Heat treatment of carbon spring steel
The annealed state spring steels for manufacturing coil springs are 65, Ø, 75, and 85 steel. This type of material has relatively poor hardenability, easy to crack, easy to decarburize, etc., and are often used to make spring washers, leaf springs and other unimportant springs. Springs with a diameter of less than 15mm can be hardened in oil. The heat treatment process and mechanical properties of the retired carbon steel are shown in Table 1.
Table 1 Heat treatment process and mechanical properties of 65, 70, 85 steel
Quenching temperature/℃ Hardness after quenching Tempering temperature/℃
Elastic Modulus
Shear modulus
Steel number 200 300 400 500
And cooling medium HRC tempered hardness HRC E/MPa G/MPa
65 800-830 Oil or water >60 58 54 44 36 205800 79184
70 790～825 Oil or water >61 59 55 45 38 196000 78792
85 780-820 Oil or water >62 60 56 46 39 191100 78400