JPH11300460A - Sleeve for die casting machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sleeve for die casting machine, in which the heat insulating property is provided to molten metal and the breakage caused by heat shock developed at the time of pouring the molten metal is hardly developed. SOLUTION: The sleeve for die casting machine is composed of a precipitation hardening type stainless steel (corresponding to SUS630, JIS-G-4303) containing <=0.07 wt.% C, <=1.0 wt.% Si, <=1.0 wt.% Mn, 3-5 wt.% Ni, 15-17.5 wt.% Cr, 3-5 wt.% Cu, 0.15-0.45 wt.% Nb and nitriding treatment is applied to this inner diameter surface. Then, instead of the SUS630 material, the similar precipitation hardening type SUS631 material can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sleeve for a die casting machine, and more particularly, to a die casting machine used for casting a molded product such as an aluminum alloy or a magnesium alloy, which is used as a molten metal receiver and a pressure cylinder. The present invention relates to a configuration suitable for a sleeve.

[0002]

2. Description of the Related Art Conventionally, a sleeve used as a molten metal receiver and a pressurizing cylinder in a die casting machine has been manufactured by JI.
Tool steels such as S-SKD61 have been used. Such a tool steel sleeve has a thermal conductivity of about 29 W / m.
-Since the temperature is relatively high as K (300 ° C), the molten metal (molten metal) injected into the sleeve is rapidly cooled, and solidification starts in a short time at a portion in contact with the sleeve. Therefore, after the molten metal is solidified at an early stage after being injected into the mold from the sleeve, molding defects such as a molten metal boundary, a poor molten metal run, and a poor filling occur. In particular, when manufacturing a thin-walled molded product with a small pouring amount, the above-mentioned molding defect frequently occurs.

[0003] In order to solve such a problem, a sleeve having a composite structure in which a ceramic inner cylinder is fitted into a steel or alloy outer cylinder has been developed (for example, Japanese Patent Laid-Open Publication No. Hei 2 (1994)).
-179346, JP-A-5-038563, etc.). A sleeve having such a composite structure has a low thermal conductivity of ceramics constituting the inner cylinder (for example,
Approximately 20 W / m · K (300 ° C.), which is excellent in heat retention for molten metal, can solve the above-mentioned problems, and can reduce the defective rate of die-cast products. Furthermore, since the ceramic inner cylinder has corrosion resistance to molten aluminum, it has an advantage that erosion hardly occurs at the molten metal falling portion.

However, since the ceramic inner cylinder has a low thermal conductivity, a large thermal stress is generated when the molten metal is injected.
There is a problem that the heat stress causes instantaneous damage.
In order to solve such a problem, some measures have been taken such as providing a stress relaxation layer between a ceramic inner cylinder and a metal outer cylinder (for example, JP-A-5-050204). Is not enough. They are,
This is a natural consequence of the general properties of ceramics, which are low in thermal conductivity, poor in toughness, and lack in reliability with respect to strength, and are considered to be difficult to solve at present.

[0005] Another disadvantage of a sleeve using a ceramic inner cylinder is that since cutting is difficult, it is necessary to rely on grinding with low machining efficiency. This is a factor that increases the manufacturing cost of the sleeve having the above-described structure.

In order to compensate for the above-mentioned drawbacks of the sleeve using the ceramic inner cylinder, a sleeve using an alloy having a low thermal conductivity has been proposed (Japanese Patent Laid-Open No. 9-263897). A sleeve using the above alloy has a thermal conductivity of 1
As low as 2 to 20 W / mK (room temperature to 300 ° C) and excellent in heat retention for molten metal,
It is possible to effectively suppress occurrence of molding defects such as defective filling. As a result, the defect rate of the die cast product can be reduced.

However, since the above alloy is manufactured by a casting method, the structure of the entire member is not uniform,
Stable strength cannot be obtained due to cavities, segregation, coarsening of crystal grains, etc., and the toughness cannot be said to be sufficient. For this reason, there is a phenomenon in which the entire sleeve is broken from the outer peripheral portion due to thermal stress generated when the molten metal is injected, and there is a problem in its life.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional sleeve for a die-casting machine, and an object of the present invention is to provide a heat insulating property comparable to that of ceramics. An object of the present invention is to provide a sleeve which is hardly damaged by thermal shock at the time of pouring a molten metal.

