JP2621889B2 - Sintering cold forging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial application field >> The present invention relates to a sintering cold forging method.

<< Conventional Technology >> The sintering cold forging method is a forming and processing method in which a preform formed by sintering a metal powder is forged in a cold state and then re-sintered to obtain a final product having a high-density composition. . In this forging method, the preform is cold forged in the die, but it is necessary to apply a lubricant to the surface of the preform in order to prevent seizure between the preform and the inner surface of the die. However, since the preform is a porous body, if a liquid lubricant is applied to the surface, the lubricant penetrates and penetrates into the inside of the preform, and not only does the surface portion not provide sufficient lubrication. In addition, since the lubricant that has penetrated inside prevents the crushing and disappearance of the minute voids inside the preform during pressure forging, a high-density forged product cannot be obtained. In the case of a metal soap, phosphoric acid, or oxalate film used in ordinary cold forging, the preform is immersed in a solution tank at the time of its formation, so that the same problem as a liquid lubricant occurs. In the case of a solid lubricant, the problem of penetration into the inside of the preform does not occur, but it is very difficult to apply the lubricant to the surface of the preform with a uniform thickness.

Therefore, some techniques for solving the above-mentioned problems have been proposed as described below. First, the first technique is the technique shown in FIG. 4 (see Japanese Patent Application Laid-Open No. 61-19702). This technique employs a first powder 21 impregnated with a lubricant.
Is thinly arranged at the contact portion with the die 22, the second powder 23 containing no lubricant is arranged on the inside, and the partitioning punch 24 is provided with a partitioning punch 24 to prevent mixing of both at the time of filling the powder (FIG. 4 (a)). As shown in FIG. 1B, the partitioning punch 24 is lowered as shown in FIG. 2B prior to pressing, and then the powders 21 and 23 are pressed and formed by a pair of upper and lower punches 25 and 26. is there.

The second technique is that, as described in JP-A-58-39705, when a sintered body preform is treated with a phosphate and a stearate, water is previously impregnated inside the preform. This prevents the processing solution from penetrating into the preform and forming a lubricious inner coating,
This is a technique to dry the preform after the coating treatment is completed to remove the internal permeation water.

The third technique is a technique of uniformly applying a solid lubricant to the surface of a preform using a barrel machine.

<< Problems to be Solved by the Invention >> However, the first technique uses two kinds of powders, so that the metal composition of the final product becomes uneven. Second,
The third technique greatly increases the work procedure and work time. In particular, the second technique completely eliminates the same adverse effects as liquid lubricant infiltration because it is extremely difficult to completely remove internal permeated water. In addition, it is difficult for the third technique to ensure the uniformity of the thickness of the lubricating layer even if a barrel is used.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sintering cold forging method capable of obtaining a dense and uniform metal composition and having good productivity. It is in.

<< Means for Solving the Problems >> In order to solve the above-mentioned problems, the present invention reduces the amount of the above lubricant when applying the lubricant to the surface of the sintered preform for cold forging which is a porous body. After controlling the temperature to obtain the viscosity, after applying the lubricant, the temperature is controlled so as to increase or solidify the lubricant so that the lubricant does not penetrate inside, and then the preform is placed in the die. And cold forged.

<Operation> In the forging method configured as described above, when the lubricant is applied to the preform, it is easy to apply the lubricant in a uniform thickness because the lubricant has a low viscosity, and the lubricant is applied. After that, since the lubricant is made highly viscous or solidified, it can prevent the lubricant from penetrating inside the preform,
When the preform is cold-forged, the high-viscosity lubricant or the solid lubricant lowers the viscosity again by the frictional heat during forging, and achieves a good lubricating action with the inner surface of the die.

<< Examples >> Examples of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. In this embodiment, a sintered preform for cold forging, which is a porous body, is cooled with liquid nitrogen in advance. A liquid lubricant is applied to the surface. Specifically, first, a preform 1 is prepared as shown in FIG. The preform 1 is obtained by sintering metal powder under pressure and dewaxing. Next, the preform 1 is immersed in liquid nitrogen 2 as shown in FIG.
After a lapse of 15 seconds, the preform 1 is taken out and the liquid lubricant 3 is applied to the surface of the preform 1 as shown in FIG. The liquid lubricant 3 has a low viscosity at room temperature. The coating method is performed by an appropriate method such as a method of dipping the preform 1 in a storage tank of the lubricant 3 in addition to a usual brush coating or spraying. After the application of the lubricant 3 is completed, the preform 1 is set in the die 4 as shown in FIG.
5 and 6 are driven in the direction of the arrow to perform cold forging, and the formed product obtained by this is re-sintered to complete a series of steps.

In the forging method described above, when the lubricant 3 is applied to the preform 1, the lubricant 3 has a low viscosity, so that the lubricant 3 can be uniformly applied with a uniform thickness. On the other hand, the applied lubricant 3 is deprived of heat by the cooled preform 1 to have a low temperature and a high viscosity. Therefore, the lubricant 3 is prevented from penetrating into the inside of the preform 1, and as a result, the minute gaps inside the preform can be sufficiently crushed and eliminated by cold forging, and a high-density forged product can be obtained. At this time, the lubricant 3 on the surface of the preform 1 is reduced in viscosity by frictional heat at the time of forging and has a good lubricating action with the inner surface of the die 4, so that seizure of the die 4 can be prevented.

