JP2000144210A - Forging method of metallic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the specified shape and dimensions and strength, to improve the quality and productivity, and to reduce the equipment cost by heat-treating a green compact obtained through the cold-pressing by a mechanical press or a hydraulic press, and pressing the green compact by a rocking press into a formed body. SOLUTION: Raw metallic powder, for example, Al-based metallic powder 1 is filled in a press die 3 covered by a lower punch 2, an upper punch 4 is pressed down by a mechanical or hydraulic press for pressing a green compact 5 of specified dimensions. After the green compact 5 is drawn out of the press die 3, it is heated for a specified time at a specified forging temperature to form a heat-treated green compact 5A, and inserted in a lower fixed die 7 covered by a punch 6, and forged through the local pressurization by the rocking motion of an upper rocking die 8 fitted to a rocking press, and a forged body (a product) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to powder metallurgy products, such as engine parts such as pistons and connecting rods,
The present invention relates to a method for forging a metal powder for producing a green body before sintering for manufacturing automobile parts, electric parts and the like.

[0002]

2. Description of the Related Art As a method for solidifying a metal powder such as an aluminum-based powder, an extrusion molding method is mainly used. In this extrusion molding method, a metal powder is put into a container, pressurized, and discharged from a hole provided in a die to form a rod-like body. Is cut and removed and cut to a required length. Since the cross-sectional shape of the green compact is determined by the shape of the die hole, it is possible to obtain a green compact having a different cross-section simply by changing the dice.

However, in this extrusion molding method, since the tip and the discard (the portion remaining in the container) are cut and removed, the yield is low, and cutting with a hard material is difficult.
Therefore, conventionally, as a method of manufacturing a compact to a required dimension (dimension close to the final product), a metal compact is filled in a pressing die and cold pressed by a machine or a hydraulic press to form a compact (a cold compound). A hot press method is employed in which the green compact is heated to a required temperature and uniaxially compression-molded (compressed by a hydraulic press or a mechanical press moving in a uniaxial direction).

Further, a high-temperature isostatic pressing method (usually HIP) for producing a uniform and high-density sintered body by making the metal powder easy to deform at a high temperature and performing isotropic compression molding.
Abbreviation).

[0005]

However, in the conventional extrusion method, there is a problem that the solidification is difficult, the yield is low, and cutting is necessary as described above. In the hot pressing method, the movement of the metal powder is small. Since the surface oxide film cannot be broken, there is a problem that it is difficult to obtain required strength. further,
The high-temperature isostatic pressing method has disadvantages that it requires large equipment and is not suitable for mass production.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and aims to secure required shape and size, improve quality and productivity, and reduce equipment costs. An object of the present invention is to provide a method for forging a metal powder that can be achieved.

[0007]

According to the present invention, the following technical measures have been taken in order to achieve the above object. That is, the feature of the present invention is that a green compact obtained by pressing a metal powder in a cold state by a mechanical or hydraulic press is heat-treated,
The point is that it is formed into a molded body by applying pressure by an oscillating press.

[0008] In this case, the metal powder is filled into a pressing die, pressed under cold (normal temperature) pressure (uniaxial compression molding) by a machine or a hydraulic press, and extracted from the pressing die to obtain a green compact having a required size. You. The green compact thus obtained is heat-treated at a required temperature (for example, lower than the recrystallization temperature of the metal powder), and then inserted into a molding die (a lower fixed die and an upper rocking die), and rocked. The swinging motion is transmitted to the upper swinging die by the dynamic press, and the green compact is locally pressurized.

