JPH08232057A - Production of die cast member - Google Patents

Abstract

PURPOSE: To provide a die cast member with required toughness and hardness by thermally spraying the surface of a die cast steel member with a self-fluxing thermal spraying alloy, heating and holding the member in an austenite region, hardening it by means of forced cooling, and then applying tempering treatment. CONSTITUTION: The surface of a die cast steel member, to be a base material, is thermally sprayed with a self-fluxing thermal spraying material such as Ni-base alloy. This die cast steel member is heated and held in the austenite region, by which the adhesion between the thermally sprayed thermal spraying material and the base material of the die cast steel is improved. Subsequently, quick cooling by forced cooling is applied to perform hardening treatment, by which the adhesion of the thermal spraying alloy is improved and also the hardness of the die cast steel is improved. Then, tempering treatment is done to improve toughness. By the formation of the self-fluxing thermal spraying alloy, the wear resistance and oxidation resistance of the die cast steel member can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die used in die casting and a method for producing a die casting member including a plunger sleeve, a plunger tip, a core pin and a sprue, and more particularly to a method for manufacturing a die casting member. The present invention relates to a method for manufacturing a die casting member suitable for use in a portion to be subjected to heat or a portion to which a severe heat cycle is applied.

[0002]

2. Description of the Related Art Generally, a die-cast steel member such as a die-casting die is brought into contact with a molten metal during casting, so that a large heat change is caused from a low temperature to a high temperature and from a high temperature to a low temperature. Therefore, it is necessary that the die cast steel member has excellent molten aluminum resistance, high temperature wear resistance and oxidation resistance. However, a normal die cast steel member cannot secure sufficient wear resistance and oxidation resistance during use.

Therefore, it is effective to improve the molten aluminum resistance, wear resistance and oxidation resistance by subjecting the surface of the die cast steel member that comes into contact with the molten metal to a film forming treatment such as thermal spraying. In addition, the inventors of the present application
It was found that a particularly excellent film can be formed by self-fluxing thermal spray, which is a seed.

The following methods have been adopted as means for forming a sprayed coating of a self-fluxing alloy on the surface of die steel.

First, a self-fluxing spray alloy is sprayed on a substrate,
Then, in order to improve the adhesion and close the pores in the film, the substrate is subjected to a heat treatment. In this case, for example, when the self-fluxing alloy is a Ni-based alloy, 1
Heat treatment is performed at a temperature of 070 to 1090 ° C. After that, the substrate is cooled in the furnace to a temperature of 500 to 600 ° C. and then cooled by cooling.

[0006]

However, in this method, the structure of the die steel mainly composed of the martensite structure is transformed into the ferrite pearlite structure or the like by the gradual cooling after the above heat treatment. Due to this transformation, the toughness and hardness are significantly reduced, and the toughness and hardness required for the die cast steel member cannot be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a die-cast member capable of maintaining toughness even when subjected to self-fluxing treatment.

[0008]

A method for manufacturing a die cast member according to the present invention comprises a step of spraying a self-fluxing sprayed alloy on the surface of a die cast steel member, and a step of heating and holding the die cast steel member in an austenite region, After the die-cast steel member is forcibly cooled and hardened, a tempering process is performed.

Further, it is preferable that the quenching treatment is a forced cooling of the die-cast steel member with air or gas. Further, the gas is preferably an inert gas selected from Ar, N ₂ and CO ₂ .

[0010]

The present inventors have found that even if a self-fluxing alloy is sprayed on a die-cast steel member as a base material and then subjected to self-fluxing treatment by heating, it has wear resistance and oxidation resistance and toughness. Various experimental studies were conducted to develop a die-cast member that would not be damaged. As a result, the inventors of the present application noted that the heating temperature in the self-fluxing treatment is close to the quenching temperature of the die-cast steel member, and the quenching treatment is performed by cooling after the self-fluxing treatment as forced cooling, and then the tempering treatment is performed. ,
It has been found that a self-fluxing sprayed alloy can be formed on the surface without losing the toughness of the base material. That is, in the present invention,
The die cast member is manufactured by the following steps.

First, a self-fluxing spray alloy is sprayed on a die steel, which is a base material. Then, heat treatment is applied to improve the adhesion between the sprayed sprayed alloy and the die steel.

