RELATIONSHIP BETWEEN FLOW CHARACTERISTICS AND SURFACE QUALITY IN INCLINED TWIN-ROLL STRIP CASTING

Good surface quality is essential for the twin roll cast stainless ste el strip to be directly cold-rolled. Thus, surface quality of AISI 304 stainless steel is one of the main problems for the twin roll strip c asting process to be put into commercial production. The surface defec ts commonly appeared in the as-cast strip of twin roll process may inc lude longitudinal and transverse cracks or wrinkles as well as unevenn ess which is mainly caused by gas trapping and surface vibration of me niscus between the two rolls. In this study, a modeling software was a pplied to simulate the flow behavior of molten pool at quasi-steady st ate in inclined twin roll casting and to investigate the relationship between flow characteristics and surface quality of the produced thin strip. The flow characteristics was drawn from the calculated flow pat terns and then correlated to the surface quality of thin strips produc ed in an experimental easter under the same casting condition as the c alculations. Through this procedures, several correlations were then f ound. First, the surface wrinkles appeared on the thin strip when the pool levels were low. The problem was improved with a higher pool leve l due to less flow violence nor meniscus fluctuation. Second, the reci rculation with a large vortex occurring around the triple intersection point of the roll/melt/air three phases was the main cause for the sl ag and/or dress trapping. Third, by using a higher roll angle along wi th an inclined feeding position nearer to the lower roll, a much stabl e flow on the meniscus surface could be obtained.