The swing press has a larger deformation capacity than a normal uniaxial compression molding press, so that the movement and deformation of the metal powder particles are large. Therefore, the local oxide film is easily broken at the deformation interface between the powder particles, the bonding between metal atoms is strongly performed, and a high-quality molded product having the required strength can be obtained with high accuracy. In addition, since the degree of restraint of the mold surface friction is small, the processing limit is greatly improved, and precision molding of thin-walled parts is possible.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show an embodiment of a metal powder forging method according to the present invention. As shown in FIG. 1, a metal powder raw material, for example, an Al-based alloy powder 1 is filled in a stamping die 3 closed by a lower haunch 2 and the upper punch 4 is pressed down by a machine or a hydraulic press (not shown). Pressed. At the beginning of pressurization, slip occurs between the powder particle surfaces in the filled state, filling large voids such as in the bridge state,
A rapid increase in the density begins, and the powder particles change from an unstable state to a stable state, and as the pressing progresses, the plastic deformation of the contact portion between the powder particles and the entire particle increases, filling the voids and increasing the density. And the green compact 5 (cold compound) having the required dimensions is formed.

The green compact 5 thus obtained is extracted from the pressing die 3 and then heated by a heating device at a predetermined forging temperature (for example, 500 ° C.) for a predetermined time (for example, 20 ° C.).
1) Heated, as shown in FIG. 1, inserted into a lower fixed mold 7 closed by a punch 6 and locally oscillated by an oscillating motion of an upper oscillating mold 8 mounted on an oscillating press. Forging is performed by pressing.

The rocking motion includes, for example, a circular motion, a chrysanthemum motion, a seesaw motion, a spiral motion, and the like, and a combination of motions can be performed according to a product shape. The movement and deformation of the metal powder particles increase with the progress of local pressurization by oscillating forging, and the oxide film is locally broken at the deformation interface between the powder particles, bonding the metal particles to each other. Is performed strongly, and a molded body (product) 9 as shown in FIGS. 2 and 3 is formed.

[0013]

EXAMPLE An Al-based alloy powder (Al-
17, a billet (compact compact) having a diameter of 50 mm and a height of 30 mm was prepared using Si-1Cu-1Ni-2Fe-2Mg powder, and was heated at a heating temperature of 500 ° C. for a heating time of 20 mm.
After heating in minutes, the product was forged using an oscillating press to obtain a product having required dimensions (diameter 60 mm, height 17 mm).

[0014] The product obtained by forging according to the method of the present invention, the extrusion method and the usual H.I. As a result of measuring the tensile strength, proof stress, and elongation of the product obtained by the P method (hot press method), it was as shown in Table 1.

[0015]

[Table 1]

As is apparent from Table 1, according to the embodiment of the present invention, the extrusion method is almost the same as that of the conventional H.p. P
Better than that of the law. In the extrusion method, a cutting operation is indispensable, and the yield is low. On the other hand, the method of the present invention does not require cutting, has a good yield, and can obtain a product of good quality. Since the oscillating press performs local pressurization, upsetting can be performed with a capacity of 1/5 to 1/10 of a general press (mechanical or hydraulic press). Capital investment for molds and foundations can be greatly reduced. In addition, since the degree of restraint of mold surface friction is small, the processing limit is greatly improved, precision molding of thin parts can be performed, and the mold replacement time is short.
Can be used for small-lot production.

[0017]

According to the present invention, a metal powder compact is heated at a predetermined forging temperature and then forged by a local press by an oscillating press. Can be obtained, and the quality and productivity (mass production) can be improved and the equipment cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of the method of the present invention.

FIG. 2 is a schematic sectional view showing a forging end state in the embodiment.

FIG. 3 is a perspective view of a product in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal powder 5 Green compact 5A Heat-treated green compact 7 Lower fixed die 8 Upper swinging die 9 Molded product (product)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E087 BA23 CB01 CB03 EA11 EA42 HA34 HA62 4K018 CA13 CA17 CA19 KA01 KA08 KA32

Claims (2)

[Claims] 1. A forging of a metal powder, wherein a green compact obtained by pressing a metal powder cold by a mechanical or hydraulic press is heated and then pressed by a rocking press to form a compact. Method. 2. The metal powder forging method according to claim 1, wherein the green compact is pressed by a swing press having a lower fixed mold and an upper swing mold.