In the process of operation, wear-resistant castings can be effectively divided into two medium quenching, three medium quenching and so on by adopting its multi-medium quenching method. The dual medium quenching in wear-resistant castings is mainly to quench the well-heated wear-resistant castings into the medium with stronger cooling ability, when the temperature of the wear-resistant castings drops to the temperature below the austenitic isothermal transformation diagram, The microstructure of martensite can be obtained by quenching into the medium with weak cooling ability.
The cooling media used for quenching of wear resistant castings are water-oil, water-air, salt-oil, oil-air, salt-oil, oil-air, salt-air, alkali-air, water-nitrate, oil-nitrate, etc. Generally, it can be effectively selected according to the hardenability of wear-resistant steel, the shape and size of wear-resistant castings, and the requirements of deformation.
The water-oil quenching widely used in the production of wear-resistant castings is mostly used in its low-alloy wear-resistant steel castings during operation, even if its brine is used for rapid cooling in high-temperature areas to suppress the decomposition of undercooled austenite, When the temperature is below 400 ℃, the oil is transferred to slow cooling immediately in order to reduce the internal stress of quenching and prevent the quenching crack.
To some extent, the time that the wear resistant castings stay in the water oil medium is a very important parameter for double medium quenching. In the water oil medium, the residence time is too long, which becomes a single liquid quenching, which can not reduce the deformation and prevent cracking.
If wear-resistant castings are put into water-air medium prematurely, the cooling rate of wear-resistant castings is slow because the temperature of the castings is still high. The transformation of non-martensitic microstructure occurs during the cooling process, and the transformation cooling medium is generally determined by the composition, shape and size of the wear-resistant castings.http://www.wuxiorient.com/