Investigation on Improvement of Center Porosity with Heavy Reduction in Continuously Cast Thick Slabs

Abstract

The heavy reduction process of START (Solidification Terminal Advanced Reduction Technique) is developed mainly to improve the center porosity of slabs. According to the simulation results of heat transfer model, the distribution of solid fraction along the slab width can be equally divided into four parts, and the part in 1/4–1/8 width is the last solidifying region with the most serious porosity. START is implemented within two segments accounting for the uneven solidification. The heavy reduction is carried out in the first segment, which the optimum solid fraction ranges from 0.53 to 0.98 and the optimum reduction amount is 9 mm. The second segment is conducted with a 3 mm reduction amount to further improve the porosity of the slab from 1/4 to 1/8 width. Both the center porosity and segregation can be improved significantly by the START process, as well as the evenness of porosity and segregation along the slab width. In addition, the in‐strand Electro‐Magnetic Stirring (SEMS) is introduced to improve the internal cracks of slabs, and the results show that the cracks are greatly improved without deterioration of center porosity.