JPS61210102A - High-accuracy production of sintered material having hollow hole - Google Patents

Abstract

PURPOSE:To form a hollow hole having a high grade of out of roundness without subjecting a sintered material having the hollow hole to a working treatment by providing a taper expanding toward the aperture side of the hollow hole to the outside circumferential wall of a core rod to be used for producing the sintered material. CONSTITUTION:A lower punch 3 is inserted into the molding cavity C of a molding pattern 1 and the core rod 4 with a supporting shaft 4B faced upward is inserted into a through-hole 3a thereof. The core rod 4 is formed with a main shaft part 4a having the taper expanding toward the direction further from the supporting shaft 4B on the shaft 4B side of the outside circumferential wall of the main shaft 4A thereof. Raw material powder for sintering is then inserted in a prescribed amt. into the cavity C and the shaft 4B is packed into the through-hole 2a of an upper punch 2 by which the powder is compacted and the molding A1 having the tentative hollow hole 10'b is obtd. The hole 10'b is tapered and therefore the taper of the hole 10'b is absorbed and annihilated when the molding A1 is subjected to the sintering treatment and sizing treatment to form a sintered body A. The circular hollow hole 10b having the high grade of out of roundness is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for producing a sintered material with high precision, the height of which is considerably larger than the inner diameter.

"Prior art" A core rod is inserted into the molding cavity of a mold, the molding cavity around the core loft is filled with raw material powder, and this raw powder is compacted in the length direction of the core rod using a punch to create a temporary hollow. A method is known in which a sintered body is produced by forming a molded body having holes, correcting the shape by performing a sinoning process, and then sintering this molded body.

"Interlayer point that the invention seeks to solve" When a sintered body is manufactured by implementing this type of method, and the height dimension is considerably larger than the inner diameter dimension, There is a problem in that the inner diameter of the hollow hole near the opening of the sintered body is smaller than the inner diameter of the hollow hole at the center of the sintered body in the longitudinal direction. This is because the compaction of the raw powder along the hole causes a partial difference in the compaction density of the raw powder, and usually the compaction density of the raw powder near the opening of the hollow hole is the same as the compaction density near the longitudinal center of the sintered body. In addition, due to the mechanism of the sinong press, straightening is performed only by applying pressure from the top, and pressure cannot be applied from below, so it is one-sided pushing, and in this case, the pressure is Since the coal is concentrated in the center in the lengthwise direction of the body, the compacted coal in this part is deformed even though it is low, and the inner diameter of this part becomes larger than the specified value, and the inner diameter near the opening becomes smaller than the specified value. For this reason, in the past, it was necessary to process the hollow hole after the sintering process to improve the inner surface precision of the hollow hole.

``Object of the Invention'' The present invention was made in view of the above circumstances, and an object of the present invention is to provide a manufacturing method capable of obtaining a sintered body having hollow holes with high roundness.

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 fill the raw material powder into the core rod. In a high-precision manufacturing method for sintered material in which a compact is compacted in the length direction to form a compact with low hollow pores and then sintered, the outer peripheral wall is tapered to widen toward the opening side of the hollow pores. "Operation" using a core rod with a tapered core The tapered low hollow hole formed in the molded body by the tapered core loft becomes a hollow hole with high inner surface precision due to deformation caused by the sintering process and the sizing process.

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

In Figure 1, 1 is a mold, 2 is an upper punch, 3 is a lower punch, 4 is a round core rod, and A shown in Figure 4 is a cylinder manufactured by carrying out the method of this example. The figure shows a shaped sintered material. Molding die 1 has upper punch 2 and lower punch 3
Four parts for forming the sintered material A are formed on the lower surface of the upper punch 2 and the upper surface of the lower punch 3, respectively. In the center of the punch 3, there are insertion holes 2a, 3 through which the core 4 is inserted.
a is formed. The core rod 4 consists of a main shaft 4A and a support shaft 4B. A main shaft portion 4a is formed on the support shaft 4B side of the outer peripheral wall, and has a taper that widens as it moves away from the support shaft 4B.

The case where the sintered material A is formed using the mold 1, the upper punch 2, the lower punch 3, 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 support shaft 4B is inserted into the insertion hole 3a of the lower punch 3.
Pass through the core lock (r4) with the side facing up.

Next, raw material powder for sintering such as hard carbide powder is poured into the molding cavity C.
Then, the upper punch 2 is inserted into the molding cavity while passing the support shaft 4B of the core 0 rod 4 through the insertion hole 2a of the upper punch 2, and sintering is performed by the upper punch 2 and the lower punch 3. As shown in Fig. 1, the powder is compacted to obtain a molded body "A1" having almost the same shape as the sintered body A and having low hollow pores 10'b. The vertical position of the core rod 4 is adjusted so that the lower half of the low hollow hole 10''b of the molded body A is formed.

