Static and dynamic tests of X70 pipeline steel

The toughness of X70 pipeline steel under low strain rate (static conditions) and impact (dynamic conditions) is tested at -60°C, -20°C and 20°C, respectively. By analyzing the load-displacement curve and fracture surface of specimens, the relation between mechanical behavior and loading rate is investigated. The results show that the toughness and the displacement at the peak load decrease with the fall of the test temperature; the displacement at the peak load of dynamic test is less than that of static test at the same temperature; the specimen thickness reduces in the front of notch and is related to the loading rate and the test temperature; the delamination crack that is perpendicular to the notch can be observed in both dynamic and static tests; the yield and peak loads of dynamic test are possibly independent of the test temperature; and both cracking and damage work increase with the test temperature. The relation between loading rate and damage work is relevant to the test temperature.