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为了研究核岛用P280GH钢管热轧成形后的冷却过程组织演变,采用物理模拟方法建立了CCT和TTT相变动力学曲线。结果表明,低冷速会形成粗大铁素体和珠光体,增大冷速可细化低温相组织,当冷速超过10℃/s时即开始出现贝氏体组织。运用叠加原理,基于有限元法,建立了试验钢冷却过程数值模型,分析了Φ219.1 mm×18.26 mm规格P280GH钢管在空冷和水冷两种冷却过程沿壁厚方向温度场、组织演变规律。结果显示,空冷条件相变组织为均匀的珠光体、无贝氏体和残余奥氏体;水冷条件获得相变组织为马氏体组织,管内外表面体积分数相差3.6%,计算结果与实际热处理工况基本一致。研究结果可为热轧P280GH钢管生产的控冷工艺提供指导。
In order to study the microstructure evolution of the cooling process of P280GH steel pipe after hot rolling, the kinetic curves of CCT and TTT transformation were established by physical simulation method. The results show that coarse ferrite and pearlite are formed at a low cooling rate, and the microstructure of the bainite begins to be refined when the cooling rate exceeds 10 ℃ / s. Based on the superposition principle and the finite element method, a numerical model of the cooling process of the test steel was established. The temperature field and microstructure evolution of Φ219.1 mm × 18.26 mm P280GH steel pipe along the wall thickness direction during air cooling and water cooling were analyzed. The results show that the phase change microstructure of the air-cooled condition is uniform pearlite without bainite and retained austenite. The phase transformation microstructure is martensitic structure under water-cooling condition, the difference between the inner and outer surface volume fraction of the tube is 3.6%. The calculated results are in agreement with the actual heat treatment Conditions are basically the same. The results can provide guidance for the controlled cooling process of hot rolled P280GH steel pipe.