节铬型铁素体不锈钢连铸板坯凝固过程热模拟

连铸板坯凝固传热主要在厚度方向进行,这造成了连铸坯大部分区域由侧面向中心凝固,因此可以近似地用非稳态定向凝固进行热模拟。利用自主研发的水平式连铸坯枝晶生长热模拟装置研究了新型节铬铁素体不锈钢连铸坯凝固组织,以期在工业生产前预测连铸工艺对其凝固组织的影响。热模拟试样热端温度采用连铸坯心部冷却曲线进行控制,并通过调节冷却水流量控制热模拟试样冷端的冷却强度,从而实现由冷端向热端的非稳态定向凝固。实验发现过热度和冷却强度对热模拟试样的等轴晶率及其平均晶粒尺寸影响不显著,但大的冷却强度会导致柱状晶长度增加。     

汽车用钢大方坯连铸二冷配水数学模型

应用开发的连铸传热数学模型对石家庄钢铁有限责任公司炼钢厂电炉车间所生产的5个钢种及2种规格铸坯的二次冷却配水进行了模拟计算；根据铸坯凝固冷却过程冶金准则的要求，经反复模拟及优化，得出了二次冷却区各段水量与拉速的二次关系式；综合考虑了过热度对铸坯凝固过程的影响，建立了新的二次冷却水控制模型，并应用于实际生产。     

Application of Hot Strength and Ductility Test to Optimization of Secondary Cooling System in Billet Continuous Casting Process

By means of Gleeble-1500 dynamic thermomechanical simulator, the continuous casting process for HRB335C steel was simulated using solidifying method and hot ductility and strength of the steel were determined. The test results indicate that there are three temperature regions of brittleness for HRB335C billet in the temperature range from 700 ℃ to solidification point; the first temperature region of brittleness is 1 300 ℃ to solidification point of the billet, the second temperature region of brittleness is 1 200-- 1 000 ℃, and the third temperature region of brittleness is 700-850 ℃ ; the steel is plastic at 850--1 000 ℃. The cracking sensitivity was studied in the different temperature zones of the brittleness for steel HRB335C and the target surface temperature curve for the secondary cooling is determined. With optimized process, the mathematical model of the steady temperature field with two-dimensional heat transfer for 150 mm×150 mm HRB335C steel billet was established to optimize the secondary cooling process. The conic relation of water distribution between secondary cooling water flux and casting speed is regressed. Keeping the surface temperature of billet before the straightening point above 1 000 ℃, the results of billet test indicate that there is free central shrinkage cavity. The billet defect is decreased greatly, and the quality of billet is obviously improved.     

Dynamic Water Modeling and Application of Billet Continuous Casting

The continuous casting process is used for solidifying molten steel into semi-finished steel.The technology of secondary cooling is extremely important for output of the casting machine and billet quality.A dynamic water model was introduced,including solidification model in the secondary cooling,feedforward control strategy based on continuous temperature measurement in tundish,and feedback control strategy based on surface temperature measurement.The mathematical model of solidification process was developed according to the principle of solidification,and the solidification model was validated by measuring billet shell thickness through shooting nail and sulfur print.Primary water distribution was calculated by the solidification model according to procedure parameters,and it was adjusted by the other two control strategies online.The model was applied on some caster and billet quality was obviously improved,indicating that the dynamic water model is better than conventional ones.     

宝钢在线二冷控制模型的研发与应用

针对连铸生产过程中的二冷配水问题,建立了铸坯的凝固传热数学模型。通过实时模拟计算铸坯的温度场,并与PID控制技术相结合,开发了在线二冷控制模型。模型能自动根据钢种、铸坯规格及工艺参数的变化动态调整二冷控制水量,将铸坯的表面温度控制在工艺目标值附近。通过设计合理的控制系统架构,确保了二冷控制系统的稳定性及可靠性。在线测温结果表明,模型具有很高的计算精度。当拉速、浇注钢水过热度变化时,模型能快速将水量调整到目标值,速度快且超调小,从而确保铸坯的表面温度跟踪误差始终限制在较小范围内;当浇注过程处于相对稳态时,铸坯的表面温度保持在目标值。目前,模型已经应用于宝钢内外的多台连铸机,应用效果良好。     

Evolution of Control Models for Secondary Cooling in Continuous Casting Process of Steel

Secondary cooling control is an important factor in the continuous steel casting process. This paper reviews popular control models and analyzes their principles and characteristics. On the basis of the review, this paper proposes a new concept called “effective‐superheat” and a new control model called “synthetical model dynamic control method based on online temperature measurement.” The model, which combines the advantages of the popular models reviewed, not only allows steady, accurate and dynamic control of slab surface temperature, but also provides the temperature profile and the end of the liquid pool. In addition, this paper also discusses the current problems with secondary cooling control and the related development trends, which may be helpful for further development of secondary cooling control technology and informationization of the continuous casting process.     

