Features and super-tall building applications of niobium microalloyed 800 MPa high strength steel plates

Building height and span are increasing, requiring the application of high performance steels to withstand the increased loads and ensure a high level of safety and durability. HSA800 is a new Nb-microalloyed high strength steel plate for structural use in buildings developed by POSCO and RIST in 2011. It has upper and lower bounds for yield (Fy) and tensile (Fu) strength of 650-770 MPa and 800-950 MPa, respectively, with a yield ratio (Fy/Fu) limit of 0.85 so as to enhance the seismic resistance of structures. Microalloys such as Nb, V and Ti are added to provide grain refinement with thermomechanical control processing (TMCP) to increase the yield and tensile strengths of the base material. As a result of the use of TMCP, which allows a reduced carbon equivalent, good weldability is also attained. The HSA800 grade was first applied in the concrete filled tubular (CFT) columns of a nine-story research institute building in Seoul, South Korea. SA800 and HSA800 will also be applied in the Lotte World Tower, the first super-tall building in South Korea with a 555 m height when completed. Through the application of HSA800, the total weight of construction steel is reduced which also contributes to a reduction in CO2 emissions from the steelmaking production process. (AU) Copyright © 2015 Companhia Brasileira de Metalurgia e Mineração (CBMM) All rights reserved.