In the molded body A manufactured as described above, the inner peripheral surface of the low hollow hole 10°b is tapered to widen toward the opening surface of the low hollow hole 10°b.

Next, the molded body A1 is sintered using a required sintering furnace and subjected to a sizing treatment to obtain a sintered body A shown in FIG. 0. During this sintering and sizing process,
Since the part of the low hollow hole 10''b of the molded body A, which is close to the opening, is greatly reduced, the 7-p of the low hollow hole 10''b is absorbed and disappears, and the cross section of the low hollow hole 10''b is The surface contour becomes a circular shape with high roundness and becomes the hollow hole 10b. Therefore, if the method described above is used to manufacture the sintered material A, the sintered material has the hollow hole 10b with high roundness. A sintered material A can be obtained.The through hole 10d of the sintered material A formed by the support shaft 4B will be formed into a threaded hole in a later step by forming a threaded groove.

In order to determine the taper ratio of the main shaft 4, the change in the inner diameter of the low hollow hole 10''b due to the firing of the rod is investigated in advance through experiments, and the cross-sectional profile of the temporary hollow hole is made true by this change in the inner diameter. Decide that it will be a circle.

"Manufacturing example" As shown in Figure 5, height 451 CI111 inner diameter 11.5
When a cylindrical sintered material 20 with an outer diameter of 20 am and a diameter of 20 am was manufactured by the method shown in the above example, the inner diameter of the lower part was smaller than the specified value by about 10 to 15 μ by the conventional method, but this error was eliminated. This confirmed the effectiveness of the method of the present invention.

By the way, when forming the hollow hole 100b over the entire length of a cylindrical sintered material by the method of the present invention, the upper half of the main shaft portion 4a is formed into a cylindrical shape, the lower half is formed with a taper,
Using this main shaft portion 4a, a molded body A2 as shown in FIG.
form. In this molded body A2, temporary hollow holes 10
The upper half of 0'b is a circular hole and the lower half is a tapered hole. This molded body A2 is sintered to obtain a sintered body A0 shown in FIG. In the hollow hole 1oob of this sintered body A0, the lower half becomes a perfect circular hole, and the upper half becomes a tapered hole that tapers upward, but this tapered hole becomes a perfect circular hole by processing in a post-process. shall be completed. Here, if a taper is formed in the upper half of the main shaft portion 4a, the main shaft portion 4a will not come off after forming the molded body A2. In addition, in the case of this example, it is necessary to process the taper hole in the post-process, but the process is less labor-intensive compared to the conventional method, which requires processing both the upper and lower halves of the hollow hole. It only takes half the time, which simplifies the processing.

"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 using a punch to fill the raw material powder with the core rod. In a high-precision manufacturing method of a sintered material having a hollow hole by compacting the core rod in the length direction to form a molded body having a temporary hollow hole, and then sintering the core rod, the outer circumferential wall has a hole on the opening side of the hollow hole. It uses a tapered core rod that widens toward the
By implementing the present invention, it is possible to form a taper that widens toward the opening of the temporary hollow hole formed in the compact, so that this tapered portion is absorbed by the deformation caused by the sintering process and the sizing process. This has the effect of making it possible to obtain a sintered material having hollow pores with high roundness. Therefore, there is no need to process hollow holes in the subsequent process, which can simplify the process6.

[Brief explanation of drawings]

Figures 1 to 4 are for showing one embodiment of the present invention, in which Figure 1 is a sectional view showing the molded state of the molded body, Figure 2 is a sectional view of the core rod, and Figure 3 is the molded body. FIG. 4 is a cross-sectional view of the sintered material, FIG. 5 is a cross-sectional view of the sintered body of the manufacturing example, and FIG. 6 is a cross-sectional view of the sintered body formed by implementing another example of the present invention. FIG. 7 is a cross-sectional view of a sintered material formed by sintering the molded body shown in FIG. 6. DESCRIPTION OF SYMBOLS 1... Molding die, 4... Core rod t4a... Main shaft part, io'b, ioo'b---Temporary hollow hole. A,,A,...Molded body = A*Ao...Sintered material. C...Molding void. Figure 1 Figure 5 100b Figure 6

Claims (1)

[Claims] A core rod is inserted into the molding cavity of the mold, the molding cavity around the core rod is filled with raw material powder, and this raw powder is compacted 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 body and then sintering it, the height of the molded body is larger than the inner diameter of the hollow hole, and the inner surface of the hollow hole has high precision. A highly accurate manufacturing method for a sintered material having a hollow hole, which is characterized by using a core rod on the outer peripheral wall with a taper that widens toward the opening side of the hollow hole. .