【作者】 龙木军；

【导师】 陈登福；

【作者基本信息】 重庆大学 ， 冶金工程， 2007， 硕士

【摘要】 连铸二冷动态轻压下技术是近年来发展比较迅速的一种新工艺。二冷动态轻压下技术的应用,可以有效地改善或消除连铸坯凝固过程中的中心偏析和中心疏松质量问题,提高生产效益。二冷动态轻压下技术在国内处于刚起步状态,大多企业都是引进国外的设备,在技术方面仍是个黑匣子,尚未把握技术要领。因此自行研究开发动态轻压下技术具有重大的意义。本文采用差分离散法建立了板坯连铸一维凝固传热模型,并应用截片阵列记忆思维模式对连铸过程铸坯的温度场实现动态模拟跟踪。在此基础上,结合PID控制算法,对连铸坯的温降规律进行实时调节控制。在二冷动态模型实时跟踪的基础上,建立板坯连铸二冷动态轻压下辊缝收缩模型。辊缝收缩模型同时考虑了铸坯的自然凝固收缩和动态轻压下消除铸坯质量缺陷。模型通过温度梯度节点法计算固态和固液两相区的自然凝固收缩。在测试钢种高温性能的前提下,了解钢种产生内裂的临界应变,并推导计算动态轻压下区域的最佳压下量。结合二冷动态模型和辊缝收缩模型,开发了板坯连铸二冷动态轻压下系统,并针对柳钢4号板坯连铸机AH36钢和Q345钢的生产实际工况进行了不同工艺条件的模拟研究。研究表明:(1)二冷动态轻压下系统响应快速,动态调节性能良好,可以有效地控制铸坯表面温度。(2)连铸坯的自然凝固收缩主要跟铸坯凝固状态有关,铸坯凝固壳厚度越大,收缩量越大,相应扇形段锥度越大。(3)在常用拉速0.9m/min～1.1m/min时,柳钢4号连铸机AH36钢和Q345钢生产动态轻压下的最佳总压下量通常在4mm～6mm。(4)拉速增大,连铸坯的凝固末端位置和动态轻压下位置后移,动态压下量也相应增大。浇铸温度增大,连铸坯的凝固末端位置到弯月面距离会增大,但对动态压下量影响不大。与浇铸温度相比,拉速变化对轻压下参数的影响较大些。二冷动态轻压下系统经过修正后,基本上能够真实反应连铸机的工作实况,可以有效辅助实际生产。更多还原

【Abstract】 Dynamic soft reduction technology for secondary cooling during continuous casting is a kind of new technology that developing quickly in recent years. Owing to the application of dynamic soft reduction technology for secondary cooling, the quality problems of center segregation and center porosity for casting slab can be improved or eliminated effectively during the solidification process in continuous casting; And productive benefits have been improved. Dynamic soft reduction technology for secondary cooling in China is now just in a start state. Most enterprises are importing foreign equipment, however, it is still a black box on the side of technology, essentials are not be grasped yet. So research and development our own technology of dynamic soft reduction is of great significance.The one dimension heat transfer model for slab continuous casting had been developed in this text, by the way of differencing discretization. Thingking mode of memory slicing array was used to simulate and trace the temperature field of casting slab during the continuous casting. Based on this, the law of temperature drop for casting slab was regulated in real time, combining with the PID control algorithm.Based on the real-time tracing of slab dynamic model for secondary cooling, the roll gap shrinking model of dynamic soft reduction for slab had been developed. In this model, natural solidification shrinkage of casting slab and dynamic soft reduction for quality defects eliminating were both considered. In the model, natural solidification shrinkage for solid phase and liquid-solid phase was calculated by the way of temperature gradient node. Under the premise of steel performance testing at high temperature, it had found out the critical strain under which the steel will engender internal crack, and deduced the optimal soft reduced amount in the area of dynamic soft reduction.Integrating the slab dynamic model for secondary cooling with roll gap shrinking model, system of dynamic soft reduction for slab continuous casting was developed. In allusion to slab caster 4# in Liu Steel, the software system was used to simulate and study the production practice of steel AH36 and Q345 under different technological conditions. The study shows that:(1) Response speed of the system of slab dynamic soft reduction is rapid, and it has good performance in dynamic regulation. The software can control the surface temperature of casting slab effectively.(2) Natural solidification shrinkage is mainly related to the solidification state of casting slab. As the solidified shell thickness increase, the shrinkage will augment, and the taper of segment will increase correspondingly.(3) Optimal dynamic soft reduction amount for steel AH36 and Q345 production in Liu Steel is usually about 4mm～6mm, within the common speed of 0.9m/min~1.1m/min.(4) As the casting speed increase, the position of solidification end and soft reduction for casting slab will shift along the drawing direction; the total dynamic soft reduced amount will increase correspondingly, too. Distances from meniscus to solidification end for casting slab will augment as the casting temperature increase. However, casting temperature has little effect on the total dynamic soft reduced amount. Compared with the casting temperature, change of the casting speed has greater effect on soft reduction parameters.System of dynamic soft reduction for secondary cooling can factually reflects the working fact of continuous caster, after being corrected. It can assist the production practice effectively.更多还原