Main causes of subsurface bubble formation in A36 steel plate

The subcutaneous bubble defects on the edge of A36 steel plate were analyzed by means of optical microscopy and scanning electron microscopy. The production of subcutaneous bubbles is mainly caused by the water bubbles in wet raw materials which are brought into molten steel to produce hydrogen bubbles. Subcutaneous bubble defects of A36 steel plate were effectively controlled by adding lime for refining ahead of time, prolonging refining and net blowing time. By controlling the deformation, rolling temperature and cooling of A36 steel plate, the mechanical properties of A36 steel plate can be achieved. The trial rolling results show that the yield strength, productivity and weldability of A36 steel plate meet the relevant standards and are worth popularizing and applying. Scanning electron microscope, energy dispersive spectrometer, optical microscope and electron probe were used to analyze the delamination and non-delamination of A36 steel plate after tensile test.

The results show that there are a lot of MnS and SiO2 inclusions in the center of the delaminated specimen and a wide ferrite band in the center of the delaminated specimen, which is the main reason for the tensile delamination of A36 steel plate. According to the analysis results, the improvement measures are put forward to reduce and eliminate such defects.