INFLUENCE OF CONTINUOUS BLOOM-CASTING MACHINE ON BLOOM STRUCTURE

摘要

Belarus Metallurgical Plant (BMP) specializes in the production of high-quality rolled bar, primarily for the auto industry. With improvement in machine components, the quality requirements on the steel increase, necessitating improvements in steel-production technology and equipment. To this end, the continuous bloom-casting machine at BMP, producing blooms of cross section 300 X 400 and 250 X 300 mm, was reconstructed in 1998. Innovations such as a mold with a chromium coating, an electromagnetic mixer, a new secondary-cooling system, and a control system for continuous casting permitted 1.5-fold increase in productivity, reduction in bloom rejection at ultrasonic monitoring, improvement in bloom macrostructure, and reduction in carbon, sulfur, and phosphorus liquations. However, reconstruction did not eliminate bloom rejection due to surface defects (primarily, longitudinal cracks) and macrostructural defects of liquation-band type. Moreover, the working life of the roller sections was reduced to 80-100 melts. To find means of improving metal quality, metallographic data were obtained for characteristic bloom defects in the most common steels (45, 45KhGNM), and the casting-machine operation was analyzed, with calculation of the loads arising in the bloom and the components of the equipment.