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

摘要： 为评估Q350EW高铬耐候钢连铸过程裂纹敏感性，利用 Gleeble3500热模拟试验机测定了Q350EW高铬耐 候钢高温热塑性，并结合Thermo-Calc热力学软件理论计算Q350EW高铬耐候钢析出相分布规律。利用扫描电镜结 合光学显微镜对高温拉伸断口宏观、微观形貌以及断口处的显微组织观察分析。研究结果表明，随着加热温度升 高，Q350EW高铬耐候钢抗拉强度降低；断面收缩率曲线在700～800 ℃附近出现凹谷，775 ℃时断面收缩率最低为 64. 9%。凹谷温度范围内断口形貌主要由韧窝组成，其断裂机理为韧性断裂；显微组织分析表明，原奥氏体晶界出 现铁素体致使塑性降低，但是由于铁素体含量较高，Q350EW高铬耐候钢塑性仍保持较高水平。通过优化连铸二次 冷却等关键工艺参数降低Q350EW高铬耐候钢铸坯裂纹风险性，建议铸坯角部弯曲矫直段温度＜750 ℃。

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