HOT ROLLING COST REDUCTION: PREVENTING REJECTIONS AND REDUCING FUEL CONSUMPTION BY THE USE OF PROTECTIVE COATINGS

摘要

Protective coatings play a major role in increasing productivity and reducing costs in metal forming processes like hot rolling and heat treatment. Most of these coatings are pioneered in India by an experienced metallurgist from the Indian Institute of Technology. This technical paper presents details and successful case studies of three such protective coatings: Oxidation and decarburisation at high temperatures are caused during heating of billets or ingots for hot rolling and during heat treatment of rolled products. Scaling leads to enormous losses by way of rejections of produce, reduced yield and increase in expensive, time-consuming operations like acid pickling, grinding etc. Billets are often subjected to excessive heat in furnaces due to unplanned downtime of rolling mill. In such cases, high oxidation and resultant decarburisation may lead to rejection of entire heat. The need to control decarburisation and scaling is gaining much importance, especially in the case of expensive grades of steel and critical hot rolled products like rail steel and spring steel. Protective anti-scale coatings and decarburisation control coatings can be used to substantially reduce oxidation and control decarburisation during billet re-heating for hot rolling and heat treatment of rolled products. Recent developments in these coatings have made coating technique viable for most grades of steel.