JPS62136502A - Powder molding method - Google Patents

Abstract

PURPOSE:To mold a cylindrical green compact having a circular conical part with high accuracy by compressively molding the powder packed into the cavity formed of a core rod, lower punch and die by an upper punch having a cylindrical projecting part and circular conical part. CONSTITUTION:The cavity 71 is formed by lowering the lower punch 2 or rising the die 4 and the core rod 1. The powder A for a sintering mechanical element is packed by a packing device 91 into the above-mentioned cavity 71 to the same height as the top surface of the die 4. The cavity 7 is then formed on the powder A by further lowering the lower punch 2 or rising the die 4 and the core rod 1. The upper punch 5 having the cylindrical projecting part 51, the circular conical shape part 53 and a land part 52 at the top end is then lowered and is fitted to the die 4 and is pushed down together with the core rod 1. The powder is thus compressively molded by the upper and lower punches in the powder molding chamber formed of the die 4, the upper punch 5 and the lower punch 2. After the upper punch 5 is removed upward, the core rod 1 and the lower punch 2 are raised to the height of the die 4 and the cylindrical green compact having the circular conical part on the inside peripheral face is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a powder compacting method in sinter metallurgy, and in particular, a sintering method that requires precision and has excellent productivity, such as those used in engine parts. This invention relates to a powder molding method for machine elements.

(Prior Art) A valve seat, which is one of the engine parts as shown in Fig. 7, has a cylindrical shape and has a conical part 63 at one end of its inner peripheral surface. Accuracy of the abutting conical portion 63 is required.

In addition, since wear resistance and heat resistance are required, high hardness special alloys with poor workability are usually used.

Therefore, during powder compression molding, the shape is almost similar to that of a finished product, and the molding is performed in a manner that reduces machining allowances.

In recent years, due to the demand for resource conservation, such valve seats, etc., are using composite materials in which parts that require heat resistance and wear resistance are made of different materials from other parts, and powder molding methods are also becoming more complex. be.

In the conventional powder compacting method, as shown in FIGS. 8 and 9, a conical portion 23.13 is provided on the lower punch 2 or the core rod 1 to form a conical portion 63 on the contact surface of the valve seat. .

In the case where the lower punch 2 in Fig. 8 is provided with the conical part 23, the strength of this conical part is considered to be unstable, and in the case where the core rod 1 in Fig. 9 is provided with the conical part 13, the conical part 23 is formed in the lower punch 2 during compression molding. It is necessary to align the height of the shaped portion 13 and the height of the lower punch 2, and there is a risk that this operation may become unstable depending on the compression conditions.

Further, powder easily enters between the core rod 1 and the lower punch 2, causing a galling phenomenon and shortening the life of the press machine.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned problems, and its purpose is particularly for use in engine parts that require precision and improve productivity. An object of the present invention is to provide an excellent powder compacting method for sintered machine elements.

(Means for Solving the Problems) As a means for achieving the above object, the powder compacting method of the present invention is characterized by the following steps using the following upper punch.

That is, the upper punch 5 has a cylindrical protrusion 51 and a conical portion 53 at its tip.

(1) First step: lower the lower punch 2 or die 4,
A void 71 formed by raising the core rod 1 is filled with powder A.

(2) Second step: Further lower the lower punch 2 or raise the die 4 and core rod 1 to form the void 7 above the powder A.

(3) Third step: Lower the upper punch 5, push down the core rod 1, and compress the powder by -1°.

(4) Fourth step: Raise the upper punch 5 and raise the core rod 1 and lower punch 2 to the height of the die 4 to take out the green compact.

In order to further obtain a composite material, as shown in FIG. 2 (2) between the first and second steps, (2) Second step: further lower the lower punch 2 or raise the die 4 and core rod 1. void 7 on powder A
2 is filled with powder B.

In addition, the other steps are performed in the same manner as steps 1 to 4 in FIG.

(Function) Since the present invention is configured in the manner described above, accurate interlocking between the lower punch 2 and the core rod 1 during compaction is not required, and it is easy to maintain precision stably. Therefore, it does not shorten the life of the press machine and has excellent productivity.

(Example) The method of the present invention will be explained based on examples.

First, Fig. 1 (1) to (4) and Fig. 2 (1) to (5) are as follows.
This order shows the process order of the present invention, and the first step is to lower the lower punch 2 as described above or to lower the die 4.
, the powder A is filled by the filling device 91 into the gap 71 formed by raising the core rod 1 . In this state, the top surface of the powder A is at the same height as the top surface of the die 4.

Next, lower the lower punch 2 further as shown in Figure 1 (2), or
Alternatively, the die 4 and the core rod 1 are raised to form the void 7 above the powder A.

In this state, the top surface of the powder A is lower than the top surface of the die 4. Therefore, when the upper punch 5 descends in the next process,
There is no danger that the powder A as shown in FIG. 3 will be pushed out and overflow onto the die 4.

