JPH0762407A - Production of metal powder sintered compact and its ornament - Google Patents

Abstract

PURPOSE:To improve a specular property by increasing the density of a metal powder sintered compact. CONSTITUTION:The compact body is obtained by executing injection molding or compacting to the mixture of metal powder and org. material, and then the compact body is degreased and sintered to obtain a metallic sintered compact. Then, the sintered compact is subjected to a hot forging or a cold forging to reduce pores and to increase density. When the density of the sintered compact is increased, the specular property is improved and the worth as an arnament is elevated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered product of metal powder whose quality is improved by hot forging or isothermal forging after obtaining a sintered product of metal powder.

[0002]

2. Description of the Related Art Conventionally, as a sintered product of metal powder, an injection molding method has been used in which a molded product obtained by injection molding a material obtained by mixing a metal powder and an organic substance is degreased and sintered to obtain a sintered product. Alternatively, a powder metallurgy method has been used in which a compact obtained by compacting a material obtained by mixing a metal powder and an organic material is sintered to obtain a sintered product. There is also an example in which a metal powder is HIP-treated and then a molded product is obtained by superplastic forging.

[0003]

However, in the conventional injection molding method, since 40% or more of the organic substance is usually mixed with the metal powder, the volume change due to the shape change due to the softening of the compound in the degreasing process and the shrinkage in the sintering process. The dimensional accuracy becomes poor due to the shape change caused by shrinkage of 40% or more. Further, in order to increase the relative density, it is necessary to maintain the temperature at a high temperature in the sintering process, and the crystal grain size becomes coarse and the strength becomes low. Further, if the sintered product is ground as it is, a beautiful mirror surface cannot be obtained due to the existence of pores, and the external appearance is remarkably impaired for a product such as a wristwatch exterior product which requires decorativeness.

The powder metallurgy method has a smaller degree of deformation than the injection molding method, but it also deforms in the sintering process and the crystal grain size becomes coarse. Even if the sintered product is polished, a clean mirror surface cannot be obtained. In order to sinter the metal powder by HIP treatment, expensive equipment is required and the cost becomes high.

As described above, the sintered product of metal powder has problems in terms of strength, specularity and cost. In addition, since titanium and titanium alloys are expensive, when the preform material is extracted from the rolled material and forged, or when the product is formed by cutting from the rolled material, the material yield is extremely low and the material cost is low. There is a problem that the cost becomes higher.

[0006]

In order to solve the above-mentioned problems, the present invention is to degrease, sinter and fire a molded body obtained by injection molding or pressure molding of a material in which a metal powder and an organic material are mixed. After obtaining a bonded body, or after compacting a material obtained by compacting a material in which a metal powder and an organic material are mixed to obtain a sintered body, the relative density is further increased by hot forging or isothermal forging. To improve strength and specularity, and to improve dimensional accuracy during hot forging and isothermal forging.

If the sintering temperature is lowered, the voids are reduced and the relative density is increased by the next forging step even when the sintering density is low, and the coarsening of the crystal grain size can be prevented, so that the strength is high and the mirror surface is high. A sintered product with good properties can be obtained. Particularly in the case of titanium or titanium alloy, which is expensive as a material, the material yield can be improved by sintering the powder, and the material can be molded into a near net shape, so that the material cost can be significantly reduced.

[0008]

[Operation] In the method for producing a sintered product of metal powder as described above, a material obtained by mixing metal powder and an organic material is injection-molded or powder-molded to obtain a molded body, which is degreased and sintered during sintering. Sintering is obtained by removing organic substances and diffusing metal powders. Further, by performing hot forging or isothermal forging on this sintered body, the number of voids is reduced and the relative density is increased.

[0009]

Embodiments of the present invention will be described below. [Embodiment 1] FIG. 1 is a process drawing of an embodiment of the present invention by injection molding. Pure titanium powder of 325 mesh or less and organic matter
(Wax, polystyrene resin, acrylic resin were mixed) in a weight ratio of 84:16, and injection molding was performed at 160 ° C. to obtain a molded product. By heating this molded body, 95% of organic substances are removed, and 10-4 torr to 10-5 to
1000, 1100, 1200, 130 in rr vacuum
Hold at 0 ° C. for 2 h. Further, the sintered product at each sintering temperature is heated to 700 ° C., and a compressibility of 10% and 20% is applied at a strain rate of 0.1 / s or less in a mold heated to 700 ° C. of the same temperature. Constant temperature forging was performed. In addition, the sintered product at each sintering temperature was heated to 900 ° C. and heated to 400 ° C. in the mold to obtain 10%,
Hot forging was performed by applying a compressibility of 20% at a strain rate of 1 / s or more. Table 1 shows the results of specularity after polishing the as-sintered sintered product and the isothermally forged and hot forged sintered product after sintering.

