【摘 要】
：
A high-performance Q370qE-HPS bridge steel with low carbon content(≤0.10wt%),Nb microalloying(0.025-0.050wt%)and low carbon equivalent(CEV)(≤0.38%)has been produced using TMCP procedure.The microstruc
【机 构】
：
State Key Laboratory of Metastable Materials Science and Technology,Yanshan University,No. 438 Hebei
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A high-performance Q370qE-HPS bridge steel with low carbon content(≤0.10wt%),Nb microalloying(0.025-0.050wt%)and low carbon equivalent(CEV)(≤0.38%)has been produced using TMCP procedure.The microstructure and mechanical properties of typical steel plates and layers parallel to rolling surface were characterized.The results show that the microstructure consists of fine-grained quasi-polygonal ferrite(QPF),less pearlite and a large number of fine dispersed Nb-rich precipitates.Consequently,an excellent combination of high strength,high toughness and low yield-to-tensile strength ratio(YR)is obtained.In addition,the QPF grain refinement and pearlite reduction take place simultaneously with increasing distance from central to surface of an identical plate or decreasing thickness of plate,leading to increase in yield strength(Rp0.2),impact energy(EKV2,-40℃)and YR,and approximately the same tensile strength(Rm).The effect of QPF grain size on Rp0.2 and effects of QPF grain size and pearlite area fraction on EKV2(-40℃)can be described by Hall-Petch formula and Boltzmann model,respectively,while the YR is in a good linear relation to QPF grain size and pearlite area fraction.
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