连铸结晶器瞬态摩擦阻力的实验研究

应用连铸结晶器凝固综合模拟装置,研究了结晶器瞬态摩擦阻力随结晶器振动的变化规律。结果显示在结晶器上部,连铸坯与结晶器之间以粘性摩擦为主,摩擦阻力的变化规律与结晶器振动的速度波形一致。应用结晶器非正弦振动,在保证负滑动期间对初始凝壳的压缩作用的同时,可以大幅度降低正滑动期间的结晶器摩擦阻力。这对防止高速连铸初始坯壳的拉裂、提高拉坯速度有重要意义。     

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.     

连铸结晶器振动过程连铸坯应力分布有限元分析

对连铸结晶器振动过程进行了有限元模拟,获得了结晶器振动过程连铸坯表层应力分布,分析了结晶器锥度、结晶器与连铸坯间摩擦系数、拉速和连铸坯厚度对连铸坯表层应力分布的影响。振动过程结晶器末端附近区域连铸坯表层出现应力集中。随结晶器锥度减小和连铸坯宽度增加,连铸坯表层最大应力增加;拉速和连铸坯与结晶器间摩擦对连铸坯表层最大应力影响很小。研究结果对分析和认识连铸坯表面振痕的产生原因和结晶器磨损具有指导作用。     

炼钢保护渣应用探讨

本文分析了常规板坯连铸结晶器、薄板坯连铸结晶器、方坯连铸结晶器和高拉速连铸结晶器的连铸特点及对结晶器保护渣性能的要求。     

连铸结晶器钢水液面控制系统探析

连铸结晶器钢水液面控制系统对于保证连铸机的稳定安全运行、优化生产操作步骤、提高铸坯质量、避免出现溢钢或漏钢问题具有重要意义。分析了连铸结晶器的钢水液面控制系统的作用与原理,阐述了连铸结晶器钢水液面控制系统设计原则,有利于加深对连铸结晶器钢水液面控制系统的理解。     

连铸结晶器与铸坯间保护渣润滑行为的研究

从传热与粘性流体力学的角度考虑,建立了铸坯与结晶器间保护渣的润滑模型。利用此模型,并在计算铸坯与结晶器温度场的基础上,确定了结晶器与铸坯间保护渣膜的厚度及存在状态。利用N-S方程推导了润滑膜中压强与速度分布以及保护渣消耗等物理量,同时计算了润滑区段的摩擦阻力,为进一步计算铸坯与结晶器间摩擦阻力提供支持。     

高拉速连铸过程传输行为特征及关键技术探析

 高拉速连铸是实现直轧、铸轧的前提保障,是实现钢铁生产流程高效化、绿色化的具体体现,是发展新一代高效连铸的主题。高拉速连铸面临最大挑战是漏钢与裂纹频发,凝固坯壳均匀生长控制应是其实现的核心内涵,重点在于结晶器技术集成,包括结晶器流动控制、保护渣类型、结晶器润滑、结晶器内腔结构、结晶器冷却结构与制度等,关键在于结晶器液位的稳定控制。阐述了高拉速连铸过程传输行为特征及其实现的关键技术。     

连铸结晶器与铸坯间保护渣润滑行为的研究

从传热与粘性流体力学的角度考虑,建立了铸坯与结晶器间保护渣的润滑模型。利用此模型,并在计算铸民结晶器温度场的基础上,确定了结晶器与铸坯间保护渣膜的厚度及存在状态。利用N－S方程推导了润滑膜中压强与速度分布以及保护渣消耗等物理量,同时计算了润滑区段的摩擦阻力,为进一步计算铸坯与结晶器间摩擦阻力提供支持。     

薄板坯连铸的技术关键—结晶器

薄板坯连铸的结晶器比常规板坯连铸的结晶器因其化渣面积较小而难化渣、熔池紊流易卷渣等导致了一些与结晶器有关的质量问题。本文从结晶器的形状及其熔池水力学两方面来讨论适用薄板坯连铸之结晶器以生产更高质量的产品。     

文献简介

钢连铸时粘连型拉漏预测系统的开发 提高连铸生产率和节能的关键是要开发高速连铸技术。而高速连铸技术应用的最大难点是结晶器内凝固坯壳与结晶器壁发生粘连,在结晶器出口处导致漏钢。现     

