热轧带钢超快速冷却技术的研究与应用

发布时间：2018-04-11 11:27

本文选题：超快冷 + 扩散性　；参考：《东北大学》2015年博士论文

【摘要】：本文依托国家“十二五”科技支撑计划中“钢铁行业绿色生产工艺技术与应用示范”项目子课题“热轧板带钢新一代TMCP装备及工艺技术开发与应用”项目,以热轧带钢超快速冷却过程数值计算为研究对象,以实现高强度均匀化冷却为研究目标,采用解析计算与数值计算方法,从热轧带钢温度场计算方法、喷嘴射流扩散性和均匀性、最优化冷却板形实现方法、轧后冷却强度分析和冷却过程中厚度方向温度变化规律五方面入手,针对超快冷设备设计及超快速冷却工艺开发过程中的重点问题和关键技术进行系统分析与研究,成功开发出超快速冷却技术,并在工业现场取得良好的应用效果。论文的主要研究内容和结果如下：(1)针对热轧带钢冷却过程的特点,采用解析方法建立了三种边界条件下热传导微分方程的解,并与集总参数法得到的解进行对比,得到不同计算误差范围内毕渥数取值范围；同时对换热系数的计算方法进行了分析,得到直接计算、反算和实验法获得换热系数的具体过程,以上研究结果对于温度场在线计算模型的选定、计算误差预测和换热系数的计算具有重要参考价值。(2)冷却水由喷嘴出口射流至空气中,与空气发生卷吸作用使得冷却水扩散,对射流扩散性问题进行研究,得到圆形喷嘴和缝隙喷嘴射流过程中轴线速度、势流核心区长度和半衰距长度变化规律；针对不同的喷嘴类型,研究了不同结构参数下喷嘴射流截面流速大小及分布规律,得到了喷嘴集束性最优时喷嘴结构参数范围,为喷嘴结构设计及选型提供技术参考。(3)具有一定湍流强度的冷却水射流至带钢表面形成射流冲击,并形成自由射流区、射流冲击区和壁面射流区。对湍流射流冲击进行研究,得到喷嘴出口速度、尺寸和喷距对射流冲击区和壁面射流区流速大小及分布的影响规律,对计算结果进行对比分析,得到降低喷距对提高各个区域的流速可起到最明显的作用,同时在带钢表面0.4mm漫流层流速最高,此后距带钢表面越远漫流层流速越低。(4)根据开发的多级阻尼结构的高密喷嘴和缝隙喷嘴,采用数值计算方法计算出不同入口速度时喷嘴长度方向流速大小及分布,经过对比分析得到喷嘴射流均匀性最优时的喷嘴结构。(5)对超快速冷却过程中板形变化规律进行研究,得到最优化的水比对于降低带钢的翘曲可起到最直接有效的作用；当上下表面换热系数基本相同,带钢边部弱冷或过冷时可出现宽度方向温度不均匀现象,但是不会出现明显的边部波浪,因此,最优化的水比设定是板形质量良好的关键。(6)以带钢冷却过程中换热系数为研究对象,得到了层流冷却、加强型冷却和超快速冷却方式下不同上集管流量时最优水比,并采用最小二乘法对最优水比进行拟合得到最优水比计算公式；喷距、水温、射流角度和喷嘴出口速度可影响带钢表面换热系数,对计算结果进行对比分析得到以上因素对换热系数的影响规律,该研究结果对于冷却设备的设计和冷却工艺参数的设定可起到指导作用;对不同冷却方式下的冷却强度进行对比分析,得到不同冷却方式下换热系数变化情况以及呈现该变化规律的原因,为轧后冷却系统改造或选型提供技术参考。(7)针对冷却过程中厚度方向温度大小及分布规律进行研究,得到了前置式超快冷和后置式超快冷厚度方向温度大小及分布的主要影响因素及其影响规律。采用最小二乘法拟合得到返红温度、返红时间和心表温差计算公式；对厚度方向边界层位置和平均温度位置进行研究,得到了其变化规律：边界层位于1/4厚度方向,同时在边界层内侧所有节点温度基本相同,边界层外侧相邻节点之间的温度差较高,且越靠近带钢表面,相邻节点之间的温度差越高；厚度方向平均温度与3/11倍厚度方向位置的温度基本相同,且在超快速冷却和层流冷却过程中计算精度最高,在返温过程中计算偏差在10℃以内,且其位置基本不受冷却速率、开冷温度和带钢厚度的影响。(8)针对超快速冷却工艺的特点开发出供水压力、集管流量及温度控制方法及控制系统,经工业化运行测试,所开发的控制系统的稳定性和控制精度较高,满足了工艺需求。本论文基于实现热轧带钢高强度均匀化冷却所做的工作,对于冷却设备设计、工艺参数制定具有重要的理论指导意义。
[Abstract]:This paper relies on the "12th Five-Year" National Science and technology support program in the "green steel industry production technology and demonstration project" hot rolling strip of a new generation of TMCP equipment and technology development and application "project, in the hot strip during ultra fast cooling numerical calculation as the research object, in order to achieve high strength homogeneous cooling research the target, the analytical calculation and numerical calculation method, calculation method of temperature field in hot rolled strip, and the uniformity of jet diffusion, realization method of shape optimization of cooling plate, thickness variation of temperature cooling after rolling and cooling process in the strength analysis of the five aspects of system analysis and research aiming at the key problems and key technology of ultra fast cooling ultra fast cooling equipment design and process development, the successful development of ultra fast cooling technology, and achieved good application in industrial field Results. The main research contents and results are as follows: (1) according to the characteristics of hot rolled strip during cooling process, the differential equations are established. Three kinds of boundary conditions of heat conduction solution by analytical method, and compare the solution with the lumped parameter method, different calculation error range of the Biot number range; at the same time calculation method of heat transfer coefficient is analyzed, by direct calculation, the specific process of the heat transfer coefficient for calculation and experimental method, the above research results of calculation model of temperature field for the selected online, calculation error prediction and heat transfer coefficient have important reference value. (2) the cooling water from the outlet of the nozzle to jet in the air, and the air entrainment of the cooling water diffusion of jet diffusion problems, get the axial velocity of circular nozzle and crevice nozzle in the process of potential core length and half From the variation of length; for different types of nozzle were studied under different structural parameters, nozzle jet flow size and distribution, the optimal structure parameters of nozzle cluster nozzle, provide technical reference for the design and selection of nozzle structure. (3) has a certain turbulent intensity of