Analysis of soft reduction on bloom internal crack by a strain model

Abstract

Soft reduction (SR) can effectively improve the strand centre quality by decreasing its porosity and segregation. However, it tends to cause internal crack defects in the bloom if an improper reduction amount or improper reduction zone is implemented on the strand. In this work, a two-dimensional non-steady solidification model and a strain model are established for 350 mm × 470 mm bloom casting. Using the strain model, the strain field for GCr15 bloom upon SR is calculated. Through the online SR test and macrostructure inspection of the cast blooms, the minimum centre solid fraction suitable for SR of the bloom is determined. The results show that the established strain model calculation agrees well with the practical bloom macrostructure inspection. Thus, with the strain model, one can calculate whether internal crack defects would occur, as well as determine the right reduction amount or proper reduction zone.