Microstructural Evolution during Austenitization and Quenching of a 5% Cr Work Roll

Abstract

The effects of a slow heating rate and a long austenitizing time with various cooling rates on the carbide dissolution and phase transformations of a 5% Cr work roll steel was investigated based on actual austenitization and quenching conditions and a large roll size using transmission and scanning electron microscopy, dilatometry, and thermodynamic calculations. When the roll temperature reached the austenitization temperature of 1173 K, the dissolution of pre-existing carbides was nearly complete due to the slow heating rate of 100 K/h, indicating that the austenite matrix had an equilibrium chemical composition at 1173 K before quenching. After quenching at cooling rates ranging from 0.1 to 3.0 K·s⁻¹ along the radial direction of the roll, the core of the roll contained ferrite, pearlite, bainite and undissolved carbides, while the surface consisted of martensite and undissolved carbides.