JPH0149764B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing a sintered material that is provided with a thick wall portion on its outer side and that requires a highly precise inner surface of a hollow hole.

"Prior art" A core rod is inserted into the molding cavity of a molding die, the molding cavity around the core rod is filled with raw material powder, and the raw powder is compacted in the length direction of the core rod using a punch to form a hollow hole. A method is known in which a sintered body is manufactured by forming a molded body having the following properties and then sintering the molded body.

"Problems to be Solved by the Invention" When using this type of method to produce a sintered material that has a thick wall part on the outer periphery and partially differs in thickness, the thin wall part and the wall thickness Due to the difference in heat capacity during sintering between the two parts, uniform thermal behavior is no longer exhibited, and the inner surface of the hollow hole closer to the thick part is closer to the inner surface than the other inner surfaces. There is a problem in that the inner surface accuracy of the hollow hole deteriorates due to the bulge.

"Object of the invention" The present invention has been made in view of the above circumstances, and
The object of the present invention is to provide a manufacturing method capable of obtaining a sintered body having hollow holes with high inner surface accuracy.

``Means for Solving the Problems'' The present invention involves inserting a core rod into a molding cavity of a mold, filling the molding cavity around the core rod with raw material powder, and using a punch to punch the raw material powder into the core rod. A method of manufacturing a sintered material having hollow holes by compacting it in the length direction to form a compact having temporary hollow holes, and sintering this compact, which requires high-precision inner surfaces of the hollow holes. In a high-precision manufacturing method for sintered material in which a pair of thick parts are provided in the outer part in the radial direction at points symmetrical positions with the hollow hole as the center, the displacement is the same as the displacement of the inner surface of the temporary hollow hole due to sintering. A core rod having an elliptical cross section with a pair of large bulges formed on the outer periphery is used, and the core rod is placed into the molding cavity with both bulges facing toward the portions corresponding to the thick parts to make a temporary hollow. A molded body having holes is formed.

"Operation" A pair of bulges of the core rod with an elliptical cross section form an elliptical temporary hollow hole that takes into account the deformation of the compact, and this temporary hollow hole is used to absorb the deformation of the compact due to the sintering process. The sintered material is transformed into a hollow hole by the method, and a sintered material having a hollow hole within a specified dimensional tolerance is obtained.

"Example" An example of the method of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is a mold, 2 is an upper punch,
3 indicates a lower punch, 4 indicates a round bar-shaped core rod, and A shown in FIGS. 4 and 5 indicates a ring-shaped sintered material manufactured by carrying out the method of this embodiment.

The mold 1 has a molding cavity C large enough to insert the upper punch 2 and the lower punch 3, and the sintered material A is formed on the lower surface of the upper punch 2 and the upper surface of the lower punch 3, respectively. The upper punch 2 and the lower punch 3 have insertion holes 2a and 3a formed in their centers for passing the core rod 4 therethrough. The core rod 4 is composed of a main shaft 4A and a support shaft 4B, and the main shaft 4A has a substantially elliptical cross section formed by connecting a round bar-shaped base 4a with bulges 4b on both sides in the diametrical direction.

The sintered material A is formed by integrally forming a flange-like rim part 11 on the outer periphery of a cylindrical boss part 10, and a pair of protrusions are formed on both sides of the boss part 10 in the radial direction to form a thick part 10a. is formed.

Next, the mold 1, upper punch 2 and lower punch 3
A case where the sintered material A is formed using the core rod 4 and the core rod 4 will be explained.

First, the lower punch 3 is inserted into the molding cavity C of the mold 1 from below, and the insertion hole 3 of the lower punch 3 is inserted into the molding cavity C of the mold 1 from below.
Pass the core rod 4 through a with the main shaft 4A facing upward. Next, a predetermined amount of raw material powder for sintering such as hard carbide powder is put into the molding cavity C, and then, while passing the main shaft 4A of the core rod 4 through the insertion hole 2a of the upper punch 2, the upper punch 2 is inserted into the molding cavity C. The raw material powder for sintering is inserted into the sintered material A and compacted by the upper punch 2 and the lower punch 3 as shown in FIG. 1 to obtain a compact A ₁ having substantially the same shape as the sintered material A. However, during this consolidation, the vertical position of the core rod 4 is adjusted so that the boss hole (temporary hollow hole) 10'b of the compact _A1 is formed by the main shaft 4A of the core rod 4, and the main shaft 4A is The circumferential position of the core rod 4 is adjusted so that the swollen portion 4b faces the thick portion 10'a of the molded body _A1 , and the core rod 4 is compacted.

