Hot Deformation Analysis of a 2 wt.-% Si Electrical Steel by Means of Torsion Tests
Steels with high amounts of silicon are used in electrical applications due to their low mangectoestriction, high electrical resistivity and reduced energy losses, but they exhibit poor formability. A fundamental study of the workability of such materials using torsion testing may help to understand and to optimise its production. Single deformation torsion tests were carried out on a steel containing 2 wt.-% Si in a temperature range of 800 to 1100°C and strain rates in the range of 0.01 to 2 s-1. A value of 299 kJ/mol was found for the apparent activation energy for hot working after applying the hyperbolic-sine equation to the mean flow stress (MFS) values computed from the test. Multiple deformation torsion tests under continuous cooling conditions were carried out in the same temperature range at strain rates from 0.2 to 1 s-1, the strain per pass and interpass time (determining the cooling rate) were varied. Different critical temperatures, which are of importance for processing this alloy, can be calculated from the dependence of MFS with the inverse absolute temperature; such a method was used to determine the temperature at which recrystallisation stops (Tnr). It was found that this temperature depends on strain rate, pass strain and interpass time. Results of the microstructure analysis of quenched samples are in good agreement with the values of Tnr.
T. Chandra, K. Tsuzaki, M. Militzer and C. Ravindran
P. Rodriguez-Calvillo et al., "Hot Deformation Analysis of a 2 wt.-% Si Electrical Steel by Means of Torsion Tests", Advanced Materials Research, Vols. 15-17, pp. 708-713, 2007