【作者】 刘俊；

【导师】 袁泽喜；

【作者基本信息】 武汉科技大学 ， 材料科学与工程， 2016， 硕士

【摘要】 本文研究了Q550GJ高强韧抗震建筑钢,采用低碳并添加了适量的Mo、Cr,Ni合金元素和Nb、Ti微合金元素设计,通过TMCP工艺得到贝氏体+铁素体的双相组织,获得高的强度、良好的韧性和较低的屈强比。通过Gleeble-1500热模拟试验,力学性能试验,OM和SEM组织观察以及CT观察孔洞萌生生长试验,得到如下重要结果:Q550GJ的CCT曲线表明,当冷却速度介于0.1~5℃/S时得到铁素体、珠光体和贝氏体,当冷却速度介于5~50℃/S时得到铁素体,贝氏体和马氏体,为控轧控冷工艺提供有效的依据。控冷工艺的开冷和终冷温度对试验钢组织和屈强比有重要影响:开冷温度越低,铁素体量越多,贝氏体量越少,降低强度和屈强比;终冷温度越低,贝氏体组织细化,M/A岛量有所增加,提高强度和屈强比。采用适当的开冷温度和终冷温度配合工艺,可以获得高强韧和较低屈强比性能的抗震建筑钢。CT观察孔洞萌生生长试验探明了Q550GJ高强韧建筑钢的韧性断裂机制为裂纹和夹杂物导致的单个大孔洞逐步缓慢连接,最后与大量M/A岛导致的小孔洞汇合连接而发的生韧性断裂。更多还原

【Abstract】 High strength & toughness anti-seismic structural steel Q550 GJ has been studied in the paper with design of low carbon content,appropriate content of alloy elements Mo,Cr,Ni and micro-alloy elements Nb & Ti.Through using TMCP process,microstructure of duplex phase bainite + ferrite can be obtained,and then high strength,excellent toughness and low yield ratio can be achieved accordingly.According to the Gleeble-1500 thermo-simulation test,mechanical test,OM/SEM inspection and CT analysis on voids initiation &growth,the conclusion can be made as below:The CCT curves of steel Q550 GJ indicate that microstructure of ferrite,pearlite and bainite can be obtained when the cooling rate is 0.1 to 5 deg.C/S;microstructure ferrite,bainite and martensite can be obtained when the cooling rate is 5 to 50 deg.C/S.The start cooling temperature and final cooling temperature of control cooling process has big influence to microstructure and yield ratio of testing steel: the lower the srart cooling temperature,the more the ferrite structure and the less the bainite,which leads to lower strength & yield ratio;the lower the final cooling temperature,the thinner the bainite structure,the more the M/A Island,which leads to higher strength and yield ratio accordingly.Through adopting appropriate start cooling temperature and final cooling temperature,the anti-seismic steel can get high strength,high toughness and low yield ratio.According to CT analysis on void initiation & growth,it’s found the ductile fracture mechanism of high strength & toughness anti-seismic steel Q550 GJ is that single large void resulted from crack & inclusion connects to each other gradually at first,and then the connections coalescence with large amount of little voids initiated from M/A Island in the end,which leads to final ductile fracture.更多还原