JPS59156530A - Cold forging method of high silicon aluminum - Google Patents

Abstract

PURPOSE:To enable cold forging and to improve wear resistance, internal quality and dimensional accuracy by annealing an aluminum alloy incorporated with a prescribed ratio of silicon thereby adjusting the hardness to a prescribed value or below. CONSTITUTION:A high silicon aluminum alloy contg. 15-20% silicon is annealed and a blank material adjusted to have <=70HRF hardness is obtd. Such blank material is charged into the die of a cold forging device and is molded under pressure by a punch. The product having excellent wear resistance, internal quality and dimensional accuracy is obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cold forging products made of aluminum alloy, such as cylinders or pistons for internal combustion engines.

Generally, in order to manufacture parts for internal combustion engines or coolers, an aluminum alloy material for forging (JIS 4032 alloy) is used as a material and this is cold forged. However, although such materials have good moldability, they have the disadvantage of poor abrasion resistance when made into products.

For this reason, high-silicon aluminum alloys have recently been used as materials for forming cylinders, etc. to improve wear resistance, but high-silicon aluminum alloy ice materials generally have a low elongation rate, so they are not suitable for cold forging. is considered unsuitable, and for this reason, cast products are formed by hot forging.

However, when casting with a mold, the internal quality is good, but productivity is poor, and there are problems such as high machining costs.Also, when die casting is used, productivity and dimensional accuracy are good, but gas is involved. There is also the problem that heat treatment cannot be performed.In addition, although internal quality and productivity are good when hot forging is used, an oxidized layer is formed due to heating, and there is also the problem of poor dimensional accuracy due to thermal expansion, etc. be.

The present invention was made based on the knowledge that even in high-silicon aluminum alloys, by keeping the silicon content within a specific range, the elongation required for cold forging can be obtained.
The objective is to provide a method for cold forging high-silicon aluminum alloys that provides a product with excellent internal quality and dimensional accuracy and good productivity.

In order to achieve the above object, the present invention first aims to increase the silicon content of a high silicon aluminum alloy as a material from 15 to 20.
%, the material is annealed to have a hardness of HRF 70 or less, and then the material is pressure-formed between a die and a punch.

An example of the implementation of the present invention will be described below based on the accompanying drawings.

1 and 2 are views explaining the outline of the cold forging method according to the present invention, and as shown in FIG. 1A and FIG. 2AK, a material 3 is placed on a knockout pin 2 in a die 1. The material 3 is then pressure-formed between the die 1 and the punch 4 as shown in FIGS. 1B and 2B, and then as shown in FIGS. 1C and 2C.゛Product 5 such as a cylinder is obtained.

Here, the content ratio of the material 3 is silicon 51-15 to 2
0%, magnesium 0.45~0.65%, copper 4~
5%, the balance being aluminum, and the hardness was reduced to HRF 70 or less by annealing. Such material 3 has a hardness of HRF70 as shown by the solid line a in FIG.
It can be seen that by setting the following, an elongation of more than 5 cm, which is the range that can be cold forged, can be obtained. Here, the broken line in the electric diagram indicates the conventional forging aluminum alloy (JIS 403
Material 3 used in the present invention has slightly inferior formability compared to conventional materials, but since conventional materials have inferior wear resistance, it is difficult to apply it to cylinders etc. As mentioned above, there are problems.

Furthermore, Fig. 4 is a graph showing the relationship between the hardness and forming stress of the high-silicon aluminum alloy material used in the method of the present invention, and it is clear from this graph that when the 51C1 hardness is HRF70 or higher, the forming stress increases rapidly. The material cannot withstand plastic deformation and defects such as cracks occur in some parts of the product. Furthermore, the higher the hardness, the shorter the life of the punch. Therefore, it is appropriate that the hardness of the material is HRF 70 or less for the reason based on FIG. 3 above.

The following table shows the relationship between hardness and mechanical strength after annealing of high silicon aluminum alloys.

〔table〕

As is clear from this table, when the hardness is increased to HRF70 or higher, the elongation rate drops extremely and cold forging becomes impossible.

Furthermore, if the silicon content is less than 15 inches, the precipitation of primary silicon will be reduced, resulting in poor wear resistance, making it unusable for parts that require wear resistance. If it is 20 inches or more, the amount of primary silicon precipitated is large, so the surface area of silicon on the material surface increases, which improves wear resistance, but primary silicon does not deform, resulting in poor plastic deformability and cold forging. Therefore, it is appropriate that the silicon content be 15 to 20%.

Next, a specific experimental example will be described.

[Experiment example]

A high-silicon aluminum alloy containing 15-18% silicon, 0.45-0.65% magnesium, and 4-5% copper was annealed to obtain a material with a hardness of 1 (RF67, outer diameter 50+mm, thickness 13mm). Then, this material was charged into a die of a cold forging machine as shown in Fig. 1, lubricated with an aluminum bonder, etc., and the punch was moved down in a 250 ton cold forging press to form a die of 1.2
Form in seconds. The cup-shaped intermediate product obtained by this molding has an outer diameter of 50mm, an inner diameter of 43+nm, and a length of 38mm, with no change in primary silicon, an inner diameter of 0.03 am, and an inner diameter of 0.1mm. , more than twice the accuracy was obtained compared to hot forging. The bottom of the cup-shaped intermediate product was then cut to form a cylinder.

As is clear from the above description, according to the present invention, the silicon content of the high-silicon aluminum alloy is increased to 15 to 20 inches, and the alloy is annealed to have a hardness of HRF70 or less, and this hardness is 1-IRF70 or less. Since the material is made of a closed high-silicon aluminum alloy, it is possible to perform cold forging, and by forming by cold forging, a product with excellent wear resistance and good internal quality and dimensional accuracy can be obtained. Furthermore, it has many effects such as improving productivity.

[Brief explanation of drawings]

The drawings show an embodiment of the method of the present invention, and FIG.
Figures 2A to C and 2A to C are diagrams explaining the outline of the cold forging method according to the present invention, Figure 3 is a graph showing the relationship between hardness and elongation, and Figure 4 is a graph showing the relationship between hardness and forming stress. This is a graph showing the relationship between In addition, in the drawing, 1 is Gui, 2 is Knockout, 3 is Material,
4 is a punch, and 5 is a product. Patent applicant Honda Motor Co., Ltd. agent
Patent Attorney Part 2 1) Part 1 Patent Attorney
Kuni Ohashi, Physician
Koyama Contingency Plan 1' Figure 2 (A) (B) (C) Figure 3
- Figure 4 pL good (HRF)

Claims (1)

[Claims] A material is charged into a die and press-formed with a punch, characterized in that the material is an aluminum alloy containing 15 to 20% silicon and is annealed to a hardness of HRF 70 or less and formed by cold forging. Cold forging method for high silicon aluminum alloy.