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Performance comparison between 40Cr and 42CrMo

- Dec 13, 2018 -

Performance comparison between 40Cr and 42CrMo

Both 40Cr and 42CrMo are commonly used as major material for screw barrels. Now, let's make these two materials clearer.

1. Performance characteristics of 40Cr steel

40Cr steel is medium carbon quenched and tempered steel and is one of the widely used steel grades.

40Cr steel has good hardenability, can be hardened to 28~60mm in diameter during water quenching, and can be hardened to 15~40mm in oil quenching. After quenching and tempering treatment, the steel has good comprehensive mechanical properties, and has good low notch sensitivity and low temperature impact toughness. After quenching and tempering, the steel is often subjected to surface induction hardening or nitriding treatment. When the hardness is 174~229HBS, the cutting performance is good, and the relative machinability is 60%. 40Cr steel is suitable for the manufacture of medium-sized molds.


The carbon content of 40Cr steel is kept at about 0.40%, which ensures the steel has good strength and toughness. The addition of Cr element is mainly to improve the hardenability of steel. When quenched and heated, the Cr element is completely dissolved in the austenite to improve the hardenability of the steel. After quenching, the Cr element solid solution strengthens the matrix structure and improves the tempering stability of the matrix structure. At high temperature tempering, part of Cr element diffuses from the matrix structure to the precipitated cementite Fe3C to form alloy cementite (Cr, Fe) 3C.


The main chemical composition (mass fraction) of 40Cr steel is: 0.37%~0.44%C, 0.17%~0.37%Si, 0.50%~0.80%Mn, 0.80%~1.10%cr, ≤0.035%P, ≤0.035%S.


The phase transition points are: Ac1770 ° C, Ac3805 ° C, Ms 328 ° C.


The initial forging temperature of 40Cr steel is 1100~1150°C, the final forging temperature is 800°C, and the size after forging is more than 60mm.


2. Performance characteristics of 42CrMo steel

42CrMo steel is medium carbon quenched and tempered steel, which is often used in the manufacture of large and medium-sized plastic molds.


Compared with 40Cr steel, 42CrMo steel has better performance than 40Cr steel, especially hardenability higher than 40Cr steel. After quenching and tempering treatment, 42CrMo steel has high fatigue strength limit and resistance to multiple impacts, and good low temperature impact toughness.


The main chemical composition (mass fraction) of 42CrMo steel is: 0.38%~0.45%c, 0.17%~0.37%Si, 0.50%~0.80%Mn, 0.90%~1.20j%Cr, 0.15%~0.25%Mo, ≤0.30% Ni, ≤0.030%P, ≤0.030%S.

The phase transition points are: Ac1730 ° C, Ac 3800 ° C, Ms 310 ° C.


The initial forging temperature of 42CrMo steel is 1130~1180°C, and the final forging temperature is 850°C. After forging, the diameter is above 50mm and needs to be slowly cooled.


The carbon content of 42CrMo steel is kept at about 0.42%, which ensures that the steel has good strength and toughness. The addition of Cr and Mo elements is mainly to improve the hardenability of steel. When quenching and heating, Cr and Mo elements are completely dissolved in austenite to improve the hardenability of steel. After quenching, the Cr and Mo elements solid solution strengthens the matrix structure and improves the tempering stability of the matrix structure. At high temperature tempering, some Cr and Mo elements diffuse from the matrix structure to the precipitated cementite Fe3C to form alloy cementite (Cr, Mo, Fe) 3C. In addition, the addition of Mo element can eliminate temper brittleness. The addition of a small amount of Ni improves the toughness of the steel.


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