Effect of Heat Input on Microstructure and Toughness of Coarse Grained Heat Affected Zone of Q890 Steel

Microstructure evolution and impact toughness measurement on a coarse grained heat affected zone (CGHAZ) of Q890steel have been investigated in this study by Gleeble 1 500 simulation technique. The results indicate that a relevant mediate energy input is recommended for welding of Q890 steel, according to a fact that an impact energy as high as 83 J is attained in the CGHAZ with t(8/5) of 20 s. It is related to the cumulative contribution of prior-phase bainitic ferrite separated martensite comprises interlocking structure of laths that can promote a sufficient subdivision of the block and finer effective grain size and the highest density of high angle boundaries. Higher heat input can result in brittle fracture in the CGHAZ since the stress concentration and triaxiality of the neighboring matrix are increased by the hard phase particles such as M-A constituents.