热轧无缝钢管非对称高强度高均匀化冷却机理研究

The hot-rolled seamless tube is air cooling to room temperature after sizing mill in traditional producing process. Since lack of effective on-line microstructure and properties control measures, the qualified rate of as-rolled properties is only 30%~40%. The rest unqualified product has to be subjected to off-line heat treatment, which results in higher cost, more energy consumption and longer production period. In this research, on-line control cooling after sizing mill for seamless tube is introduced, flow rheological behaviors of fluid on tube surface and heat transfer mechanism of temperature field distribution under thermal-fluid coupling, will be deeply studied. Meanwhile, the cooling mechanism will also be analyzed to obtain the high-efficiency and high-homogeneous in asymmetric cooling condition. According to numerical simulation and experiments, the characteristics of flow interaction, heat transfer zone distribution and heat transfer uniformity are investigated, which affected by process parameters such as rotational speed of tube, pressure of jet cooling water, cooling water of different quadrants, jet imping angle, cooling strategy, etc. The relationship between process parameters and heat exchange efficiency and cooling homogeneous, change law of thermal loads of surface and the parameters will be constructed. The model of temperature and heat transfer coefficient for asymmetric cooling system under jet flow will be established. The on-line cooling control theory applied on hot-rolled seamless tube will possess important theoretical basis for industrial application.

热轧无缝钢管传统生产流程中，钢管热轧定径后，采用空冷方式冷却至室温。由于缺乏有效的组织在线调控手段，导致热轧产品性能合格率仅为30~40%，余下产品必须再进行离线热处理，生产成本高、能源消耗大、生产周期长。本课题在钢管定径后引入在线控制冷却，围绕热轧无缝钢管控制冷却下表面流体流变行为及热/流耦合作用下温度场演变规律、非对称冷却条件下环形断面高强度高均匀化冷却机理开展研究。采用数值模拟和实验研究相结合的方式，研究钢管旋转运行速度、冷却水压力、不同象限冷却水量、喷射角度和冷却策略等工艺参数变化对流体间交互作用规律、热交换区域分布及换热均匀性的影响，构建冷却工艺参数与换热效率及冷却均匀性之间的关系，研究钢管圆周方向表面热载荷与各参数之间的变化规律，创建非对称射流冲击条件下钢管冷却换热系数模型与温度解析模型。本研究为在线控制冷却在热轧无缝钢管领域的工业化应用提供了理论基础。

热轧无缝钢管由于环形断面的特征使得其均匀化冷却机制显著区别于板材，控制冷却技术工艺在其生产领域受到极大限制，严重制约着热轧无缝钢管产品的进一步提升与发展。本项目针对热轧无缝钢管控制冷却技术存在的问题，采用有限元模拟与实验相结合的研究方法，对于钢管环形断面特征下的冷却换热机理开展研究。结合流体力学相关知识，研究射流冲击冷却条件下钢管表面流体速度场、压力场等流体相互作用，总结归纳了各工艺参数对于流场分布的影响规律；通过有限元模拟结果与实验结果的相互验证，针对钢管表面换热特点进行了分区性描述，并结合所获钢管温度场，获得了关键工艺参数对于钢管冷却强度及冷却均匀性的影响规律；此外，以所获钢管冷却换热理论为基础，建立了热轧无缝钢管环形大断面非对称射流条件下的换热模型和温度解析模型，并将其应用于PQF460热轧无缝钢管生产线，大大提高了机械性能和合格率，成功实现了低成本生产，解决了基于射流冷却的热轧无缝钢管在线控制冷却技术工业化应用中的核心难题。