Seismic and fire resistant niobium-molybdenum-bearing long and plate products

The compelling need for development of higher performance steels for seismic and fire resistant steel applications is driven by the recent catastrophic earthquakes and/or tsunamis in Haiti, Peru, China and Japan. Current research and development projects throughout the world are focused on the development of a family of niobium-molybdenum-bearing S500 and S600 grades of bars, beams and plates with superior toughness, fatigue resistance, fire resistance, seismic resistance, reduced yield to tensile ratio variation within a heat of steel and overall superior performance. The engineered nucleation and controlled growth of complex nano-co-precipitation, containing Nb and Mo, contribute significantly to a mechanism that results in enhanced performance under seismic and/or fire environmental conditions. The successful high quality production of these Nb-Mo steels with higher strength and elongation behavior may require slight process metallurgy adjustments to the melting and hot rolling practices to consistently manufacture and initiate the optimum precipitate size, distribution and volume fraction of (Nb,Mo)(C,N) in these value added earthquake/fire resistant grades. Rebar, long product and plate producers, who intend to supply these earthquake and fire resistant steels, should incorporate the successful process metallurgy strategies and operating procedures exercised today in producing advanced high strength and toughness steels for automotive, pipeline and critical structural applications, such as fracture-critical beams, forging quality bars, ship plate and pressure vessels. (AU) Copyright © 2014 Companhia Brasileira de Metalurgia e Mineração (CBMM) All rights reserved.