Generally, when the thermal spraying alloy is a Ni-based alloy, the heat treatment temperature applied after the thermal spraying of the die steel is 1
070 to 1090 ° C, while the quenching temperature of conventional die steel is 1030 to 1050 ° C.

As described above, since the respective temperature ranges are extremely close to each other, after heating to the temperature of the self-fluxing treatment, quenching treatment is performed by quenching by forced cooling and the adhesion of the sprayed alloy is improved. The hardness of the die steel can be improved.

That is, in this series of heat treatment, the die steel becomes austenite-based by heating the die steel at the temperature of the self-fluxing treatment, and thereafter, the die steel is forcibly cooled rather than gradually cooled to obtain high hardness. It transforms to the martensite structure that it has.

However, as it is, the die steel has a high hardness, but becomes extremely brittle, so at least 1
It is necessary to improve the toughness by performing tempering treatment more than once.

When the die cast steel member is forcibly cooled, it is possible to blow air or gas onto the die cast steel member. In addition, as the gas, Ar,
It is also possible to use an inert gas such as N ₂ or CO ₂ .

Further, the formation of the self-fluxing sprayed coating in the present invention can be applied regardless of the type of die cast steel member as long as the heating temperature at the time of self-melting treatment is near the quenching temperature of the die cast steel member as the base material. It is possible.

The base material in the present invention is not limited to die steel, but can be applied to die cast steel members made of alloy steel that can be quenched and tempered.

[0019]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples that depart from the claims of the present invention.

FIG. 1 is a schematic diagram showing a heat treatment pattern in which the horizontal axis represents time and the vertical axis represents heat treatment temperature. Further, FIG. 1 (a) shows a heat treatment pattern of the present invention, and FIG. 1 (b) shows a heat treatment pattern in a conventional self-melting treatment.

In this embodiment, after a self-fluxing sprayed coating was formed using SKD61 steel as a substrate, a heat treatment pattern (a) of this embodiment shown in FIG. 1 and a conventional heat treatment method (b) of self-fluxing treatment were used. 2 types of heat treatment were performed. That is, in Examples and Comparative Examples, after spraying the sprayed alloy on the substrate, 10 ° C
The substrate is heated at a heating rate of 10 / min to 1070 ° C.
After reaching the temperature of 90 ° C., it was kept for 1 hour.

Thereafter, as shown in FIG. 1 (a), in this embodiment, after the substrate is rapidly cooled by forced cooling, 550 and 60 are used.
Tempering was carried out at a temperature of 0 ° C. for 3 hours.

On the other hand, in the comparative example, as shown in FIG.
Furnace cooling at a cooling rate of 80 ° C./hour, the substrate temperature is 5
After the temperature was lowered to 00 ° C, cooling was performed at a cooling rate of 100 ° C / hour.

The base material hardness and impact value of Examples and Comparative Examples by the above heat treatment are shown in Table 1 below. The toughness is JI
The impact value was measured using a U-notch Charpy test piece of S specification No. 4, and a Ni-based alloy containing WC was used as the thermal spraying alloy.

[0025]

[Table 1] As shown in Table 1 above, the base metal hardness of the substrate according to the method for manufacturing a die cast steel member according to the embodiment of the present invention is three times or more than the base material hardness of the substrate according to the conventional heat treatment method. The impact value was 4 times or more.

[0026]

As described above, according to the present invention,
By forming a self-fluxing sprayed alloy, it is possible to improve wear resistance and oxidation resistance of a die cast steel member, and to manufacture a die cast member capable of maintaining toughness even when subjected to this self-fluxing treatment. You can

[Brief description of drawings]

FIG. 1 is a schematic view showing a heat treatment pattern (a) of the present invention and a heat treatment pattern (b) in a conventional self-fluxing treatment.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C21D 1/18 C21D 1/18 X 9/00 9352-4K 9/00 Z C23C 4/06 C23C 4/06

Claims (3)

[Claims] 1. A step of spraying a self-fluxing alloy on the surface of a die-cast steel member, a step of heating and holding the die-cast steel member in an austenite region, and a tempering treatment after the die-cast steel member is forcibly cooled and quenched. A method of manufacturing a die casting member, the method including: 2. The quenching treatment is performed by using air or gas,
The method for manufacturing a die cast member according to claim 1, wherein the die cast steel member is forcibly cooled. 3. The method of manufacturing a die casting member according to claim 2, wherein the gas is an inert gas selected from Ar, N ₂ and CO ₂ .