Next, a second embodiment of the present invention will be described. In this embodiment, a solid lubricant is applied to the surface of the preform 1 in a molten state. Specifically, first, a preform 1 is prepared as shown in FIG. This preform 1 is the same as that described in the first embodiment. Next, the preform 1 is immersed in a solution 8 of a fixed lubricant (for example, solid paraffin) melted by being heated by a heater 7 and is taken out and naturally cooled. The solution 8 is heated until it has a relatively low viscosity. Next, as shown in FIG. 2 (d), the preform 1 is set in the die 4 and a pair of upper and lower punches 5, 6 are driven in the direction of the arrow to perform cold forging. After resintering, a series of steps is completed.

In the forging method described above, since the solid lubricant solution 8 has a low viscosity, the solid lubricant 9 having a uniform thickness and a uniform thickness on the surface thereof is obtained only by immersing the preform 1 in the solution 8 and taking out the preform 1. It can be easily formed. Since the preform 1 is immediately taken out of the solution 8, there is no possibility that the solution 8 permeates into the preform 1. As a result, the minute voids inside the preform 1 are sufficiently crushed and eliminated by cold forging, and a high-density forged product is obtained. In addition,
During this forging, the solid lubricant layer 9 on the surface of the preform 1
Is separated by the frictional heat generated by forging, and has a good lubricating action with the inner surface of the die 4, so that seizure of the inner surface of the die 4 can be prevented.

When there is a possibility that poor lubrication may occur in the solid lubricant layer 9 such as when the preform 1 is forged at a high pressure of 7 to 10 ton / cm ² , for example, as shown in FIG. Liquid lubricant 10 may be applied.

Since the surface of the preform 1 is so-called sealed by the solid lubricant layer 9, there is no possibility that the liquid lubricant 10 permeates into the inside of the preform 1.

<< Experimental Results >> Next, experimental results according to the above-described first embodiment will be described. Similar results were obtained in the second embodiment.

○ Preform used: Diffusion alloy steel powder (component Fe, 4%
Ni, 1.5% Cu, 0.5% Mo), a mixture of 0.5% graphite and 1% lubricant was mixed and compacted at a pressure of 5 ton / cm ² and dewaxed at 800 ° C for 1 hour in a reducing atmosphere. Use sintered one.

○ Surface temperature of preform: 0 ° C ○ Liquid lubricant used: Hytarbe OE-100 (component:
Oil, phosphate, extreme pressure additive) ○ Temperature and viscosity of liquid lubricant ・ 180cp at room temperature (20 ℃) ・ 500cp at 5 ℃ on preform surface ○ Cold forging pressure: 10ton / cm ² ○ Product density: 7.52 g / cm ³ Note that 10 in the die I wipe a cloth after brushing the lubricant having a high viscosity on the surface of the preform prepared in the same conditions
The product density is 7.45 g / c when pressed at ton / cm ²
Since it was m ³ , the result of the present invention was obtained with a high density of 0.07 g / cm ³ . It was also observed that the number of surface pores that reduced the product strength was significantly reduced.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. The lubricant may be used, and the cooling temperature of the preform and the melting temperature of the lubricant may be controlled optimally according to the temperature-viscosity characteristics of each lubricant.

<< Effects of the Invention >> As described above, when the lubricant is applied to the surface of the sintered preform for cold forging, which is a porous body, the temperature is controlled so that the lubricant has a low viscosity. The uniform thickness of the lubricant makes it easy to apply evenly, and after the lubricant has been applied, the temperature of the lubricant is controlled so as to increase or solidify, so the lubricant penetrates into the preform Can be prevented, whereby the minute voids inside the preform can be effectively crushed and eliminated, and a uniform and high-density forged product can be obtained. In addition, the high-viscosity lubricant or solid lubricant on the surface of the preform is reduced in viscosity by frictional heat during forging, so that good lubrication is performed with the inner surface of the die and seizure of the die can be prevented.

[Brief description of the drawings]

1 (a) to 1 (d) are process diagrams showing a first embodiment of the present invention, FIGS. 2 (a) to 2 (d) are process diagrams showing a second embodiment of the present invention, and FIG. FIGS. 4 (a) to 4 (c) are sectional views of a preform showing a modification of the second embodiment, and FIGS. DESCRIPTION OF SYMBOLS 1 ... Preform 2, ... Liquid nitrogen 3,10 ... Liquid lubricant, 4 ... Dies 7 ... Heater 8 ... Solid lubricant solution, 9 ... Solid lubricant layer

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Yoshiho Kamata 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References “Third Edition Iron and Steel Handbook Vol.・ Surface treatment, heat treatment, welding ”(May 31, 1982, published by Maruzen Co., Ltd.) 52-53

Claims (1)

(57) [Claims] When a lubricant is applied to the surface of a sintered preform for cold forging, which is a porous body, the temperature is controlled so as to reduce the viscosity of the lubricant, and after the lubricant is applied, The temperature is controlled so as to increase or solidify the lubricant so that the lubricant does not penetrate into the interior, and then the preform is disposed in a die and cold forged. Sintering cold forging method.