Prevention method of deformation First, in the heat treatment of forgings, the parts to reduce deformation should be placed vertically as far as possible, vertically on the furnace bottom, supported by two horizontal points, and the fulcrum position should be between one third and one quarter of the total length, and horizontally placed on the heat-resistant steel fixture. Secondly, in the cooling process of parts, the type of quenching medium, cooling performance and hardening ability are all related to deformation. The change of cooling performance can be adjusted by changing the viscosity, temperature, liquid level and pressure of the medium, using additives and stirring. The higher the viscosity and temperature of quenching oil, the smaller the elliptical deformation. At rest, the deformation is very small. The following methods can effectively reduce deformation: ① salt bath quenching; ② high temperature oil quenching; ③QSQ method; ④ decompression quenching; ⑤ Three-stage quenching in one pot. Salt bath quenching is similar to high temperature oil quenching, which is quenched at martensite transformation temperature, which increases the uniformity of martensite transformation. QSQ is double liquid quenching. Vacuum quenching is to prolong the steam film stage by reducing the surface pressure of quenching medium, and the cooling speed in high temperature area is reduced, so that the cooling speed of each part is uniform. One-pot three-stage quenching has simple structure. Firstly, the parts are oil-cooled from the quenching temperature to a temperature slightly higher than the Ms point, then taken out of the furnace and placed in the atmosphere to make the whole temperature of the parts uniform, and then oil-cooled to make the martensite transformation uniform and the deformation irregularity greatly improved.