The Study on the Microstructure and Mechanical Properties of 400MPa Grade Bar Prepared by Controlled Cooling after Finish Rolling
The production process of bars in Baosteel Nantong Co. Ltd. was adjusted by both decreasing heating temperature and adding controlling cooling procedure after finish rolling for upgrade of bars. A set of water cooling system was also installed behind the finishing mill. On-line tests were conducted, and then the microstructure and mechanical properties of the bars with HRB335 composition and φ22mm diameter were studied. The results showed that the microstructures of the bar cooled by water were ferrite and pearlite with grain sizes of 8.5 to 12 grades, which were finer than that of the bar without water cooling. While the thin outer layer microstructures of the bar cooled by water were mainly tempered sorbite with small amount of tempered troosite. The average yield strength ReL and tensile strength Rm of the bars with water cooling increased 105MPa and 73MPa respectively compared with those of the bars without water cooling. The reason of this strengthening was attributed to the synthetic role of fine grains and phase transformation and precipitation mechanism. In addition, The ration of Rm/ReL could be higher than 1.25, which is the request of earthquake-proof performance for HRB400E, only when the self-tempering temperatures of the bars were higher than 640℃.
controlled cooling hot rolling bar fine grain strengthening self-tempering
ZHANG Jun-wei DING Lei XIAO Yi HU Xiao-dong HU Lin
School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan 114051, Ch Baosteel Nantong Co. Ltd., Nantong 226002,China; School of Electrical Engineering, Anhui University
国际会议
The 6th International Conference on High Strength Low Alloy Steels(第六届高强度低合金钢国际会议HSLA Steels2011)
北京
英文
655-658
2011-05-31（万方平台首次上网日期，不代表论文的发表时间）