Vacuum heat treatment of 20CrMnTi steel

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20CrMnTi is a low carbon alloy steel with high mechanical properties, and the surface of the parts is carburized 0.7-1.1mm. After carburizing quenching and low temperature tempering, the surface hardness is 58-62HRC, and the core hardness is 30-45HRC. The process performance of 20CrMnTi is better, and its machinability is improved by normalizing after forging. In addition, 20CrMnTi also has good hardenability. Due to the influence of alloying element titanium, it is not sensitive to overheating, so it can be directly cooled and quenched after carburizing. And the carburizing speed is faster, the transition layer is more uniform, and the deformation after carburizing and quenching is small. It is suitable for manufacturing important parts that bear high-speed and medium-load, impact and friction. Therefore, it is more appropriate to select 20CrMnTi steel according to the working conditions of the gear. After carburizing at 910-940°C, quenching at 870°C, and tempering at 180-200°C, the mechanical properties have tensile strength ≥1100Mpa, yield strength ≥850Mpa, elongation ≥10%, area shrinkage ≥45%, impact toughness ≥680 , the hardness is 58-62HRC.

The composition table of 20CrMnTi alloy is as follows:

(1)20CrMnTi steel by adding Cr and Mn elements, mainly to improve the hardenability of the steel.

(2)20CrMnTi steel adding Ti element is mainly to refine the grain.

(3) When 20CrMnTi steel is quenched and heated, Cr, Mn and Si elements are completely dissolved in austenite to improve the hardenability of the steel. Ti element is pinned to austenite grain boundaries in the form of carbide TiC, preventing the growth of austenite grains.

(4) After quenching of 20CrMnTi steel, Cr, Mn, Si elements solid solution strengthen the matrix structure, and improve the tempering stability of the matrix structure.

(5) When 20CrMnTi steel is tempered at low temperature, some Cr and Mn elements diffuse from the matrix structure into the precipitated cementite Fe3C to form alloy cementite (Cr, Mn, Fe) 3C to improve its hardness. Alloy cementite (Cr, Mn, Fe) 3C and carbide TiC work together with the matrix structure to make the steel produce higher strength, hardness and wear resistance, while maintaining good toughness.

(6) 20CrMnTi steel has uniform carbon layer after carburizing or carbonitriding, excellent processing and heat treatment process performance, not easy to overheat, can be directly quenched after carburizing, and quenching deformation is small.

(7)20CrMnTi steel has excellent cutting performance after normalizing, the relative processing performance is 75%, and the surface roughness is low.

(8) Due to the addition of Cr and Mn elements, 20CrMnTi steel is prone to temper brittleness, so the tempering temperature must be strictly controlled, generally within the range of 180~200℃.

The technological process of 20CrMnTi pump gear:

Transformation point of 20CrMnTi steel/℃：

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