高压气瓶钢34Mn2V 200 mm×200 mm轧坯角部拉裂缺陷的控制工艺

通过工艺对比分析了34Mn2V高压气瓶用钢中间包浇铸温度、结晶器液面波动、[Als]、中问包炉次和280 mm×380 mm连铸坯拉速波动对轧坯角部拉裂的影响。提出减小RH加Al量,按[Als]0.01%控制;RH后喂Ca-Si线;适当提高连铸钢液温度,控制中间包钢水温度1 520～1 530℃;控制浇铸过程塞棒吹氩量≤10 L/min;结晶器液位波动±3 mm等工艺措施。应用结果表明,轧坯角部拉裂缺陷率由原来的23.57%降至1.21%。     

Hydrogen Potential Sources in Refractory Materials during Steel Casting

It is well known that the presence of dissolved hydrogen in cast steel can cause defects that appear in hot rolling and forging of steel parts with heavy sections, and also contributes to the formation of internal cracks and blowholes during the solidification of the liquid steel. These problems are especially important in the continuous casting process. So, hydrogen levels must be kept at a minimum in this process. The aim of this work is to investigate possible sources of hydrogen, focusing on the materials that are in contact with the liquid steel during casting. The tundish refractory lining, shrouding tube, tundish covering agents, and casting powders were analysed. The results showed that not only the control of humidity content in those materials is critical, but the phase transformations that the materials suffer during the casting process are important as well.     

板坯连铸异钢种连浇混浇坯长度及成分变化模型的开发及应用

基于建立的连铸中间包及结晶器内钢液混合过程的物理模型,开发了板坯连铸异钢种连浇过程混浇坯长度及成分变化模型。以某钢厂单流板坯连铸机220 mm×1560 mm断面Q235与Q335Ti钢的混浇过程为研究对象,采用水模型试验结合数值模拟确定模型的关键参数,并通过开展现场试验对混浇坯取样验证模型的准确性。结果证明:混浇坯成分取样与模型预测的成分偏差小于5%,且模型预测的混浇坯长度与人工确定的一致。故采用该模型可跟踪不同混浇工况下中间包内及铸流上钢液的混合行为,准确预测混浇坯的长度以及成分变化规律。采用该模型研究了拉速及中间包内剩余钢液质量对混交坯长度及不同浇注长度铸坯C元素质量分数变化的影响规律。发现当拉速保持不变时,中间包内剩余钢液越多,混浇坯越长;当中间包内剩余钢液质量保持不变时,拉速越大混浇坯越短。相比而言,中间包内剩余钢液质量比拉速对混浇坯长度的影响更大。另外当拉速不变时,随着中间包内剩余钢液质量的增加,C元素质量分数由0.16%变化到0.18%的速率减慢;当中间包内剩余钢液质量不变时,随着拉速的增加,C元素质量分数由0.16%变化到0.18%的速率增加。因此异钢种连浇过程,适当提高拉速以及减少中间包内剩余钢液质量,可有效减少混浇坯长度,成分变化速率降低。      

浸入式水口吸入空气机理及吹氩量控制模型

 连铸过程浸入式水口本身及其与上水口连接处容易吸入空气,导致钢水二次氧化,随之可能造成水口结瘤及断浇,导致严重的连铸事故。通过向水口内部吹入氩气可以防止空气吸入,吹氩量控制不当容易引起铸坯缺陷。基于伯努利原理和质量守恒定律建立了从中间包到结晶器的速度-质量模型,探讨了以上部件吸入空气的机理。首先研究了理想与考虑压损2种情况下水口直径、水口浸入深度、中间包液位、铸坯宽度和拉坯速度对水口入口的钢液横截面积与出口的钢液横截面积之比(A_A/A_P)的影响,然后对水口结构进行了优化,并建立了吹氩量控制模型。结果表明,为防止水口吸入空气,应尽量减小水口直径、降低中间包液位和水口浸入深度的高度差、增大拉坯速度和铸坯断面宽度。其中水口直径提高10%,A_A/A_P从2.15增大至2.62;铸坯宽度和拉坯速度对A_A/A_P影响略低于水口直径,同样提高10%,A_A/A_P均从2.15降低至1.96;中间包液位和浸入深度对A_A/A_P影响最小。基于此研究结果,水口结构优化为符合钢液流束的圆台形,并结合水口内真空区体积确定了吹氩量控制模型,使得水口内始终保持微正压。本研究结果为减小甚至消除水口的空气吸入、控制氩气吹入量提供了理论基础,对高品质钢的生产及节能降耗具有重要意义。     

