Effect of controlled rolling and controlled cooling process on microstructure and properties of high strength and low yield ratio building steel
Aiming at the key problem of how to realize the coupling matching of high yield strength and low yield ratio for high strength seismic building steel,based on the self-designed chemical composition,the microstructure and properties of the test steel were investigated by controlled rolling and controlled cooling process.The results show that under the process conditions of'two-stage controlled rolling+water cooling(final cooling temperature 660 ℃)',the microstructure of the test steel is a multi-phase structure composed of ferrite,pearlite and bainite,which realizes a good match of strength,plasticity and low yield ratio.The average yield strength is about 660.0 MPa,the average tensile strength is about 1 196.7 MPa,the average elongation after fracture is about 14.8％,and the average yield ratio is as low as 0.55.The solid solution strengthening of Mn and Si elements in the test steel,as well as the fine grain strengthening and dislocation strengthening caused by bainite and pearlite structures are the main mechanisms for obtaining high strength and low yield ratio.
building steelhigh strengthlow yield ratiocontrolled rolling and controlled cooling processmultiphase microstructure
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