Danieli Advanced Cooling System (Q-Flow+) in Hot Strip Mills for AHSS HRC Production

摘要

India is one of the fastest growing markets for automotive industry and by 2020, it is expected that car production in the country is likely to be almost 8 million units requiring more than 7 million tonnes of automotive steel. The major automotive steel producers in India are Tata Steel, JSW, POSCO with Bhushan Steel, supplying some quantities of automotive steel to car manufacturers located in Northern India. SAIL and ArcelorMittal are planning for a joint venture 1.5 mtpy plant, which may start production in 2019-20. But, there is a lot more space for new plants to come up in order to meet the demand of 7 million tonnes by 2020. Top steel companies in the country are, therefore, increasing their manufacturing capacity of automotive steel to entrench themselves in the auto segment and several have roped in foreign partners for the high-technology products needed. The main target of all auto manufacturers is to reduce the weight of the car by using lighter but stronger steel, which resulted in the development of Advanced High Strength Steel (AHSS). AHSS are complex, sophisticated materials, with carefully selected chemical compositions and multiphase microstructures resulting from precisely controlled heating and cooling processes. Various strengthening mechanisms are employed to achieve a range of strength, ductility, toughness, and fatigue properties. These steels are not the mild steels of yesterday - rather they are uniquely lightweight and engineered to meet the challenges of today's vehicles for stringent safety regulations, emissions reduction, solid performance, at affordable costs. The metallurgy and processing of AHSS grades are somewhat different from the conventional steels. All AHSS are generally produced by precisely controlling the cooling rate from austenite or austenite plus ferrite phase. This is done either on the run-out table of the Hot Strip Mill (for HRC) or in the cooling section of Continuous Annealing Furnaces of CAUCGL for cold rolled or zinc coated products. In this paper, we will briefly discuss about the cooling models developed by Danieli for the Laminar Cooling Section of Hot Strip Mills to produce AHSS grades like Dual Phase (DP), Transformation-Induced Plasticity (TRIP) and Martensitic (MS) steels.