Effects of continuous casting mould fluxes on reducing longitudinal and star cracks on a slab surface

In the continuous casting production of medium carbon steel (whose mass fraction of carbon is 0.09 % to 0.16 %)and high strength low alloy steel (whose mass fraction of Mn is 0.90 % to 1.40 %), flecks occurnng the most often are usuallylongitudinal and star cracks. In additional to the employment of a galvanized plate mould, two kinds of fluxes with specialproperties were studied and used to harmonize the conflicts between the function of heat transfer and lubncation. An industrialapplication revealed that the crystallizing temperature (To) and crystal ratio (R) of fluxes have a crucible effect on impeding theoccurrence of above defects on a slab surface. In the case of slab section (180 to 240) minx(1000 to 1400) mm and castingspeed Vc of (0.7 to 1.2) m/min, the optimized parameters of fluxes are Tc of (1170 to 1190) ℃, R of 80 % to 9.5 % formedium carbon steel, and Tc of (1100 to 11.50) ℃, plus R of 40 % to 60 % for high strength low alloy steel.