高温冷却后对焊连接Q345钢材力学性能研究  

Study on mechanical properties of butt⁃welded Q345 steel after high temperature cooling

作　　者：李杰 张春涛[1,2] LI Jie;ZHANG Chuntao(College of Civil Engineering and Architecture,Southwest University of Science and Technology,Mianyang 621010,China;Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province,Mianyang 621010,China)

机构地区：[1]西南科技大学土木工程与建筑学院,绵阳621010 [2]工程材料与结构冲击振动四川省重点实验室,绵阳621010

出　　处：《建筑结构》2024年第16期60-68,共9页Building Structure

基　　金：国家自然科学基金项目(51508482);西藏自治区科技计划项目(ZYYD2021000083)。

摘　　要：钢材的力学性能会因火灾温度不同而发生明显变化,尤其是钢结构连接节点在火灾后的残余力学性能对钢结构完整性起至关重要的作用。对模拟火灾后对焊连接Q345结构钢的力学性能展开深入研究,观察20~900℃高温冷却后对焊连接Q345钢材的断裂特征,获得其应力-应变曲线及力学性能等关键参数;同时,通过仪器设备观察试件断口形貌和金相变化,从微观结构探究其宏观力学性能变化的原因。结果发现:600℃为试件力学性能发生变化的临界温度,当火灾温度不超过600℃时,屈服强度和极限强度的变化较小且均未超过9%;当温度超过600℃时,屈服强度和极限强度随温度升高而逐渐降低,900℃时分别为初始值的69%和84%。此外,高温后试件的断口表面均存在大量形状、尺寸不同的韧窝;常温下焊缝的微观组织大多由超低碳贝氏体和针状铁素体组成,而靠近焊缝热影响区域的母材则由铁素体及贝氏体组成;温度不超过500℃时,母材的金相组织无明显变化;而900℃后试件主要由晶体尺寸更大的铁素体及部分渗碳体组织组成。The mechanical properties of steel will change significantly due to different fire temperatures.In particular,the residual mechanical properties of steel structure connection joints after fire play a vital role in the integrity of steel structures.The mechanical properties of butt⁃welded Q345 structural steel after simulated fire were studied in depth.The fracture characteristics of butt⁃welded Q345 steel after high temperature cooling at 20~900℃were observed,and the key parameters such as stress⁃strain curve and mechanical properties were obtained.Meanwhile,the fracture morphology and metallographic changes of the specimens were observed by instruments and equipment,and the reasons for the changes of macroscopic mechanical properties were explored from the microstructure.The results show that 600℃is the critical temperature for the change of mechanical properties of the specimen.When the fire temperature does not exceed 600℃,the change of yield strength and ultimate strength is small and does not exceed 9%.When the temperature exceeds 600℃,the yield strength and ultimate strength gradually decrease with the increase of temperature,which are 69%and 84%of the initial value at 900℃,respectively.In addition,there are a large number of dimples with different shapes and sizes on the fracture surface of the specimens after high temperature.The microstructure of the weld at room temperature is mostly composed of ultra⁃low carbon bainite and acicular ferrite,while the base metal near the heat affected zone of the weld is composed of ferrite and bainite.When the temperature is not more than 500℃,the microstructure of the base metal has no obvious change.After 900℃,the specimen is mainly composed of ferrite and partial cementite with larger crystal size.

关 键 词：Q345钢材 对焊连接 高温 力学性能 金相分析 

分 类 号：TU397[建筑科学—结构工程]