Hot Temperature Mechanical Behavior of High‐Permeability 6.5 wt% Si Electrical Steel in a Mushy Zone

Abstract

Twin‐roll strip casting (TRSC) technology is successfully applied to obtain 6.5 wt% Si electrical steel (6.5 wt% Si steel) in a laboratory platform, although there are problems in the strip surface quality control restricting further industrial applications of the TRSC. Hot temperature mechanical behavior in the mushy zone associated with the cracking susceptibility of 6.5 wt% Si steel is studied using the Gleeble‐3800 simulation system in the temperature range of 1350–1435 °C and a strain rate of 3 s−1. The characteristic temperatures including zero strength temperature (ZST) and zero ductility temperature (ZDT) are qualitatively determined, and the hot brittle temperature range in the mushy zone is further confirmed. Results indicate the tensile strength and ductility both increase with decreasing tensile temperature once the solidus fraction reaches a critical value. The ZST and ZDT in the mushy zone are determined to be ≈1427 and ≈1390 °C, respectively, and the hot brittle temperature range is 1390–1427 °C. The critical strain for internal crack generation in the hot brittle temperature range is estimated to be ≈0.24% on the basis of an empirical model developed by Y. M. Won. To reduce the cracking susceptibility of studied 6.5 wt% Si steel under TRSC, a rolling process is prohibited in the temperature range of 1390–1427 °C.