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 sy...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 R eL and tensile strength R m 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 R m /R eL 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℃.展开更多
基金financial supports by both the Institution of Higher Education Scientific Research Plan Projects of Liaoning Provincial Education Department,No.20060434Nantong Industrial Science and Technology Creativity Program,No.AA2007003
文摘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 R eL and tensile strength R m 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 R m /R eL 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℃.
