Influence of acicular ferrite on yielding behavior of HRB400 reinforcing steel bars containing niobium
CAO Lei1，ZHENG Bing-qian1，WANG Yun-chuan1，ZHOU Cong1，YANG Zhong-min2
（1. Steelmaking and Rolling Division, Jiangsu Yonggang Group Co., Ltd.， Zhangjiagang 215628， Jiangsu， China 2. Institute of Structural Steels， Central Iron and Steel Research Institute， Beijing 100081， China）
Abstract：The yielding behaviors of two 400 MPa grade hot rolled rebars which were 20MnSiV and 16MnVNb，respectively，were compared and studied. Under the same rolling process，comparing with the HRB400 rebar containing vanadium，the niobium micro-alloyed steel did not possess the sharp yield point in the stress-strain curve. The chemical composition analysis，the microhardness test of the experimental steels were carried out. The optical microscope，the scanning electronic microscope and the transmission electronic microscope were utilized to characterize the microstructures of the experimental steels. The results showed that the microstructures of 20MnSiV steel were ferrite and pearlite，and those of 16MnVNb steel were equiaxed ferrite，pearlite and acicular ferrite which was surrounded by degenerated pearlite. The microhardness of acicular ferrite where high density dislocation was detected was between that of pearlite and ferrite. An excess of acicular ferrite was the reason for the disappearance of the yield plateau of the niobium micro-alloyed HRB400 rebar.
2016, Vol. 26 
