In this paper,CCT(continuous cooling transformation)diagrams are determined for Nb-containing reinforcing bars with different Nb,Mn additions,and initial austenite grain sizes by simulating industrial conditions via d...In this paper,CCT(continuous cooling transformation)diagrams are determined for Nb-containing reinforcing bars with different Nb,Mn additions,and initial austenite grain sizes by simulating industrial conditions via dilatometry tests.It was found that coarse austenite grain size,high Mn content and Nb remaining in solution all increase hardenability of Nb-containing rebars,namely lower Ar3 for acicular phase transformation products,which leads to continuous yielding during tensile deformation when the volume fraction of acicular ferrite or bainite microstructure reaches a certain volume fraction.By coupling with actual cooling rates for different size rebars,it can be explained why bainitic structure is prone to form in the center of rebars,especially for small size rebars.In order to achieve required ferrite-pearlite microstructure,cooling strategy is optimized for industrial production.展开更多
Nowadays there is a continuous demand,particularly from the automotive industry,for cheaper,lighter and more reliable components.It is not surprising then that steel research has been focused during the last decades i...Nowadays there is a continuous demand,particularly from the automotive industry,for cheaper,lighter and more reliable components.It is not surprising then that steel research has been focused during the last decades in new qualities and processes.This paper is dealing with the use of vanadium microalloyed steels on one of those new processes,warm forging.For its low precipitation temperature and its recognised ability to strengthen steel microstructures via austenite grain growth control,precipitation hardening and interference of the static recrystallization process,vanadium in microalloyed steels seem to be an appropriate candidate for warm forging.展开更多
文摘In this paper,CCT(continuous cooling transformation)diagrams are determined for Nb-containing reinforcing bars with different Nb,Mn additions,and initial austenite grain sizes by simulating industrial conditions via dilatometry tests.It was found that coarse austenite grain size,high Mn content and Nb remaining in solution all increase hardenability of Nb-containing rebars,namely lower Ar3 for acicular phase transformation products,which leads to continuous yielding during tensile deformation when the volume fraction of acicular ferrite or bainite microstructure reaches a certain volume fraction.By coupling with actual cooling rates for different size rebars,it can be explained why bainitic structure is prone to form in the center of rebars,especially for small size rebars.In order to achieve required ferrite-pearlite microstructure,cooling strategy is optimized for industrial production.
基金VANITECthe Spanish Ministerio de Ciencia e Innovacion for their financial support
文摘Nowadays there is a continuous demand,particularly from the automotive industry,for cheaper,lighter and more reliable components.It is not surprising then that steel research has been focused during the last decades in new qualities and processes.This paper is dealing with the use of vanadium microalloyed steels on one of those new processes,warm forging.For its low precipitation temperature and its recognised ability to strengthen steel microstructures via austenite grain growth control,precipitation hardening and interference of the static recrystallization process,vanadium in microalloyed steels seem to be an appropriate candidate for warm forging.
