FEM Simulation and Industrial Validation of Void Closure in a Large Cross-Section Hot Rolled Low-Alloy Steel

摘要

Every steel ingot casting suffers from heterogeneities such as solidification shrinkage [primary & secondary shrinkage cavities] and central looseness with distributed pores as shown in Fig.l. The as-cast ingot exhibits varying degree of micro-segregation depending on the depth of the solidification layer and grain structure. Using high temperature mechanical deformation, the heterogeneous structure has to be broken down, porosities need to be well consolidated and grain structure has to be refined for quality wrought product. Small ingots are directly hot deformed by hot rolling in many steel plants to achieve the desired reduction in cross section. Hot rolling gives higher productivity and surface quality than hot forging. However, in hot rolling the plastic flow of metal is concentrated at the surface compared to its core. Hence, it is of greater importance to assess the extent of void closure and soundness in the hot rolling of the as-cast ingot steel. The lack of consolidation towards the core is detected usually in the final stages of quality inspection and may lead to rejection of the product after value addition.