Deformation Behavior and Grain Refinement during Multi-pass Hot Compression of Mn18Cr18N Steel

Abstract

The multi-pass hot compression experiment method was used to study the hot deformation behavior and recrystallization evolution of electro-slag-remelted (ESR) Mn18Cr18N steel deformed to the strain of 0.69 at the temperatures of 1373 K and 1473 K with a strain rate of 1 s⁻¹ and the interval holding time ranging from 3 to 10 s during three-pass, four-pass and five-pass compressions with the same reduction of per pass. The enveloping curves of peak stresses during the multi-pass hot compressions showed the strain cumulative recovery type or the strain cumulative softening type. The softening rate during the multi-pass hot compressions increased with the increase of temperature, per pass reduction and interval holding time. The elongated parent grains with a small amount of new DRX grains at the grain boundaries were generated at lower temperature during multi-pass deformation. Partially DRX recrystallized grains or fully DRX refined uniform recrystallized grains could be obtained with the increase of interval holding time and temperature, and both of them were mixed grains of dynamic recrystallization (DRX), static recrystallization (SRX) and meta-dynamic recrystallization (MDRX). The proportion of twins in the recrystallized grains was relatively high, indicating that the recrystallization mechanism during the multi-pass hot deformation of the ESR steel was dominant by twinning at a strain rate of 1 s^-1. A fully DRX refined uniform recrystallized grains with an average grain size of about 24 μm could be obtained when the sample deformed to 0.69 after four-pass compression at 1473 K with the interval holding time of 10 s.