高品质车轮钢二冷区冷却方式

为了探索高品质低成本车轮钢生产工艺,比较了两种二冷区冷却方式(气雾冷却和全水冷却)对车轮钢铸坯表面温度、凝固组织与宏观偏析的影响.结果表明:两种冷却方式下的二冷区矫直段铸坯表面温度均高于950℃,处于高温塑性区,可避免产生矫直裂纹;两种冷却方式均得到了均匀对称的凝固组织;虽然气雾冷却可略微增加等轴晶比例和降低铸坯中心偏析,但是使铸坯枝晶间距变得较为粗大,并且加重了1/2半径附近处的偏析,对随后的加工和成品的质量更为不利.综合考虑实验结果和生产成本,认为全水冷却方式更适合高品质车轮钢的生产.     

连铸二次冷却研究的进展

从连铸坯凝固传热数学模型、二次冷却配水与控制、钢的高温力学性能和二次冷却喷嘴冷态及热态特性等方面综述了连铸二次冷却研究的进展,分析了相关研究对优化二次冷却控制和提高铸坯质量的参考作用.对运用经典方法研究特殊钢连铸的二次冷却控制技术具有借鉴作用.     

基于目标温度的方坯连铸二冷配水方案优化

通过建立铸坯传热数学模型,对连铸凝固过程进行了解析。制定了二冷配水制度优化原则,基于目标温度控制原则开发出二冷配水控制模型。对不同钢种、拉速等工艺条件下的连铸工艺设计出二冷总水量、水量分配和水量与拉速的关系式,并对配水方案进行了凝固与传热的预测和验证。     

板坯连铸二冷区凝固传热过程与控制

依据安钢板坯连铸机的具体条件,建立了连铸板坯凝固传热数学模型,实现了随铸坯钢种、断面尺寸及拉速变化对各回路水量连续实时控制.经现场应用表明,利用配水模型所制定的二冷配水制度是合理的,效果良好.     

武钢大方坯连铸二冷制度的优化

以武钢第一炼钢厂大方坯连铸机为研究对象,建立了凝固传热数学模型,根据铸坯凝固冷却过程冶金准则的要求,经模拟及优化,得出了SWRH82B钢二次冷却区各段水量与拉速的二次关系式,建立了新的二次冷却水控制模型,并应用到生产实际,明显提高了铸坯质量.     

连铸工艺参数对20CrMnTi齿轮钢150 mm x 150 mm铸坯凝固组织影响数值模拟和生产应用

为改善20CrMnTi钢小方坯凝固组织,基于ProCAST软件中的CAFE模型,对其凝固组织进行数值模拟,研究了不同钢水过热度、铸坯拉速、二冷比水量对凝固组织的影响。模拟结果表明,降低钢水过热度、提高铸坯拉速、降低二冷比水量均可达到增大铸坯等轴晶率和细化晶粒的目的,其中过热度对其影响最大。过热度每降低10℃,等轴晶率平均增加3.7%;拉速每增加0.1 m/min,铸坯等轴晶率平均增加1.8%;比水量每降低0.1 L/kg,铸坯等轴晶率平均增加1.65%。生产应用表明,钢水过热度30℃时,当拉速由原2.2 m/min降低至2.1 m/min,二冷比水量由0.6 L/kg提高至0.7 L/kg,铸坯中心疏松明显减少。     

Design and Simulation Test of Advanced Secondary Cooling Control System of Continuous Casting Based on Fuzzy Self-Adaptive PID

To improve billet quality and the trackability and stability of secondary cooling water during continuous casting, the superheat is introduced into the water distribution for secondary cooling to design the relevant control system, based on the water distribution model, superheat and fuzzy self-adaptive PID (process identity) . A spray cooling system is set up for simulation test in laboratory to test the step signal from the conventional, integral separated and fuzzy self-adaptive PID controllers and the simulation casting. And the on-site test is done in some steel plant. The test results show that the fuzzy self-adaptive PID controller's performance is better than that of the other two controllers, which provides a basis for further study and application.     

