The Large Bloom Continuous Casting Secondary Cooling System Controlled Study

A bloom continuous Casting machine main cast quality steel and alloy steel, such as heavy rail steel, hard-line steel, spring steel, bearing steel, alloy structural steel, and other key species. Cooling slab is an important link in the process of the entire bloom continuous casting production, it has a direct impact on the quality and output of billet. The formation of billet internal cracks, surface cracks, the dark belly and centres segregation defects has close ties with cooling.Being a high-carbon steel, heavy rail steel of Pangang's major product has a poor thermal conductivity. while casting, a strong continuous casting slab cooling will increase the danger of the split; but cooling intensity inadequate will result in a bulging arising from the billet shell creep and form centre carbon segregation. And vanadiferous heavy rail steel also has strong crack sensitivity in the continuous casting process, because of the micro-alloy element——Vanadium——and Carbon, Nitrogen compounds form the precipitation to increase the brittleness of steel and to come into being the corner cracks in straightening process of slab. Therefore, how to determine a reasonable control of the cooling system becomes Pangang focus on the subject.In order to make target surface temperature appropriate in secondary cooling zones and to avoid the spray room temperature online, secondary cooling control system of the 2nd bloom caster has developed a dynamic computer control Methods. The system is based on the variation of temperature ductility of rail steel and the high-temperature heat transfer mechanism, and calculate the enthalpy along the direction of temperature, ultimately gain the surface temperature along the direction of flow and billet shell thickness, then adjuct and amend the cooling water by the spray control algorithm based on the difference between its temperature and the goals so that the surface temperature settings to achieve the best range.The secondary cooling control scheme suitable for rail steel ensures the billet internal quality and mechanical properties, and meets the requirements of follow-on products using billets. So far since 2006, billet pass rate reached 99.84%, billet surface without clearance rate of≥95%, the center porosity, the centre segregation, the centre cracks, and other indicators Merit, and the secondary cooling control scheme is for the 2nd billet caster production, efficiency and product development as well as technical and economic indicators of a substantial increase provided technical support.