50# steel properties and application

50# steel is a medium carbon high-strength carbon structural steel with medium machinability, low cold deformation plasticity, poor weldability, no temper brittleness during heat treatment, but low hardenability. The critical diameter in water is 13 * 30mm, and there is a tendency to crack during water quenching. 50# steel is usually used after heat treatment such as normalizing, quenching and tempering, or high-frequency surface quenching.

Executive specification for 50# steel: GB/T 699

Chemical composition of 50# steel:
(Mass fraction,%) C 0.47-0.55, Si 0.17-0.37, Mn 0.50-0.80, P ≤0.035, S ≤0.035, Ni ≤0.30, Cr ≤0.15, Cu ≤0.25.

Mechanical properties of 50# steel:
Tensile strength σb (MPa): ≥630(64)
Yield strength σs (MPa)：≥375(38)
Elongation δ5 (％)：≥14
Section shortening ψ (％)：≥40
Impact energy Akv (J): ≥ 31 (4)
Impact toughness value α kv (J/cm2)：≥39(4)
Hardness: no heat treatment, ≤ 241HB; Annealed steel, ≤ 207HB
Sample size: 25 mm

50# steel is suitable for manufacturing mechanical parts with small dynamic load, impact load and good wear resistance requirements, such as casting gears, shaft collision discs, machine tool spindles, engine spindles, rolls, pull rods, tension spring washers, etc.