High Temperature Plasticity of X65 Grade Cu-bearing Pipeline Steel

The high temperature tensile test of X65 grade low carbon low nickel Cu-bearing pipeline steel containing 1.8wt% copper and 1.0wt% nickel was carried out with Gleeble-3800 thermal simulation testing machine to study the high temperature plasticity at different temperatures (850-1 300℃). The results show that the tensile strength of the Cu-bearing pipeline steel showed an overall downward trend with increasing test temperature; the tensile strength at 850℃ reached 105 MPa, while the tensile strength at 1 300℃ was reduced to about 30 MPa. With increasing test temperature, the percentage reduction of area of the Cu-bearing pipeline steel showed an overall increase trend. When the test temperature was higher than 1 050℃, the percentage reduction of area was above 80%, showing good high temperature plasticity; the percentage reduction of area at 850-1 000℃ was about 60%, indicating the large deformation of the pipeline steel should be avoided in the range of 850-1 000℃. When the test temperature was higher than 1 050℃, the improvement of plasticity was related to dynamic recrystallization. In the continuous casting temperature range (1 100-1 250℃), the Cu-bearing pipeline steel had excellent high temperature plasticity, which could ensure the metallurgical quality of the continuous casting billet.