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, expanding and shrinking, resulting in alternating thermal stress. When this stress exceeds the elastic limit of die material, repeated plastic deformation will occur, causing thermal fatigue.

At the same time, the surface of die is corroded and oxidized by molten metal for a long time, which 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 subject to high temperature, high pressure and thermal stress during molten metal injection, which is easy to deform and even crack. Therefore, die steel should have sufficient high temperature strength and toughness, high hardness and heat resistance at working temperature.

3. Good thermal conductivity

Aluminum alloy die casting die must have good thermal conductivity in order to ensure other properties under the high temperature of 600-700 ℃ for a long time.

4. Good resistance to molten metal damage

With the large-scale die-casting machine, the die-casting pressure is also increasing, which has been increased from 20-30Mpa at low pressure to 150-500mpa at high pressure. High temperature and high pressure casting can produce obvious melting damage, and the mold has great resistance to this.

Therefore, the mold material must have large high-temperature strength and 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, without decarburization layer.

5. Good permeability 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.