Regarding the molded article _A1 produced as above,
The cross-sectional profile of the boss hole 10'b is formed into a substantially elliptical shape that matches the outer shape of the main shaft 4A of the core rod 4, as shown in FIG.

Next, the molded body _A1 is sintered using a required sintering furnace,
A sintered material A shown in FIGS. 4 and 5 is obtained. During this sintering, the thick part 10'a of the molded body _A1 expands more than the other parts.
The inner circumferential surface of the boss portion 10' inside 0'a bulges more inward than the other inner circumferential surface portions. As a result, the third
The cross-sectional outline of the boss hole 10'b shown in the figure becomes a perfect circle after sintering, and the highly accurate boss hole (hollow hole) 10c
A sintered material A having the following properties can be obtained.

Note that in order to determine the cross-sectional shape of the main shaft 4, the change in the inner diameter of the boss hole 10'c due to sintering is investigated in advance through experiments, and the cross-sectional contour of the boss hole is determined to be true due to this change in the inner diameter. Decide that it will be a circle. That is, specifically, the bulging portion 4b may be formed so as to face the thick portion side of the molded material _A1 .

By the way, when the present inventor manufactured a sintered material A having the shape shown in FIGS. 4 and 5 by implementing the method of the present invention, it was found that the inner surface error between the boss hole 10c and the perfectly circular hole was determined by the conventional method. 10μ for those with a maximum temperature of about 30μm
It was demonstrated that by implementing the method of the present invention, it is possible to manufacture a sintered material having highly accurate boss holes.

``Effects of the Invention'' As explained above, the present invention involves inserting a core rod into the molding cavity of a mold, filling the molding cavity around the core rod with raw material powder, and punching the raw material powder into the core rod using a punch. A method of manufacturing a sintered material having hollow holes by compacting it in the length direction to form a compact having temporary hollow holes, and sintering this compact, which requires high-precision inner surfaces of the hollow holes. In a high-precision manufacturing method for sintered material in which a pair of thick parts are provided in the outer part in the radial direction at points symmetrical positions with the hollow hole as the center, the displacement is the same as the displacement of the inner surface of the temporary hollow hole due to sintering. A core rod having an elliptical cross section with a pair of large bulges formed on the outer periphery is used, and the core rod is placed into the molding cavity with both bulges facing toward the portions corresponding to the thick parts to make a temporary hollow. Since a molded body with holes is formed, during molding, a core rod with an elliptical cross section is used to widen the diameter of the temporary hollow hole corresponding to a pair of thick parts of the molded body to form an elliptical shape. After that, by deforming the temporary hollow hole due to the difference in expansion during sintering, it is possible to form a hollow hole within specified dimensional tolerances. Therefore, according to the method of the present invention, a sintered body having hollow holes with high inner surface precision can be manufactured without using special equipment or a special method.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention, and FIG. 1 is a sectional view showing the molded state of the molded body, FIG. 2 is a sectional view of the core rod, and FIG. 3 is a boss hole of the molded body. 4 is a plan view of the sintered material, and FIG. 5 is a sectional view taken along the line - in FIG. 4. 1...Molding mold, 2...Upper punch, 3...Lower punch, 4...Core rod, A...Sintered material, C...Molding cavity, 4A...Main shaft, 4b...Bulging portion, 10a
... Thick part, A ₁ ... Molded body, 10'b... Boss hole (temporary hollow hole), 10'a... Thick part, 10c... Boss hole (hollow hole).

Claims (1)

[Claims] 1. Insert a core rod into the molding cavity of the mold, fill the molding cavity around the core rod with raw material powder, and compact the raw material powder in the length direction of the core rod using a punch to form a temporary hollow hole. A method of manufacturing a sintered material having a hollow hole by forming a compact and sintering the compact, which requires a high-precision inner surface of the hollow hole, and a pair of thick parts in the radial direction on the outer side. In a high-precision manufacturing method for a sintered material in which sintered materials are provided at points symmetrical positions around a hollow hole, a pair of bulges having the same size as the displacement of the inner surface of the temporary hollow hole due to sintering are formed on the outer periphery. Using a core rod with an elliptical surface,
Sintering in which hollow holes are formed, characterized in that a core rod is placed in a molding cavity with both the bulging portions facing toward the portions corresponding to the thick portions to form a molded body having temporary hollow holes. High-precision manufacturing method for materials.