Refinement of Prior Austenite Grain in Advanced Pipeline Steel

Abstract

A series of fundamental and applied investigations were carried out to develop high grade pipeline steel with high Mn high Nb design, and it mostly focused on that the static and dynamic recrystallization behaviors of high Mn high Nb pipeline steel. Various experimental methods were adopted, which include stress relaxation tests, physical metallurgical modeling analysis, the etching of prior austenite grains and TEM observation of precipitates. According to the results, new control rolling technology is bring forward under high Mn high Nb approach, as a consequence, fine and homogeneous prior austenite grains can be generated by complete static recrystallization prior to finish rolling, and the coarsening can be suppressed largely by drag effect, through proper finish rolling process, prior austenite grain will be flatten fully and uniformly to higher flow stress or Sv, and the mixed grains structure caused by partial dynamic recrystallization may be avoided. The physical metallurgy principle for refinement of prior austenite grain through rough rolling and pancake through finish rolling can be adopted for refinement the austenite grain in high Mn high Nb structural steel.