Run-out table bottom jet cooling

在过去的几十年里，先进钢材有了巨大的发展，为汽车、能源和建筑等广泛的应用提供了性能改进的钢材产品。钢铁制造商的这些进步是通过设计创新的加工路径和更好的过程控制来实现的。在这里，流程模型的开发产生了重大影响。对于热轧钢来说，在冷却台上喷水冷却是调整钢性能的关键冶金工具。在冷却过程中，由具有面心立方（FCC）晶体结构的奥氏体转变为具有体心立方（BCC）晶体结构的铁素体。具体而言，根据钢的化学性质和加工路径，可以获得不同的转化产物，形成复杂的多相组织，为性能设计提供了新的范式。为了实现这一潜力，精确控制冷却路径至关重要，因为这决定了相变动力学和由此产生的微观结构。热移动钢板的水冷却是一个复杂的瞬态传热问题，包括成核、转变和膜沸腾。目前的运行表冷却模型在很大程度上是经验性质的。有必要开发更基本的模型。迄今为止，该领域的研究主要集中在顶部表面冷却，而底部射流冷却的研究却很少受到重视。因此，提出的项目旨在提供系统的底部射流冷却研究，以开发底部射流的冷却模型，该模型严格地解释了潜在的沸腾机制。该项目是与加拿大汽车钢板生产的领导者ArcelorMittal Dofasco合作进行的。实验研究将在一个试验规模的试验台设施上进行，为模型开发提供指导。提出的传热相关性将被纳入现有的ArcelorMittal Dofasco热连轧工艺模型，以便该模型可以用工业数据进行验证。该项目为三名研究生提供了培训机会。

There has been a tremendous development of advanced steels over the past few decades to provide steel products with improved properties for a wide range of applications including automotive, energy and construction. These advancements by steelmakers were critically enabled by design of innovative processing paths and better process control. Here, the development of process models has had a significant impact. For hot rolled steels cooling by water sprays on the run-out table is a key metallurgical tool to tailor the properties of the steel. During the cooling the phase transformation occurs from austenite with a face-centred cubic (FCC) crystal structure to ferrite with a body-centred cubic (BCC) crystal structure. In detail, depending on steel chemistry and processing path, different transformation products can be obtained to create complex multi-phase microstructures which offer new paradigms for the design of properties. To realize this potential it is critical to control the cooling path precisely as this determines the phase transformation kinetics and the resulting microstructures. Cooling of hot moving steel sheets by water is a complex transient heat transfer problem including nucleate, transition and film boiling regimes. Current run-out table cooling models are to a large degree empirical in nature. There is a need to develop more fundamentally based models. Research in this area has so far emphasized top surface cooling whereas bottom jet cooling studies have received far less attention. Thus, the proposed project is designed to provide a systematic bottom jet cooling study to develop a cooling model for bottom jets that rigorously accounts for the underlying boiling mechanisms. The project is conducted in collaboration with ArcelorMittal Dofasco - Canada's leader in the production of automotive steel sheets. Experimental studies will be carried on a pilot scale run-out table facility to provide guidance for the model development. The proposed heat transfer correlations will then be incorporated into an existing hot strip mill process model of ArcelorMittal Dofasco such that the model can be validated with industrial data. The project offers training opportunities for three graduate students.