Experimental and FE analysis of void closure in hot rolling of stainless steel

Casting metal products are characterized by undesired void defects due to the shrinkage occurring during the solidification of molten material. In order to deliver safe and sound components satisfying the customer requirements, these defects need to be reduced or if possible eliminated. Hot metal forming processes can be used for this purpose therefore, the calibration of their parameters is a fundamental task. In this paper a study of the void closure during hot rolling of 316L stainless steel slabs coming from continuous casting has been conducted. The effects of the hot rolling main parameters (i.e. percentage of reduction, cooling time, and side of reduction) on void closure index have been investigated by means of FE analysis. Data coming from experimental tests performed by Cogne Acciai Speciali S.p.a. were utilised to validate the model and the research results. A correlation between void closure indexes and the residual voids along the hot rolled slabs axis was found for AISI 316L stainless steel. Moreover, new geometric indexes depending on the rolling parameters were defined. Also in this case a correlation between these new indexes and the void closure was found.