Production practice shows that surface strengthening treatment is an important measure to improve the quality of die-casting molds and prolong the service life of the molds. Die-casting mold
1.Carburizing
Carburizing is currently the most widely used chemical heat treatment method in the machinery industry. Its process characteristics are: heating medium-low-high-carbon low-alloy mold steel and medium-high-carbon high-alloy steel mold in a carburizing active medium (carburizing agent), and heating it to 900 ° -930 ° C, so that carbon atoms penetrate into the surface Layer, followed by quenching and low temperature tempering, so that the surface layer and the core of the mold have different compositions, structures and properties.
2.Nitriding
The process of infiltrating nitrogen into the surface of steel is called nitriding of steel. Nitriding can enable mold parts to achieve higher surface hardness, wear resistance, fatigue performance, red hardness and corrosion resistance than carburizing. Because the nitriding temperature is low (500-570 ° C), the deformation of the mold parts after nitriding is small.
Nitriding methods include solid nitriding, liquid nitriding, and gas nitriding. At present, new technologies such as ion nitriding, vacuum nitriding, electrolytic catalytic nitriding, and high-frequency nitriding are being widely used to shorten the nitriding time and obtain a high-quality nitriding layer.
3. Nitrogen and carbonitriding
Nitrogen and carbonitriding is a low-temperature nitrogen and carbonitriding process (530 ° C-580 ° C) in which nitrogen and carbon are simultaneously infiltrated in a medium containing activated carbon and nitrogen atoms. The nitrocarburizing layer has less brittleness, and the nitriding time is much shorter than the nitriding time. After nitrocarburizing, the die-casting mold can significantly improve its thermal fatigue performance.
The harsh working conditions require the die casting mold to have good high temperature mechanical properties, cold and hot fatigue resistance, liquid metal erosion resistance, oxidation resistance and high hardenability and wear resistance. Heat treatment is the main factor determining these properties.
The heat treatment of the die-casting mold is to change the microstructure of the steel, so that the surface of the mold obtains high hardness and wear resistance, while the core still has sufficient strength and toughness, and at the same time effectively prevents molten metal from sticking and eroding. Selecting the right heat treatment process can reduce scrap and significantly increase mold life.
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