[0010]

[Table 1]

The sintered products after sintering are 1000 and 110.
Sintering at 0,1200 ° C. had many pores and no mirror surface was obtained, but sintering at 1300 ° C. gave a relatively good mirror surface with few voids. The sintered product which was subjected to isothermal forging or hot forging after sintering had a reduced number of pores except for the sintering at 1000 ° C., and a relatively good mirror surface was obtained. However, when a compressibility of 20% was applied by hot forging after sintering, cracking occurred. However, even if the material has a relatively good mirror surface, the hardness is Vvs hardness Hv1 in the case of pure titanium.
Since it was as low as 50 to 200, undulation occurred on the surface due to polishing and a perfect mirror surface could not be obtained.

[Embodiment 2] FIG. 2 is a process drawing of the powder compacting of the present invention. Pure titanium powder of 100 mesh or less and stearic acid were mixed at a weight ratio of 99: 1, and pressed by a press at a pressure of 30 kgf / mm2 to obtain a molded body. This molded body is 10-4 torr to 10-
1000, 1100, 1200 in a vacuum of 5 torr,
It was held at 1300 ° C for 2 hours. Further, the sintered product at each sintering temperature is heated to 700 ° C., and a compressibility of 10% and 20% is applied at a strain rate of 0.1 / s or less in a mold heated to 700 ° C. of the same temperature. Constant temperature forging was performed. In addition, the sintered product at each sintering temperature was heated to 900 ° C and then heated to 400 ° C in the mold.
Hot forging was performed by applying a compressibility of 0% and 20% at a strain rate of 1 / s or more. Table 2 shows the results of specularity after polishing the as-sintered sintered product and the isothermally forged and hot forged sintered products after sintering.

[0013]

[Table 2]

The sintered products after sintering are 1000 and 110.
The sintering at 0,1200 ° C had many pores and no mirror surface was obtained, but the sintered product at 1300 ° C had few pores and a relatively good mirror surface was obtained. Sintered products that have undergone isothermal forging or hot forging after sintering, even if the sintering temperature is 1000 ° C,
A relatively good mirror surface was obtained. 100 for injection molding
There were considerable holes in 0 ° C sintering, and many holes remained in the subsequent forging, and no mirror surface was obtained. However, in the compacted product, there were relatively holes even at 1000 ° C sintering. In the next forging, the number of voids was reduced and a mirror surface was obtained. However, similarly to the injection molding, when a compressibility of 20% was applied by hot forging after sintering, cracking occurred. However, even in the case of a material having a relatively good mirror surface, in the case of pure titanium, the hardness is Hv150-2 in Vickers hardness.
Since it was as low as 00, undulation occurred on the surface due to polishing, and a perfect mirror surface could not be obtained.

[Embodiment 3] Next, pure titanium powder of 325 mesh or less and 60% Al-40 of 325 mesh or less.
% V alloy powder mixed at a ratio of 9: 1 and an organic substance (mixed with wax, polystyrene, acrylic resin) at a weight ratio of 84:16 and injection molded at 160 ° C. And degreasing under the same conditions as in Example 1,
Sintering was performed. Furthermore, the sintered product at each sintering temperature is 850
1 ℃ in the mold heated to 850 ℃ of the same temperature
Isothermal forging was performed by applying a compressibility of 0% and 20% at a strain rate of 0.1 / s or less. In addition, the sintered product at each sintering temperature is 90
10% in a mold heated to 0 ℃ and heated to 400 ℃, 20
% For the strain rate of 1 / s or more, and hot forging was performed. Table 3 shows the results of specularity after polishing the as-sintered sintered product and the isothermally forged and hot forged sintered product after sintering.

[0016]

[Table 3]

The sintered products after sintering are 1000 and 110.
Sintering at 0,1200 ° C. resulted in many pores and no mirror surface was obtained, but sintering at 1300 ° C. gave a good mirror surface with few voids. Sintered products that have undergone isothermal forging or hot forging after sintering have reduced pores except for sintering at 1000 ° C.
A good mirror surface was obtained. However, when a compressibility of 20% was applied by hot forging after sintering, cracking occurred. Unlike the case of pure titanium, Ti
-6% Al-4% V alloy, so the hardness is Hv350
And it was hard and a good mirror surface was obtained by polishing.

