Carbon extraction replica analysis was employed to measure the quantities and size distributions of particles in Ti-Nb
Microalloyed Steel', 1, 1605699)"; href="/tags/microalloyed-steel/">microalloyed steel and its simulated CGHAZ. And the
microstructure and impact
toughness of CGHAZs in Ti-Nb microalloyed steel and a kind of HSLA steel with similar chemical content and manufacture process were investigated with OM, TEM and series charpy impact test. Experiment results and analysis show that the particles in the steel were irregular in shape, and exhibited a slight size-dependence in that the relative content of Nb decrease with the increase of particle size. The Nb contents of particles in parent metal fell in a wide range from 0.25～0.82. During the weld thermal cycling, the particles prohibit the original austenite grain from coarsening, prevent the formation of coarse upper bainite, accelerate the formation of acicular ferrite, and promote the decomposition of M-A constituent into
ferrite and cementite, thus improve the toughness of
CGHAZ in HSLA steel remarkably. With the t_(8/5)increasing from 16s to 120s, the toughness of CGHAZ in Ti microalloyed steel increased because that secondary microstructure of CGHAZ change from upper bainite to acicular ferrite and the
austenite grain size coarsening is not serious.
More abstracts about the Study on Microstructure and Toughness of CGHAZ in Ti-Nb Microalloyed Steel