Effect of Quenching Temperature on Microstructures and Mechanical Properties of Boron-Nickel-Added Nb-Treated HSLA H-Beams
To lower the fracture appearance transition temperature (FATT) of Nb-treated HSLA H-beams further, boron-nickel-added Nb-treated HSLA H-beams were tempered after they were quenched at 870, 910 and 950°C respectively. Microstructures and mechanical properties, especially low temperature toughness of the experimental steels were investigated by scanning electron microscopy (SEM), uniaxial tensile test and Charpy impact test (V-notch). The results indicate that the FATTs of quenched & tempered specimens are all below -70С and that of some specimens is even below -90°С . Tensile strength of all quenched & tempered steels and their total elongation value are above 570 MPa and 21 % respectively. It can be seen that dual-phase microstructure of ferrite and tempered martensite in steels leads to the best low temperature toughness, and carbides along grain boundaries are beneficial to low temperature toughness.
Jianmin Zeng, Taosen Li, Shaojian Ma, Zhengyi Jiang and Daoguo Yang
W. Xiao et al., "Effect of Quenching Temperature on Microstructures and Mechanical Properties of Boron-Nickel-Added Nb-Treated HSLA H-Beams", Advanced Materials Research, Vols. 194-196, pp. 165-168, 2011