Per: FELIPE BASTOS (CBMM), Zhang Weiqiang (Kunming Iron and Steel Group Co., Ltd.), Zhang Yongqing (CITIC Metal Co., Ltd), Guo Aimin (CITIC METAL CO., LTD), Leonardo silvestre (CBMM), Marcelo Rebellato (Eurosport-RMS)
Abstract:
This work reviews the new version of GB1499.2-2018 Chinese national standard and specifications governing production of high-strength reinforcing hot rolled ribbed bars. In addition, it discusses the main concerns from Chinese rebar makers that might affect production and application of Nb-bearing rebars, like reheating temperature required to dissolve given niobium additions, the promotion of bainite microstructure and continuous yielding, as well as Nb strengthening effects.
Through extensive investigation involving both thermomechanical simulation tests and industrial trial, the existing state and effects of Niobium along the reheating, rolling and cooling are illustrated. At the end, optimum processing conditions has been established to produce high strength rebars for the specified requirements. That reflected in an amount of about 20.0 million tons of Nb-bearing rebar being produced in China in 2018 with required tensile properties and microstructure, and helped rebar makers to reduce production costs considerably. Based on production data, Niobium demonstrated positive strengthening effect for high strength rebars, in particular for small size rebars with earthquake resistant performance. What is more, the results of the research enrich the knowledge of the application of Niobium in steels under no TMCP rolling conditions.
