RELATIONSHIP BETWEEN THE TOUGHNESS AND FINE MICROSTRUCTURES OF M-A CONSTITUENTS IN RESTRAINED MULTIPASS TIG WELDED HAZS OF 15CrMoV BAINITIC STEEL

This paper studies the relationship between the toughness and fine microstructures of M-A constituents in the multipass TIG welding of 15CrMoV Steel under restrained and non-restrained conditions.It is found thai the restrained condition gives rise to better HAZ toughness,due to less M-A constituents,less twin martensite but more dislocation martensite in M-A constituents,higher dislocation density in ferrite and larger amount of V₄C₃ fine carbides precipitated from matrix.