Comparison of Grain Size in Plain Carbon Hot-Rolled Sheets Manufactured by CSP and Conventional Rolling Processing

Average grain size and grain size distribution in as hot-rolled SPHC, SPHD, and SPHE sheets manufactured by compact strip production (CSP) processing and traditional continuous casting and rolling (CCR) processing respectively were investigated by quantitative metallographic method. The results show that the average grain size and distribution width of grain size in sheets manufactured by CSP processing was obviously larger than that by CCR processing. It was analyzed that multi-phase transformation and high reduction ratio in CCR processing resulted in refining grain size, which would be dominant reason for controlling grain size. In plain carbon steels such as SPHC, SPHD and SPHE, the effect of fine precipitation in CSP on behavior of deformation and recrystallization of austenite during rolling, and consequent refinement of grain size seem not to be as important as the effect of re-heating and roughing in CCR processing. Homogenizing in re-heating and refining grain size in roughing in CCR processing would refine final grain size and also make grain size homogenized. Very coarse grain size would result in mixed grain size, large distribution width of grain size due to interaction of static and dynamic recrystallization in CSP processing.