A study on HAZ’s microstructure and grain size of 10CrNi3MoV steel

This paper deals with microstructure and grain size of HAZ of 590 MPa high strength ship-structure steel with welding simulator. While t 8/5 time is short, 10CrNi3MoV steel’s microstructure of coarse grain heat-affected zone (CGHAZ) is lath martensite structure and a small amount of twined martensite structure; while t 8/5 time is long, it is mainly granular bainite structure. After second thermal cycle with peak temperature between critical temperature Ac 1′ and Ac 3′, CGHAZ has the inheritance of coarse grain and coarse microstructure. Welding energy input (determined by t 8/5 time) has an effect on the inheritance of coarse microstructure, but no influence on the inheritance of coarse grain. In detail, with a shorter t 8/5 time, there is an inheritance of coarse microstructure and grains. With a longer t 8/5 time, there is only the inheritance of coarse grains. While t 8/5 increases, the scope of temperature of causing it diminishes. Therefore, the inheritance of coarse microstructure connects with the high speed of heating and cooling.