The properties of 42SiMn are basically the same as those of 35SiMn steel, but the strength, wear resistance and hardenability are slightly higher, and the critical hardenability diameter of steel in water is 27.5 ~ 50mm；; The critical quenching diameter in oil is13 ~ 30 mm. Under certain conditions, the strength, wear resistance and hot workability of this steel are better than those of 40Cr steel, and the deformation resistance and scale formation are similar to those of 40Cr steel. This kind of steel is mainly used as surface hardening steel. Used to manufacture gear parts with medium speed and load for high frequency quenching and medium temperature tempering; Under the conditions of high-frequency quenching and tempering at low temperature after quenching and tempering, it is used to manufacture large-section parts with high surface hardness and good wear resistance, such as spindles, shafts and gears. It can also be used to manufacture parts with medium speed and high load, such as gears, spindles, hydraulic pump rotors and sliders. After quenching, it is in a medium-low temperature tempering state. This steel can also replace 40CrNi steel.
The chemical composition of 42SiMn is as follows: