铸轧流程钢坯（板）周期传热边界特征与温度场的协同机制

Accurate control of the heating and cooling of billet during cast-rolling is necessary to improve the steel billet microstructure and to enhance the performance indicators. The heat transfer boundary conditions play a vital role to the temperature distribution in the billet. To date, there has been a lack of adequate understanding of the law and mechanism of such complex heat transfer processes. This proposed project intends to study the coupling mechanism and regulation between the periodic heat transfer boundary condition and temperature distribution inside steel billet (slab) during cast-rolling. The characteristic boundary function will be obtained by collecting heat transfer data at the billet boundary, analyzing the features of process, establishing a pattern recognition model, and using inverse approximate calculations in combination with heat transfer model. The effects of the amplitude and period and their coupling on the temperature distribution inside the billet will be studied, especially on the effects of temperature and gradients between sections. The coupled effects of amplitude, period, and the cooling density on the temperature distribution are of special concern in this project. Through the completion of this project, the following goals will be achieved: (1) to propose a method for obtain a continuous and characteristic heat transfer boundary condition, (2) to understand how the parameters of a periodic heat transfer boundary affect the temperature distribution inside the steel billet, (3) to ascertain the coupling mechanism between the heat transfer boundary condition and heat transfer processes, and (4) to provide the scientific basis for the microstructure and functionality of steel billet.

精准控制钢坯加热或冷却过程，是改善钢坯微观组织，提高性能指标的重要保证。钢坯边界传热条件对其温度场起着至关重要的作用。铸轧流程中钢坯从连铸到精整历经多点冷却和加热周期性复杂传热过程。目前,对这种复杂传热过程的规律及其机制尚不清楚。本项目针对上述边界周期变化特征的传热过程，研究周期传热边界特征与温度场的协同机制。通过采集钢坯传热边界数据，分析工艺特点，建立模式识别模型，结合传热模型反演逼近计算，得到特征边界函数。研究边界函数的振幅和周期及其耦合对钢坯内温度分布、尤其是温度水平和断面梯度的影响规律；研究振幅、周期和冷却密度对温度场的协同影响规律，揭示其协同作用机理。通过本项目的研究，提出传热边界连续化、特征化方法，探索周期边界特征参数对钢坯温度场影响规律，揭示传热边界特征与传热过程的耦合机制，为钢坯组织和性能研究提供科学依据。

本项目通过传热边界条件特征参数与板坯温度场的协同机制研究，提出传热边界连续化、特征化方法，探索周期边界特征参数对钢坯温度场影响规律，揭示传热边界特征与传热过程的耦合机制，为钢坯组织和性能研究提供科学依据。研究过程中，把铸轧系统分成连铸、加热炉、轧制和层流冷却四个生产单元。采用工艺及理论分析方法对传热边界的特征进行研究，研究发现加热炉炉温可以由三角函数和线性函数叠加而成，轧制单元换热系数主要为梯形波或者矩形波，连铸、层流冷却单元换热系数为以喷头为中心的半波正弦构成的分段函数。在进行传热边界特征分析的基础上，利用数值模拟结合工业现场试验数据分析了特征参数变化对温度场的影响规律，并用层流冷却试验台研究了特征参数之间的协同作用对板坯温度场的影响规律，最后把部分研究成果在企业进行应用，建立企业加热炉在线能效评价系统。