Structure Formation in the Production of Sheet Steel by Continuous Casting and Deformation

Attention focuses on improving the quality of steel sheet for welded pipe. The main factors affecting sheet quality for thick-sheet mills are described. A possible approach to improving the quality of the steel sheet is to use continuous casting and deformation technology. The stress state of the steel in the cyclic deformation zone is determined. A prototype industrial system for continuous casting and deformation is used to produce 09G2S steel sheet. The associated stress in the cyclic deformation zone is determined for welded pipe. Experimental results for the prototype system are obtained. The microstructure is analyzed; the microhardness is determined; and the steel composition is analyzed in different sections of the strip cross section. The development of nonuniform structure in ferrite–pearlite steel is analyzed over the sheet thickness with thermomechanical treatment of steel in the mold. In the central light layer of the strip, ferrite microstructure is predominantly formed; meanwhile, the basic matrix is characterized by sharp decrease in carbon concentration. In the forging of low-carbon steel, similar structure may be seen in the first stage, when the excess high-temperature ferrite, which solidifies first, runs mainly along the center of the strip. The pearlite grains in the light layer are comparable in size with the pearlite grains in the basic metal. Deposits of rack morphology, which would increase the brittle failure, are not formed.