【作者】 王启明；

【导师】 陈登福；

【作者基本信息】 重庆大学 ， 金属材料工程， 2008， 硕士

【摘要】 连铸技术是钢铁生产中的重要技术,研究连铸坯的高温性能对指导生产具有十分重要的意义。在连铸坯的生产中,钢种的高温性能是判断铸坯是否产生裂纹的重要指标,也是对连铸过程进行数值仿真的重要参数,对改善其凝固冷却速度,制定二冷动态轻压下的相关参数具有重要价值。本论文的主要任务是对板坯连铸机生产的低合金钢A和耐候钢B连铸坯进行热物理性能测试和高温力学性能测试,并将所得的钢种物性参数应用到连铸坯温度场仿真和组织模拟模型中,并结合实际工艺进行了分析。在Gleeble-1500D热模拟机上进行从600℃到1300℃的高温拉伸实验,获得了两个钢种的力学性能参数。以断面收缩率为主要指标找出了这两种钢的高温脆性温度区,低合金钢A二次脆性区出现在725～900℃左右,耐候钢B二次脆性区出现在775～950℃左右,确定了低合金钢A和耐候钢B连铸坯在二冷区及矫直点处的温度尽可能分别控制在950℃以上和1000℃以上。采用热膨胀仪DIL402和综合热分析仪STA449对两个钢种进行热膨胀性能测试和差热分析试验,获得了两个钢种不同温度下的热膨胀性能、潜热、固相线和液相线等热物理性能参数,为研究连铸过程的铸坯的凝固特性提供了宝贵的资料和依据。运用实验得到的钢种物性参数和连铸板坯表面温度测试的结果,确定出合适的边界条件,应用到板坯连铸二次冷却计算机仿真软件中,对钢厂板坯连铸机的二冷制度进行了优化,根据优化后的实际生产结果,证明所得钢种物性参数对二冷制度的优化有十分重要的作用。同时钢种物性参数和铸坯表面温度测试结果也是连铸坯组织模拟的重要基础数据。本文将元胞自动机(CA)和有限差分法(FD)结合起来,建立了连铸坯凝固时内部等轴晶和柱状晶的随机形核和生长模型,元胞自动机模拟凝固组织,有限差分法计算温度分布和溶质扩散。通过该模型对三种不同工况下连铸坯凝固组织的模拟,再现了连铸坯内部组织的演变规律,对晶粒的随机形核、晶粒的择优生长、竞争生长以及晶粒的随机取向有比较好的体现。分析了不同工艺因素对等轴晶和柱状晶竞争生长的影响,模拟结果与工艺实践和理论分析一致。更多还原

【Abstract】 Continuous casting is one of the most active technologies in steel industry, and the high-temperature properties of continuous cast slab are very important for guiding its production process. The high-temperature physical and mechanical properties parameters are also very important during the slab continuous cast process despite improving solidification cooling system, judging cracks in casting slab and establishing parameters of dynamic soft reduction in continuous casting. Paper select steel A and B slab casting in One Iron and Steel Company to test part of mechanical behavior and physical property of steel casting blank under high temperature; on the mathematical model of heat transfer and stress variety in slab continuous casting process.The test and measurement on two steel grades temperature expansion and differential thermal analysis are made according to the actual situation. Through these test and analysis the two steels high temperature physical property of casting slab like temperature expansion, heat capacity, latent heat, solidus curve and liquid line etc are achieved. In different speed of heating, we obtained the heat capacity of casting slab in the heating process and cooling process.Mechanical property variations with the temperature changing from 600 degree centigrade to 1300 degree centigrade are gotten through the Tension test t on the Gleeble-1500D and the steel high temperature brittleness zone especial the third one are determined according to the reduction rate of the cross-section. The second brittle zone of steel B is about between 775 degree centigrade and 950 degree centigrade. The second brittle zone of steel A is about between 725 degree centigrade and 900 degree centigrade.The steel properties have been used to defining suitable bound conditions which are very useful for the casting slab secondary cooling simulation software. Then with the simulation an optimal of the secondary cooling system in the continuous slab casting at No.4 steel making and rolling plant of One Iron and Steel Corp. The practical production shows good results after the optimal, it proved that the steel properties have very important meaning to optimal of the secondary cooling system.Also the steel properties and surface temperature tests of casting slab results are very important basis data of continuous casting slab’s microstructure simulation. The Cellular Automaton (CA) is coupled with Finite Difference Method (FDM) here to establish the stochastic nucleation and growth model. The CA is used to simulate the solidification structure, where the FDM is used to calculate the temperature and solute diffusion. Three different casting condition have been simulated by the model, the results show good in agreement with the regulation of microstructure evolvement rule and the stochastic nucleation、preferred growth、competitive growth and random orientation of grain. The effects of processing parameters on the competition growth between columnar and equiaxed grains are analyzed. The results are in agreement with practical process and theoretical analysis.更多还原