Development of Nb-V microalloying and low Mo alloyed Q345 fire-resistant steel
CHEN Lin-heng1, WANG Wen-tao2,3, LI Zhao-dong2, CUI Qiang1, SUI Feng-li3, ZHANG Ke3
1. Research Institute, Nanjing Iron and Steel Co., Ltd., Nanjing 210035, Jiangsu, China; 2. Institute of Structural Steels, Central Iron and Steel Research Institute, Beijing 100081, China; 3. School of Metallurgical Engineering, Anhui University of Technology, Ma'anshan 243002, Anhui, China
Abstract:In order to promote the market application of fire-resistant steel,the low-cost Q345 fire-resistant steel was successfully developed,adopting the composition design of low C,low Mo (about 0.2%)and Nb,V,Ti composite microalloying. The continuous cooling transformation (CCT)of experimental steel was measured by Formastor-Digital automatic transformation tester. The influence of different cooling processes on the microstructure and hardness of the experimental steel was studied by Gleeble-1500 thermal simulation test machine. The microstructure and nano second phase of hot rolled and high temperature tensile samples were characterized in detail by SEM,EBSD,TEM and physicochemical phase analysis. The strength mechanism of the experimental steel at room temperature and high temperature was quantitatively analyzed. The ferrite+bainite microstructure was obtained by laminar cooling started at 760-780 ℃ but finished at 400-600 ℃. After high temperature tensile test at 600 ℃,the mass percent of MC phase and the percentage of particles below 18 nm in the experimental steel are increased by 16.4% and 9.8% respectively,compared with those of the hot-rolled sample. These newly precipitated nano particles play a good role in precipitation strengthening at high temperature. It makes up to some extent for the loss of high-temperature yield strength,which is caused by the decrease of shear modulus at high temperature and by the failure of fine grain strengthening. The solid solution strengthening and precipitation strengthening are the main high-temperature strengthening methods of Q345 fire-resistant steel.
陈林恒, 王文涛, 李昭东, 崔强, 隋凤利, 张可. Nb-V微合金化低钼型Q345耐火钢的开发[J]. 钢铁, 2020, 55(11): 91-102.
CHEN Lin-heng, WANG Wen-tao, LI Zhao-dong, CUI Qiang, SUI Feng-li, ZHANG Ke. Development of Nb-V microalloying and low Mo alloyed Q345 fire-resistant steel[J]. Iron and Steel, 2020, 55(11): 91-102.
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