Study on Meniscus Temperature Fluctuation during Mold Oscillation in Continuous Casting by Modeling Experiments

The temperature of the meniscus in continuous casting was measured during mold oscillation by modeling experiments. It is found that the temperature of meniscus varied periodically along with mold oscillation. Based on the above phenomenon, the mechanism of some techniques, such as, hot top mold, high frequency and low amplitude mold oscillation, soft contact mold electromagnetic continuous casting and so on, which can improve the quality of continuous casting billets, was analyzed. The results show that the decrease of the temperature fluctuation of early solidification shell is their common mechanism.

THEORETICAL STUDY OF AN OSCILLATING WAVEFORM FUNCTION AND PARAMETERS FOR CONTROLLING THE NON-SINUSOIDAL OSCILLATION OF A MOLD

A new non-sinusoidal oscillation waveform is constructed for controlling themold oscillation during continuous casting. Casting velocity and oscillation parameters are thenestablished for a computer model of the continuous casting process. The waveform distortioncoefficient ? of waveform function is close to the waveform distortion rate a, so s is taken for awhen the basic parameters are selected initially. The waveform function can be created for the servohydraulic system or the mechanical driving system. Industrial scale experiments show the waveformfunction is effective.

Motion Stability Analysis of Non-sinusoidal Oscillation of Mold Driven by Servomotor

The investments of the electro-hydraulic servo system of the mold non-sinusoidal oscillator are great, the modification ratio of the mechanical type is unable to be adjusted online, and some continuous casters suffer from server resonance during the casting. A mold non-sinusoidal oscillation mechanism driven by servomotor is proposed and the prototype is produced in the lab, the investment is low and the modification ratio is can be adjusted online, and the stability problem is studied. At first the dynamics model of the servomotor non-sinusoidal oscillation is established, and the kinematics differential function is deduced. Furthermore, based on the harmonic balance method, the eigenvalues of the system are solved; the criterion of the stability of the system is put forward. In addition, the eigenvalues and harmonic with different oscillating parameters are analyzed. Analytical results show that the real parts of the eigenvalues are positive, the system will be unstable, and the resonance will occur when the positive real parts of the eigenvalues are extremum. A foundation is established for solving the running smooth problem and next application of this mechanism.

Mechanism analysis of non-sinusoidal oscillation of continuous casting mold synchronously driven by double servomotors

Due to the disadvantages of complexity,high maintenance and vast investment of the electro-hydraulic servo oscillator,a new mechanical device synchronously driven by double servomotors was proposed. The working principle of the non-sinusoidal oscillator was analyzed and the model of the oscillator was validated via simulation software.Then,taking advantage of resonance technology,the hinging force and moment were calculated. The results showed that the hinging force and driving moment reduced,which was useful in reducing the impact of the hinge and prolonging the service life of the bearing. Besides,the best initial spring pressure was 0. 9 times the mold gravity,which improved the oscillation system stability and reduced the load fluctuation and servomotor driving power.

Elastodynamic analysis of synergistic oscillation system driven by double servomotors for continuous casting mold

Based on the principle of speed superposition,the oscillation system for continuous casting mold synchronously driven by double servomotors can adjust all parameters online with high reliability and high bearing capacity.The elastodynamic model of the oscillation system was presented to analyze the oscillation characteristics affected by multiple parameters.Firstly,the working principle of the system was illustrated,with the kinematic model of the system given.Considering the elastic deformation of mechanical components,the lumped parameter method was used to establish the equivalent component and elastodynamic model of the oscillation system.Based on Runge–Kutta method,the oscillation response of the system was calculated.The validity of the elastodynamic model was validated by comparing the simulated solution and experimental data,and the oscillation characteristics of the system were analyzed emphatically with model parameters.The results showed that the first three harmonic frequencies of the eccentric shafts are the main cause of harmonic resonance,which has a strong relationship with the system error.The increase in the fluctuation coefficients and the decrease in the phase difference enhanced the elastic oscillation of the system.System elastic error tends to show linear growth with the increase in the friction force of the slab.

Investigation and Application of Non-sinusoidal Oscillation Technique of Mold

To improve the slab quality, a kind of non-sinusoidal oscillation technique of mold driven by elliptic gears was developed. The waveform functions of non-sinusoidal oscillation were determined, and the calculation method and curves of technological parameters for non-sinusoidal oscillation were given. At the case of waveform deviation factor a equal to 0.31 and oscillation amplitude h equal to ±2.7 mm, the relationship between oscillation frequency and casting speed is determined, and the technological parameters for non-sinusoidal oscillation are calculated. The testing results of industrial application indicated that this technique could not only improve the Slab surface quality, but also reduce the steel breakout.

Optimization of Oscillation Model for Slab Continuous Casting Mould Based on Mould Friction Measurements in Plant Trial

Lubrication and friction between the mould and strand are strongly influenced by mould oscillation, and play an important role in slab quality and operating safety during continuous casting processes. Investigation of mould oscillation is therefore essential for getting a better online control of the mould processes. A feasible approach for the development and optimization of mould oscillation was put forward, which combined online measurement of mould friction, design of negative oscillating parameters and evaluation for powder consumption. Three different control models including sinusoidal and non-sinusoidal oscillation for mould oscillations were developed to investigate and evaluate the effects of oscillation on mould friction and powder lubrication. For the purpose of investigating mould friction between mould and strand, online measurement was carried out on a slab continuous caster equipped with a hydraulic oscillator. Also the comparison of the mould friction in sinusoidal and non-sinusoidal mould oscillation was made for subsequent analysis. The industrial experiment result shows that the combination of inverse control model and non-sinusoidal oscillation mode will contribute to the proper powder consumption, leading to a suitable effect of friction force on strand surface, especially for high speed continuous casting. The proposed method provides reliable basis for guiding and optimizing mould oscillation among control models, sinusoidal oscillation and non-sinusoidal oscillation.

连铸结晶器缓振行为分析

连铸结晶器采用8段式非正弦振动波形可使铸坯裂纹更少,裂纹愈合能力更强,但是其对应加速度大,容易产生振动冲击影响结晶器运行.以钢板弹簧和柔性弹簧对结晶器振动过程进行刚性加持和柔性减振,利用钢板弹簧和柔性弹簧的弹簧力平衡振动冲击产生的惯性力,可以达到减小冲击的目的.计算分析发现相同载荷下柔性弹簧比钢板弹簧的应力大,且每增加10%载荷,柔性弹簧最大应力比钢板弹簧多增加21.23 N.通过二分法计算发现,柔性弹簧平衡87.5%的惯性力,钢板弹簧平衡12.5%的惯性力,可以减小90%以上因加速度产生的冲击,为连铸结晶器8段式非正弦振动波形应用提供参考.

摆动触发的连铸结晶器非正弦振动系统及工艺参数研究

通过控制电机的角速度实现非正弦振动各种参数的在线调节,提出一种摆动触发的对置伺服电机驱动结晶器振动装置。首先,阐述振动装置的工作原理,并建立其三维模型;其次,基于整体函数非正弦振动波形,给出实现该波形的伺服电机角速度曲线及工艺参数的计算方法;最后,绘制多工艺参数等值曲线,根据某钢厂连铸机的振动工艺参数,确定出非正弦振动合理的拉坯速度与频率和振幅的同步控制模型。研究表明,理论计算的非正弦振动工艺参数满足取值限度要求,对于进一步减小铸坯振痕深度、改善铸坯与结晶器之间的润滑、提高拉坯速度和铸坯表面质量,具有重要的参考价值。

构造结晶器非正弦振动波形函数的方法

提出了两种构造结晶器非正弦振动波形函数的方法。所构造的两种波形函数均用于液压伺服系统驱动的结晶器振动试验装置，效果良好。

连铸结晶器液位波动的数值模拟

应用SOLA—VOF方法研究了板坯连铸结晶器自由表面的形状及钢水流动行为,计算得出了具有实际物理意义的液位波动值。通过数值模拟浸入水口出流角度及出流速度对液位波动的影响关系,指出液位波动的波形与回流区大小及位置密切相关,并分析了液位波动的形成原因。

结晶器非正弦振动波形及参数研究

提出了一种既具有非正弦振动的全部特征，又具有正弦振动优点的非正弦振动波形；给出了确定振动参数的方法。

椭圆齿轮驱动结晶器非正弦振动的研究

开发并应用了椭圆齿轮驱动结晶器非正弦振动装置。在分析非正弦振动产生原理的基础上,给出了振动的位移、速度和加速度函数,并提出了实现机构——椭圆齿轮驱动机构。采用了弹簧缓冲的结晶器谐振技术,提高了振动平稳性,减少了振动冲击和驱动电动机功率。对振动的工艺参数和动力学特性进行了分析。工业应用表明此技术对减少拉漏、减轻振痕、提高铸坯表面质量及提高拉坯速度等方面效果显著。

