Study On Solute Migration Of Stainless Steel Continuous Casting Slab During Rolling Process By Original Position Statistic Distribution Analysis Technique

The cooling process of stainless steel continuous casting slab is from outside to inside. Since the center temperature is higher than the edge, some of the low melting point and inclusion elements are easily enriched in center line, forming segregation band. The application of electromagnetic stirring technology can effectively prevent the center segregation. At the same time, however, the white band is usually also accompanied, causing the nonuniformity of partial microstructure and chemical composition. The existence of this segregation can affect the performance of steels and cause the surface defect during the rolling process. Therefore, it is highly concerned by researchers of metallurgical process to study on solute migration of stainless steel continuous casting slab during rolling process in order to realize the optimizing of metallurgical process and control the quality of products.In this thesis, combined with hot-rolling and cold-rolling technology stinless steel, the solute states and distribution rules of continuous casting slab with200mm thick are studied by spark discharge atomic emission spectrometric original position statistic analysis technology; based on researching the assembled certificated reference materials and ensuring the stability of signals, the solute states and distribution rules of hot-rolled sheet with3mm thick and cold-rolled sheet with1mm thick are studied by laser ablation-inductively coupled plasma mass spectrometry original position statistic analysis technology. Combined with microscopic analysis techniques, it is the first time to study the rules of distribution and migration of the solute, formation and evolution of white band, and evolution of inclusions.1) There is a ringlike segregation band in the cross-section of stainless steel continuous casting slab. The distributions of C, Ti and Si in this segregation band are negative segregation band, while the distributions of Al and Ca in the white band gathering show serious positive segregation. It corresponds exactly to the white band in macroscopic structure and morphology and caused by electromagnetic stirring.2) The number of Al inclusion in white band is more than the number of that in central part. The proportion of Al-Ca inclusion in white band is higher, while the proportion of pure Al-0inclusion in central part is higher; the proportion of the inclusion with small particles in white band is slightly more, while in central part the inclusions with large particles is slightly more.3) After rolling process, the slabs are squeezed and deformed accompanied with the change in position of segregation band and refining of inclusion. The discontinuous punctiform or zonal segregations are formed and transfer to the follow-up products. The segregations are improved to some extent, but cannot eliminate completely.4) From slab to hot-rolled sheet and cold-rolled sheet, the proportions of Al-Ca (Mg) inclusion decrease and the proportion of Al-0inclusion increase. Meanwhile, the proportions of the inclusion with small particles increase greatly and the inclusions with large particles decrease somewhat. The average particle size of Al inclusion decreases successively from slab to hot-rolled sheet and cold-rolled sheet.