Physico-chemical profile and corrosion mechanism of the failure grate bar from iron ore sintering process

Abstract

The grate bars are a critical and easily consumable component of the sintering machine, and the control of their corrosion is of great importance to reduce their consumption. This investigation focused on revealing the physicochemical profile of the failure sintering grate bar and the potential corrosion mechanism. The results showed that the superficial area of the failure grate bar consisted of the adhesive layer, corrosion layer, and metal layer from outside to inside. The adhesion layer is characterised by a loose structure, consisting of higher contents of alkali chloride salts and sulphate, which were the typical corrosive substances. The main components of the corrosion layer were Fe2O3 and Cr2O3; the metal layer structure was dense, which remained the original composition of the grate bar. Based on the characteristics of sintering flue gas, the potential corrosion mechanism was summarised into three main types: (a) high-temperature oxidation, due to the periodic exposure of the grate bars to the high-temperature sintering flue; (b) chlorine corrosion, due to the existence of HCl, alkali (heavy) metal chloride salts (KCl, NaCl, PbCl2) in sintering flue gas, which formed the adhesive layer of grate bars; (c) sulphate corrosion, due to the existence of high SO2 contents and sulphate in the flue gas. The research findings are important to guide the development of grate bar corrosion control technologies.