Microstructural Analysis and Hardening Mechanism of High-Strength Low-Carbon Weathering Steel: Effect of Coiling Temperature

The thermal simulation experiments were performed to study the effect of coiling temperature on the microstructures and hardening mechanisms of a high-strength low-carbon weathering steel. The results showed that the experimental steels showed the microstructure of granular bainite and acicular ferrite when the coiling temperature was from 550 to 600 °C. When the coiling temperature was from 600 to 650 °C, the microstructure of experimental steels was polygonal ferrite and pearlite. The mean grain size did not change much with the coiling temperature. The main strengthening factor was grain refinement strengthening. The fraction of precipitation strengthening was the second, and its effect was the highest which accounted for 26.7% when the coiling temperature was 600 °C. As the coiling temperature increased from 600 to 650 °C, a discernible decrease in dislocation density was found, leading to a significant decline in the dislocation strengthening. The hardness of the experimental steel was the highest as 252 HV when the coiling temperature was 600 °C.