JPH02255241A - Production of forged piston made of aluminum alloy - Google Patents

Abstract

PURPOSE:To prevent the cracking at the time of forging the piston from a stock made of a rapidly solidified aluminum alloy powder by forging the stock while increasing the chipping allowances in the skirt part in the thrust and counter-thrust directions which are the directions orthogonal with a piston part. CONSTITUTION:The rapidly solidified aluminum powder is forged by increasing the chipping allowances 10A, 10B in the skirt part 6 of the thrust and counter- thrust directions which are the directions orthogonal with the piston part 6 at the time of producing the piston 5 by subjecting the stock P formed by extrusion of the above-mentioned powder to a die forging. The chipping allowances 10A, 10B are thereafter removed by a chipping. The difference in the sectional area between a pin boss part A and the thrust and counter- thrust directions B of a forging die 1 is, therefore, decreased and the fluid resistance in the circumferential direction of the piston at the time of the forging is uniformized. As a result, the cracking at the front end of the skirt part 6 is effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a forged aluminum alloy piston.

(Prior art and problems to be solved by the invention) In general, aluminum alloys used as materials for automobile engine pistons are required to have high-temperature strength, wear resistance, low expansion coefficient, etc. Hypereutectic HE〇-S
It is desirable to use an i-based alloy. However, when trying to manufacture a piston made of the above-mentioned eutectic or hypereutectic A (1-9i alloy) by casting, the Si product becomes too large and brittle, and the workability deteriorates. Therefore, in order to solve this problem, attempts have been made in recent years to manufacture pistons by forging instead of casting.

On the other hand, in order to reduce the weight of the piston and cope with the increased heat load, materials with even better high-temperature strength and thermal expansion characteristics (
For example, attempts have been made to manufacture pistons by forging high-St rapidly solidified aluminum powder alloys.

By the way, the forged piston described above is manufactured by die forging a cylindrical extruded material P made of rapidly solidified aluminum powder alloy using the forging apparatus shown in FIGS. 6 and 7. That is, the side die 2 and the lower die 3 constitute a forging die l having a cylindrical space, and the cylindrical material P is placed inside the forging die l to form the inner periphery of the piston 5 (see FIG. 8). Forging is performed using a punch 4 having a surface shape.

At this time, as shown in FIG. 9, the cross-sectional area of the space formed between the outer peripheral surface of the punch 4 and the inner peripheral surface of the side mold 2 is Since the thrust/anti-thrust parts B, B in orthogonal directions are significantly different, there is a large difference in material flow resistance during forging between the pin bosses iA, A and the thrust/anti-thrust parts B, B. Become. Moreover, although the rapidly solidified aluminum powder alloy constituting the extruded material P exhibits excellent properties in terms of high-temperature strength and thermal expansion properties, it exhibits difficult formability during forging. Due to the difference in flow resistance, tensile stress is generated on the free surface of the tip of the skirt portion 6 of the piston 5, and as a result, as shown in FIG. 8, a crack (K) may occur at the tip of the skirt portion 6. For such cracks, K
Even if the cracked part is removed after forging, the occurrence of this may have a negative effect on the strength of the piston as a product, so there is currently a need to develop a forging method that does not cause cracks. be.

Note that the method of die forging an extruded rod-shaped material is well known as disclosed in Japanese Patent Application Laid-Open No. 59-206133. No consideration has been given to measures to avoid the occurrence of cracks when a piston is manufactured by die forging from a forged material consisting of.

The present invention has been made in view of the above points, and an object of the present invention is to prevent the occurrence of cracks when a piston is forged from a material made of rapidly solidified aluminum powder alloy.

(Method for Solving the Problems) In the present invention, as a method for solving the above problems, when manufacturing a piston by die forging an extruded material made of rapidly solidified aluminum powder alloy, the pin boss portion and Forging is performed by increasing the machining allowance in the skirt portion in the thrust and anti-thrust directions, which are perpendicular directions, and then the machining allowance is removed by cutting.

(Function) In the present invention, the following effects can be obtained by the above method.

In other words, by increasing the machining allowance in the skirt part in the thrust/anti-thrust direction, which is perpendicular to the pin boss part, forging increases the difference in cross-sectional area between the pin boss part and the thrust/anti-thrust part in the forging die. becomes small, and the flow resistance in the circumferential direction of the piston during forging becomes almost uniform.

