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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。 相似文献
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Application of Hot Strength and Ductility Test to Optimization of Secondary Cooling System in Billet Continuous Casting Process 总被引:1,自引:0,他引:1
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. 相似文献
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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. 相似文献
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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。 相似文献
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Zhichao Dou Qing Liu Bao Wang Xiaofeng Zhang Jianfeng Zhang Zhigang Hu 《国际钢铁研究》2011,82(10):1220-1227
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. 相似文献
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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. 相似文献
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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。 相似文献
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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. 相似文献
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A transient simulation and dynamic spray cooling control model for continuous steel casting 总被引:6,自引:0,他引:6
Richard A. Hardin Kai Liu Christoph Beckermann Atul Kapoor 《Metallurgical and Materials Transactions B》2003,34(3):297-306
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. 相似文献
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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。 相似文献
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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。 相似文献
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