薄板坯连铸带液芯轻压下过程的力学计算

为了给实际薄板坯连铸带液芯轻压下的设备设计和工艺设计提供依据，对薄板坯连铸带液芯轻压下过程中的铸坯变形抗力、拉坯阻力及其变化特性进行了理论计算。分析比较了不同轻压下设备(二冷支撑段辊列)条件下，连铸及轻压下过程的工艺参数对它们的影响。结果表明，在二冷支撑段辊列运动挤压铸坯阶段，最后一对支撑辊的移动量、挤压速度、拉坯速度、支撑辊间距离、辊径和对数以及坯壳温度对铸坯变形抗力和拉坯阻力有很大影响；而在二冷支撑段辊列稳定挤压铸坯阶段，只有总轻压下变形量及坯壳厚度影响较大。     

CSP薄板坯连铸低碳钢结晶器保护渣的研究

高拉速薄板坯连铸保护渣与常规板坯连铸保护渣在物理性能上有较大差异，通过对保护渣理化性能、熔化特性的研究，确定了适合高拉速薄板坯低碳钢连铸用保护渣的理化指标。     

Theoretical model for determining optimum soft reduction zone of continuous casting steel

Abstract

A theoretical model for determining the optimum soft reduction zone of continuous casting steel was developed. According to the theoretical analysis of the solute segregation behaviour in the mushy zone with the soft reduction by one pair of pinch rolls, there is an optimum soft reduction position for each element of steel, and all optimum soft reduction positions of different solute elements should be included in order to eliminate the centreline segregation effectively. The theoretical analysis shows that the carbon content has a great effect on the optimum soft reduction zone, and the cooling rate could affect both the optimum soft reduction positions of the segregation prone elements (P, S) and the optimum soft reduction zone of continuous casting steel. Plant trials of steel SWRH82B with soft reduction were carried out to validate the theoretical model, and the results show that the solute element segregation in the centreline of the strand has been improved with the optimum soft reduction zone.     

微合金钢薄板坯连铸边角裂纹控制

微合金钢薄板坯连铸过程高发边角部裂纹,致使热轧卷板边部产生翘皮、烂边等质量缺陷,是钢铁行业的共性技术难题。本文立足于某钢厂QStE380TM低碳含铌钛微合金钢薄板坯连铸生产,检测分析了铸坯角部组织金相结构与碳氮化物析出特点、不同冷却与变形速率条件下钢的断面收缩率,并数值仿真研究了不同结构结晶器和二冷区铸坯温度与应力的演变规律。结果表明:微合金钢薄板坯连铸过程存在明显的第三脆性区,且变形速率越大,第三脆性区越显著。传统薄板坯连铸工艺条件下,结晶器的中上部及其出口至液芯压下段的二冷高温区,铸坯角部冷速较低,致使其组织晶界含铌钛微合金碳氮化物呈链状析出。铸坯在液芯压下过程,低塑性角部因受较大变形与应力作用而引发裂纹缺陷。实施沿高度方向有效补偿坯壳凝固收缩的窄面高斯凹型曲面结晶器及其足辊区超强冷工艺,可分别提升铸坯角部冷速至10和20 ℃·s?1以上,从而促使铸坯角部组织碳氮化物弥散析出,并促进铸坯窄面在液芯压下过程金属宽展流动而降低角部压下应力,大幅降低了微合金钢薄板坯边角部裂纹发生率。      

Thin slab casting with liquid core reduction

Abstract

A liquid core reduction method has been developed for the flexible production of slabs of extensive thickness. In this method, achievement of the target slab thickness and the prevention of internal cracking are of prime importance. Using an experimental continuous caster, a series of tests of thin slab casting with liquid core reduction was conducted. The caster had three segments (1–3) for reduction at exit from the bending unit. The slabs were reduced in each segment with tapered alignment of the rollers over a 1 m length. The amount of reduction in each of the segments was changed in several patterns. The slabs were able to be reduced by 40–25 mm from 100 or 90 mm thickness without internal cracking. The variation in the amount of reduction in each segment was assessed by solidification analysis and strain analysis during liquid core reduction. In reduction along a tapered alignment, the incremental strain produced by the reduction can be comparatively low. The optimum reduction pattern to obtain the target slab thickness and to minimise tensile strain caused by the reduction has been established.     