[Example 4] Pure titanium powder of 100 mesh or less and 60% Al-40% V alloy powder were mixed with stearic acid at a weight ratio of 99: 1, and 30 kgf / It was pressed at a pressure of mm2 to obtain a molded body. This molded body is 10-4 torr to 10-5 to
1000, 1100, 1200, 130 in rr vacuum
Hold at 0 ° C. for 2 h. Furthermore, the sintered product at each sintering temperature is heated to 850 ° C., and the compressibility of 10% and 20% is set at a strain rate of 0.1 / s or less in the mold heated to the same temperature of 850 ° C. The constant temperature forging was performed. In addition, the sintered product at each sintering temperature was heated to 900 ° C and then heated to 400 ° C in a mold 10
% And 20% compressibility was applied at a strain rate of 1 / s or more, and hot forging was performed. Table 2 shows the results of specularity after polishing the as-sintered sintered product and the isothermally forged and hot forged sintered products after sintering.

[0019]

[Table 4]

The sintered products after sintering are 1000 and 110.
Sintering at 0,1200 ° C had many pores and no mirror surface was obtained, but the sintered product at 1300 ° C had few pores and a good mirror surface was obtained. Sintered products that were subjected to isothermal forging or hot forging after sintering had good mirror surfaces even when the sintering temperature was 1000 ° C. In the case of injection molding, there were considerable holes in the sintering at 1000 ° C, and in the subsequent forging there were many holes and no mirror surface was obtained, but in the case of compacting, sintering at 1000 ° C However, there were few holes and the number of holes decreased in the next forging, and a good mirror surface was obtained. However,
Similar to injection molding, when a compression ratio of 20% was applied by hot forging after sintering, cracking occurred. Unlike the case of pure titanium, Ti-6% Al after sintering in this example.
Since it is a -4% V alloy, hardness is H for those with few holes.
V350 was hard and a good mirror surface was obtained by polishing.

[Embodiment 5] Pure titanium powder of 100 mesh or less was mixed with 0.5, 1.8, and 4% by weight of iron powder of 10 μm or less to prepare three kinds of mixed powders. It was pressed at a pressure of 30 kgf / mm2 to obtain a molded body. This molded body is 10-4 torr to 10-5 torr
In vacuum at 1300 ° C. for 2 h. Furthermore, the sintered product is heated to 650 to 750 ° C., and 650 to 750 at the same temperature.
A wristwatch was produced by performing constant temperature forging by giving a working rate of 20% at a strain rate of 0.1 / s or less in a mold heated to ℃. FIG. 3 shows a wristwatch made according to the present invention.

As described above, the voids in the surface layer are reduced by performing constant temperature forging or hot forging after degreasing and sintering a molded product obtained by mixing metal powder and an organic substance and injection molding or compacting. Therefore, it becomes possible to improve specularity. Further, since the forging is performed after the sintering, the dimensional accuracy is improved as compared with the sintered product. The same can be said for metal powders such as titanium alloys and stainless steels other than the examples.

[0023]

As described above, according to the present invention, since isothermal forging or hot forging is performed after powder metallurgy of metal, the surface layer of the sintered body becomes dense and a good mirror surface state can be obtained. Further, the forging improves the dimensional accuracy as compared with the sintered body.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a process of combining injection molding and forging according to the present invention.

FIG. 2 is an explanatory view showing a process of combining the powder compacting and forging of the present invention.

FIG. 3 is a view showing a wristwatch provided with a timepiece exterior component made according to the present invention.

[Explanation of symbols]

 1 Body 2 Band 3 Bezel 4 Crown

Claims (3)

[Claims] 1. A molded body obtained by injection molding or pressure molding of a material in which a metal powder and an organic material are mixed is degreased and sintered to obtain a sintered body, or the metal powder and the organic material are mixed. Manufacture of a metal powder sintered product, characterized in that a green body obtained by compacting the formed material is sintered to obtain a sintered body, and then the sintered body is subjected to hot forging or isothermal forging. Method. 2. The method for producing a metal powder sintered product according to claim 1, wherein titanium powder or a mixed powder obtained by mixing titanium powder with another metal powder is used as the metal powder. 3. A decorative article such as an exterior article made of the metal powder sintered product produced according to claim 1 or 2.