Effect of Water Cooling Process on Microstructure and Mechanical Properties of Q420qE Bridge Steel

The effects of the water cooling process on the microstructure and mechanical properties of Q420qE bridge steel were studied. The results indicate that by controlling the water cooling process, a complete bainite structure or the mixed structure of ferrite +bainite can be obtained, and the proportion of each phase and the thickness of the structure can be controlled. Decreasing the initial cooling temperature can produce precipitation ferrite, which can effectively reduce the yield ratio. Increasing the cooling rate can significantly refine the ferrite and bainite, increasing yield ratio, and increasing the impact toughness. There is no obvious difference in the morphology of the first precipitation ferrite when the final cooling temperature is decreased, the content of acicular ferrite and bainite increases, and the yield strength does not change significantly, the tensile strength increases, and the yield strength ratio decreases.