中厚板淬火过程的热力学数值模拟及实验

 以高密度管流冲击钢板表面时的对流换热边界为基础，采用ANSYS三维有限元对中厚板淬火中的钢板温度场、应力场及应变场进行了数值模拟，并对模拟得到的温度与时间、应力以及塑性应变的关系进行分析，得到了淬火冷却过程中保持钢板平直状态下应力、应变及变形的特点，为采用适当工艺措施使中厚板淬火获得平直板形提供了理论依据。     

中厚板淬火过程的横向冷却曲线

针对中原板淬火过程中均匀喷水时造成钢板变形的现象，提出了非均匀喷水的补偿方法，采用有限元分析方法，对钢板在多股集管冲击射流作用下的温度场分布进行了数值模拟，得到钢板横向冷却曲线，为无约束淬火机上集管的工艺设计提供了理论依据。     

相变对无约束淬火控冷工艺参数的影响

以高密集射流冷却时钢板表面的对流换热边界为基础,采用有限元分析对不锈钢1Cr18Ni9Ti和合金钢20CrMnTi常压无约束淬火过程的温度场、应力应变场进行数值模拟,分析对比了2种钢板的温度及X向应力变化规律,且对不同上下水量比下2种钢板的厚度方向的变形量进行了比较,分析了淬火过程马氏体相变对钢板变形的影响,为优化控冷工艺更好控制板形提供了依据.     

基于ANSYS平台的中厚板控冷过程的横向冷却曲线

针对中厚板控冷过程中均匀喷水时造成钢板变形的现象，提出了非均匀喷水的补偿方法，利用ANSYS大型有限元分析软件对钢板在多股集管冲击射流作用下的温度场分布进行了数值模拟，得到钢板横向冷却曲线，为控冷装置上集管的工艺设计提供了理论依据．     

圆形冲击射流对水层的穿透深度研究

要使中厚板淬火控冷装置获得最佳的冷却能力,必须要保证冲击射流可以穿透钢板表面的滞留水层。通过实验和数值模拟的方法,研究了圆形冲击射流对水层的穿透深度与射流速度、射流直径和射流高度的关系,并给出了穿透深度与射流出口弗鲁德数Fr的拟合曲线关联式。     

基于ANSYS平台的中厚板控冷过程的横向冷却曲线

针对中厚板控冷过程中均匀喷水时造成钢板变形的现象,提出了非均匀喷水的补偿方法,利用ANSYS大型有限元分析软件对钢板在多股集管冲击射流作用下的温度场分布进行了数值模拟,得到钢板横向冷却曲线,为控冷装置上集管的工艺设计提供了理论依据。     

钢板轧后冷却过程的数值模拟及变形分析

 针对钢板冷却发生翘曲变形的问题，利用热弹塑性有限元法对中厚板冷却过程的温度场及应力应变场进行数值模拟。采用分步循环加载的方法精确模拟不同换热边界条件，温度场模拟结果与实测值吻合较好。将热分析得到的温度场作为载荷进行钢板冷却过程应力应变的模拟，模拟结果表明塑性应变差出现在水冷的开始阶段。因此为了获得平直的板形，必须调整上下集管水量比，尽量减小水冷开始时上下表面的应力和塑性应变差。     

缝隙流冷却特性分析

压辊式淬火机由高压区和低压区组成，其中高压区在钢板的淬火过程中起着重要作用，本文目的是研究高压区缝隙喷嘴冲击射流的流体力学特性和热传递特性，应用CFD软件对其进行数值计算，得出其速度、压力、平面换热系数曲线，为淬火工艺提供依据。     

气体射流冲击高温钢板的瞬态换热实验研究

采用实验的方法研究了单个圆形喷嘴冲击射流冷却高温钢板的瞬态传热特性.实验中喷嘴到被冲击表面距离H/D为4和8,射流Re数为在22 700到31 000的范围内.实验结果表明,提高气体流量可以有效提升圆形喷嘴的换热能力.射流冲击距离H/D和射流Re数对Nu数具有明显的影响.在对瞬态实验结果的分析表明,随着实验工件表面温度的降低,换热系数和Nu数逐步降低,说明被冲击表面温度对气体射流冲击换热系数和Nu数具有一定的影响.在气体射流冲击冷却过程中,被冷却物体表面温度对换热系数的影响不可忽略.     

