THE INFLUENCE OF HEAVY REDUCTION ON THE QUALITY OF HIGH PERFORMANCE BUILDING Z STEEL CASTING BILLET AT THE END OF CONTINUOUS CASTING MACHINE
In order to solve the problem of center segregation inside the slab and low pass rate of plate inspection(below 80％),HBIS Group Tangshan Heavy Plate Co Ltd.implemented heavy pressure technology in the 10# and 11# sector position of 280 mm × 1 800 mm slab continuous casting machine,and the total pressure reduction reached 24 mm.In the production of high performance builiding Z steel,the density of the slab was increased.The center segregation is obviously improved,and the grain size of the billet is obviously refined with the increase of the reduction amount.This study analyzed the effect of heavy pressure on the internal quality of slab continuous casting through macroscopic and metallographic analysis,as well as experiments on carbon segregation index,density,and true density of the billets.The experimental results show that with the increase of reduction,the central segregation and porosity of the billet gradually improve,and the low magnification C-grade product rate increases from 85％to 98％;The microstructure of the continuous casting billet also undergoes grain refinement,which has a significant grain refinement effect;When the central segregation of the billet is C-grade 1.0,the central carbon segregation index can be effectively controlled within 1.10;The overall increase in true density of the casting billet,with a 0.17％increase in true density at the center of the billet under heavy pressing process;Grade C≤0.5,with a proportion of ≥98％;The comprehensive proportion of C-grade segregation rate(≤0.5 grade ratio)in the center of the billet reaches 92.9％.After the application of heavy reduction technology,the grain size of high performance building Z steel billet significantly refined with the increase of reduction amount,and the center segregation was significantly improved.
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