关键词: Q350EW高铬耐候钢, 高温热塑性, 断口形貌, 显微组织, 析出相

Abstract: To evaluate the crack sensitivity of Q350EW high-chromium weathering resistant steel during continuous cast⁃ ing， the high-temperature thermoplastic characteristics of Q350EW high-chromium weathering resistant steel were studied using Gleeble3500 thermal simulation testing machine， and the distribution of precipitates in the steel was calculated us⁃ ing Thermo-Calc thermodynamic software. Scanning electron microscopy and optical microscopy were used to observe and analyze the macrostructure and microstructure morphology of high-temperature tensile fractures and microstructure at the fractures. The research results indicate that as the heating temperature increases， the tensile strength of the test steel de⁃ creases； The cross-sectional shrinkage curve shows a concave valley around 700 ℃-800 ℃， with the lowest cross-sectional shrinkage of 64. 9% at 775 ℃. The fracture morphology within the range of concave valley temperature is mainly composed of ductile dimples， and its fracture mechanism is ductile fracture. Microscopic analysis shows that ferrite appears at the grain boundaries of the original austenite， leading to a decrease in plasticity. However， due to the high content of ferrite， the plasticity of Q350EW high chromium weather resistant steel still remains at a high level. By optimizing key process pa⁃ rameters such as secondary cooling during continuous casting， the risk of cracking in Q350EW high chromium weather re⁃ sistant steel billets can be reduced. It is recommended that the temperature of the corner bending and straightening section of the billets be less than 750 ℃.

Key words: Q350EW High Chromium Weathering Steel, Hot Ductility, Fracture Morphology, Microstructure, Precipi? tate Phase