A transient simulation and dynamic spray cooling control model for continuous steel casting

A two-dimensional heat-transfer model for transient simulation and control of a continuous steel slab caster is presented. Slab temperature and solidification are computed by the model as a function of time-varying casting speed, secondary spray cooling water flow rates and temperature, slab thickness, steel chemistry, and pouring and ambient temperatures. Typically, the solidification path, temperature-solid fraction relationship, is prescribed. However, if these data are not available, a microsegregation solidification model that approximates the effects of steel chemistry and cooling rate is incorporated in the caster model. Measured slab surface temperatures recorded from an operating caster are compared with predictions from the transient model. These demonstrate that the model typically can predict the temperature response at the slab surface within 30 °C. Results of several simulations are given to demonstrate the effects of changing casting conditions on the slab thermal profile, end of liquid pool, and solidification end point. A control methodology and algorithm suitable for online control of a continuous casting machine is described, and the ability to control the surface temperature profile by dynamically adjusting secondary spray cooling flow rates is demonstrated by simulation. Results from a preliminary version of the model that is capable of running in real time are presented and are compared with the slower, but more realistic, version of the model.     

基于凝固传热模型的轴承钢GCr15二冷研究与应用

采用Gleeble 3500热应力/应变模拟机对轴承钢GCr15进行了高温力学性能测定,根据实际测量的结果,优化原有二冷制度并提出了适合轴承钢二冷冶金准则的二冷水表。并根据实际情况建立了大方坯连铸凝固传热模型,通过射钉试验表明模型准确可靠,在此基础之上提出了基于凝固传热模型的动态二冷控制方法,通过生产实践表明采用特征拉速控制二冷配水可以有效改善铸坯质量。     

16MnNb钢圆坯连铸二冷制度的研究

 以某钢厂圆坯连铸机为研究对象,建立了连铸坯凝固传热模型。在不同拉速下对280 mm断面圆坯二次冷却过程进行仿真优化,确定了16MnNb钢合适的二冷制度。根据仿真结果,在最小工作拉速(0.9 m/min)下,矫直点处铸坯内弧表面中心温度为947 ℃,有效避开了铸坯的二次低延性区。在最大工作拉速(1.2 m/min)下,铸坯出结晶器时,其凝固坯壳厚度为19 mm,二冷初期产生漏钢等质量问题的可能性较小。不同拉速下,横断面温度场分布均匀。经低倍检测发现,铸坯表面及内部质量良好,无裂纹、疏松、缩孔等质量缺陷。     

板坯连铸过程数值模拟分析

基于传热学基本原理、凝固理论和有限单元法,建立了凝固传热有限差分数学模型,对连铸凝固全过程进行模拟分析,结果表明,拉速越大,铸坯中心及表面温度越高,出结晶器坯壳厚度越薄;过热度增大,铸坯中心及表面温度均上升,出结晶器坯壳厚度减薄;冷却水量相对增大时,铸坯出结晶器坯壳厚度增大,二冷区温度下降较快。连铸坯凝固模型可用来确定常规拉速范围及不同拉速下的凝固壳厚度、凝固末端位置以及铸坯表面温度分布。     

钢液连铸二次冷却先进工艺模型的发展与研究

 钢液连铸二次冷却的效果直接影响连铸坯质量,为了合理地控制二次冷却过程,多种静态和动态控制工艺模型被提出。系统综述了目前二冷静态和动态控制工艺模型的发展,包括二冷区各回路水量与拉速呈一次线性或二次曲线关系的二冷控制工艺模型、基于修正有效拉速的二冷动态控制工艺模型和基于在线传热计算的二冷动态控制工艺模型等,以及基于钢液过热度和二冷进水温度的二冷控制先进工艺模型和基于在线温度测量反馈调节各回路水量的二冷动态控制工艺模型。随着二冷控制工艺模型的发展,其控制的实时性、可靠性、准确性以及运行的稳定性也逐渐提高,从而为高质量铸坯生产及智能化二冷控制奠定了基础。     

不锈钢板坯连铸温度场及二冷配水优化的研究

采用有限元法编制了计算不锈钢板坯在连铸时凝固过程温度场及坯壳的生长随时间的变化。将计算结果与实测结果进行了比较 ,得出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     

基于射钉法的板坯连铸工艺优化

利用射钉法测定了连铸机板坯冷却过程凝固坯壳厚度,重点分析了中间包钢水过热度、拉速、二冷区冷却制度与铸坯凝固系数之间的关系,对凝固系数影响大小的顺序为:过热度＞拉速＞比水量.采取控制中包钢水过热度及拉速,优化二冷配水工艺,调整铸机扇形段开口度等措施,铸坯中心偏析平均级别由B1.5 ～ B2.0降低至B0.5～ B1.0,试样分层缺陷改判率由0.36％降低至0.06％.