is locally oxidized, and after removing the organic binder, the sintering is executed. As the other way, this part is made to the structure to be hardly reduced and the sintering is executed and the speed to combine the particles is made locally slow and this part is made porous, to obtain the powder sintered product.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a powder sintered product.

(Prior Art) A technique for creating parts by forming metal powder into a desired shape and heating the powder at a temperature below its melting point to bond the powders has been conventionally known as powder metallurgy. Powder sintered products obtained by such techniques are used for various parts including automobile parts, and are one of today's indispensable metal parts processing techniques. This technique is also extremely important for ceramics, which are difficult to melt into shapes.

In this technology, the key point is how to increase the density to improve properties such as mechanical strength and corrosion resistance, but instead of intentionally increasing the density, it is made porous and impregnated with oil to be used as a bearing. It is also used as a catalyst carrier due to its large surface area.

(Problem to be solved by the invention) As mentioned above, by intentionally making the powder sintered product porous, new uses can be expanded. The reality is that it lacks strength and is also poor in corrosion resistance, which has limited its use.

Incidentally, in many cases, it is not necessary that the entire part be porous, and only a limited functional part is porous, but it is currently difficult to make the entire part porous. Therefore, in order to make a part porous, it is necessary to attach the porous part to the required location by brazing, gluing, etc., and the strength and adhesion at the interface have been problems.

The present invention was made to solve the above problems, and its purpose is to create a powder sintered product that can be used under high loads by making only the necessary parts porous. It is about providing.

(Means for Solving the Problems) In order to achieve the above object, the present invention molds powder into a desired shape by a molding means, and at that time, changes the amount of organic binder added to the powder. Using two types of materials with different shrinkage rates, placing the material with a higher shrinkage rate in the area where you want to make it porous, and oxidizing the area locally prior to sintering, then sintering. or sintering in a state that is difficult to reduce locally during sintering to make the powder partially porous. Using a powder and its oxide powder, by changing the amount of organic binder added to each powder, the sintering time shrinkage ratio is made larger for the oxide powder than for the metal powder, and, Either you can place a material with a high sintering time reduction rate in the area you want to make porous and sinter it, or you can sinter the area you want to make porous locally in a state that is difficult to reduce. It is characterized by making it porous.

(Function) With the above configuration, in the method of the present invention, two types of materials having different shrinkage rates during sintering are prepared and molded by changing the mixing ratio of the molding powder and the organic binder added thereto. During this process, a material with a high shrinkage rate is placed in the area where you want to make it porous. Then, by locally oxidizing the part that you want to make porous and removing the organic binder, or by sintering this part in a state that is difficult to reduce, the powder can be partially bonded. This process slows down the bonding speed and makes this part porous.

In addition, in the method of the present invention, an organic binder is added to each of the metal powder and its metal oxide, and the shrinkage rate of the organic binder and agent added to the metal oxide is set to a large value, so that when molding, a porous The metal oxide is placed on the part where the metal oxide is desired to be oxidized. Next, the portion is made porous by sintering using the same method as described above.

(Example) Hereinafter, preferred examples of the present invention will be described based on the drawings.

1 and 2 show process diagrams for carrying out the method of the invention.

The characteristic feature of the present invention is that the powder is molded into a desired shape by a molding means, and the sintering time reduction rate is changed by changing the amount of organic binder added to the powder at that time. A material with a high shrinkage rate is placed in the area where the material is to be made porous, and the area is locally oxidized before sintering, or sintered locally during sintering. By performing sintering in a state where it is difficult to reduce the material to porosity, the material is partially made porous.

In this example, the material was 5K with an average particle size of 12 μm.
H51 powder was used. In order to impart fluidity to this powder, an organic binder containing a mixture of stearic acid, paraffin, ethylene-vinyl acetate copolymer, and methacrylic acid ester was added and kneaded in a pressure kneader under heating at 150°C. . At this time, two types of molding materials were manufactured by changing the mixing ratio of the powder to be kneaded and the organic binder.

That is, one of them is powder: organic binder - 55:45
(volume ratio) and mix this molding material to "Material A
), the other is powder:organic binder-50:5
0 (volume ratio) (this molding material was
(referred to as "Material B").

Injection molding was used as the molding method, and two-color molding was performed because two types of materials were used.

Then, two gates were provided in the mold, as shown in Fig. 1(a).
As shown in FIG. 2(a), material B having a high shrinkage rate was filled in the area where it was desired to make it porous. The molded article thus formed was heated to 500° C. over 36 hours in a non-oxidizing atmosphere to remove the organic binder.