中厚板控冷及淬火冷却形式选用分析

 目前对常压柱状流及中高压射流的冷却能力一般仅停留在定性认识基础上,而没有从量上揭示这两种喷流形式冷却能力。利用ANSYS对中厚板控冷及淬火中常压柱状流及中高压喷射流冷却的钢板温度场进行了实验及数值模拟,研究两种不同形式的喷流在实际冷却中温降速率大小,研究两种喷流的最大冷却能力,得到两种喷流在实际装置中最大淬火钢板厚度,从而为控冷及淬火装置的选型及设计提供理论依据。     

雾化冲击射流冷却热轧钢板的研究

利用有限元耦合场数值模拟计算方法对热轧钢板雾化冲击射流冷却进行模拟计算,结果表明,在其它条件相同的情况下,单喷嘴喷射时,在上喷和下喷的喷嘴附近冷却能力相同;多喷嘴喷射时,横向存在二次冷却,钢板表面横向温度分布总体上呈现逐渐降低的趋势。     

中厚板淬火过程中冷却变形影响因素分析

利用ANSYS三维热弹塑性有限元对中厚板淬火中的钢板变形进行热力数值模拟,并结合实验研究对钢板冷却变形影响因素进行分析,以量化方式研究了喷流形式(高压喷射流与常压管流)、上下喷嘴水比、纵向喷嘴分布间距(辊距)、钢板运行速度对钢板冷却变形的影响,为淬火过程获得平直板形提供理论基础.     

带钢连退线风管式冷却过程的数值模拟

 喷射气体冷却是带钢连续退火和镀后冷却过程中最重要的冷却方法,不同的冷却器结构对冷却性能影响很大。针对带钢连续退火及镀后冷却风管式冷却器工艺过程,将计算区域划分为2个子区域,经过网格独立性检验,在一定网格数目基础上利用数值模拟软件进行数值模拟研究。通过对风箱风管区域研究获取冷却器的压力流量公式,对冲击射流冷却区域研究获取带钢表面对流换热系数及带钢冷却速度变化。典型工况下带钢表面平均对流换热系数为117.29W/(m2·K),带钢冷却速度14.0℃/s。     

Heat Transfer during Multiple Jet Impingement on the Top Surface of Hot Rolled Steel Strip

Using a unique pilot facility a series of tests were conducted using three top jets to simulate the heat transfer that occurs during run‐out table (ROT) cooling. Steel samples instrumented with internal thermocouples were tested on this facility and the effect of top jet configuration (nozzle spacing of 40 to 115mm), and water flow rate (15 and 30 1/min) were quantified using moving plate samples. The multiple top jet work indicated that heat transfer across the plate width varies significantly and is high directly under the nozzle but decreases rapidly away from the nozzle in the interaction region. As cooling progresses a much larger wetted region occurs and more uniform cooling is experienced across the plate. Multiple jet cooling experiments have also confirmed that nozzle spacing does have an effect on heat transfer. This effect is predominate in the interaction region where closer nozzle spacing leads to enhanced and more uniform heat transfer in the lateral direction across the plate width away from the nozzle. As expected higher water flow rates led to higher heat transfer both under the nozzle and in the interaction region.     

