Aluminum alloy die-casting mold maintenance method
In the process of using aluminum alloy die-casting molds, various problems often occur. How to maintain aluminum alloy die-casting molds can be solved by using aluminum alloy die-casting molds when problems occur.
It is well known that the use conditions of aluminum alloy die-casting molds are extremely poor. Taking an aluminum alloy mold and an aluminum die-casting mold as an example, the melting point of aluminum is 580-740 ° C, and when used, the temperature of the aluminum liquid is controlled at 650-720 ° C. Die-casting without preheating the mold, the surface temperature of the cavity rises from room temperature to liquid temperature, and the surface of the cavity is subjected to great tensile stress. When the top part is opened, the cavity surface is subjected to extremely large compressive stress. After thousands of times of die casting, cracks and other defects are formed on the surface of the mold.
Common inspection methods include corrosion inspection, metallographic inspection, and ultrasonic inspection.
(1) Corrosion inspection. Mainly check the porosity, hemiplegia, cracks, cracks, non-metallic inclusions, and hammer cracks and joints on the surface.
(2) Metallographic examination. Mainly check the segregation, distribution state, crystal grain size and intergranular inclusions of carbides on the grain boundary of the material.
(3) Ultrasound examination. Mainly check the defects and size inside the material.
In the case of severe erosion and cracking, the surface of the mold can be nitrided to improve the hardness and wear resistance of the mold surface. However, the hardness of the nitriding matrix should be 35-43HRC. When the temperature is lower than 35HRC, the nitrided layer cannot be firmly bonded to the substrate. After a period of use, the large piece will fall off: above 43HRC, it will easily cause the surface of the cavity to be broken. When nitriding, the thickness of the nitriding layer should not exceed 0.15mm. If it is too thick, there will be a phenomenon of falling off at the parting surface and sharp corners.