Test results showed that the creeps of spring of steel 44Si2CrV quenched + medium tempering and removed decarburized layer happened at room temperature as stress was higher than critical creep stress value

and the higher tensile or shear strength

the higher critical creep stress. The critical creep stress τ

cc

of steel 44Si2CrV quenched at 900 P and tempered at 500°C was 700 MPa

τ

cc

quenched at 900°C and tempered at 380 °C was 800 MPa. The plastic deformation speed was higher at creep beginning

then decreased abruptly. The creep stopped at certain stress for definite time. After loading for a long time and creep of spring stopped

as the spring was heated at 200 °C for 2 h air cooled

the free height of spring increased

and the creep of spring restarted again when it is loaded with original stress.