[0009]

The sleeve for a die casting machine according to the present invention has a C content of 0.07% by weight or less and a Si content of 1.0% or less.
0 wt% or less, Mn: 1.0 wt% or less, Ni: 3 wt%
% To 5 wt%, Cr: 15 wt% to 17.5 w
t% or less, Cu: 3 wt% or more and 5 wt% or less, Nb:
It is made of precipitation hardened stainless steel containing 0.15 wt% or more and 0.45 wt% or less, and is characterized in that its inner surface is subjected to nitriding treatment.

Alternatively, instead of the precipitation hardening stainless steel having the above composition, C: 0.09 wt% or less, Si:
1.0 wt% or less, Mn: 1.0 wt% or less, Ni:
6.5 wt% or more and 7.75 wt% or less, Cr: 16 wt%
% Or more and 18 wt% or less, and Al: 0.75 wt% or more and 1.50 wt% or less.

According to the sleeve for a die casting machine of the present invention, the sleeve is made of a precipitation hardening stainless steel (equivalent to SUS630 or SUS631: JIS-G-4303) having a relatively low thermal conductivity of about 20 W / m · K. Since it is composed, it is excellent in heat retention for molten metal. In addition, the above precipitation hardening stainless steel has corrosion resistance to molten metal such as aluminum,
Since it has high strength even at a high temperature, it can withstand a large thermal stress generated when the molten metal is poured.

Further, the above-mentioned precipitation hardening stainless steel can be increased in surface hardness by performing a nitriding treatment. Therefore, the abrasion resistance and the heat crack resistance of the inner diameter surface of the sleeve which is the sliding surface of the plunger can be improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sleeve for a die casting machine was manufactured in the following steps. a. A cylindrical member having a flange-shaped protrusion on the outer peripheral surface having the shape shown in FIG.
0.5 wt%, Mn: 0.7 wt%, Ni: 4.2 wt%
%, Cr: 16.8 wt%, Cu: 3.6 wt%, N
b: It is prepared by cutting using a SUS630 material having a composition of 0.3 wt% and subjected to solution heat treatment. However, at this stage, a grinding allowance (excess wall) is left on the inner diameter side.

B. After holding the above member at a temperature of 1040 ° C. for 2 hours, the member is air-cooled to perform a precipitation hardening treatment. c. A grinding process is performed on the inner diameter side of the above member to finish the shape shown in FIG.

D. The surface of the member is subjected to a nitriding treatment in an ion atmosphere to complete a sleeve. The sleeve manufactured according to the above process was attached to a cold-chamber die-casting machine, and a magnesium alloy was die-cast to prepare a personal computer case (1 mm thick). In this test, the following results were obtained.

A. The amount of hot water for die casting is
It is reduced by 38% compared to the sleeve made of KD61 alone. b. The casting defect of the product was reduced, and the non-defective product rate was improved by 16% as compared with the conventional sleeve made of SKD61 alone. c. For the above reasons, the cost per die-cast product is reduced by 20% as compared with the conventional sleeve made of SKD61 alone.

[0017]

According to the sleeve for a die-casting machine of the present invention, the heat retention of the sleeve is improved, so that the yield of die-cast products can be improved and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a view showing an example of the shape of a sleeve for a die casting machine according to the present invention.

Claims (2)

[Claims] C: 0.07 wt% or less, Si: 1.0
wt% or less, Mn: 1.0 wt% or less, Ni: 3 wt%
Not less than 5 wt%, Cr: not less than 15 wt% and 17.5 wt%
%, Cu: 3 wt% or more and 5 wt% or less, Nb: 0.1 wt% or less.
A sleeve for a die casting machine, comprising a precipitation hardening stainless steel containing 15 wt% or more and 0.45 wt% or less, and a nitriding treatment performed on an inner diameter surface thereof. 2. C: 0.09 wt% or less, Si: 1.0
wt% or less, Mn: 1.0 wt% or less, Ni: 6.5 w
t% to 7.75 wt%, Cr: 16 wt% to 1
8 wt% or less, Al: 0.75 wt% or more and 1.50 w
t% or less, comprising precipitation hardened stainless steel,
A sleeve for a die casting machine, wherein a nitriding treatment is applied to an inner diameter surface thereof.