Performance requirements of aluminum alloy die casting die steel

According to the service conditions and common failure forms of aluminum alloy die casting die, the main performance requirements of steel for aluminum alloy die casting die are as follows:

1. High tempering resistance and cold and hot fatigue resistance.

A large number of aluminum alloy die-casting dies produced continuously shall maintain their high hardness under a certain temperature for a long time, and shall not stick to the die and produce oxide scale. Therefore, the die should have good oxidation resistance and tempering stability. The surface of aluminum alloy die casting die is repeatedly heated and cooled by high temperature, which expands and shrinks continuously, resulting in alternating thermal stress. When the stress exceeds the elastic limit of the die material, repeated plastic deformation occurs, resulting in thermal fatigue. Colleagues, when the die surface is corroded and oxidized by molten metal for a long time, it will gradually produce micro cracks. In most cases, thermal fatigue is the most important factor to determine the life of die-casting die.

2. Sufficient strength, hardness, plasticity and heat resistance.

Aluminum alloy die casting die is easy to deform and even crack under the action of high temperature, high pressure and thermal stress during molten metal injection. Therefore, die steel should have sufficient high temperature strength and toughness, high hardness and heat resistance at working temperature.

3. Good thermal conductivity.

The aluminum alloy die casting die is under the high temperature of 600 ~ 700 ℃ for a long time to ensure other properties. Must have good thermal conductivity.

4. Good resistance to molten metal damage.

With the large-scale die-casting machine, the die-casting pressure is also increasing, from 20 ~ 30MPa of low pressure to 150 ~ 500MPa of high pressure. High temperature and high pressure casting can produce obvious melting damage, and the mold should have great resistance to this. Therefore, the die material must have high temperature strength. With a small affinity for molten metal, the mold shows that the roughness is small, and is attached with appropriate protective layers such as oxidation mold and nitriding layer, but there is no decarburization layer.

5. Good hardenability and small heat treatment deformation.

The general manufacturing method of die-casting die is to carve the annealed die material into the cavity, and then heat treat to obtain the required hardness, or heat treat the die material to obtain the required hardness, and then carve the cavity. The manufacturing method of engraving the cavity first and then heat treatment has high hardness and strength, which is not easy to produce melting loss and thermal fatigue. No matter which method is used for heat treatment, it is necessary to obtain uniform hardness, so it is required to have good hardenability, especially carving the cavity before heat treatment. Materials with small heat treatment deformation should be used, which is particularly important for large molds.