First,after hot rolling, steel internal non-metallic inclusions (mainly sulfides and oxides, and silicate) is pressed into thin slices, delamination (interlayer) phenomenon. Layering the steel in the thickness direction of the tensile performance deteriorated significantly, and there may be an interlayer tears during weld shrinkage. Weld shrinkage induced local strain reaches the yield point strain often several times larger than the load caused by the strain.
Second, the residual stress caused by uneven cooling. The residual stress in the absence of external force internal self-equilibrium stress, hot-rolled steel sections have such a variety of residual stress, the greater the general steel-sectional dimension, the greater the residual stress. Although the residual stress from equilibrium, but still has some influence on the properties of steel members under loads. Aspects such as deformation, stability, fatigue, etc. are likely to have an adverse effect.
