Q345D大方坯连铸过程数值模拟

以Q345D大方坯为研究对象,采用二维传热模型对铸坯进行温度场计算.计算了不同拉速、过热度和二冷水量下铸坯温度分布和坯壳生长情况,分析了拉速、过热度和水量对铸坯的温度分布和坯壳生长的影响.得到了不同工艺下,铸坯温度分布规律和凝固坯壳生长规律,为实际生产提供一定的指导.     

大方坯连铸过程中铸坯传热及凝固行为的研究

结晶器和二冷区传热对大方坯产品质量和铸机的生产率有重要影响，本文讨论了包钢引进的全国最大的方坯连铸机在拉坯时结晶器和二冷区传热情况以及坯壳凝固生长，铸坯温度的变化规律。着重讨论了电磁搅拌，过热度和拉速对坯壳凝固和生长规律的影响，指出控制铸坯凝固的主要因素是凝固潜热，影响凝固未端的最主要因素是拉速，而电磁搅拌对其影响区内的传热和坯壳生长和铸坯温度亦有重大影响。     

拉坯速度对连铸大方坯凝固的影响

结合现场研究,利用显式有限差分法计算出不同工艺条件下的铸坯凝固情况;进行了拉坯速度对出结晶器坯壳厚度、铸坯表面温度、铸坯凝固终点位置和铸坯质量影响的模拟分析研究.模拟结果表明,拉速对铸坯表面温度和凝固终点的影响较大,随拉速的增大,表面温度升高,出结晶器坯壳厚度减薄,铸坯液相穴拉长.     

包钢大方坯连铸机结晶器凝固传热的数值模拟

根据包钢的现场条件,建立了大方坯连铸机结晶器内二维非稳态凝固传热数学模型,采用有限差分法对数学模型求解,得出结晶器中铸坯的温度分布规律和凝固坯壳生成规律,同时研究了拉坯速度对坯壳生成厚度的影响。     

高拉速条件下防止连铸坯菱变（脱方）应采取哪些措施

菱变(脱方)是结晶器4个面不均匀冷却所致，由于受结晶器壁的约束在出结晶器之前，铸坯坯壳呈方形，但坯壳厚度不均匀，冷却强的角部形成锐角，冷却弱的角部形成钝角，在二冷区喷水冷却时，即使4个面冷却均匀但坯壳厚度不均匀而造成的温度不一致，可能导致坯壳不均匀收缩而造成菱变(脱方)，高拉速条件下坯壳厚度减薄，更容易造成菱变(脱方)，高拉速条件下防止连铸坯菱变(脱方)应采取如下措施：     

方坯连铸凝固传热数值模拟及二冷动态控制

二冷是影响连铸机生产和铸坯质量的重要因素,针对连铸二冷区的均匀冷却问题,建立了方坯连铸机数学模型,其中包括铸坯凝固传热模型和二冷配水控制模型．采用二维有限元差分法求解凝固传热模型,分析了铸流在二冷区的凝固过程中温度场分布和凝固坯壳厚度,为建立二冷控制模型提供了依据和输入数据．建立了基于中间包钢水连续测温和有效拉速实现二冷动态前馈控制模型。该控制模型成功应用于实际铸机的二冷配水,应用结果表明：二冷动态控制模型具有比传统二冷配水控制模型更好的控制效果,铸坯质量有了明显提高．     

威钢1号ROKOP小方坯连铸的二冷制度分析

针对威钢1号ROKOP铸机的特点，建立了连铸凝固的二维传热数学模型，在模型中，提出了喷嘴的有效喷淋系数和有效比水量的概念。用建立的数模仿真和优化，获得了拉速提高后、二冷区采用五段喷水结构下的二次制度和铸坯表面温度的变化规律。同时通过计算还获得了原有的二次两段喷水结构的铸坯表面温度的变化规律。比较表明，原有的两段结构铸坯在二冷区表温回升大，容易在凝固前沿产生中间裂纹优化后的五段结构基本消除了这一质量问题，并已被生产实践所证明。     

二冷强度对连铸小方坯凝固过程影响规律的数模研究

针对连铸小方坯的中心疏松等质量缺陷,建立了凝固传热数学模型,以研究二冷强度对连铸小方坯凝固过程的影响规律,优化二冷制度,改善铸坯质量.本文基于射钉和测温实验所建立的小方坯凝固传热模型精细度较高,用此模型深入研究二冷喷嘴的数量和喷射范围对小方坯凝固传热的影响;经验证,模拟结果与实测结果误差在1.7％以内.利用该模型定量分析了二冷强度对铸坯温度,凝固坯壳厚度和凝固终点的影响规律.结果表明,随着二冷强度的增大,二冷区内的铸坯表面中心温度降低,而进入空冷区后则逐渐趋于一致.二冷强度每增加10％,足辊段出口处温度平均降低8℃,二冷一段出口处温度平均降低10.75℃,二冷二段出口处温度平均降低10.75℃,二冷三段出口处温度平均降低9.75℃,铸坯凝固终点缩短约0.168m.     

高拉速情况下容易出现的铸坯缺陷

连铸机拉坯速度与铸坯质量有着非常复杂的关系。由于拉速提高，钢水在结晶器中的流动状态更加激烈，传热及凝固过程易于波动，高拉速时容易出现偏角纵裂纹漏钢、铸坯表面纵裂纹。拉速提高，钢水中夹杂物上浮困难，二次冷却区液心长度增长，受各种应力的作用，铸流在此区间的湍流影响范围较大，易于产生内裂和偏析。     

Q235小方坯连铸过程中凝固特性的研究

分析了Q235凝固时的结晶特性,柱状晶容易生长.数值计算了小方坯连铸机在2.6 m/min拉速、不同二冷配水下铸坯的温度场和凝固前沿温度梯度.在弱水冷却时,铸坯坯壳凝固前沿温度梯度比较小,得到细小的柱状晶和少量等轴晶.连铸坯中间裂纹主要与二冷水相关,合适的二冷配水可降低或消除中间裂纹.     

小方坯连铸二冷配水对凝固与传热的影响

研究小方坯连铸在二次冷却过程中的坯壳凝固情况,建立了传热过程的二维非稳态数学模型,计算出在整个连铸过程中温度变化和温度场分布,并得出在二冷区铸坯凝固速度与换热系数的关系.     

Q345D板坯连铸凝固传热过程数值模拟

基于凝固传热学理论,以300 mm厚Q345D板坯连铸过程为研究对象,建立了板坯二维凝固传热数学模型。利用等效比热法对凝固潜热进行处理,分析了拉速、过热度、二冷区喷水量以及二冷区长度变化对出结晶器坯壳厚度、铸坯表面温度等凝固参数的影响。结果表明,适当提高拉速、降低过热度和增加二冷段长度,可以促进连铸坯凝固,降低板坯缺陷,提高生产效率。     

Generalized constructal optimization for the secondary cooling process of slab continuous casting based on entransy theory

Based on constructal theory and entransy theory,a generalized constructal optimization of a solidification heat transfer process of slab continuous casting for a specified total water flow rate in the secondary cooling zone was carried out.A complex function was taken as the optimization objective to perform the casting.The complex function was composed of the functions of the entransy dissipation and surface temperature gradient of the slab.The optimal water distribution at the sections of the secondary cooling zone were obtained.The effects of the total water flow rate in the secondary cooling zone,casting speed,superheat and water distribution on the generalized constructal optimizations of the secondary cooling process were analyzed.The results show that on comparing the optimization results obtained based on the optimal water distributions of the 8 sections in the secondary cooling zone with those based on the initial ones,the complex function and the functions of the entransy dissipation and surface temperature gradient after optimization decreased by 43.25%,5.90%and 80.60%,respectively.The quality and energy storage of the slab had obviously improved in this case.The complex function,composed of the functions of the entransy dissipation and surface temperature gradient of the slab,was a compromise between the internal and surface temperature gradients of the slab.Essentially,it is also the compromise between energy storage and quality of the slab.The"generalized constructal optimization"based on the minimum complex function can provide an optimal alternative scheme from the point of view of improving energy storage and quality for the parameter design and dynamic operation of the solidification heat transfer process of slab continuous casting.     

