不同冷却速度下500 MPa级抗震钢筋组织的演变规律

Evolution Law of Anti-seismic Rebars of 500 MPa Grade under Different Cooling Rates

为了分析冷却速度对Nb-V微合金化高强度抗震钢筋微观组织演变规律的影响,利用热模拟试验机、金相显微镜、场发射扫描电子显微镜和维氏硬度计进行相变规律研究、显微组织形貌观察和维氏硬度测试,利用热膨胀法和金相法测定了实验钢的连续冷却转变(continuous cooling transformation,CCT)曲线。结果表明:当冷却速度为0.3~0.5℃/s时,获得的相变组织为铁素体和珠光体;当冷却速度为1~3℃/s时,获得的相变组织为铁素体、珠光体和贝氏体;当冷却速度为5~10℃/s时,获得的相变组织为铁素体和贝氏体;当冷却速度为15℃/s时,获得的相变组织为铁素体、贝氏体和马氏体;当冷却速度为20℃/s时,获得的相变组织为马氏体;当冷却速度小于5℃/s时,实验钢室温组织的显微硬度随着冷却速度的增加而增大,硬度曲线的斜率变化相对迅速;当冷却速度为5~20℃/s时,实验钢获得相变组织的显微硬度随冷却速度的提升缓慢增加;当冷却速度达到20℃/s时,实验钢获得相变组织的显微硬度最大。

In order to analyze the effect of cooling rate on the microstructure evolution of Nb-V microalloyed high-strength seismic rebar,the phase transformation law investigation,microstructure morphology observation and Vickers hardness test were carried out by means of thermal simulation test machine,metallographic microscope,field emission scanning electron microscope and Vickers hardness tester,and the continuous cooling transformation(CCT)curve of test steel was measured by means of thermal expansion method and metallographic method.The results show that the transformation structure of ferrite and pearlite is obtained at a cooling rate of 0.3~0.5℃/s.The transformation structure of ferrite,pearlite and bainite is gained at a cooling rate of 1~3℃/s.The transformation structure of ferrite and bainite is obtained at a cooling rate of 5~10℃/s.The transformation structure of ferrite,bainite and martensite is obtained at a cooling rate of 15℃/s.When the cooling rate is 20℃/s,the transformation structure is martensite.When the cooling rate is less than 5℃/s,the microhardness of the test steel increases with the increase of the cooling rate,and the slope of the hardness curve changes rapidly.With the increase of the cooling rate,the microhardness of the test steel having obtained the transformation structure increases slowly at a cooling rate of 5~20℃/s.When the cooling rate reaches 20℃/s,the microhardness of the test steel having obtained the transformation structure is the largest.