宽板坯结晶器保护渣的开发

宽板坯连铸与常规板坯连铸相比有着较大的差异.通过对保护渣理化性能、绝热保温性能的研究,确定了适合于宽板坯中碳钢连铸用保护渣的理化指标,并开发出XCN-Z型保护渣.工业应用表明:研制的XCN-Z型宽板坯连铸用保护渣使用效果好,能满足拉速为1.3～1.5 m/min的中碳钢中厚板坯连铸连轧的要求.     

薄板铸机开浇冷齿形成的分析与解决

本钢炼钢厂薄板坯连铸机在开浇初期,特别是在低碳钢的生产时,结晶器内几乎每个浇次开浇时都会产生冷齿,由于薄板坯铸机拉速高,冷齿现象极易产生漏钢的事故,并产生7m左右的废坯,增加了生产成本。因此主要对能够引起冷齿的生产和设备各种相关的因素进行分析,并通过生产实践的方法找出最佳的解决办法。     

Analysis of thin-slab casting by the compact-strip process: Part II. Effect of operating and design parameters on solidification and bulging

The mathematical model to compute the thermal evolution and solidification of thin slabs, previously presented in Part I of this article, was used in combination with a three-dimensional (3-D) finite-element thermomechanical model to analyze how actual operation conditions can lead to excessive deflection and jamming of the slab shell at the pinch rolls. The models suggest that these phenomena arise from a sudden loss of control of the metallurgical length stemming from the coupling of inappropriate steel superheats and casting velocities to deficient heat-extraction conditions at the mold or secondary cooling system. The bulging deformation was calculated with an elastic and creep model that takes into account the temperature distribution across the shell thickness and the different times that shell elements have to creep exposure, i.e., according to the time that rows of elements require to reach their current position in the casting direction at a given casting speed. The last point was simulated by varying the duration of application of the ferrostatic load to the inside surface of each row of elements. The conditions forecast by the models as being responsible for excessive bulging agree very well with those present during the occurrence of these events in the plant. Since bulging after the last containment roll is a major limitation to productivity, this article also presents a parametric evaluation of the casting-speed limits that two compact-strip process (CSP) casters with different supported lengths may have as a function of steel superheat, mold heat-extraction level, water flow rate of the spray and air-mist nozzles, and slab thickness.     

采用薄板坯连铸生产高表面质量冷轧钢板的可行性分析

薄板坯连铸由于拉速高,结晶器容量小,结晶器钢水液面波动高度和表面流速显著高于传统连铸,因此容易造成保护渣卷渣,这是薄板坯连铸生产高表面质量冷轧钢板钢种的主要困难所在。NUCOR、蒂森一克鲁伯等企业采用薄板坯连铸连轧工艺生产冷轧钢板的实践也表明,在表面质量方面与传统工艺产品尚有较大的差距。采用薄板坯连铸工艺生产优质冷轧钢种,应适当增加铸坯厚度,以降低拉速和增加结晶器对钢水流的缓冲作用,可采用120mm厚铸坯(结晶器出口),3m／min左右拉速。为了减少结晶器保护渣卷渣,应对中等厚度薄板坯连铸结晶器内钢水流动控制(SEN结构参数、SEN浸入深度、拉速等)、电磁制动、保护渣等开展深入的试验研究。     

MCCR产线低碳钢高拉速技术研究与应用

通过统计和分析现场数据,得出限制MCCR薄板坯连铸连轧低碳钢拉速提高的主要因素为结晶器热像图中的冷齿和结晶器液面波动,对冷齿和液面波动的成因进行研究,并提出有效控制措施。研究结果表明,结晶器热像图中的冷齿与结晶器弯月面凝固收缩特性相关,受冷却铜板厚度、碳当量、拉速及保护渣影响,反映到铸坯实物上为凹陷或者裂纹缺陷,需合理匹配形成最优参数组合,以降低因冷齿造成的漏钢风险。当结晶器铜板厚度减薄量在6.7%以内时,一冷水维持原设计流量;当结晶器铜板厚度减薄量在6.8%～11.1%时,拉速4.0 m/min以上时需降低10%的一冷水流量;当结晶器铜板厚度减薄量在11.2%～15.6%时,所有拉速下需降低18%的一冷水流量,同时使用高碱度B型保护渣。针对高拉速下结晶器液面波动问题,通过数值模拟研究浸入式水口插入深度、拉速、结晶器断面宽度及电磁制动等参数对结晶器内流场和温度场的影响规律,得到不同拉速和不同断面条件下电磁制动电流的合理配置,使得拉速达到5.5 m/min时钢液面最大流速仍小于0.3 m/s。上述研究结果应用后,结晶器冷齿问题得到有效缓解,110 mm厚的薄板坯最高拉速达到5.8 m/m...     

