Influence of niobium on the microstructure and properties of CrMo cast steel for liner plate

In this paper the influence of heat-treatment and Nb on the microstructure and properties of a low alloy CrMo wear-resistant steel lining plate were investigated. Based on an appropriate chemical composition design, excellent combinations of hardness and impact toughness have been achieved for the lining plate application. It was found that with a double heat treatment of 920 °C (8 h) + 550 °C (20 h), adding Nb in the range 0.025 to 0.028 wt.% improved the strength and hardness of the low alloy CrMo wear-resistant steel by 13% and 16% respectively, while the impact toughness was slightly reduced. With a heat treatment of 880 °C (8 h) + 550 °C (20 h), adding 0.03 wt.%Nb increased the strength and hardness of the low alloy CrMo wear-resistant steel by 10% and 16% respectively, while the elongation and reduction of area were raised from 2 to 4% and 0.5 to 2% respectively, and the impact toughness was only slightly reduced. Analysis of the microstructure after heat treatment revealed the interlamellar spacing of the pearlitic matrix after the higher temperature processing is smaller than it is after the lower temperature processing. (AU) Copyright © 2018 Companhia Brasileira de Metalurgia e Mineração (CBMM) All rights reserved