The role of various chemical elements in 15CrMo alloy steel

15CrMo alloy steel is a kind of seamless steel, and its performance is much higher than that of ordinary seamless steel. Because this kind of steel contains more Cr, its high temperature resistance and corrosion resistance are not comparable to other seamless steel pipes. Therefore, 15CrMo alloy steel is widely used in petroleum, chemical, electric power, boiler and other industries.

15CrMo alloy steel chemical composition (mass fraction) (%)

Grade	C	Si	Mn	Cr	Mo	Ni	B	V
15CrMo alloy steel	0.12~0.18	0.17~0.37	0.40~0.70	0.80~1.10	0.40~0.55	—	—	—

C, forming pearlite or dispersed precipitated alloy carbides in 15CrMo alloy steel can strengthen the steel and greatly improve the toughness and welding performance of 15CrMo alloy steel.

Mn, high Mn/C ratio is good for improving the yield strength and impact toughness of 15CrMo alloy steel. The change in the stress/strain characteristics of the 15CrMo alloy steel due to high manganese can offset the strength loss of the bauschinger effect.

Si, most low-alloy high-strength steels are not alloyed with silicon, but in hot-rolled ferrite-martensitic multiphase steels, silicon is an indispensable additive element.

Mo, 15CrMo alloy steel containing molybdenum (~0.15%Mo) has higher strength and higher toughness than traditional ferrite-pearlite steel. Molybdenum has an inhibitory effect on the pearlite transformation of steel during cooling.

Nb, V, Ti, adding 0.05 to 0.15% Nb (or V, Ti) to low-carbon manganese steel or low-carbon manganese-molybdenum steel has obvious grain refinement and precipitation hardening effects. Titanium forms sulfides in steel to improve the anisotropy of impact absorption and cold formability.

Rare earth elements (RE)，trace amounts (about 0.001%) of rare earth metals do not affect the strength of 15CrMo alloy steel pipes. Its main function is to desulfurize and prevent laminar tearing of steel.