A remarkable feature of wear-resistant plate thin strip continuous casting is that it has a very high cooling rate, usually the cooling rate is 102 ~ 103K·s-1, and the secondary dendrite spacing is between 5 ~ 50μm, which belongs to the category of sub-rapid solidification. Compared with traditional continuous casting, the solidification structure of thin strip steel is finer, the distribution of impurity elements is more uniform, and the size of non-metallic inclusions and precipitates is smaller, so the performance of thin strip has been significantly improved.
The production process of direct casting of near-final strip steel with a thickness of 1 ~ 5mm by continuous casting machine is called thin strip continuous casting or direct strip continuous casting. Thin strip continuous casting omits the hot rolling and intermediate heating processes in traditional strip production, and directly processes liquid metal into finished or semi-finished metal thin strip. Cold rolled sheet can be produced without hot rolling or slightly hot rolling (1 ~ 2 frames). Compared with the traditional sheet production process, it can significantly shorten the process flow, greatly reduce the product cost, and improve the product quality and performance.
In order to determine the formation and transformation behavior of residual ferrite during the solidification process of thin strip continuous casting AISI304 wear-resistant plate, the solidification structure and residual ferrite characteristics of thin strip continuous casting AISI304 wear-resistant plate were studied by means of color metallography, electrolytic erosion, electron backscatter diffraction analysis and X-ray diffraction analysis. The results show that the solidification structure of AISI304 thin strip is composed of three parts: surface cell crystal region, middle columnar crystal region and central equiaxial crystal region. The ferrite residue in the surface cell zone is rod-like, the ferrite residue in the columnar zone is fishbone, and the ferrite residue in the central isaxed zone is curved dendritic. The mass fraction of residual ferrite in the surface cell zone is 4.6% ~ 6.6%, that in the columnar zone is 3.6% ~ 3.7%, and that in the central equiaxed zone is 11.27% ~ 11.34%. The residual ferrite is distributed in a "W" shape along the thickness direction.
