Application and heat treatment specification of 42CrMo alloy steel

42CrMo alloy steel has similar properties to 35CrMo steel. Due to the increase of carbon and chromium content, its strength and hardenability are better than 35CrMo alloy steel. After quenching and tempering, it has higher fatigue strength and multiple impact resistance, good low-temperature impact toughness, and no obvious temper brittleness. It is generally used after quenching and tempering.

42CrMo alloy steel is generally used to manufacture important parts with higher strength requirements than 35CrMo and larger section size, such as shafts, gears, connecting rods, gearbox gears, supercharger gears, engine cylinders, springs, spring clips, 1200-2000mm oil drill pipe joints, fishing tools and substitutes for quenched and tempered steel with higher nickel content.

Chemical composition (mass fraction) of 42CrMo alloy steel: C 0.38% - 0.45%, Si 0.17% - 0.37%, Mn 0.50% - 0.80%, Cr 0.90% - 1.20%, Mo 0.15% - 0.25%, Ni ≤ 0.030%, P ≤ 0.030%, S ≤ 0.030%.

Heat treatment specification for 42CrMo alloy steel:
Hot working specification
Heating temperature 1150 - 1200℃, starting temperature 1130 - 1180℃, ending temperature>850℃, φ> 50 mm, slow cooling.

Normalizing specification
The normalizing temperature is 850 - 900℃, and the furnace is air cooled.

High temperature tempering specification
Tempering temperature 680 - 700℃, air cooling after discharging.

Quenching and tempering specifications
Preheating temperature 680 - 700℃, quenching temperature 840 - 880℃, oil cooling, tempering temperature 580℃, water cooling or oil cooling, hardness ≤ 217HBW.

Specification for intercritical quenching
Quenching temperature 900℃, tempering temperature 560℃, hardness (37 ± 1) HRC

Specification for induction hardening and tempering
Quenching temperature 900℃, tempering temperature 150 - 180℃, hardness 54 - 60HRC.