宽厚板连铸结晶器摩擦行为在线测试与分析

 结晶器/铸坯摩擦行为是影响并决定铸坯表面质量的重要因素。以宽厚板坯连铸结晶器为对象,在线检测基于液压振动装置的结晶器/铸坯摩擦力,测试和分析浇铸温度、铸坯断面、拉速与结晶器振动方式等主要工艺参数对摩擦力的影响,为考察和调控结晶器/铸坯摩擦行为提供试验基础。相同工艺条件下,摩擦力随浇铸温度的升高而降低,随铸坯断面尺寸的增加而增大。正弦、非正弦振动方式与拉速-振频、振幅振动控制模型的合理匹配,能够显著改善高拉速下的结晶器/铸坯摩擦行为,结晶器振动工艺的开发和优化对于充分发挥液压振动装置设备潜力,稳定高拉速下铸坯表面质量具有积极意义。     

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.     

板坯结晶器钢液流动传热和摩擦行为的数值模拟

结晶器摩擦力对连铸顺行非常重要,而钢液流动行为会影响铸坯温度场和保护渣分布,可能对铸坯摩擦力产生一定的影响.利用Fluent软件建立结晶器内钢液流动、传热三维数学模型,并将温度场数据导入Ansys计算铸坯应变,然后根据铸坯-保护渣-结晶器摩擦行为数学模型讨论了渣膜润滑情况,对比了不同水口底部形状下结晶器内液态、固态和总摩擦力.结果表明:不考虑水口射流时结晶器总摩擦力比考虑水口时增大约29.4％;浸入式水口底部形状分别为凸底、平底和凹底3种情况下铸坯窄面中心温度依次降低,凝固壳厚度依次增大,固态摩擦力依次增大,总摩擦力依次增大,液态摩擦力相差较小.     

大板坯液压振动结晶器摩擦力检测与分析

对大板坯结晶器摩擦力进行了在线检测试验研究。分析了摩擦力在升拉速、换水口、粘结及降拉速时相关参数的变化特征,指出结晶器摩擦力与结晶器和铸坯的相对运动速度呈相同的变化趋势,前者的变化滞后于后者,且经反复震荡后与拉速保持一致;同时结晶器摩擦力可以预测粘结漏钢事故。     

板坯连铸结晶器/铸坯瞬态摩擦行为的实验研究

合理控制结晶器与铸坯间的润滑和摩擦状况是实现高效连铸技术的关键环节之一,摩擦力作为表征润滑效果的重要参数已受到广泛关注。以板坯连铸机为研究对象,对液压振动条件下结晶器和铸坯间的瞬态摩擦力进行测试和分析。探讨了瞬态摩擦力及相关参数的变化特点,并对正弦、非正弦振动方式下的摩擦力检测结果进行了对比分析,同时讨论了正常工况与漏钢发生前摩擦力的变化特点。为结晶器/铸坯摩擦行为的深入研究和优化连铸工艺等提供了实验基础和技术支持。     

正弦振动结晶器摩擦力与负滑脱参数对比分析

结晶器摩擦力是反映结晶器与铸坯间相互作用、评价保护渣润滑性能的重要参数.由于摩擦力的检测与计算比较复杂,一般通过对振动工艺参数的理论分析来估算结晶器与铸坯间的润滑与摩擦.基于液压振动装置的板坯连铸试验平台,对结晶器摩擦力和振动速度进行了检测实验研究.通过对理论与实测计算结果的对比分析,讨论了结晶器摩擦力状态与负滑脱参数的关系及二者随拉速的变化趋势.该研究在制定适宜的振频-拉速匹配关系、定量理解结晶器与铸坯间的瞬态摩擦行为等方面具有一定的指导作用.     

方坯连铸保护渣渣膜润滑行为的理论研究

应用传热学和粘性流体力学原理，用数学模拟的方法描述了方坯连铸结晶器内保护渣的润滑行为，计算不同浇注条件下铸坯所受摩擦力，分析了各种因素对铸坯所受摩擦力的影响。     

结晶器/铸坯气隙内渣膜润滑行为的数学模拟

建立了连铸保护渣润滑行为的数学模型,对不同连铸工艺参数对结晶器内铸坯摩擦力的影响进行了预测和讨论.结果表明,对于一给定的保护渣,存在一个最佳拉坯速度,低于或高于这一速度都会使摩擦力增大;增大结晶器振动的振幅、频率和结晶器倒锥度,铸坯所受到的摩擦力增大.     

板坯连铸结晶器摩擦力周期行为的研究

 结晶器摩擦力是反映连铸生产状况的重要参数,研究结晶器摩擦力的周期行为特点对于理解铸坯与结晶器间的相互作用,评价保护渣的润滑特点有着重要的意义。基于液压振动装置的板坯连铸机,对结晶器摩擦力进行了瞬态检测,分析了结晶器摩擦力的周期行为特点。研究结果表明：在稳定拉坯阶段,结晶器摩擦力在两种振动模式下具有相似的周期变化过程;周期内摩擦力最值的出现位置呈现出一定的规律性和不确定性;开浇阶段摩擦力会在长时间内维持正值且波动剧烈。     

