Surface quality of stainless steel type 304 cast by twin-roll type strip caster

For the development of strip casting technique for direct production of thin strips from molten metal, casting experiments of SUS304 steel is made in a twin roll strip caster. Longitudinal and transverse cracks and small depressions are the main defects appearing on the surface of directly cast strips. Water model experiments are applied to find the conditions for pouring the molten metal uniformly over the whole strip width and reducing the fluctuations of meniscus. By reduction of the fall height of pouring metal, optimization of pouring position and increase in the ratio of pouring rate to molten steel weight on the rolls, uniformity in the thickness of solidified shell is achieved and consequently occurrence of the longitudinal cracks and small depressions are decreased. In addition, the heat transfer coefficient between rolls and cast strip is determined from the measurements such as temperature changes in cooling water, temperature in the interior of rolls and on the surface of casting strips during casting. By using the measured heat transfer coefficient, optimum casting conditions are found for the completion of solidification at the kissing point of rolls to optimize the roll separating force on cast strips and thus for the prevention of transverse cracks.