JP2000167652A - Die for die casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a die for die casting machine excellent in the heat retaining property of molten metal and also, the strength and the ductility and having the long service life. SOLUTION: A fixed die 1 is fitted to the front surface of a fixed plate 2. A movable die 7 faced to the fixed die 1 is disposed and fitted to the front surface of a movable plate 8, and on this front surface, a cavity 9 is formed. A JIS-SKD 61-made die sleeve 3 is inserted so as to penetrate the fixed die 1 from the rear surface to the front surface. A heat insulating layer 5 made of a precipitation hardening series stainless steel (IS-SUS 630) is arranged between the die sleeve 3 and the fixed die 1 body. A plunger sleeve 4 made of the same JIS-SKD 61 is inserted so as to penetrate the fixed plate 2 for the rear surface to the front surface. The rear end of the die sleeve 3 is connected with the front end of the plunger sleeve 4. In this case the thermal conductivity at 300 deg.C of the heat insulating layer 5 is 10-25 W/m.K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for a die casting machine such as aluminum or magnesium.

[0002]

2. Description of the Related Art In a die casting machine, a mold sleeve for passing a molten metal through a fixed die and feeding the molten metal to the inside of the fixed die is conventionally provided with an alloy tool steel (for example, JIS-JIS) for a hot die.
SKD61) had been used.

[0003] The sleeve made of alloy tool steel has a relatively high thermal conductivity of about 29 W / m · K (300 ° C). Coagulation easily starts. For this reason, when it is fed into the mold cavity through the sleeve,
There has been a problem that the molten metal solidifies immediately, and a hot water boundary and poor running of the molten metal occur. In particular, in the production of thin-walled molded products with a small amount of pouring, there was a tendency that molding defects such as a hot water boundary, a poor running water, and a poor filling occurred frequently.

In order to solve such a problem, Japanese Patent Application Laid-Open No. Hei 2-179346 or Japanese Patent Application Laid-Open No. Hei 5-038563 discloses a method in which a ceramic inner cylinder is fitted into a metal or steel outer cylinder. A composite sleeve is described. Since these ceramic inner cylinders have a low thermal conductivity (about 20 W / m · K (300 ° C.)), they are excellent in the heat retaining property against the molten metal and are unlikely to cause the above-described problems. Therefore, it is effective in reducing the defective rate of the die-cast product. Furthermore, since the ceramic inner cylinder has excellent corrosion resistance to molten aluminum, it has the advantage that erosion by the molten metal is unlikely to occur.

However, since the ceramic inner cylinder has a low thermal conductivity, a large thermal stress is generated when the molten metal is poured, and there is a danger that the inner cylinder will be instantaneously damaged. JP-A-5-050204 describes a structure in which a stress relaxation layer is provided between a ceramic inner cylinder and a metal outer cylinder as a measure for solving such a problem. However, the effect is not enough. They are,
It is based on the basic properties of ceramics, which have low thermal conductivity, poor toughness, and low reliability with respect to strength, and are considered to be difficult to solve at present.

Another disadvantage of the sleeve using the ceramic inner cylinder is that it is difficult to perform a cutting process, and it is necessary to rely on a grinding process with low machining efficiency. This is,
This is a factor that increases the sleeve manufacturing cost.

Japanese Unexamined Patent Publication No. 9-263897 discloses an alloy steel (Si-Si) having a relatively low thermal conductivity developed to compensate for the above-mentioned disadvantage of the sleeve using the ceramic inner cylinder.
Ni-Cr stainless steel). This alloy steel has a thermal conductivity of 16 to 20 W / m · K.
(300 ° C.), which is relatively low, and has excellent heat retention properties against the molten metal. Therefore, it is effective in reducing the defective rate of the die-cast product.

