Application status of automobile niobium steel sheets in China

Nb microalloyed hot and cold rolled steel sheets are used in the automobile industry. With the development of metallurgical industry in China, the research on Nb alloyed steel began in the 1960s and numerous Nb steel grades have been developed after the 1980s. Hot rolled Nb alloyed steel sheet grades are mainly used according to the following specifications: QSTE340TM - QSTE500TM (Nb-Ti) for structural applications, 420L - 610L (Nb) for beams, RCL420(Nb) for wheels, DP steel RS50, 490SXR, 540SXR, 440QZR and 480QZR (Nb) for drive tubes, etc. Through precipitation and grain refinement, higher strength, excellent ductility, and stable performance has been achieved for hot rolled Nb alloyed steels. Therefore, these steel sheets have been widely applied in the Chinese automotive industry since the 1990s. The production of interstitial free steel (IF steel) started in the 1990s in China. Based on IF steel sheets, ULC-BH (Nb) and high strength IF steel (Nb-Ti) were produced by using Ti and/or Nb to fix the interstitials. Due to excellent deep drawing and extra-deep drawing properties, IF steel sheets have been applied in Chinese automotive industry. Another application for Nb steel sheets is cold rolled high yield strength steel sheets (Nb). This paper introduces the categories, properties andapplication of Nb alloyed steel sheets in the Chinese automotive industry. (AU)