Leaner alloy design for structural-grade hot rolled coils: Effects on rolling load, microstructure and process stability

A major integrated steel producer manufacturing structural-grade hot-rolled coils and plates observed significant challenges in rolling operations associated with richer chemistries containing higher levels of carbon and manganese. Elevated alloy content increased flow stress during deformation, resulting in higher rolling loads, greater mill energy demand, and a higher incidence of cobbles during thin-gauge rolling. To improve operational stability and overall process efficiency, a leaner chemistry route with reduced carbon and manganese content was developed and industrially validated. Production trials demonstrated a 16%–34% reduction in rolling load, accompanied by a 15-min decrease in average furnace residence time, contributing to enhanced productivity. Mechanical testing confirmed that the modified grade satisfied all specification requirements while exhibiting improved ductility and a cleaner ferrite–pearlite microstructure with lower inclusion density. Additionally, optimised alloy design enabled a reduction in multiple ferroalloys consumption by 2.11 kg per tonne of crude steel, resulting in annual cost savings exceeding Rs. 2.5 crore. These findings establish leaner chemistry as an effective and sustainable pathway for producing cost-efficient, high-quality structural steels while improving process robustness.