After this, as shown in Fig. 1(b) (C), the area to be made porous is locally oxidized and then sintered, or as shown in Fig. 2(b) (C), By burying only the area around the part to be made porous in alumina powder and performing sintering in a state where local reduction is difficult,
A powder sintered product as shown in Figure (d) was obtained.

In this way, locally oxidizing the area where you want to make it porous, or performing sintering in a state that is difficult to reduce, slows down the bonding speed of the powder and leaves many pores in that area. It's for a reason.

Note that the sintering conditions at this time were that the temperature was raised to 1250°C over 6 hours and held at 1250°C for 1 hour. In addition, sintering was performed under vacuum, and the degree of vacuum was 10-2 to 10-3 torr.
It was held on a stand to avoid creating a strongly reducing atmosphere.

The sintered crystal produced in this way has some porous parts, but the density of the pores decreases toward the inner surface, and the state changes continuously until suddenly the pores appear. There was no loss or cracking of the adhesive interface.

In addition, in the present invention, when molding powder into a desired shape by a molding means, metal powder and its oxide powder are used, and shrinkage during sintering is achieved by changing the amount of organic binder added to each powder. Either make the oxide powder have a higher shrinkage ratio than the metal powder, and perform sintering by placing a material with a high shrinkage rate during sintering in the area where you want to make it porous, or make it porous. It is characterized in that it is made partially porous by performing sintering in a state where it is difficult to locally reduce the desired area.

In this example, as in the previous example, SKI+51 powder with an average particle size of 12 μm and the powder heat-treated at 500° C. for 2 hours under atmospheric pressure were prepared as the materials used. These powders and an organic binder were kneaded under heat in a pressurized niegu. At this time, the mixing ratio of 5K1151 powder and organic binder was powder: organic binder -55: 4
5 (volume ratio) and the mixing ratio of the heat-treated powder and the organic binder is powder:organic binder-50:
50 (volume ratio) (Material B).

The subsequent processing was the same as in the previous example, as shown in FIGS. 3(a) to 3(d), except that the degree of vacuum during sintering was set to 10-'torr, which is different from the above.

In each of the above examples, the shrinkage during sintering was changed by changing the compounding ratio of the organic binder between the parts where porous parts were to be made and the parts which were not. This is to reduce shrinkage and prevent distortion.

FIG. 4 shows an example in which the present invention is applied to a bearing, in which material B is placed at the location where it is desired to be made porous and molded.
Sintering is performed in the process described above.

(Effects of the Invention) As explained above, the present invention consists of forming a necessary shape using molding materials with different shrinkage rates, placing a material with a large shrinkage rate in the part where it is desired to make it porous, and locally forming this part. By oxidizing or sintering in a state that is difficult to reduce and making it partially porous, it is also possible to form the necessary shape from metal powder and its oxide, and to increase the shrinkage rate of the metal oxide. By placing metal oxides in the areas where you want to make them more porous and sintering them to make them locally difficult to reduce, you can make only the necessary areas porous. This makes it possible to manufacture parts with a high degree of precision, and it can be used even under high loads that were previously unusable.

[Brief explanation of drawings]

Figures 1 (a) to (d), Figures 2 (a) to (d), and Figures 3 (a) to (d) are process explanatory diagrams for carrying out the method of the present invention, respectively, and Figure 4 is FIG. 3 is a diagram showing an example in which the method of the present invention is applied to a bearing. Material A・・Molding material with high shrinkage rate Material B・・Molding material with low shrinkage rate (1 other person) Procedural amendment (method) % formula % Title of invention Process for manufacturing powder sintered products 3゜ Person making the amendment Related to the case Patent applicant name Matsushita Electric Works Co., Ltd. 4゜Representative〒151 Column 6゜Detailed description of the invention'' in the specification Contents of amendment

Claims (2)

[Claims] (1) Powder is molded into a desired shape using a molding method, and two types of materials are used in which the shrinkage rate during sintering is changed by changing the amount of organic binder added to the powder, and porous Place a material with a high shrinkage rate in the area where you want to improve quality, and then sinter the area after locally oxidizing it prior to sintering, or sinter in a state that is difficult to locally reduce during sintering. A method for producing a powder sintered product characterized by partially making it porous by performing. (2) When molding powder into a desired shape using a molding means, metal powder and its oxide powder are used, and the shrinkage rate during sintering can be adjusted by changing the amount of organic binder added to each powder. Either make the oxide powder larger than the oxide powder, and place a material with a high shrinkage rate during sintering in the area where you want to make it porous, or perform sintering on the area where you want to make it porous. A method for producing a powder sintered product, characterized in that the powder is partially made porous by sintering in a state that is difficult to reduce.