Effect of Separation on Strengths of Thermo-Mechanical Control Process Steel(Part 1)

摘要

Recently, Thermo-Mechanical Control Process (TMCP) type 50kgf/mm2-class high-tensile steel plates are used to welded structures such as large LPG-tank, ship-hull, etc. for higher efficiency and lower cost. But, in some cases, the occurrence of "separation" in TMCP steel plate becomes a problem. Last year, it became clear that the TMCP steel plate with high maximum separation index (SImax) was excellent in brittle crack propagation-arrest characteristic. In this paper, we had studied the effect of separation on the fracture toughness and fatigue strength of TMCP steel plates. To reiterate the results written in it, they are as follows. 1) The occurrence of separation in TMCP steel plate improve its fracture toughness. 2) The fatigue strength is influenced by the angle between fatigue crack direcion and ferritepearlite layers in the steel plate with separation appearance.