GCr15 bearing steel bloom continuous casting dynamic soft reduction process

Abstract

The invention relates to a GCr15 bearing steel bloom continuous casting dynamic soft reduction process, which belongs to the technical field of metallurgical continuous casting and is used for solvingthe problems that the GCr15 bearing steel bloom continuous casting is easy to cause central segregation, central looseness, central parosity and other casting slab internal quality defects. The technical scheme is as follows: the reduction of a continuous casting soft reduction region is controlled through the change of central solid phase rate fs of a casting slab, and the relationship between the reduction of a soft reduction rack and the central solid phase rate of the casting slab is given out. The adoption of the soft reduction process of dynamic control can significantly reduce the central segregation of the GCr15 bearing steel casting slab, the central carbon segregation index of the casting slab is 0.95-1.08, and the average central segregation is 1.03; the process can also obviously improve the central looseness and the central parosity of the GCr15 bearing steel casting slab, the proportion of the central looseness of the casting slab which is not more than 1.0 grade is morethan 90%, and the central parosity is not more than 0.5 grade.

Description

technical field [0001] The invention relates to a continuous casting process, in particular to a GCr15 bearing steel bloom continuous casting dynamic soft reduction process capable of eliminating or reducing bloom center segregation, center looseness, center shrinkage cavity and other internal quality defects of the billet, which belongs to metallurgical continuous casting technology field. Background technique [0002] GCr15 bearing steel is a high-carbon chromium bearing steel with high carbon content and alloy content, large temperature changes in the solidification interval, long solidification gap length, and wide mushy zone, so it is easy to form serious central segregation during the solidification process, and in the later stage It is difficult to be effectively eliminated during heating and rolling. The existence of central segregation in high-carbon chromium bearing steel makes continuous casting bearing steel only suitable for ferrules but not rolling elements (b...

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Problems solved by technology

The above studies have played a certain role in solving the problems of GCr15 bearing steel center segregation, porosity, and shrinkage cavities, but there are still the following problems: (1) Electromagnetic stirring technology cannot effectively compensate for the solidification shrinkage of molten steel, and at the end of molten steel solidification When changing, the stirring position cannot be adjusted, which limits the realization of the process; (2) The light reduction of GCr15 bearing steel bloom continuous casting in the above reports belongs to "static light reduction", and "static light reduction" means light reduction The lower position, reduction amount and reduction rate are fixed during the continuous casting process, and the solidification end position of the slab is an important parameter to determine whether the soft reduction process is reasonable. Therefore, in the continuous casting casting speed, over When the heat, cooling intensity, etc. change, it is difficult to successfully reduce the center defects such as center segregation and center porosity of the continuous casting slab by using the static light reduction process

In addition, national patent 200710048924.9 discloses a dynamic light reduction process for continuous casting of heavy rail steel blooms, but because the carbon content and alloy element content of GCr15 bearing steel and heavy rail steel are very different, and the high temperature plasticity of GCr15 bearing steel is very Poor, the highest reduction of area at 1150°C does not exceed 60%, the high brittleness zone is 950-1050°C and 1250°C-melting point, GCr15 bearing steel is a steel with high carbon content, and the crack sensitivity is very strong, so this The dynamic soft reduction process proposed in the patent is not suitable for GCr15 bearing steel with high carbon content and chromium element that can improve the strength and hardness of the slab

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