结晶器非正弦振动理论的研究

建立了非正弦振动波形的计算方法,首次提出了一个基于电液伺服振动系统的振幅和振动频率可调的分级匹配控制模型,使正常拉坯时,振动频率为１００～１２０ｍｉｎ＾－１负滑动率为－１０％～－２０％,负滑动时间稳定在０．０６ｓ左右,开发了电液伺服结晶器振动系统,热试结果表明,应用非正弦振动可使初始凝固坯壳在正滑动其期间所受的摩擦阻力降低４０％,皱痕深度大为减轻,铸坯表面质量明显提高。     

Online Measurement for Transient Mold Friction Based on the Hydraulic Oscillators of Continuous-Casting Mold

The interaction of the strand shell surface and mold copper plates has significant effects on the slab surface quality and casting productivity. This article focuses on developing a reliable approach to measure the transient friction force between the slab and the mold for the purpose of the investigation of lubrication and friction behavior inside a mold. This method is presented to monitor transient mold frictions for the slab continuous caster equipped with hydraulic oscillators. A mathematical model is also developed to calculate the empty working force of the no casting state, and a new algorithm, based on the particle swarm optimization, is proposed to predict the dynamic characteristic parameters of mold oscillation. The results have shown that the method has a sufficient sensitivity to variation, especially to the periodical variation of the mold friction, and it has been identified that the transient mold friction can be used as an effective index with regard to detecting mold oscillation and optimizing the casting parameters for process control. It may lay the practical foundation for the online detection of powder lubrication and the visualization of the continuous-casting mold process.     

连铸振动结晶器内液态保护渣消耗机理

通过引入材料学中变截面悬臂梁理论,计算了连铸结晶器弯月面以下初凝坯壳受力,分析了结晶器正弦振动条件下初凝坯壳变形行为,并阐明液态保护渣消耗机理.结果表明,保护渣消耗于正滑脱中后期至下一个正滑脱前中期,包括整个负滑脱时期,负滑脱中期渣道宽度是保护渣消耗的限制性因素.通过增大黏度、振频和振幅使负滑脱时期内保护渣消耗量降低,从而增大了正滑脱时期内渣耗占整个周期内渣耗的比重,使正滑脱时期成为保护渣的主要消耗期.反之,负滑脱时期为保护渣主要消耗期.     

高拉速连铸结晶器振动参数对板坯表面裂纹形成的影响

 结晶器振动导致初凝坯壳受力和变形是产生铸坯表面裂纹的主要原因。通过计算2.0 m/min拉速时弯月面区最大液体摩擦力和最大渣道动态压力,分析了高拉速下结晶器振动参数变化对板坯表面纵裂纹和横裂纹形成的影响,并结合振动参数对结晶器润滑和振动状态的影响,阐明减少表面裂纹的振动参数控制措施。研究结果表明：提高振频和振幅均增大铸坯表面裂纹形成的可能,振频影响强于振幅;增大非正弦振动因子降低了坯壳撕裂可能性,且对润滑有利,但使振痕加深,振动冲击加剧;适当降低振频,增大振幅和非正弦振动因子可抑制表面裂纹形成。     

连铸结晶器非正弦振动振幅的确定

利用结晶器液体摩擦力模型,结合具有最佳振动模式特点的非正弦振动形式,分析了2．0 m／min拉速时非正弦振动振幅对液体摩擦力的影响,给出了振幅选取原则和确定方法。通过对连铸1 270 mm×210 mm SPHC钢(≤0．08％C)的计算结果表明:振动采用小振幅能限制最大液体摩擦力,增大保护渣耗量,减少负滑脱时间;选定2．0m／min拉速,适宜振幅为±4 mm;随拉速提高振幅适当增大,可适时改善振动效果。     

