Effects of trace elements on properties of 30CrMo steel

The addition of alloy elements has great influence on the properties of steel. The strengthening effect of alloying elements on 30CrMo steel under quenching and tempering is remarkable. W, Mo, V have remarkable effect on improving the heat hardness of steel, which can not only improve the ability to maintain high hardness at high temperature, but also improve the wear resistance of steel; Cr, W, Mo, AL, Si can improve the heat resistance of steel, and Cr can improve the corrosion resistance of steel.

30CrMo steel is a quenched and tempered steel. The alloying elements mainly affect the hardenability and tempering stability of the 30CrMo steel. The addition of alloying elements can improve the hardenability of 30CrMo steel and ensure that martensite is easily obtained during quenching. However, the effect of alloying elements on improving the hardness of martensite is very limited. The hardness of alloy steel and carbon steel is basically the same under the condition of obtaining martensite completely. On the other hand, alloying elements can also improve the tempering stability of 30CrMo steel, make the carbides precipitated during tempering more fine, uniform and stable, and keep the fine grains of martensite and high density dislocations to a higher temperature. Under the same conditions, alloy steel has higher strength than carbon steel.

In addition, some alloying elements can also cause secondary hardening of the steel and obtain good high temperature properties. When the martensite is formed by quenching, the dislocation density increases and the yield strength increases with the dislocation density. When martensite is formed, the austenite is divided into many smaller regions with different orientations, resulting in the effect equivalent to crystal refinement. Alloying elements in martensite also play a role of solid solution strengthening. Martensite is a supersaturated solid solution. Carbide precipitates during tempering, which greatly improves the toughness. The precipitated carbide particles can cause strong second phase strengthening.