【作者】 姜涛；

【导师】 朱苗勇；

【作者基本信息】 东北大学 ， 钢铁冶金， 2012， 硕士

【摘要】 连铸动态轻压下技术已成为改善连铸坯中心偏析和缩孔的最有效手段之一,是现代连铸机先进性的一个重要标志。本文以国内某厂的宽厚板坯连铸机为研究对象,进行了板坯动态轻压下过程关键工艺参数的研究。本文的主要研究内容和取得主要结果如下：(1)连铸二冷喷嘴冷却特性研究。通过对连铸机喷嘴冷却特性研究,获得了各喷嘴的流量特性、水流密度分布和喷射角度,并分析评价了连铸机现有二冷制度的合理性。(2)铸坯高温力学性能测定。通过测定Q345B和AH36典型钢种的高温力学性能,包括热膨胀、收缩系数、零强度温度、零塑性温度、高温抗拉强度、断面收缩率,为轻压下的二冷配水工艺参数的制定提供基础,并为离线压下模拟模型提供精确的物性参数。(3)宽厚板坯温度场和热收缩的模拟研究。通过加载铸坯的实时温度场分布,结合测定的高温物性参数对铸坯连铸过程进行热力耦合计算,计算铸坯在整个连铸过程的热收缩量,为轻压下在线控制模型提供重要工艺参数。计算结果表明：拉速对铸坯的热收缩影响明显,拉速越大,铸坯的热收缩总量越少。(4)宽厚板坯压下速率和压下率的模拟研究。通过对压下率理论模型的分析,利用生产工艺和测定的高温力学性能参数,对宽厚板坯轻压下过程进行有限元仿真计算,获得了不同拉速、钢种下的压下速率和压下率。结果表明：板坯的压下速率和压下率均沿拉坯方向近似线性减少；压下速率取值范围不随拉速的变化而变化；钢种对压下速率和压下率的影响较小。(5)宽厚板坯压下效率的模拟研究。通过对压下效率理论模型分析,结合测定的高温力学性能参数和板坯的生产工艺,对宽厚板坯轻压下过程进行三维有限元仿真研究,计算各钢种在不同压下量和固相率下的压下效率。结果表明：2080mm×260mm断面,压下量小于4.5mm时,压下效率随压下量的增加而增加；当压下量大于4.5mm时,压下效率增加不明显；2080mm×300mm断面,压下量小于5.5rnm时,压下效率随压下量的增加而增加；压下量大于5.5mm时,压下效率增加不明显。(6)轻压下模型工艺参数的应用。结合现场板坯生产工艺,利用轻压下模型研究的工艺参数,对现场模型进行了优化,调整了压下区间和压下量,Q345B和AH36典型钢种低倍中心偏析C级1.0以内比率达到95%。更多还原

【Abstract】 Dynamic soft reduction technology has become one of the best methods to improve center segregation and shrinkage in continuous casting products, and it is also an important sign of modern caster. Taking a domestic wide and thick slab caster as research object, research of the soft reduction key process parameters was carried out in the paper. The main content and conclusion in the research are as follows:(1) The study of cooling characteristics of the secondary cooling nozzles in continuous casting. The parameters of the flow characteristics, water flow density distribution and spraying angle of the nozzles were obtained from the study. At the same time, the rationality of secondary cooling system of the caster was analyzed and evaluated.(2) Determination of the high temperature mechanical properties of the slab. The determination lays a foundation of the process parameters of second cooling water and provides accurate physical parameters of the offline soft reduction simulation model. The high temperature mechanical properties include thermal expansion and contraction coefficient, zero strength temperature, zero ductility temperature, tensile strength and reduction of area at high temperature.(3) The study of the temperature distribution and the thermal shrinkage of the wide and thick slab. Based on the temperature distribution of the slab and the high temperature mechanical properties determined, the shrinkage value of the slab was calculated in the continuous casting process, to provide important process parameters of online soft reduction control model. The results show that the casting speed plays a great influence on the slab shrinkage, and with the increase of the casting speed the thermal shrinkage value decrease.(4) The simulation study of the wide and thick slab reduction rate and reduction ratio. The model of the reduction theory was analyzed. Using the high temperature mechanical properties and the production process, a finite element simulation calculation was made for modeling the process of the slab soft reduction to obtain slab reduction rate and reduction ratio in different casting speed and steel grades. The results show that the reduction rate and reduction ratio decrease approximately linearly along the casting direction of the strand, that the reduction rate does not change with the change of casting speed and that the steel grade has little effect on reduction rate and reduction ratio.(5) The simulation of the slab reduction efficiency. The theory model of reduction efficiency was analyzed. Combined with the high temperature mechanical properties and the production process, a three-dimensional finite element simulation calculation was made for the process of the slab soft reduction to obtain reduction efficiency in different reduction amount and different solid fraction. The result shows that in2080mm×260mm section the reduction efficiency increases with the reduction amount when it is less than4.5mm,and that when the reduction amount is bigger than4.5mm, the reduction efficiency remain basically unchanged. In2080mm×300mm section, the reduction efficiency increases with the reduction amount when it is less than5.5mm,and that when the reduction amount is bigger than5.5mm, the reduction efficiency remain basically unchanged.(6) The application of process parameters of soft reduction model. Combined with slab production process, the online model is optimized, including reduction zone and reduction amount. The ratio of class C of1.0for center segregation is95%for Q345B and AH36.更多还原