Delivery state and mechanical properties of 20CrMn alloy steel plate

20CrMn is a grade of alloy structural steel stipulated by the Chinese national standard. Unified digital code: A22202. Standard: GB/T 3077. 20CrMn is a carburizing steel, which can also be used as a quenched and tempered steel, and its hardenability is similar to that of 20CrNi. 20CrMn steel is used as shafts and connecting rods working at high speed and high bending load, gear shafts, gears, water pump rotors, clutches, small shafts and mandrels working at high speed and high load without strong impact load.

20CrMn alloy steel chemical composition mass fraction (%):
Carbon C: 0.17 to 0.23, Silicon Si: 0.17 to 0.37, Manganese Mn: 0.90-1.20
Sulfur S: Allowable residual content≤0.035
Phosphorus P: Allowable residual content≤0.035
Chromium Cr: 0.90-1.20
Nickel Ni: Allowable residual content≤0.030
Copper Cu: Allowable residual content≤0.030

Mechanical properties of 20CrMn alloy steel:
Tensile strength σb (MPa): ≥930(95)
Yield strength σs (MPa): ≥735(75)
Elongation δ5 (%): ≥10
Area shrinkage ψ (%): ≥45
Impact energy Akv (J): ≥47
Impact toughness value αkv (J/cm2): ≥59(6)
Brinell hardness: (HBS100/3000) (annealed or tempered at high temperature): ≦187

Delivery status of 20CrMn alloy steel: delivered with heat treatment (normalizing, annealing or high temperature tempering) or without heat treatment, and the delivery status should be indicated in the contract.

20CrMn alloy steel heat treatment:
Quenching heating temperature (℃): 850; Coolant: oil
Tempering heating temperature (℃): 200; coolant: water, air

Main features of 20CrMn alloy steel:
Carburized steel with high strength, toughness and good hardenability. The properties obtained after heat treatment are better than 20Cr. The quenching deformation is small, the low temperature toughness is good, and the machinability is good; but the welding performance is low. 20CrMn alloy steel is generally used after carburizing and quenching or quenching and tempering.