高拉速连铸结晶器非正弦振动因子研究

通过分析连铸结晶器振动过程参数和结晶器内摩擦力,确定了一种新的非正弦振动形式下1．8和2．0m/min拉速时的非正弦振动因子,并阐明了非正弦振动因子随拉速提高的变化觇律．结果表明：1．8和2．0m/min拉速时非正弦振动因子适宜值为0．2,与实际应用值一致；振动频率和振幅不变,拉速由2．0 m/min升至2．2m/min,非正弦振动因子应增至0．25,以改善振动效果．

连铸结晶器振动下弯月面处温度波动的模拟实验

设计了连铸结晶器弯月面处传热模拟实验,测量了在结晶器振动情况下弯月面处的温度,发现该处的温度随着结晶器的振动而产生周期性的变化.实验结果表明,结晶器振动频率越大,振动幅值、结晶器冷却强度以及结晶器与铸坯间的接触压力越小,因结晶器振动而产生的弯月面温度波动亦越小.据此认为,连铸弯月面温度波动是导致铸坯表面缺陷产生的一个重要原因.基于此“温度波动”现象,分析了包括高频小振幅振动、软接触结晶器电磁连铸、热顶结晶器等诸多技术改善铸坯表面质量的机理.

机械驱动结晶器非正弦振动的开发

采用运动的叠加原理 ,开发出一种机械驱动的非正弦振动装置。生产实践证明 ,它同液压伺服系统驱动的非正弦振动系统相比具有投资省、操作维护方便、可靠性高等优点。现已应用于首钢第一炼钢厂的板坯连铸机 ,并取得显著的效果。

连铸机振动系统动态性能分析及其谐振现象研究

建立了集几何非线性和载荷非线性于一体的连铸机四偏心式多连杆振动机构运动弹性动力学分析力学与数学模型。将该系统划分为６个广义子结构，分别应用变截面梁单元和集中参数法建模。考虑了碟形平衡弹簧非线性、导向板弹簧几何非线性、铸坯摩擦力，以及传动轴扭转刚度等多种因素。给出了系统方程装配的位移协调关系式。发现了该系统存在明显的复杂谐振现象，讨论了该谐振现象的成因。

液压振动下板坯连铸结晶器摩擦力检测实验研究

结晶器和铸坯之间的润滑与摩擦行为是影响连铸坯质量及生产效率的重要因素。基于宝钢板坯连铸试验平台,开展了液压振动下的结晶器摩擦力检测实验研究。通过检测不同振动参数下,冷态和拉坯时振动系统输出力的变化情况,计算出结晶器与铸坯间摩擦阻力。分析了摩擦力的周期变化行为,讨论了拉坯过程中相关参数的变化特征。为探究结晶器与铸坯间摩擦行为、优化与开发连铸工艺等提供实验基础与技术支持。

高拉速下连铸坯振痕形成机理及振动参数优化

通过分析2.0m/min拉速稳定浇铸时振动周期内弯月面初凝坯壳的受力情况,阐述了高拉速连铸坯表面振痕形成过程,给出振动参数与最大液体摩擦力和最大保护渣渣道动态压力关系;结合振动参数对振动过程参数的影响和实际设备状况,提出了振动参数优化方向,确定了拉速升至2.2m/min时的振动参数值.结果表明.弯月面初凝坯壳在钢水静压力、摩擦力和保护渣渣道压力作用下随凝固进程形成振痕,振痕生成位置取决于初凝坯壳糊状区固相分率;随拉速提高,应降低振频、增大振幅和非正弦振动因子,以改善振动效果和振痕形貌;拉速升至2.2m/min时的适宜振频、振幅和非正弦振动因子分别为145min^(-1),±5.0mm和0.25.

连铸结晶器非正弦振动参数及同步控制模型的研究

给出了一种用于连铸生产的非正弦振动波形，并对其波形参数和振动工艺参数进行了讨论。结果表明：这种非正弦振动波形具有较好的拉坯速度适应范围，能够满足连铸生产的要求。另外，还对其波形参数的选择方法进行了探讨，导出了该非正弦振动的同步控制模型。