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.

Method to Investigate Mechanical Behavior of Steel Casting near Solidus Temperature

“…The conventional hot tensile (CHT) test after remelting the specimen has been widely used to determine the ZST, ZDT, as well as the mechanical properties of the solidifying steel. [ 3,21–23 ] In this method, the center part of a cylindrical sample, which usually has a diameter of around 10 mm and a length of around 100 mm, is heated by an induction coil or Joule‐resistant heater. The center part of the specimen is heated, melted, and solidified sequentially under a controlled thermal cycle.…”

Effect of Ordered Phases and Microstructures on the Iron Loss of 6.5 wt% Si Electrical Steel Quenched at Various Cooling Rates

“…However, the brittle ordered phases (B2 and D0 3 ), which can be easily formed in the rolling processes of 6.5 wt% Si electrical steel, result in the near-zero plasticity of the material at room temperature. [2][3][4] In recent years, a large amount of research [5][6][7][8][9][10][11][12] has reported that certain alloying elements can effectively reduce the quantity of ordered phases in this steel and improve its plasticity. Moreover, our previous studies have found that an addition of 0.5 wt% Cu could facilitates successful production of 6.5 wt% Si electrical steel sheets in a laboratory via warm rolling.…”