(Effects of the Invention) According to the present invention, when manufacturing a piston by performing die forging on an extruded material made of rapidly solidified aluminum powder alloy, the skirts in the thrust and anti-thrust directions that are perpendicular to the pin boss portion By increasing the machining allowance at the forging part and then removing the machining allowance by cutting, the difference in cross-sectional area between the pin and boss part and the thrust/anti-thrust part in the forging die is reduced. As a result, the flow resistance in the circumferential direction of the piston during forging is made uniform, and as a result, it is possible to effectively prevent the occurrence of cracks at the tip of the skirt portion.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The forging apparatus used in the method of the present invention, as shown in FIGS. 1 and 2, consists of a side die 2 and a lower die 3, and includes a forging die 1 having a cylindrical space, and a forging die l inside the forging die l. It is equipped with a punch 4 that is placed in the space. The outer peripheral shape of the punch 4 is similar to that of the piston 5 (fourth
The shape of the inner circumferential surface is the same as that shown in FIG. Then, when the bonder 4 is press-fitted into the forging die 1, the cross-sectional area of the space formed between the outer circumferential surface of the punch 4 and the inner circumferential surface of the side die 2 is as shown in FIG. The thrust/anti-thrust part B, the side mold 2 on the B side so that the parts A, A and the thrust/anti-thrust part B, in the direction orthogonal to the pin boss part A, are almost equal to each other.
is deeply gouged out.

Next, a method for manufacturing a piston using the forging device having the above configuration will be explained.

A (1-Si-Fe series rapidly solidified aluminum powder alloy is extruded and formed into a cylindrical extruded material P. After heating it to 450°C and setting it in the space of the forging die l, it is punched backwards with a punch 4. Extrusion forging was performed to obtain a forged product 5 for piston molding as shown in FIGS. 4 and 5.

The forged product 5 is a thrust/anti-thrust part B.

Cutting allowance 10B at B, wall thickness of IOB is pin boss part A
, A has a machining allowance of 10A, which is greatly increased compared to the thickness of IOA.

Therefore, during the above-mentioned forging process, the extruded material P set in the forging die 1 is plastically deformed by the pressing force of the punch 4, and the gap between the inner circumferential surface of the forging die l and the outer circumferential surface of the punch 4 is This will fill the space formed in the
As described above, the cross-sectional area of the space formed between the outer peripheral surface of the punch 4 and the inner peripheral surface of the side die 2 is the pin boss portion A.

A, the pin boss part A, and the thrust/anti-thrust part B in the direction orthogonal to A are made to be approximately equal, so that the flow resistance in the circumferential direction of the piston during forging is almost uniform, and the skirt part 6 This will prevent cracks from occurring at the tip.

Therefore, the machining allowance IOA, I
The OB is removed by a cutting process performed as piston profile processing to obtain the desired piston shape.

As described above, according to the method of the present invention, the generation of cracks at the tip of the skirt part in piston forging from rapidly solidified aluminum powder alloy material is prevented by increasing the cutting allowance in the thrust and anti-thrust directions of the piston. This can be effectively prevented.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view schematically showing a forging device used in the method of the present invention, Fig. 2 is a cross-sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a circumferential section of the piston in the forging device shown in Fig. 1. FIG. 4 is a sectional view of a forged product for piston forming produced by the method of the present invention, FIG. 5 is a plan view of the forged product shown in FIG. 4, and FIG. The figure is a sectional view of a forging device used for conventional piston forging, FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6, and FIG. 8 is a plan view of a piston manufactured by the forging device shown in FIG. 6. FIG. 9 is a diagram showing changes in the cross-sectional area of each part in the circumferential direction of the piston in the forging apparatus shown in FIG. 6. ■・・・・・・Forging die 2・・・・・・・・・Side die 3・・・・・・Lower die 4・・・・・・Punch 5・・・・− ... Piston 6 ... Skirt part 10A, IOB ... Cutting allowance A ... Pin boss part B ... Thrust/anti-thrust part P ...・
...Extruded material Figure 2 Figure 4 Figure 5 Screws Bi-waru Bi-formed convex cup Side buried bottom type Punch Piston skirt part Cutting allowance Pin Boss part Thrust/anti-thrust part Extruded material Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1. When manufacturing a piston by die forging an extruded material made of rapidly solidified aluminum powder alloy, forging is performed by increasing the machining allowance in the thrust and anti-thrust directions of the skirt, which are orthogonal to the pin boss. A method for manufacturing an aluminum alloy forged piston, characterized in that the machining allowance is then removed by cutting.