鞍钢中薄板坯连铸关键技术研究与应用

鞍钢股份有限公司炼钢总厂为了降低汽车钢板夹杂缺陷,解决铸机絮流堵塞问题,采取了铸坯火焰清理技术和上水口、浸入式水口优化技术;针对中碳钢铸坯角部横裂纹问题采用了倒角结晶器技术.结果表明,汽车钢板轧后缺陷率降低40％,中碳钢铸坯角部横裂纹减少95％,实现了中碳钢热装热送.     

含硼中碳钢铸坯角部横裂纹影响因素分析

基于含硼中碳钢A36一LB的生产实践，分析了钢水成分、钢中硼含量、振动曲线、结晶器水量、二冷制度及对弧、辊缝精度等对铸坯角部裂纹的影响，并提出了相应的控制措施，如控制钢水叫（S）≤0．015％、w（Mn）／w（S）〉37．6；w（Ca）／w（A1。）〉O．09；结晶器振动冲程减小11mm，并提高振频使负滑脱时间降低32％左右；结晶器宽面和窄面水量稳定在4000和380L／rain，并采用弱冷冷却曲线、降低二冷水总水量，同时减少铸坯边部水量50％以提高边部温度；定期进行辊缝仪测试，加强检修力度和及时更换不良辊列，使其精度控制在合理范围内等，这些措施有效地改善了铸坯角部裂纹，使其降级比率和质量异议均低于当月该厂生产的Q235B钢。     

提高热送铸坯温度的试验研究

采用远红外非接触测温和射钉法对武钢三炼钢新近投产的板坯连铸机典型二冷模式下铸坯的表面温度及凝固坯壳厚度进行了研究,发现通过矫直区进入水平段之后铸坯表面温度持续降低,机尾近铸坯表面温度仅为710－820℃。根据坯壳厚度变化得出的典型二冷模式下综合凝固系数K在24－27mm/min^1/2之间,根据凝固终点与K的关系,将浇铸低碳铝镇静钢时拉速由以往的1．1m/min左右提高到1．4－1．5m/min,使铸坯的凝固终点向机尾延伸,铸坯出机表面温度提高到了目前920－940℃。     

M-EMS 对中碳钢连铸方坯碳偏析的影响

180 mm×180 nm 方坯结晶器电磁搅拌电流强度对中碳钢铸坯碳偏析及显微凝固组织的研究结果表明:结晶器电磁搅拌电流强度增大,铸坯等轴晶比例增加,二次枝晶间距减小,连铸坯中心碳偏析减小,但铸坯中间碳偏析增大,因此中碳钢方坯的电磁搅拌电流强度不宜过大.中碳钢方坯中间碳偏析与坯壳处出现白亮带有关.     

液芯大压下对薄板坯低倍组织的影响

通过在马钢股份有限公司CSP连铸连轧生产线上进行了液芯大压下的工业性试验,研究了最大液芯压下量从原设计的20 mm增加到35 mm时对低碳钢、中碳钢和硅钢低倍组织的影响.研究结果表明:在试验研究的范围内,压下量对铸坯内裂纹和三角区裂纹没有明显影响;液芯大压下能够改善铸坯中心偏析,随着压下量的增加,中心偏析程度降低,对中碳钢Q235B和硅钢MGW1300效果更明显.     

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。     

通过减少振痕深度细化铸态方坯表面奥氏体晶粒

在连铸钢生产过程中，细化铸态方坯表面层的奥氏体晶粒有助于减少其表面裂纹的产生。本研究目的在于阐明冷却速率对铸态奥氏体晶粒尺寸及其长大机理的影响，在小振幅和高频率的振动条件下，可以减少振痕的深度和间隔距离，并且细化铸坯表面奥氏体晶粒。在奥氏体相温度区，估计平均冷却速率从6K／s变化到16K／s，其速率与振痕特征有关，此外我们发现：甚至当振痕的特征发生变化时，奥氏体晶粒长大方向也没有发生变化。通过方坯表面的奥氏体晶粒尺寸也可确定铸坯表面层下的奥氏体晶粒尺寸。     

首钢小方坯铸机的操作与设计改进

首钢第二炼钢厂通过提高连浇炉数使1991年铸机作业率提高到73.47％，达到了126万吨设计生产能力。但因断流率较高，整炉浇注率只有79．93％，连浇炉数每提高1％，铸坯产量仅增加0．65个百分点。为此，该厂从1992年开始围绕减少铸机断流、提高整炉烧成率开展了大量工作。1993年该厂引进两台八流小方坯连铸机，通过完善铸机设备和工艺条件、强化设备管理、降低故障停机、坚持低温快注、提高连浇炉数等一系列加强生产组织的措施，使断流率大幅度降低，连浇护数和铸机作业率进一步提高，创出两台铸机年产120mm×120mm钢坯156．036万吨，单流产9…     

减少连铸坯表面振痕的方法研究

分析了结晶器振动产生连铸坯表面振痕的生成机理,论述了振痕对连铸坯质量的影响,研究和探讨了减少铸坯表面振痕的途径,提出了减少连铸坯表面振痕、提高连铸坯表面质量的有效措施。     

减少连铸坯表面振痕的方法研究

分析了结晶器振动产生连铸坯表面振痕的生成机理,论述了振痕对连铸坯质量的影响,研究和探讨了减少铸坯表面振痕的途径,提出了减少连铸坯表面振痕,提高连铸坯表面质量的有效措施。     

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 α 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.     