不锈钢板坯连铸温度场及凝固末端位置的研究

采用有限元法计算了不锈钢板坯在连铸时凝固过程中温度场及坯壳的生长随时间的变化，讨论了过热度，拉速及二冷配水量对温度场及凝固末端位置的影响。结果表明，影响铸坯温度场和凝固末端位置的主要因素是拉速和二冷配水，而过热度影响较小。     

Establishment and Application of A Mathematical Model for Rectangular Billet Continuos Casting

A two dimension unsteady heat transfer model is established for rectangular billet casting. Solidification process of liquid steel in secondary cooling zone was analyzed using direct difference method. The influence of operation parameters including casting speed and temperature of liquid steel was investigated. Experimental results have been used for increasing the casting speed.     

气雾射流动态传热实验研究

设计搭建了气雾射流动态传热实验装置,建立了二维非稳态导热反问题模型,研究了表面温度和表面热流密度的时间分布.结果表明在冷却过程中缸体穿越喷射区与淌水区历经了几个不同的换热阶段,温度曲线出现了明显的周期性的特点,成功的模拟了连铸二冷气雾冷却周期性换热的特征.     

Mathematical model of heat transfer for bloom continuous casting

A mathematical model for heat transfer during solidification in continuous casting of automobile steel, was established on researching under the influence of the solidifying process of bloom quality of CCM in the EAF steelmaking shop, at Shijiazhuang Iron and Steel Co. Ltd. Several steel grades were chosen to research, such as, 40Cr and 42CrMo. According to the results of the high temperature mechanical property tests of blooms, the respective temperature curves for controlling the solidification of different steels were acquired, and a simulating software was developed. The model was verified using two methods, which were bloom pinshooting and surface strand temperature measuring experiments. The model provided references for research on the solidifying process and optimization of a secondary cooling system for automobile steel. Moreover, it was already applied to real production. The calculated temperature distribution and solidification trend of blooms had offered a reliable theory for optimizing the solidifying process of blooms, increasing withdrawal speed, and improving bloom quality. Meanwhile, a new secondary cooling system was designed to optimize a secondary cooling water distribution, including choice and arrangements of nozzles, calculation of cooling water quantity, and so on. 2008 University of Science and Technology Beijing. All rights reserved.     

Heat-transfer model on the improvement of continuous casting slab temperature

A heat transfer model on the solidification process has been established on the basis of the technical conditions of the slab caster in No.3 steel works of Wuhan Iron & Steel Corporation, and the temperature field in the solidifying slab was calculated which was verified by the measured slab surface temperature. The influences of the main operating factors including casting speed, spray cooling patterns, superheat of melt and slab size on the solidification process were analyzed and the means of enhancing the slab temperature was brought forward. Raising the casting speed to 1.3 m/min, controlling the flowrate of secondary cooling water and improving the cooling pattern at the lower segments of secondary cooling zone could improve the slab temperature effectively. And the increasing the superheat is adverse to the production of high temperature slab.     

影响亚包晶钢铸坯表面纵裂纹的因素研究

采用金相、扫描电镜、连续测温等方法对亚包晶钢铸坯表面纵裂纹产生原因进行了系统研究,研究结果表明:当钢水过热度35℃和15℃浇铸时,铸坯表面纵裂纹发生率明显提高;随着拉速的增加铸坯纵裂纹发生率呈上升趋势;在同一拉速条件下,铸坯内弧比外弧更易于生成凹陷和裂纹;结晶器铜板热流密度不均是铸坯纵裂纹产生的主要原因,并在二冷区进一步扩展。