Study On Mechanical Properties Of Q460 High Strength Steel And Its Bolt Connections After Cooling From High Temperatures

High-strength structural steel has been widely used in buildings,such as houses,transmission towers,bridges and industrial plants because of its good mechanical properties.High-strength steel may be exposed to fire during the service period of the building.After the fire,the mechanical properties of the steel will be reduced,causing damage to the components,and in severe cases,it will lead to the overall collapse of the structure,causing safe accidents and economic losses.Therefore,this article focuses on the Q460 high-strength structural steel which extensively used in construction,and studies its material and bolt connection mechanical properties after cooling from high temperatureThe main research contents are as follows:(1)Study on Mechanical Properties of Q460 High strength Steel after High Temperature Through experimental research,we can obtain the stress-strain curve,yield strength,ultimate strength,elastic modulus and elongation of Q460 high-strength steel after natural cooling,water cooling and foam extinguishing cooling methods from high temperature.I study the influence of cooling method and temperature on the mechanical properties of Q460 highstrength steel,compare the change of mechanical properties with other types of steel after high temperature,and use the least square method and regression analysis to establish the mathematics of the mechanical parameters of Q460 high-strength steel under different cooling methods expression from different temperatures.(2)Microstructure analysis of Q460 high strength steel after high temperature We observe the fracture morphology of Q460 high-strength steel after high temperature by scanning electron microscope,we analyze the influence of high temperature and cooling method on its fracture flatness,dimple size and morphology;through metallographic analysis,we study the effect of high temperature and cooling method on Q460 high strength the influence of the microscopic substance and grain size of steel,we also explore the influence of microscopic substance changes on its macroscopic mechanical properties.(3)Study on mechanical properties of Q460 high strength bolts after high temperature Through heating,cooling and static tension,we obtain the load-displacement curve of the Q460 high-strength bolt connection after cooling from high temperatures,and analyse the influence of temperature and cooling method on the deformation capacity and ultimate bearing capacity of the bolt connection specimens,Mathematical expressions of bearing capacity and deformation parameters changing with temperature are established in the different cooling methods.;using the calculation formula given in "Steel Structure Design Standard",combined with the residual factor of the bearing capacity of Q460 high-strength steel after high temperature in this article,calculate the bolt connection plate after high temperature Bearing capacity,the difference between the calculated value and the test value is analyzed,and the calculation formula given in the code is discussed and revised,which provides a reference for the evaluation of the bearing capacity of Q460 high-strength steel structural members after high temperature.