提高方圆坯铸机连浇炉数的工艺及装备技术

 攀钢钒提钒炼钢厂2009年10月中旬投产的方圆坯连铸机单中间包连浇炉数较低,影响了炼钢生产组织。分析了浇注铝镇静钢水口堵塞原因,通过研究脱氧工艺、夹杂物变性处理工艺及优化二冷喷嘴结构与布置方式、改进拉矫设备及工艺,改善了钢水可浇性,提高了铸机拉速,铝镇静钢因水口堵塞造成的流次断浇率由投产初期的12.9%降至2.0%以下,单中间包连浇炉数由投产初期的4～5炉提高到7～10炉,硅镇静钢单中间包连浇炉数由6～9炉提高到8～14炉,从而保证了方圆坯铸机生产顺行,降低了生产成本。     

连铸参数对中间包内控流元件冶金性能的影响

根据相似原理,以浇铸Φ380 mm铸坯的28 t 3流T型中间包为原型,通过实验相似比λ=1:2水模型,研究了拉速0.3～0.9 m/min、液位600～1200 mm连铸条件下,控流元件对中间包内流场特性的影响。结果表明,当实际生产的中间包液位为500 mm左右时,拉速<0.4 m/min时,控流元件改善其流场的作用不明显,不需加入控流元件;当拉速≥0.4 m/min和<0.7 m/min时,可选用带挡墙结构的中间包;当拉速≥0.7 m/min,可考虑挡墙加湍流抑制器的结构,以优化中间包内流场特性。通过对中间包内流场的分析得出,设置控流元件时,应尽量降低注流混乱度并使钢水湍动能尽可能多的消耗在浇铸区。     

中间包上水口环形吹氩下气泡大小和迁移行为研究

摘要：通过水模型实验研究了上水口环形吹氩工艺下中间包和结晶器内气泡形貌,并结合数值模拟分析了透气砖位置、拉坯速度和吹氩量对中间包和结晶器内气泡尺寸、气泡迁移和中间包近液面钢液流动的影响。结果表明：上水口环形吹氩形成以塞棒为中心的圆台状气泡羽流,气泡浓度沿径向向外逐渐减少;附壁效应使得气泡羽流偏向塞棒壁面流动,增大气泡的碰撞聚并概率和近塞棒壁面的羽流上升速度,对中间包液面产生较大冲击作用;同时,部分细小气泡会随钢液进入水口及结晶器内部;增大吹氩量,中间包内环形气泡羽流中气泡数目明显增多,中间包近液面钢液上升速度增大;增大拉坯速度,环形气泡羽流的宽度和气泡数量逐渐减小,近液面速度减小;增大透气环距水口中心距离,中间包内气泡弥散度增大,环形气泡羽流宽度也随之增大,气泡羽流对中间包液面冲击作用减弱;增大吹氩量和拉坯速度、减小透气环距水口中心距离,进入结晶器的气量和气泡尺寸逐渐增大。实验条件下,透气环内外径为110mm/140mm、拉坯速度为1.2m/min时,吹氩量为4L/min较为合适。     

Study on dimension and migration behavior of bubble under annular argon blowing at tundish upper nozzle