However, since the above alloy is manufactured by casting, it has a non-uniform structure as a whole, and it is difficult to obtain stable strength due to casting cavities, segregation, and coarsening of crystal grains.
Low toughness. For this reason, there is an example in which the entire sleeve is damaged from the outer peripheral portion by thermal stress generated at the time of pouring the molten metal, and the service life is not sufficient.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional die for a die-casting machine. An object of the present invention is to provide a die structure for a die casting machine having excellent strength and toughness and a long life.

[0010]

SUMMARY OF THE INVENTION A die for a die casting machine according to the present invention is a die made of an alloy tool steel for a fixed die and a hot die for passing a molten metal through the fixed die into the fixed die. The thermal conductivity at 300 ° C is 1
A heat insulating layer made of an alloy steel of 0 W / m · K or more and 25 W / m · K or less is provided.

According to the die for a die casting machine of the present invention, a heat insulating layer having a relatively low thermal conductivity is provided between the die sleeve and the fixed die (main body). It is excellent, and the molding defects such as the above-mentioned hot water boundary, poor running water, and poor filling hardly occur.

Further, since the tool sleeve is made of alloy tool steel (JIS G 4404 (1983) SKD type or SKT type) for a hot die, it has excellent strength and toughness and realizes a long life. can do.

As the alloy steel satisfying the above-mentioned thermal conductivity conditions, for example, precipitation hardening stainless steel (SU)
S630 or SUS630; JIS G 4303
(1991).

[0014]

FIG. 1 shows an example of a die for a die casting machine according to the present invention.

The fixed die 1 is mounted on the front of the fixed platen 2. A moving die 7 is arranged facing the fixed die 1, and the moving die 7 is attached to a front surface of a moving board 8. A cavity 9 is formed on the front surface of the movable die 7.

A mold sleeve 3 (outside diameter 119 mm, inside diameter 70 mm) made of alloy tool steel JIS-SKD61 for a hot die is fitted so as to penetrate the fixed die 1 from the rear surface to the front surface. Between the mold sleeve 3 and the main body of the fixed die 1, a heat insulating layer 5 made of precipitation hardening stainless steel SUS630 and having a thickness of 5 mm is provided. Also,
JIS so that the fixed board 4 penetrates from the back to the front
-A plunger sleeve 4 made of SKD61 is fitted. The rear end of the mold sleeve 3 is a plunger sleeve 4
Connected to the front end of the The thermal conductivity of SUS630 at 300 ° C. is 22.5 W / m · K.

Next, a method of manufacturing the fixed die 1 will be described. In the base material portion of the fixed die 1, a through hole for the mold sleeve 3 penetrating from the rear surface to the front surface is previously formed.
Is formed in consideration of the thickness. A cylindrical member made of SUS630 serving as the heat insulating layer 5 is fitted into the through hole by a cold fitting method. Next, S inside the cylindrical member
A mold sleeve made of KD61 is fitted by a cold fitting method or the like.

The fixed die 1 manufactured under the above conditions was attached to a cold-chamber die casting machine, and a personal computer case (1 mm in wall thickness) was manufactured from a magnesium alloy. As a result, casting defects of the product are reduced, and the non-defective rate is 1 compared to the case where the fixed die 1 using only the mold sleeve of the conventional SKD61 material is used.
By 1%, the cost per product could be reduced by 10%.

[Brief description of the drawings]

FIG. 1 is a view showing an example of a die casting mold according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fixed die, 2 ... Fixed board, 3 ... Mold sleeve, 4 ... Plunger sleeve, 5 ... Heat insulation layer, 7 ... Moving die, 8 ... Moving board, 9 ... cavity.

Claims (2)

[Claims] 1. A thermal conductivity at a temperature of 300 ° C. between a fixed die and an alloy tool steel mold sleeve for a hot die that penetrates the fixed die and feeds a molten metal into the fixed die. Characterized in that a heat insulating layer made of an alloy steel of 10 W / m · K or more and 25 W / m · K or less is provided. 2. The die according to claim 1, wherein the alloy steel is a precipitation hardening stainless steel.