surface cooling water jet to form jet strip the impact and the formation of free jet region, the impact area and wall jet jet to surface area. The research on turbulent jet impingement, from the nozzle exit velocity, size and jet distance influence on the size and distribution of jet flow region and wall jet region, the comparative analysis of the calculation results, reduce the jet distance of each the regional velocity plays the most significant role, at the same time on the strip surface layer flow velocity 0.4mm is highest, then from the strip surface is far lower. The velocity of cross flow layer (4) according to the development. High density nozzle and slit nozzle level damping structure, by using the numerical method to calculate the different entrance speed nozzle length direction flow size and distribution, through comparative analysis by jet nozzle structure uniformity best. (5) to study the variation of shape of ultra fast cooling process in optimum water ratio for to reduce the warpage of the strip can play the most effective role; when the upper and lower surface heat transfer coefficient is basically the same, appear the phenomenon of uneven temperature along the width of the strip edge can be weak cold or cold, but does not appear obvious side wave, therefore, the optimization of water than the set is a key quality good shape. (6) a strip in the cooling process of the heat transfer coefficient as the research object, the laminar cooling, enhanced cooling and ultra fast cooling under different set tube flow optimal water ratio, and using least squares The multiplication of the optimal ratio of water than the fitting formula of optimal water; spray distance, water temperature, jet angle and jet velocity can affect the strip surface heat transfer coefficient of influence comparison between the above factors on the heat transfer coefficient on the calculation results, the results of the study on cooling equipment design and cooling process parameter setting can play a guiding role; to analyze the cooling intensity under different cooling conditions, obtained under different cooling conditions for the change of heat coefficient and presenting the change rule of reason, to provide technical reference for cooling system modification or selection. (7) research on the thickness of the cooling process the temperature of size and distribution the main influencing factors, front and rear mounted ultra fast cooling and ultra fast cooling temperature, the size and distribution of the thickness and the influence law fitting using least squares method. Get red temperature, red time and surface temperature calculation formula; to study the thickness of boundary layer position and the average temperature, and obtains the variation rule of boundary layer of 1/4 thickness, and all the nodes in the boundary layer inside temperature is basically the same, the higher the difference between the boundary layer adjacent to the outside of the node and the temperature. The more close to the strip surface, the temperature difference between adjacent nodes is higher; the thickness and average temperature of 3/11 times the thickness direction the temperature is basically the same, and in the ultra fast cooling and laminar cooling process in the highest accuracy, the calculation deviation is within 10 DEG C temperature in the return process, and its position is not affected by the cooling rate. Effect of cooling temperature and strip thickness. (8) the ultra fast cooling process. The characteristics of the development of water supply pressure, pipe flow and temperature control method and control system, the industrial operation test, the The stability and control accuracy of the developed control system is high, which meets the process requirements. This paper is based on the work of achieving high strength homogenization cooling of hot rolled strip, which has important theoretical guiding significance for the design of cooling equipment and the formulation of process parameters.

【学位授予单位】：东北大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG335.56

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