Hot Ductility Behavior of an 8 Pct Cr Roller Steel

摘要

The hot ductility of an 8 pct Cr roller steel was determined between 1173 K and 1473 K (900 A degrees C and 1200 A degrees C) at strain rates of 0.01 to 10 s(-1) through tensile testing. The fracture morphology was observed using scanning electron microscopy, and the microstructure was examined through optical microscopy and transmission electron microscopy. The dependence of the hot ductility behavior on the deformation conditions, grain size, and precipitation was analyzed. The relationship between the reduction in area and the natural logarithm of the Zener-Hollomon parameter (lnZ) was found to be a second-order polynomial. When lnZ was greater than 40 s(-1), the hot ductility was poor and fracture was mainly caused by incompatible deformation between the grains. When lnZ was between 32 and 40 s(-1), the hot ductility was excellent and the main fracture mechanism was void linking. When lnZ was below 32 s(-1), the hot ductility was poor and fracture was mainly caused by grain boundary sliding. A fine grain structure is beneficial for homogenous deformation and dynamic recrystallization, which induces better hot ductility. The effect of M7C3 carbide particles dispersed in the matrix on the hot ductility was small. The grain growth kinetics in the 8 pct Cr steel were obtained between 1373 K and 1473 K (1100 A degrees C and 1200 A degrees C). Finally, optimized preheating and forging procedures for 8 pct Cr steel rollers are provided. (C) The Minerals, Metals & Materials Society and ASM International 2015