高频磁场下连铸保护渣润滑行为数学模型

摘要：为了研究高频磁场下连铸保护渣在结晶器内的润滑状况，建立了高频磁场下连铸保护渣润滑行为数学模型，并应用该数学模型研究了初始凝固时磁场作用下渣道宽度、弯月面高度、渣道动压、渣耗、摩擦力等因素对保护渣润滑行为的影响。结果发现，磁场的作用拓宽了保护渣渣道宽度，增大了弯月面高度，使保护渣渣道入口及出口宽度增加，使初始凝固点下移，改善了传热条件有利于铸坯表面质量提升；磁场的作用减小了因结晶器振动而产生的正压和负压，并且正、负压都是随着磁场强度的增大而减小，但磁场强度存在一个最佳值；磁场的作用增大了渣耗量，改善了铸坯与结晶器之间的润滑；铸坯与结晶器之间摩擦力随着磁场强度的增大而减小，当磁场强度为40mT时，总摩擦力减小趋于平缓，因此磁场强度为40mT左右时对减小摩擦力的作用效果较好。     

外加液态保护渣连铸生产实践与前景展望

 外加液态保护渣可以提高铸坯质量和可浇性。在某厂板坯连铸机上,分别采用液态保护渣和固态保护渣进行多钢种浇注试验,对比液态保护渣和固态保护渣消耗量、结晶器温度分布、拉坯摩擦力及铸坯质量,并对液态保护渣的应用前景进行展望。结果显示,液态保护渣比固态保护渣消耗量增加60%左右,结晶器温度分布更均匀,连铸拉坯摩擦力降低约15%,铸坯质量有所提高。这说明在连铸过程中,液态保护渣使结晶器和铸坯间传热更均匀;液态保护渣润滑效果更好,可以提高铸坯质量。同时,有望不添加F-、Na+等有害离子,改善环保问题。     

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.     

Mould lubrication and friction behaviour with hydraulic oscillators in slab continuous casting

Abstract

It is very important to obtain reliable lubrication from casting powder both at the meniscus and in the gap between strand and mould as it affects slab surface quality and caster productivity. With knowledge of mould friction, a quantitative insight into the behaviour of powder during caster operation is possible. In the present research, the friction was studied based on a slab continuous caster equipped with hydraulic oscillators. The effects of mould oscillation and the abrupt change of casting speed on mould friction force were evaluated, and the characteristics of lubrication behaviour in a casting sequence were investigated. In particular, a comparison between the mould friction force between sinusoidal oscillation mode and non-sinusoidal oscillation mode was made. Finally, the characteristics of friction before a breakout are discussed. The experimental and analytical results may contribute to the development of mould friction online measurement and more clearly learn the lubrication behaviour in different conditions.     

Investigations on the Transient Mould Friction Force in Slab Continuous Casting based on Fast Fourier Transformation

In continuous casting, the friction forces in the mould reflect the lubrication between the mould and slab, moreover, they affect the slab surface quality and caster productivity. In the present research the friction force is calculated by measuring the difference of working forces during HOT and COLD tests, which are carried out on the slab continuous caster equipped with hydraulic oscillators. Through analysing the mould friction using the Fast Fourier Transformation (FFT) method, the effects of mould oscillation mode and casting speed on the mould friction force are evaluated. The characteristics of the friction signal in the frequency domain are also investigated. Especially, the characteristics of friction force fluctuations before breakouts are discussed. The experimental and analytical results may contribute to more clearly understand the transient lubrication behaviour not only in the time domain but also in the frequency domain, which is also useful for the application of FFT in data analysis of mould processes.     

连铸结晶器检测控制技术的新发展

详尽介绍了到目前为止所开发及使用的各种传感器及其功能与应用范围，如：连铸机结晶器铜板温度的测量、检测结晶器中钢水液位所用仪表、结晶器振荡的监测，结晶器和板坯之间摩擦力的检测。测量结晶器铜板壁和铸坯之间缝隙中的渣膜厚度和结晶器内钢水池上熔融保护渣层深度的技术……等等。阐述了这些检测控制技术对连铸技术发展所起的重要作用。在建新连铸机或改造老连铸机时，必须采用各种行之有效的检测和控制方法，并不断开发新方     

Challenge to control mould heat transfer during thin slab casting

Abstract

At the thin slab caster of Tata Steel, IJmuiden, mild cooling mould powders were introduced with the aim to control the mould heat transfer during casting. These mild cooling mould powders are characterised by specific values of basicity, solidification point and chemical composition. Application of these mould powders resulted in a redistribution of mould heat transfer during casting, i.e. a reduced and more stable mould heat transfer in the critical upper part of the mould and an increased mould heat transfer in the lower part of the mould. The average mould heat transfer and hence the shell thickness at mould exit are comparable to the standard powder. The application of mild cooling mould powders also resulted in improved solidification behaviour of the steel shell. A thinner chill zone with smaller thickness variations was observed. Furthermore, it was found that the mould taper required optimisation to match the changes in shrinkage behaviour to ensure uniform solidification. The use of mild cooling powders was observed to give an increase in mould friction. Mould thermal monitoring indicated that the solid slag films fractured (sheeting) in the upper part of the mould. However, no operational problems were reported, which indicate that the first 200 mm under the steel meniscus is essential for initial solidification and for the formation of a homogeneous steel shell. All these findings can be understood by considering the crystallisation properties of the mould slag, which include the cooling rate. Mild cooling has been shown to provide uniform heat transfer and adequate lubrication for high speed thin slab casting.