The water model experiments were carried out to study the bubble morphology in the tundish and mold with the process of annular argon blowing at tundish upper nozzle. The effects of the position of gas permeable brick, the casting speed and the argon flow rate on the bubble size distribution, the bubble migration behavior and the flow behavior of liquid steel near the liquid level in tundish were further investigated, coupled with the numerical simulation. The results show that with the process of annular argon blowing at tundish upper nozzle, a frustum cone shaped bubble plume can be formed around the stopper rod. The concentration of argon bubbles gradually decreases outward along the radial direction of the stopper rod. Owing to the wall attached effect, the bubble plumes float upward along the stopper rod, which can increase the collision probability between bubbles and the velocity of bubble plumes, causing a larger impact strength on the liquid level in tundish. In addition, a part of small bubbles are wrapped into the nozzle and the mold due to the drag force of liquid steel. With increasing argon flow rate, the number of bubbles in annular bubble plumes and the vertical velocity of liquid steel near the liquid level in tundish increase significantly. With increasing casting speed, the width and the bubble number of annular bubble plumes gradually decrease, leading to a decrease of the vertical velocity of liquid steel near the liquid level in tundish. Increasing the distance between the annular gas permeable brick and the center of tundish upper nozzle, the dispersion of bubbles and the width of bubble plumes increase, and the impact strength of bubbles acting on the liquid level in tundish becomes weaker. As the argon flow rate and the casting speed increase, and the distance between the gas permeable brick and the center of tundish upper nozzle decreases, the gas volume and bubble size in the mold increase. Under the experimental conditions, when the inner and outer diameters of the annular gas permeable brick are 110mm and 140mm, respectively, and the casting speed is 1.2m/min, the appropriate argon flow rate is 4L/min.     

三流非对称中间包流场水模拟研究

在保证产量的情况下,为使夹杂物充分上浮去除,钢水温度均匀,进一步提高某钢厂320 mm×480 mm连铸方坯的生产质量,针对三流非对称中间包,设计1∶3水模拟试验和数值模拟,进行不同拉速和有无挡坝的研究。通过速度场和温度场的数值模拟以及不同拉速下的水模拟,可以发现,随着拉速的增加,三个水口的停留时间减小,并且三个水口的停留时间有一定差距。添加挡坝后随着拉速的增加,平均停留时间减小得更为缓慢。速度场和温度场的分布规律并不随拉速的变化而变化,但拉速的增加会使中间包内的速度和温度上升。     

Development of laboratory scale thin strip caster and investigation of direct casting of AISI 304 stainless steel

Abstract

An unequal diameter (1 : 3), two roll thin strip casting machine has been designed and fabricated for investigation of the direct casting of thin strip on a laboratory scale. The system consists of a preheatable shallow tundish with online heating facility, water cooled rotating rolls (chill and auxiliary) for solidification of the liquid metal, and a stripper assembly. The machine has a variable speed. Roll gap setting and roll pressure adjustment are two important features of the machine. It is also possible to vary the placement angle of the auxiliary roll with respect to the chill roll. A heat transfer model was developed, based on experimental casting results. Experiments were conducted using AISI 304 grade stainless steel. Up to 100 kg of steel was cast without interruption into strips of widths 100 and 200 mm and thickness varying between 1 and 2 mm. Some of the process parameters affecting the quality of the strip were identified.     

Molten Steel Flow in a Slab Continuous-casting Tundish

Fields of fluid flow and temperature, and residence time distribution (RTD) curves were investigated by mathematical simulation in a one-strand tundish for continuous casting. It was known from the investigation that a big “spring uprush” formed on surface around the long shroud when molten steel flowed into a turbulence inhibitor (TI) with extending lips and rushed up reversely out of the TI, while four small “spring uprushes” existed on surface when a TI without extending lips because the liquid steel flowed mainly out of the 4 corners of the TI. The flow of liquid steel in the former tundish configuration was not reasonable and the height of an area where temperature was less than 1819 K was about half of liquid surface height on the right side of the stopper, which meant that big dead zone existed in the former tundish configuration. In the optimal one, the height of such area was only seventh of the liquid surface height. The RTD curves obtained from the mathematical simulation basically agreed with those from the physical modeling and the flow characteristics obtained from these two methods agreed with each other.     

顶旋型湍流抑制器对单流板坯中间包内湍流行为的影响

摘要：设计了一种顶旋型湍流抑制器,使钢液产生旋转流场,降低钢/渣界面速度,促进夹杂物的去除,达到净化钢液的目的,并利用数值模拟的方法,对单流板坯中间包在稳态和非稳态时的流场进行研究。结果表明：使用新型抑制器相较于不使用和使用普通抑制器,对中间包稳态浇注流场有明显的改善,死区体积明显减小。拉速和中间包容量改变时,新型抑制器比普通抑制器对中间包液面波动的抑制效果更好。当拉速为1.15、1.55和1.85m/min时,使用新型抑制器的中间包自由液面的平均速度分别为0.040、0.053和0.062m/s,相较于普通抑制器分别降低了21.6%、24.3%和26.2%。当中间包容量为40、30和25t时,使用新型抑制器相比于普通抑制器,自由液面的湍动能分别减少了20.9%、25.0%和26.3%。     

