Research and Development of a Yield Strength 400 MPa Class Structural Steel Plate with Enhanced Weldability
A 400 MPa yield strength structural steel plate with enhanced weldability was produced by using advanced steel making technology and thermo-mechanical controlled processing technique. A microstructure consisting of acicular ferrite (3~8 μm) and polygonal ferrite was observed in the rolled plate, which exhibits a yield strength ≥ 420 MPa, tensile strength ≥ 560 MPa, elongation ≥ 26 % and charpy impact toughness ≥ 300 J at-40 °C. Three-wire flux copper backing submerged arc welding with heat input of 230 kJ/cm was applied to butt weld the 36 mm thick plate, and defect-free joint with satisfactory mechanical properties were produced. The coarse grain heat affected zone (CGHAZ) contains mostly intra-granular nucleated ferrite plus a few grain boundary ferrite and ferrite side plate, and shows charpy impact toughness ≥ 90 J at-40 °C. The enhancement impact toughness of CGHAZ resultant from high heat input welding is due to improvement of intra-granular ferrite formation induced by Ca and Ti containing oxides and sulphides.
B. Mishra, M. Ionescu and T. Chandra
Y. Zhang et al., "Research and Development of a Yield Strength 400 MPa Class Structural Steel Plate with Enhanced Weldability", Materials Science Forum, Vols. 783-786, pp. 1046-1052, 2014