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。     

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.     

连铸结晶器混合驱动系统的非正弦振动波形

 针对频率、振幅和波形均可在线调整的连铸结晶器电动式混合驱动系统,提出与其运行模式相匹配的非正弦振动波形。首先阐明新型驱动系统非正弦波形的发生机理;然后按照激波机构的运行特点,考虑系统运行过程中的平稳性和运动约束条件,构建了激波机构的速度函数,进而根据驱动系统运动学推导出以频率、振幅和偏斜率为基本参数的结晶器非正弦振动波形;最后给出非正弦波形的关键工艺参数计算公式,讨论了[vc-f、h]同步控制模型中控制参数与振动工艺参数的关联规律,并以某中碳钢板坯连铸生产为例,利用关联规律,得到了完全符合振动工艺原则的非正弦控制模型,从而验证了该非正弦波形的有效性和实用性。     

板坯结晶器与振动台振动特征分析

应用自行开发的软硬件系统,对板坯连铸机结晶器及振动台进行测试与分析,发现其振动特征随拉速而变化的规律,提出了用相位分析判定振型的方法。     

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。     

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。     

Effect of oscillation-mark formation on the surface quality of continuously cast steel slabs

In a study of early solidification during the continuous casting of steel slabs, the effect of the formation of oscillation marks on the surface quality of the slabs has been examined by metallographic in-vestigation of slab samples and by performing a set of mathematical analyses. Positive segregation of solute elements, especially phosphorus and manganese, has been observed at the bottom of the oscillation marks and has been classified into two categories. One type is observed at the end of the overflow region on subsurface hooks which originate from partial solidification of the meniscus. A heat-flow model which takes into account the shape of the oscillation marks has revealed that this type of positive segregation is caused by local delay of solidification at the bottom of the oscillation marks. The other type of positive segregation has been found in a layer on the bottom of the oscillation marks without subsurface hooks. This form of segregation cannot be explained by the heat-flow model, but is likely due to a penetration mechanism in which the negative pressure in the flux channel generated during the upward motion of the mold draws out interdendritic liquid from the semi-solidified shell. Transverse cracks are found along the bottom of oscillation marks. The surface of the transverse cracks exhibits an interdendritic appearance in the vicinity of the slab surface, which implies that the cracks are initiated as hot tears in the mold region. A heat-flow analysis predicts that deep oscillation marks cause nonuniformity of the shell in the mold, which also was observed in the metallographic in-vestigation. According to the heat-flow analysis, not only the depth but also the pitch of the oscillation marks affects the shell profile. Therefore increasing the frequency of mold oscillation effectively reduces transverse cracks, by decreasing both the depth and the pitch of oscillation marks. Formerly Graduate Student in the Department of Metal-lurgical Engineering, University of British Columbia An erratum to this article is available at .     

330mm厚度连铸坯技术的开发与应用

舞钢第二炼钢厂通过对3鹕每机进行技术改造,成功实现了330mm厚规格铸坯的生产和板坯轻压下、结晶器液压振动、浸入式水口快速更换、小辊密排、电磁搅拌等多项连铸新技术的应用。新技术的应用提高板坯的内部质量,减少偏析、疏松以及中心裂纹的产生。高拉速又提高了2#、3#板坯连铸机的产能。既满足了产量的需求,又为内部及表面质量提供了重要保证。     

Trials for Reducing Depth of Oscillation Marks in Continuous Casting

Improvement of surface defects in a continuously cast slab or billet is important for saving surface scarfing and for carrying out direct rolling. Deep oscillation marks, one type of the surface defects, sometimes cause surface cracking and positive segregation. In this study, the mechanism by which oscillation marks are formed was investigated by using a continuously cast simulator, which is a billet‐type machine. Then attempts were made to reduce the depth of oscillation marks by two methods in which electromagnetic force, which is the most effective means for reducing depth, was not used. The two methods were use of an adiabatic board for preventing solidification of a meniscus and the use of a board for suppressing the flow of flux. Overlapping of a molten metal on a meniscus resulted in formation of oscillation marks in tin. On the other hand, bending of a solidified shell also resulted in formation of oscillation marks in a tin‐lead alloy. The depth of the oscillation marks formed by the overlapping mechanism was greater than that formed by the bending mechanism. Both mechanisms depended on the strength of the solidified shell. Therefore, two trials to reduce the depth of oscillation marks formed by the overlapping mechanism were carried out. In one trial, an adiabatic board was inserted into the molten metal. Reduction in depth of the oscillation marks reduced up to about 86% was achieved when high viscosity flux was used. However, the adiabatic board was not effective when low viscosity flux was used. In the other trial, a board was inserted into a molten flux layer with a depth of 10 mm in depth in order to suppress the flow of the flux and to change the direction of flux flow, and the depth of oscillation marks was reduced by about 33%. Therefore, both of these methods are effective for reducing the depth of oscillation marks in a continuously cast billet.