Effect of asymmetric casting of conticaster on liquid steel in tundish

The flow characteristic and temperature characteristic of steel liquid in tundish at asymmetric casting were studied using SolidWorks, ANSYS, etc.It has an important impact on flow field in tundish for asymmetry casting of conticaster, which can lead to the change of tundish temperature distribution. When a strand of conticaster on one side is closed, the flow rate of steel liquid can be reduced and more backflow regions can be formed in this side of tundish. Simultaneously, the region of lower temperature steel liquid in middle part of tundish moves to the other side obviously, and the phenomenon is more noteworthy when an edge strand of conticaster is closed.     

薄板坯连铸连轧技术推动传统连铸高速化

薄板坯铸机生产达到了较高的浇铸速度。从薄板坯连铸轧技术“薄、快、连”的特点出发，分析了变截面结晶器、铸轧、非正弱振动、电磁制动在薄板坯连铸中的作用。经技术特点对比，认为厚板坯的高速浇铸条件好于或不次于薄板坯，厚板坯连铸可以达到薄板连铸同样高的铸速水平（4－6m/min）并适用于单流的连铸直轧生产。     

六流小方坯连铸中间包结构优化仿真

以鞍钢六流小方坯T型中间包为对象设计了中间包结构优化方案,应用数值模拟方法研究不同方案的中间包钢液流动状态和温度场情况。模拟结果表明,中间包纵向侧壁钢液液面高度处内部宽度为463 mm时的优化效果最佳。结构优化后的中间包用于浇铸高碳钢,各流钢水出口最大温差降低了7℃,塞棒侵蚀减轻,单中包浇铸由12罐提高到17~18罐。     

The applicability of an isokinetic steel feeding system for near-net-shape strip casting

For the near-net-shape casting of thin steel strips a liquid steel feeding system is developed. This article at first describes the development of a water model for the complete casting machine (cold tests). In this model the control concept for the low-pressure tundish is designed and tested. As a subsequent stage to the water model trials, the functional ability of the casting machine concepts, and particularly to the tundish concepts, is verified in separately conducted tundish tests and also in strip casting trials (hot tests).     

连铸中间包快速更换定径水口技术的应用

为提高中间包使用寿命，合钢第二炼钢厂采用手摆式连铸中间包快速更换定径水口技术。该技术装置由上下两块滑动水口组成，其中下水口通过一个滑道与备用水口连在一起。当下水口侵蚀严重需要更换时，利用杠杆原理，用人力将备用水口推到工作位置以取代原来的下水口，达到稳定钢流的目的。在30机R6m小方坯连铸机上应用共计9个浇次表明，在其它条件基本相同的情况下，平均单包连浇55．78炉(最高63炉)，平均连浇21．60h(最高24．23h)。钢水收得率由98．11％提高到98．36％，吨钢成本降低3．25元。     

稀土钢连铸喂丝工艺存在的问题及对策

稀土钢连铸中间包和结晶器喂丝，生成的稀土氧化物使中间包覆盖剂、结晶器保护渣的使用性能发生变化，稀土夹杂物容易导致水口堵塞、结瘤。针对这些问题，建议研究开发稀土钢连铸专用中间包覆盖剂和结晶器保护渣，同时采取适当的措施防止水口结瘤的产生。     

降低大方坯中间包临界液面高度工艺研究

中间包底部水口附近结构和流场形态影响中包临界液面高度。通过在中间包底部水口附近加抑流件的水模型优化实验及工业试验,确认了加抑流件可以降低中包临界液面高度,在工业生产中抑流件使用是安全的,中间包合理停浇液面对尾坯纯净度无影响。     

冷轧无取向电工钢连铸生产实践

通过对连铸过程生产实践的总结以及现场数据分析,研究了太钢在生产冷轧无取向电工钢时连铸过程中间包钢水增碳、二次氧化、钢水吸氮以及在冷轧过程中钢板表面重皮、夹杂缺陷等的原因以及解决措施。结果表明,通过采用专用冷轧无取向电工钢中间包覆盖剂和结晶器保护渣、加强钢水从大包至中间包保护浇注、稳定连铸过程拉速和液面自动检测控制等措施解决上述存在的问题。