The formation of oscillation marks in the continuous casting of steel slabs

The formation of oscillation marks on the surface of continuously cast slabs has been studied by metallographically examining slab samples and by performing a set of mathematical analyses of heat flow, lubrication, and meniscus shape in the meniscus region of the mold. The metallographic study has revealed that, in agreement with previous work, the oscillation marks can be classified principally according to the presence or absence of a small “hook” in the subsurface structure at the base of individual oscillation marks. The depth of the oscillation marks exhibiting subsurface hooks varies with the carbon content, reaching a maximum at about 0.1 pct carbon, while the oscillation marks without hooks show no carbon dependence. The analysis of heat flow at the meniscus, which is based on a measured mold heat-flux distribution, indicates that depending on the level of superheat, the meniscus may partially freeze within the period of a typical mold oscillation cycle. Lubrication theory has shown that, owing to the geometry of the mold flux channel between the solidifying shell at the meniscus and the straight mold wall, significant pressure gradients capable of deforming the meniscus can be generated in the flux by the reciprocating motion of the mold relative to the shell. A force balance on the interface between the steel and the mold flux has been applied to compute the shape of the meniscus as a function of the pressure developed in the lubricating flux at different stages in the mold oscillation cycle. This has demonstrated that the “contact” point between the meniscus and mold moves out of phase with (by π/2), and has a greater amplitude than, the mold displacement so that just at, or near, the end of the negative strip time molten steel can overflow at the meniscus. From these studies a reasonable mechanism of oscillation-mark formation emerges which involves interaction between the oscillating mold and the meniscusvia pressure gradients in the mold flux, meniscus solidification, and overflow. The mechanism is consistent with industrial observations. E. TAKEUCHI, on study leave from Nippon Steel Corporation     

A Study for Initial Solidification of Sn-Pb Alloy During Continuous Casting: Part II. Effects of Casting Parameters on Initial Solidification and Shell Surface

The initial shell solidification of liquid steel in the mold has significant influence on both surface and internal quality of the final slab, and it is mainly determined by the high transient high temperature thermodynamics occurring in the mold. This study investigated the effects of casting parameters like casting temperature, mold oscillation frequency, and stroke on the initial solidification of a Sn-Pb alloy through the use of a mold simulator to allow the clear understanding of the inter-relationship between irregular shell solidification, heat transfer, negative strip time (NST), and casting conditions. Results suggested that the shell surface oscillation marks (OMs) are strongly depending upon the fluctuations of meniscus responding temperatures and heat flux. An abrupt sudden fluctuation of high frequency temperature and heat flux at the meniscus during the NST would deteriorate the shell surface and leads to deep OMs. The fluctuations of responding temperature and heat flux are determined by the NST, meniscus solidification, and oil infiltration, which in turn are influenced by casting conditions, like casting temperature, oscillation frequency, stroke, etc.     

南钢方坯连铸结晶器振动参数优化的研究

针对南钢方坯连铸在拉速提高后,振动参数在保持原模式条件下,低拉速范围结晶器导前偏大,结晶器与铸坯间的机械作用力大;高拉速下负滑脱时间偏小,保护渣耗量低,造成铸坯振痕弯曲、外凸、严重时出现钩形振痕现象的特点,对结晶器振动参数进行了优化。实践表明,采用优化的振动参数,提高了铸坯的润滑,降低了拉坯阻力,消除了钩形振痕,振痕恢复至正常圆角凹陷形。     

Dynamic Response of Mold Oscillator Interacting with Steel Slabs

A mathematical model to show the dynamic response of the mold oscillator was suggested.The model con-sidered a frictional interaction between the mold oscillator and slab as several connected nodes.The governing equa-tion considered the slab as a multi-degree-of-freedom (DoF)system,and included a hysteresis model to describe elastic-plastic behavior of the slab;the mold oscillator was given two DoF by utilizing pressure and displacement ex-periment data.Simulations indicate that the mold and slab execute various vibrations,and that mold oscillation marks are caused by a stick-and-slip phenomenon during intervals,in which the slab contacting the mold moves downward compared to the other slab (negative strip time).The slab shows the formation of mold oscillation marks to previous formation criterion equally when the mold velocity is faster than the casting speed about downward.The oscillation mark will grow up over 2 Hz exciting frequency with constant 4 mm stroke in simulations.Finally,the negative strip time was compared to the frictional force,hysteresis variable,and plastic force to investigate forma-tion mechanism of the oscillation marks.     

基于液压振动的结晶器非正弦振动

 基于宝钢板坯连铸的实测数据,对液压振动装置下结晶器非正弦振动模型相关特性进行了测试和分析。探讨了不同偏斜角度下非正弦振动波形的特点及振动装置驱动力的变化趋势,同时对拉速-振频反向控制模型下,正弦与非正弦振动方式的负滑脱等参数计算结果进行了分析,并对结晶器摩擦力的实测结果进行了讨论。结果表明,结晶器非正弦振动进一步优化了工艺参数,比传统的正弦振动更适合高速板坯连铸生产。