两种类型薄板坯连铸连轧生产线配置研究

薄板坯连铸连轧工艺有两个发展趋向:超薄带钢生产线和多品种生产线。针对这两种不同类型生产线的要求,提出了相应的总体配置方案,包括生产线产能和产品的品种及规格确定;铸坯合理厚度、薄板坯连铸机流数、机型、结晶器类型的选择;加热方式的选择及辊底式加热炉炉长的计算;粗轧机组和精轧机组的配置及铁素体轧制和半无头轧制技术的应用等。     

Steel strips in the context of near net shape casting production

Following the replacement of ingots by continuously cast slabs the next logical step towards near net shape casting has been the development of thin slab casting machines. These are now beginning to match the quality and productivity levels possible with conventional machines. The next step in this evolution towards lower cost operation is high speed thin strip casting machines. The merits of twin roll casters versus belt casting machines for friction free casting of low carbon steels, suggest that a belt caster will be needed for achieving high productivities and associated cooling lengths required for the production of hot strip in the 5–20 mm thickness range.     

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.     

攀钢连铸高效化技术

介绍了高效连铸以及相关技术在攀钢的应用及效果。通过对钢包精炼的改进和中间包冶金技术的优化,提高了钢水洁净度;结合复合辊、低过热度浇注技术的采用和二冷技术与高速连铸保护渣的研制等新技术、新工艺的研究与应用,全面改善了高拉速条件下的铸坯质量,使攀钢板坯连铸机的铸坯产量、质量以及铸机作业率均有较大的提高。     

Modelling recalescence after stock reduction during hot strip rolling

Abstract

The relationships between stock recalescence time/distance and process variables, such as exit thickness, reduction, rolling speed, work roll diameter and slab–roll heat transfer coefficient during hot strip rolling, have been established. The behaviour of the temperature gradient was analysed and used to estimate the slab and transfer bar mean temperatures from measured surface temperature in three hot strip mills located in northeast México. It was found that the recalescence critical variables, in order of importance in minimising temperature measurement variation, are slab–roll heat transfer coefficient, reduction, exit thickness and roll speed.     

双辊连铸工艺参数对薄带坯质量的影响

介绍了双辊薄带坯连铸的表面质量和内在质量与连铸工艺的关系。对于辊径为φ500mm．辊面宽250mm的双辊连铸机（浇注奥氏体不锈钢带坯）而言,控制连铸速度18—22m／min,双辊间熔池液位高度约110mm,铸辊压力25—40kN,熔池采用层流式布流,水口深度约10mm,以及液面采用惰性气体保护时,可以最大限度获得裂纹少、板型好、表面光洁、内部夹杂少的较佳表面质量和内在质量的铸带坯。     

Development of Continuous Electrical Steel and Casting Technology of New Products

 The development of continuous casting technology of electrical steel was analyzed. The technologies and products characteristics of conventional continuous casting, thin slab continuous casting and rolling, middle thin slab continuous casting and rolling and twin-roll thin strip were compared. Conventional continuous casting technology was widely adopted in producing electrical steel; thin slab continuous casting and rolling and middle thin slab continuous casting and rolling technology industrialized electrical steel; and study of twin-roll thin strip casting technology was focused on fundamental experiments.     

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。      

薄板坯连铸连轧采用铁索体轧制生产低碳钢板卷工艺技术研究

基于唐钢薄板坯连铸连轧生产线工艺设备，通过理论分析和现场试验，确定了低碳钢板卷铁素体轧制工艺，分析了铁素体轧制板卷组织与性能的关系，以及工艺参数对板卷组织与性能的影响，并指出薄板坯连铸连轧生产线可通过采用铁素体轧制生产性能良好的低碳软钢。     

400mm厚连铸坯轧制时缺陷的压合模拟

对某宽厚板厂最新投产的400mm连铸坯,以刚-粘塑性有限元模拟分析了其轧制Q345特厚钢板时的缺陷压合过程和临界压合条件。结果表明：在足够的压下率下,特厚板中心矩形裂纹能够被压合;缺陷尺寸、轧辊半径和坯料厚度对缺陷压合影响很大。缺陷尺寸和轧辊半径越大、坯料厚度越小,压合所需的临界压下率越小;在1120mm×4300m...