连铸结晶器弯月面动压润滑行为机理研究

发布时间：2018-06-02 21:07

本文选题：连铸结晶器 + 渣道形状　；参考：《东北大学》2012年硕士论文

【摘要】：结晶器是连铸机中最重要的组成部分,过热钢液在其内由液态转变为固态,完成初始凝固过程,其弯月面行为直接决定了连铸坯的表面质量。探索保护渣在弯月面处结晶器铜板与初始凝固坯壳间的润滑机理及规律对完善漏钢预报,提高铸坯表面质量等都有着极其重要的意义。由于检测手段和现场生产条件的限制,要直接获得弯月面处的保护渣润滑状态几乎不可能。因此,通过数值模拟手段研究弯月面处保护渣润滑行为就显得尤为重要。为此,本文以某钢厂宽厚板坯连铸结晶器为研究对象,建立结晶器弯月面区域保护渣动压润滑理论模型,优化结晶器振动参数,主要研究内容和获得结论如下： (1)结晶器弯月面处保护渣分布规律研究。通过建立的结晶器铜板三维热-力耦合模型和二维铸坯非稳态传热模型,得到结晶器铜板热面温度场和法向变形量分布以及凝固坯壳表面温度分布和凝固坯壳厚度,从而计算得出保护渣厚度分布。液态渣膜厚度沿结晶器高度方向逐渐降低,在距弯月面200mm处液态渣消失,满足收敛性形状要求。取距弯月面80mm的范围,对保护渣厚度作线性拟合,建立弯月面处的结晶器保护渣动压润滑模型。 (2)结晶器弯月面动压润滑行为理论研究。在动压润滑理论建立的基础上,根据保护渣动量、质量守恒方程,推导出液态保护渣渣道内的速度、压力、摩擦力分布计算公式。计算结果表明：黏度为0.1Pa-s的保护渣在正弦振动条件下,在弯月面区域内液态渣的相对速度呈连续分布,越靠近铸坯界面速度梯度越大,且同一位置处振动速度越大,相对速度梯度越大；因振动形成的压力分布在研究范围内先增大后减小,正滑脱时期内产生相对正压,发挥承载作用抵抗钢水静压,形成动压润滑,负滑脱时期内产生的相对压力为负压,将保护渣吸入渣道；摩擦力随距弯月面的距离和结晶器振动速度的增大而增大,且摩擦力增大幅度与振动速度增加幅度一致。 (3)结晶器弯月面动压润滑效果主要影响因素研究。①改变结晶器保护渣黏度时,对渣道内速度分布影响较小,压力分布和液态摩擦力影响较大。保护渣黏度分别为1.0Pa-s,0.5Pa.s和0.1Pa.s,结晶器以1.25m/min的最大上振速度运动时,随着保护渣黏度的增大,渣道内产生的压力越大,抵抗钢水静压力作用越强；润滑状态越差,液态摩擦力变化越剧烈。②改变拉速时,液态渣道内的速度分布变化趋势、压力以及液态摩擦力分布方式基本不变,随着拉速的增大,渣道内产生的压力减小,摩擦力增大。 (4)结晶器振动参数优化准则研究。动压润滑理论分析表明：非正弦振动时,在最大上振速度尽量大的前提下,延长正滑动时间是维持良好润滑效果的首要考虑因素。在保证结晶器顺行的前提下,可以适当增大非正弦因子a,振动频率f和振幅s,提高动压润滑效果,利于铸坯的脱模、裂纹愈合和增加液渣消耗。
[Abstract]:The mold is the most important part in the continuous casting machine. The superheated steel changes from liquid state to solid state and completes the initial solidification process. Its meniscus behavior directly determines the surface quality of continuous casting billet. It is of great significance to explore the lubrication mechanism and regularity of mould copper plate and initial solidified shell at the meniscus for improving the prediction of steel breakout and improving the surface quality of billet. It is almost impossible to obtain the lubrication state of mold powder directly because of the limitation of testing means and production conditions. Therefore, it is very important to study the lubrication behavior of mold powder at meniscus by numerical simulation. In this paper, a theoretical model of hydrodynamic lubrication for mold meniscus is established to optimize the vibration parameters of mould. The main research contents and conclusions are as follows: (1) in this paper, the mould for wide and thick slab continuous casting is taken as the research object, and the theoretical model of hydrodynamic lubrication of mold meniscus is established, and the vibration parameters of mold are optimized. 1) study on the distribution of mold powder at the meniscus of the mould. Based on the three-dimensional thermal-mechanical coupled model and the two-dimensional unsteady heat transfer model, the temperature field and normal deformation distribution on the hot surface, the surface temperature distribution and the thickness of the solidified billet shell are obtained. The thickness distribution of mold powder is calculated. The thickness of liquid slag film decreases gradually along the direction of mold height and disappears at the distance from meniscus to the meniscus 200mm to meet the requirements of convergent shape. Taking the range of 80mm from meniscus, the thickness of mold slag is fitted linearly, and the dynamic lubrication model of mold slag at meniscus is established. (2) theoretical study on the dynamic lubrication behavior of the meniscus of the mould. Based on the theory of hydrodynamic lubrication and the conservation equation of the momentum and mass of the mold slag, the formulas for calculating the velocity, pressure and friction force in the channel of the liquid mold slag are derived. The results show that the relative velocity of liquid slag in the region of meniscus is continuous under the condition of sinusoidal vibration with viscosity of 0.1Pa-s. The closer the velocity gradient is to the interface of the billet, the greater the velocity of vibration is at the same position. The larger the relative velocity gradient is, the larger the pressure distribution due to vibration first increases and then decreases within the range of study, and the relative positive pressure is produced during the period of positive slip, which exerts the bearing capacity to resist the hydrostatic pressure of molten steel and forms hydrodynamic lubrication. The relative pressure produced during the period of negative slippage is negative pressure, and the friction force increases with the increase of the distance from the meniscus and the vibration velocity of the mould, and the increase of the friction force is consistent with the increase of the vibration velocity. The main factors affecting the hydrodynamic lubrication effect of mold meniscus 1. When the viscosity of mold flux is changed, the velocity distribution in slag channel is less affected, and the pressure distribution and liquid friction force are greatly affected. The viscosity of mold slag is 1.0 Pa-sn 0.5 Pa.s and 0.1 Pa.s.When the mould moves at the maximum upswing velocity of 1.25m/min, with the increase of the viscosity of mold slag, the greater the pressure produced in the slag channel, the stronger the resistance to the static pressure of molten steel, and the worse the lubricating state is. When the liquid friction force changes sharply, the velocity distribution in the slag channel changes, and the pressure and the distribution mode of the liquid friction force basically remain unchanged. With the increase of the drawing speed, the pressure in the slag channel decreases and the friction force increases. The optimization criteria of mould vibration parameters are studied. The theoretical analysis of hydrodynamic lubrication shows that the extension of the positive sliding time is the primary factor to maintain the good lubricating effect under the premise of the maximum up vibration speed when the vibration is not sinusoidal. On the premise of ensuring the mold running smoothly, the non-sinusoidal factor a, vibration frequency f and amplitude s can be increased appropriately, and the hydrodynamic lubrication effect can be improved, which is beneficial to the release of casting billet, crack healing and increasing the consumption of liquid slag.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TF341.6;TH117.2

【参考文献】