Ultrafine austenite grains with average size of 2μm were successfully obtained by combining thermo-mechanical control process followed by reheating in a vanadium microalloyed steel.The mixed microstructure transforme...Ultrafine austenite grains with average size of 2μm were successfully obtained by combining thermo-mechanical control process followed by reheating in a vanadium microalloyed steel.The mixed microstructure transformed from pancaked austenite formed during controlled rolling has a higher density of high angle boundaries,compared to that transformed from equiaxial austenite.It contributes to increasing nucleation density of austenite grain during the reheating process.A certain volume fraction of undissolved nano-sized（Ti,V）C particles,which are formed during the controlled rolling process and/or the reheating process,effectively inhibit austenite grain growth and consequently refine austenite grain size significantly.The critical grain size of austenite calculated by Gladman model agrees well with the experimental result.展开更多
Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations.Usually,decreasing the grain size is the only approach by which both...Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations.Usually,decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased.However,low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study.By direct tracking of the morphological evolution during phase transformation,it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite,whereas small austenite grain size leads to grain boundary nucleation of bainite.This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.展开更多
基金Sponsored by National Basic Research Program of China(2010CB630805)
文摘Ultrafine austenite grains with average size of 2μm were successfully obtained by combining thermo-mechanical control process followed by reheating in a vanadium microalloyed steel.The mixed microstructure transformed from pancaked austenite formed during controlled rolling has a higher density of high angle boundaries,compared to that transformed from equiaxial austenite.It contributes to increasing nucleation density of austenite grain during the reheating process.A certain volume fraction of undissolved nano-sized（Ti,V）C particles,which are formed during the controlled rolling process and/or the reheating process,effectively inhibit austenite grain growth and consequently refine austenite grain size significantly.The critical grain size of austenite calculated by Gladman model agrees well with the experimental result.
文摘Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations.Usually,decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased.However,low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study.By direct tracking of the morphological evolution during phase transformation,it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite,whereas small austenite grain size leads to grain boundary nucleation of bainite.This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.
