| Because of its high strength,high hardness and high annual output,high-strength steel has become one of the most widely used main building materials in modern architecture.In addition,high-strength steel has a wide range of applications in industrial and mechanical fields,such as mechanical cranes,railways,etc.With the increasing use of high-strength steel,it is inevitable to suffer the impact of earthquakes and high temperatures.Therefore,the hysteretic behavior of high-strength steel has been studied by a large number of scholars at home and abroad.Most of the research is on the hysteretic behavior of steel structural members.In the past decade,the research on the hysteretic behavior of high-strength steel specimens has also gradually increased.However,there are few studies on the hysteretic properties of high-strength steel after being subjected to high temperatures.Therefore,this article has conducted a study on the hysteretic properties of Q690 high-strength steel after high-temperature cooling,and explored the relationship between the hysteretic properties and microstructure of Q690 high-strength steel.The research contents are as follows:(1)Study on mechanical properties of Q690 high-strength steel The metal tensile test of Q690 high-strength steel without high temperature treatment at normal temperature is carried out by universal testing machine to test the mechanical properties of this batch of Q690 high-strength steel specimens,such as ultimate strength,yield strength,elastic modulus,etc.(2)Study on Hysteresis Properties of Q690 High Strength Steel after High Temperature Cooling The Q690 high strength steel specimens heated to different target temperatures were cooled to room temperature by three cooling methods: air cooling,water cooling and foam fire extinguishing cooling.The specimens were subjected to low cycle reciprocating loading using an electro-hydraulic servo fatigue machine,and the hysteresis properties of the specimens after loading were measured.The effects of different target temperatures and cooling methods on the hysteretic properties of Q690 high-strength steel were studied.(3)Study on Macro and Micro Morphology of Q690 High Strength Steel after High Temperature Cooling Macroscopic observation was used to observe the impact on the surface of Q690high-strength steel after high temperature cooling,and the fracture surface of the specimen was taken down for SEM tungsten filament electron microscope scanning to study the impact of different working conditions on the microscopic morphology of the fracture surface of the specimen.Finally,the fracture of the test piece is metallographically scanned to observe the change of its microstructure.(4)Establishing a parametric relationship between macroscopic mechanical properties and microscopic particle numbers First,use Image-Pro software to count the proportion of particles with different particle sizes at the fracture of the test piece,and then calculate the correlation between the hysteretic property of Q690 high-strength steel and the proportion of particles through correlation calculation,and obtain the determined parameter relationship. |
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