Effect of Quenching and Tempering on Strain-Fatigue Behavior of CT80 Grade Coiled Tube Steel

The specimens of CT80 grade coiled tube steel were treated at 950 ℃ quenching+550 ℃ tempering, and 950 ℃ quenching+650 ℃ tempering, respectively. By tests of axial low cycle fatigue, the fatigue properties of samples after different processes of quenching and tempering were compared. And the fracture morphology was analyzed. The results show that the processing techniques of 950 ℃ quenching and 650 ℃ tempering can improve the fatigue property of CT80 steel effectively. The fatigue cracks originated from the sample surface and had multi-fatigue source characteristic.