Effects of Controlled Cooling Rate on Microstructure and Mechanical Properties of Q390qE Bridge Steel
Gleeble-3500 thermal simulation machine was used to simulate the cooling control process of Q390qE bridge steel with different cooling rates,and the effects of different cooling rates on the microstructure and mechanical properties of Q390qE steel were studied by metallographic microscope,transmission electron microscope and universal testing machine.The results show that Q390qE test steel with cooling rate of 5-15℃/s is mainly granular bainite and a small amount of needle ferrite.With the increase of cooling rate,the bainite content in Q390qE test steel microstructure increases gradually.The tensile strength,yield strength and yield strength ratio of the test steel are continuously improved.The cooling rate of 5-10℃/s is the ideal controlled cooling rate of Q390qE test steel,and its yield strength is more than 400 MPa,and the yield strength ratio is not more than 0.83.
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