Key Technology Research Of High-Medium Carbon Steel Produced By TSCR

Based on the characteristics of thin slab casting and direct rolling technology, the key technologiesof hot rolling high-medium carbon strip steel were studied, including the control of compositionsegregation and decarburization in surface, and the high precision rolling technique.1）The control techniques of composition segregation: researchs show the segregation along slabthickness of C and Mn and Cr and P and V improve when casting speed increases with the same degreeof superheat; while the segregation of C and Cr are aggravated with the increase of superheating degreeat the central section of Continuous casting billet. The interval time between adding carbon process andcalcium treatment is suggested to be more than5minutes, to decease composition fluctation in moltensteel and finished product. With these improvement, carben segregation index of high-medium carbonsteel investigated can be controlled below1.18, carben segregation index in finished product can becontrolled below1.1,better than carben segregation index1.5～2.0in traditional procedure.2）The control techniques of decarburization: Experiments indicate the decarburization depth relateto heating temperature and heating time, total rolling deformation and control cooling process afterrolling. The following processes should be adopted to diminish the decarburization depth:①Increasing the slab temperature before entering furnace, and heating the slab rapidly to decrease theheating time in furnace;②Decrease the heating temperature as far as possible;③Increasing the slabthickness to increase rolling reduce ratio；④Increasing the cooling speed after rolling. With theapplications of these processes, the single-face decarburization depth in high-medium carbon steel dropdown to60percent of the depth in traditional procedure, or even thinner.3）The control techniques of high precision rolling. The slab shape was well-control bydiminishing composition segregation and strenth heterogeneity, optimizing the cooling parameter tocontrol rolls’ temperature and thermal crown, and match rolls to decrease roll wear and extend rollingperiod. It was achieved that flatness is controlled below±10I and thickness tolerance is controlledbelow±25um to satisfy the precision requirement of hot rolling high-medium carbon steel strip.