薄板坯连铸结晶器热流分布研究

通过结晶器温度检测软件在线采集了武汉钢铁(集团)公司CSP结晶器铜板的温度,根据热电偶实测温度及连铸机冷却参数,计算了浇铸不同断面SPHC钢时不同拉速的热流值,并建立了结晶器热流的二维分布模型。结果表明,结晶器受水口射流影响,热流与温度在宽面横向分布很不均匀,表现出明显的双峰结构。相同工况条件下在铜板宽度方向上温度和热流密度分布具有相似性,距离弯月面越近,热流密度和温度的波动越大,弯月面处热流密度最大值达到4.6 MW/m2。     

Development of accelerated cooling for new plate mill

Abstract

The aim of the paper is to design the new wide plate mill. The work on the new cooling technology was supported by extensive laboratory testing while a simulator with full scale testing of cooling units was used. The principal objective of the investigation was to establish the design specification of equipment for accelerated cooling, particularly with respect to the product dimensions and steel grades. The possibilities of accelerated cooling are limited by technical parameters of cooling equipment such as thickness of water layer, flowrate, spray height, position of cooled surface to the nozzles and water or plate speed. These parameters were studied for different product temperatures and water impingement densities from 50 to 110 l s^?1 m^?2. The heat transfer coefficient was determined and compared for each case. There were three recognised significant cooling regions: water layer region, impinging jet region without water layer and impinging region with water layer, which must be taken into account. The application of the new cooling technology showed better flatness product and productivity higher than previous accelerated cooling system, even shorter cooling length. The rejection ratio by flatness problem of new mill was nearly half of the previous one.     

喷嘴射流特征对连铸二冷区蒸汽膜穿透行为的影响

 连铸二冷区铸坯表面温度通常高于900 ℃,此时喷淋液滴接触高温铸坯时不会湿润铸坯表面,仅在其上形成一层蒸汽膜,阻碍了液滴与铸坯表面接触传热。针对以上问题,以国内某钢厂连铸二冷区的扁平型水喷嘴为原型,建立了喷嘴射流仿真计算模型,并对所建模型进行了理论和实验室验证;采用数值模拟的方法研究了喷嘴自由射流区的流场分布,运用连铸喷嘴冷却检测系统测量获得了射流液滴粒径演变规律;结合数值模拟和实验室测定结果,定量分析了喷嘴在不同水流量下射流液滴冲击铸坯表面蒸汽膜深度的变化规律。结果表明,该喷嘴的最大射流速度在喷嘴出口处,射流在喷嘴出口附近出能维持较大的射流速度,且随着水量的增加,射流保持高射流速度的距离也增长;整体射流的轴向速度占比均在80%以上。当喷淋水量越大时,射流液滴粒径变得越小;随着距喷嘴出口距离的增加,射流中心处的液滴粒径逐渐增大并达到最大值;当水流量为9和12 L/min时,液滴粒径基本相同,这表明当水流量增加到一定值时,冷却水量的增加不影响液滴粒径分布。在不同水流量下,随着喷淋距离的增加,液滴穿透铸坯表面蒸汽膜深度呈先增大后略微减小的变化规律,在喷射距离为100~200 mm范围内时,液滴穿透深度最大,这表明喷射高度在该范围时,喷淋冷却效果最好。     

Cooling of a moving steel strip by an array of round jets

Starting from slabs of known dimensions and chemical composition in a hot strip mill, homogeneous strips of predetermined geometry and mechanical properties may be produced. While the geometry and the surface quality are influenced by the deformation process, mechanical properties depend on the cooling process applied immediately after the last stand. Accelerated cooling of steel strips is one of the best ways to achieve both high cooling efficiency and desirable product qualities. A mathematical model is developed to predict the thermal behaviour of steel strips cooled by an array of round jets. Parameters such as the arrangement of the cooling line, nozzle diameter, jet velocity and temperature, and the strip chemical composition (thermophysical properties), thickness and velocity are considered. The governing equation was solved numerically, and the boundary conditions were imposed in different cooling regimes along the cooling line in the form of experimentally and analytically obtained heat transfer coefficients. The mathematical model was validated by comparing predictions for an industrial cooling line with measured starting and coiling temperatures.