Next, in the third step shown in FIG. 1(3), the upper punch 5 descends and pushes down the core rod 1 with the cylindrical protrusion 51. At the same time, the upper punch 5 fits into the die 4, and the die 4 and the upper punch 5. Form a compacting chamber with the lower punch 2. - Compression by upper and lower punches is used to obtain a uniform density in the compression method.

The last process is the process of taking out the green compact, as shown in Figure 1 (4).
As shown in the figure, the green compact is taken out by raising the core rod 1 and lower punch 2 to the height of the die 4.

In order to obtain a composite material, the step of filling powder B shown in FIG. 2(2) is added between the first and second steps of the above steps.

That is, after filling the powder A in the first step, the filling device 92 fills the powder B into the gap 72 formed by lowering the lower punch 2 or raising the die 4 and the core rod 1. In this state, the height of the top surface of the powder B matches the height of the top surface of the die 4.

After that, follow the same steps as in Fig. 1 (2) to (4) to obtain Fig. 2 (
3) As shown in (5), voids 7 are formed on powder B,
It is compression molded and then taken out.

In the present invention, as shown in FIG. 5 as another embodiment,
A conical protrusion 23 is formed on the outer periphery of the lower punch 2, or an internal hollow-shaped step 43 is formed on the inner periphery of the die 4 as shown in FIG.
By using the lower punch 2 or the die 4 which has been formed, a chamfered portion 64 is formed at one end of the outer peripheral surface opposite to the conical portion 63 at one end of the inner peripheral surface of the powder compact.

When applied to a valve seat, the outer circumferential chamfer, which is essential when assembling to a cylinder head, can also be formed by one compression, contributing to improved productivity.

(Effects of the Invention) According to the powder compacting method of the present invention as described above, the following effects can be obtained.

That is, first of all, accurate interlocking between the lower punch 2 and the core rod 1 during powder compacting is not required, and it is easy to stably maintain accuracy.

Furthermore, the conical part 63 of the valve seat 6, which requires the most precision in forming, is formed on the cylindrical protruding part 5 of the upper punch 5.
1. Since the molding is performed by the conical portion 53 and the land portion 52, there is no possibility of molding defects in these parts, and the molding can be performed with high precision.

Further, the conical portion 53 acts as a wedge against the upper surface of the powder during the compression process, and the powder can be compressed more reliably in the vicinity of the conical portion. This makes it possible to form the conical portion 63 of the valve seat 6 with a stable and high density, and to prevent defects such as the generation of large pores.

Furthermore, the present invention has a remarkable effect on composite powder molding.

That is, in the composite powder molding of the present invention shown in FIGS. 2(1) to 5), as shown in FIG.
As the conical portion 53 descends, it is pushed toward the periphery and is formed to cover the inner circumferential surface 64 of the valve seat. For this reason, the inner circumferential surface of the valve seat 6 is subject to a high heat load and requires heat resistance.
Covering No. 4 with powder B greatly improves performance.

Although the present invention has been described with respect to a valve seat, it may also be applied to similarly shaped sintered mechanical elements, such as a piston ring with a tapered outer circumferential surface.

[Brief explanation of drawings]

FIG. 1 is an embodiment diagram showing the powder compacting method of the present invention. FIG. 2 is an embodiment diagram showing the composite powder molding method of the present invention. Figure 3: A diagram showing the state of powder compression. FIG. 4: A sectional view of a valve seat formed by composite powder molding of the present invention. Figures 5 and 6N: Diagrams showing other embodiments of the present invention. Figure 7: Valve seat sectional view. Figures 8 and 9: Diagrams showing the conventional powder compaction method. Futan explanation 1, core rod 2. Lower punch 4. Die 5. Upper punch 6, valve seat 7. Air gap 63, conical part

Claims (3)

[Claims] (1) In a method for forming a cylindrical green compact having a conical part 63 at one end of the inner peripheral surface formed by filling powder into a mold and compressing the powder, the upper punch 5 has a cylindrical protruding part 51 at the tip. , has a conical part 53 corresponding to the shape of the conical part 63, and fills the powder A into the gap 71 formed by lowering the lower punch 2 or raising the die 4 and core rod 1; After lowering the punch 2 or raising the die 4 core rod 1 to form a void 7 above the powder A, the upper punch 5 is lowered and the core rod 1 is pushed down to compression mold the powder. Powder forming method. (2) In the powder compacting method, lowering the lower punch 2 or lowering the die 4 and core rod 1
Fill the void 71 formed by raising the powder A with the powder A, and further lower the lower punch 2 or raise the die 4 and core rod 1 to form the void 72 above the powder A.
is filled with powder B, and after lowering the lower punch 2 or raising the die 4 and core rod 1 to form a void 7 above the powder B, the upper punch 5 is lowered and the core rod 1 is lowered. The powder molding method according to claim 1, characterized in that the powder molding method is formed by compression molding a pressed powder. (3) In the powder compacting method, a conical protrusion 23 is provided on the outer periphery of the lower punch 2, or a conical step 43 is provided on the inner periphery of the die 4, and the powder is compression-molded, and one end of the outer periphery of the compact is formed. The powder compacting method according to claim 1, characterized in that a chamfered portion 64 is formed.