Influence of Carbon and Chromium on Mechanical and Hot Wear Properties of Multi-component White Cast Irons for Steel Rolling Mill Rolls

Abstract

Multi-component white cast irons are becoming increasingly popular as materials for rolling mill rolls due to its excellent wear resistance. In this research, influence of carbon (C) and chromium (Cr) contents on mechanical properties, hot wear properties and their correlation were investigated using Fe-5%Mo5%W-5%V-5%Co-Cr-C alloy. Martensitic matrix was obtained in a wide area with Cr content more than 5% and carbon-balance (Cba1) of :! 0.8%. Hardness was over 600HV. Ferrite or pearlite was formed in areas with low Cbal , and lamellar pearlite in areas with high Cba1 and low Cr. Austenite was found to partially remain in 1%C-I0%Cr iron. Macro-hardness and matrix hardness basically showed similar tendency and macro-hardness was higher than matrix hardness for pearlite matrix. The maximum tensile strength was 1006MPa in 1.5%C之.5%Criron. Low matrix hardness and a large carbide content decreased tensile strength. Compressive 0.2% proof strength showed a maximum value of 2.14GPa in 1.5%C司7.5% Cr iron. Hardness of above 600HV and chemical composition of more than 5% and Cr content -1 % to + 1 % Cbal content are desirable for achieving 0.2% proof strength necessary to withstand Hertzian contact stress in the finishing train of hot strip mill . Fracture toughness was high in high hardness areas and it decreases in cast irons with excess carbide and low matrix hardness. Wear resistance was basically better in cast irons with high hardness and high fracture toughness.