JP2000317608A - Die for die casting and die casting method using this die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cast a formed product having thin thickness and a formed product having complicated shape with the comparatively easy method by forming the portion at least at a cavity surface side in a die with an alloy steel having a specified thermal conductivity. SOLUTION: A fixed die 14 and a movable die 19 are composed of base materials 14a, 19a and the portions 14b, 19b at the cavity surface side having about 5 mm thickness and metallurgically joined with the base materials 14a, 19a by using a hot hydrostatic pressing method. The base materials 14a, 19a are formed with a tool steel, etc., having 30 W/(m.K) heat conductivity at 300 deg.C. The portions 14b, 19b at the cavity surface side are formed with a precipitation hardening type stainless steel having low thermal conductivity, such as 16-20 W/(m.K) at 300 deg.C. A nitriding treatment on the surfaces of the portions 14b, 19b at the cavity surface side is desirably applied. In this way, the misrun generated at the starting time of a die casting can be eliminated at early time, and even if the temp. control is not stricly executed, the good product is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die used for die casting of aluminum, magnesium and their alloys, and more particularly to the molding of thin-walled molded products such as personal computer cases and molded products having complicated shapes. TECHNICAL FIELD The present invention relates to a die casting mold suitable for a die and a die casting method using the same.

[0002]

2. Description of the Related Art Conventionally, tool steel such as SKD61 (JIS) has been used for a die casting die used for this type of molding. This tool steel has a thermal conductivity of 29 W /
(MK) (300 ° C), which is relatively high, the molten metal cast in the mold begins to solidify in a short time, especially in thin-walled molded products or molded products with complicated shapes. Failure occurs. Therefore, conventionally, the mold is heated by an electric heater, or high-temperature oil is circulated in the mold,
The temperature of the mold was adjusted.

[0003]

However, in die casting, molding cannot be performed unless the temperature of the mold is kept lower than the melting point of the molten metal to be cast. For this reason, it is necessary to maintain the temperature of the mold, which is controlled by an electric heater or high-temperature oil, properly. If this temperature is low, poor running of the molten metal will occur. It takes a long time to solidify the mold, which causes problems such as a long molding time, and has a drawback that it is difficult to control the mold temperature.

[0004] The present invention solves the above-mentioned disadvantages,
An object of the present invention is to provide a die-casting die capable of relatively easily die-casting a thin-walled molded product or a molded product having a complicated shape, and a die-casting method using the same.

[0005]

According to the present invention, there is provided a die-casting die, wherein at least a cavity surface side portion of the die has a thermal conductivity of 10-2.
It is formed of an alloy steel of 5 W / (m · K) (300 ° C.), and the present invention includes a die casting method performed using this mold.

According to the present invention, since the thermal conductivity of the cavity surface side portion in contact with the molten metal is lower than that of the conventional mold, even if the temperature of the mold is lower than the conventionally appropriate temperature, the casting is performed. The solidified molten metal is less likely to solidify and the occurrence of poor running around the molten metal is suppressed. When the thermal conductivity of the cavity surface side portion exceeds 25 W / (m · K) (300 ° C.), this effect is reduced, and 10 W / (m · K) (300 ° C.)
C), the delay of solidification of the molten metal after filling increases, so that 10 to 25 W / (m · K) (300
C). The delay in solidification of the molten metal can be eliminated or slightly suppressed by reducing the thickness of the alloy steel on the surface side of the cavity or setting the temperature of the mold low.

The heat conductivity is 10 to 25 W / (m ·
K) (300 ° C.) as an alloy steel, hot tool steel-based product name: YHD (manufactured by Hitachi Metals) (about 20 W / (m · K)
(300 ° C)), high speed tool steel SKH57 (JIS)
And its equivalent (about 23W / (mK) (300
℃)), precipitation hardening stainless steel (16-20 W / (m
・ K) (300 ℃)), but the base material of the mold is SK
In the case of D61 (JIS), it is preferable to use precipitation hardening stainless steel because of its close thermal expansion coefficient. In this case, nitriding treatment is required to increase the hardness of the cavity surface at least and extend the life of the mold. Is preferably applied.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 10 denotes a fixed die plate of the die casting machine, and 11 denotes a movable die plate. A sleeve 13 is attached to the fixed die plate 10 through a bush 12 with a flange.
A fixed mold 14 is attached. The fixed mold 14 is provided with a mold sleeve 15 which is concentric with the sleeve 13 and has the same inner diameter as the inner diameter of the sleeve 13. In addition, 16 is a pouring port, 17 is a plunger, 1
8 is a plunger chip.

The movable die plate 11 has a fixed mold 14
And a movable mold 19 paired with the movable mold 19. A cavity 20 corresponding to a molded product obtained by die casting and a runner 21 extending from the inner diameter of the mold sleeve 15 to the cavity 20 are formed between the two dies 14 and 19.

The two dies 14 and 19 are provided with base materials 14a and 19, respectively.
a and a 5 mm-thick cavity surface side portion 14b, 19b which is metallurgically joined to the base materials 14a, 19a by hot isostatic pressing (or brazing). The base members 14a and 19a are made of tool steel such as SKD61 (JIS) used for a conventional mold or S
KD8 (JIS) (Thermal conductivity: 30 W / (m · K) (3
00 ° C)), and the cavity surface side portions 14b and 19b have a thermal conductivity of 16 to 20 W / (m ·
K) SUS630 (JIS) or SUS631 (JIS), which is a precipitation hardening stainless steel as low as 300 ° C
And the cavity surface side portions 14b, 19b
Is subjected to a nitriding treatment.

Using the two dies 14 and 19, the thickness is 1
mm of a personal computer case made of a magnesium alloy, it is possible to eliminate the run-out failure particularly at the time of starting the die-casting at an early stage. According to the dies 14, 19, the temperature of the dies 14, 19 It was confirmed that good products could be obtained without strict management as in the past.

In the above-described embodiment, the dies 14, 19
Of the cavity surface side portions 14b and 19b having a thermal conductivity of 1
An example in which the alloy steel was formed from a low alloy steel of 6 to 20 W / (m · K) (300 ° C.) was shown.
4b and 19b have a thermal conductivity of 10 to 20 W / m · K (30
0 ° C.), and the entire molds 14 and 19 have a thermal conductivity of 10 to 20 W / (m · K) (300
C.).

[0013]

As described above, according to the present invention, it is possible to relatively easily die-cast a thin-walled molded product or a molded product having a complicated shape. Can be formed at a higher yield rate.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixed die plate 11 Moving die plate 12 Bush with a brim 13 Sleeve 14 Fixed die 14a Base material 14b Cavity surface side part 15 Mold sleeve 16 Pouring port 17 Plunger 18 Plunger chip 19 Moving die 19a Base material 19b Cavity surface side part 20 cavity 21 runner

Claims (4)

[Claims] In a die casting mold, at least a cavity surface side portion of the mold has a thermal conductivity of 10 to 10.
A die casting die formed of an alloy steel of 25 W / (m · K) (300 ° C.). 2. The die casting die according to claim 1, wherein the alloy steel is a precipitation hardening stainless steel, and at least a surface of the cavity is subjected to a nitriding treatment. 3. In the die casting method, at least the thermal conductivity of the cavity surface side portion is 10 to 25 W / (m · m).
K) A die casting method using a mold formed of (300 ° C.) alloy steel. 4. The die casting method according to claim 3, wherein the alloy steel is a precipitation hardening stainless steel, and at least a surface of the cavity is subjected to a nitriding treatment.