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。     

攀钢板坯连铸二冷配水模型的开发与应用

通过建立连铸板坯二维非稳态传热数学模型,分析了拉速、冷却强度和钢水过热度对铸坯表面温度的影响,改进和了现行的二冷配水制度。为进一步扩大攀钢板坯连铸新品种和提高铸坯质量奠定了基础。     

攀钢高拉速板坯连铸保护渣的开发

根据攀钢2号板坯连铸的工艺特点，在分析了高速连铸对保护渣性能要求的基础上，研究开发出了适应高拉速浇注的连铸保护渣，工业试验结果表明，研究开发的XIZ-DT高拉速用连铸保护渣，在拉速≥1．75m／min时，结晶器内熔化状况良好，保护渣消耗量0．38-0．42kg／t，所浇铸坯表面质量良好，铸坯表面无清理率98．70％，能够满足攀钢2号板坯高速浇注的需求。     

高拉速板坯连铸保护渣的应用

根据攀钢2^#板坯连铸的工艺特点，在分析了高速连铸对保护渣性能要求的基础上，研究开发出了适应高拉速浇注的连铸保护渣，工业试验结果表明，研究开发的YC—DT高拉速用连铸保护渣，在拉速≥1.70m/min时不仅结晶器内熔化状况良好，而且保护渣消耗量适宜，所浇铸坯表面质量良好，能够满足攀钢2^#板坯高速浇注的需求。     

低合金钢连铸工艺研究

研究了连铸低合金钢的拉速、二冷配水，结晶器保护渣，结晶器喂稀土丝等工艺，解决了低合金钢连铸工艺容易拉生铸坯表面裂纹，水口堵塞等问题，为攀钢1350板坯连铸机生产低合金钢奠定基础。     

常规低碳钢板坯的高速连铸工艺技术

 高速连铸具有显著减少建设投资、大幅提高产量和降低物料消耗等优势。但欧、美及国内多数钢厂均使用中低拉速连铸常规厚度板坯，主要原因是高速连铸拉漏风险增加与卷渣导致的表面质量恶化。为解决上述问题，以日本JFE为代表的钢企开发了一系列关键技术，JFE福山No.5 铸机连铸厚度220 mm低碳钢板坯最大拉速达到3.0 m/min。阐述了国内外常规板坯铸机的高速连铸发展历程。基于JFE福山No.5 CCM和首钢京唐No.3 CCM低碳钢高速连铸实践，综述了高速连铸的3项关键技术，分别是强冷却能力结晶器技术、高速连铸结晶器卷渣控制技术和电磁冶金技术，为生产冷轧薄板钢种为主的钢厂提高铸机拉速提供参考。     

连铸二冷区铸坯表面温度测量

介绍了ＣＩＴ－Ｍ型红外辐射测温系统的工艺特点,利用该系统实测了板坯连铸的典型钢种在不同拉速条件下的铸坯表面温度。分析了拉速和冷却强度对铸坯表面温度的影响,为攀钢板坯连铸二冷配水制度的优化提供了依据。     

高拉速条件下减少连铸板坯内部缺陷的技术及应用

介绍了攀钢在提高板坯连铸拉速过程中所出现的铸坯内部典型缺陷及其产生原因,以及采取的相应技术措施和取得的效果,这些实用技术措施确保了攀钢成功地实施高效板坯连铸技术。     

攀钢高效连铸取得成果

“九五”国家攻关项目攀钢“高效板坯连铸技术研究”,在攀钢连铸生产中推广后 ,已取得重要成果。铸坯产能比设计能力增加 60万 t,达到 1 60万 t;铸机最大拉速达1 .8m/min,平均为 1 .3～ 1 .5m/min;铸机作业率最高达到93.3% ,平均 90 .4% ;铸坯质量合格率最高为 99.8% ,平均 99.6%。以高拉速、高铸机作业率、高铸坯质量为特点的高效板坯连铸技术 ,使攀钢获得了良好的经济效益 ,并为实现全连铸创造了有利条件。攀钢高效连铸取得成果@苗山     

生产高质量气瓶钢时无缺陷板坯连铸工艺的最新进展

气瓶钢为裂纹敏感钢种,在Krakatan钢厂3号板坯连铸机上研究,减少板坯表面纵裂纹、横裂纹和星形裂纹,从而取消板坯清理,采用优化连铸工艺参数(如选择合适连铸保护渣、优化二冷冷却、液面控制、过热度、拉速等),研究其与板坯表面质量之间的关系.所选择的保护渣粘度和熔点低,冷却水强度从0.67L/kg钢,降低到0.58L/kg钢,拉速为1.1m/min,液面控制精度为±5%,钢水的含碳量0.09%左右.结果表明,横裂纹和纵裂纹减少90%,星形裂纹从62.21%减少到28.87%,板坯表面清理率从85.54%减少到25%以下,板坯修理损失率从3.4%降到0.05%.     

Effect of Casting Speed on Slab Broadening in Continuous Casting

A three‐dimensional viscoelastic‐plastic thermal‐mechanical coupled finite element model was based on the basis of the secondary development of commercial software (MSC, Marc software, USA) to simulation the effect of casting speed on slab broadening in the secondary cooling zone. The results show that the ratio of ultimate broadening increased with increasing casting speed for various steel grades, but the change in broadening lagged that in casting speed. When the casting speeds were 1.0 m/min, 1.1 m/min, and 1.2 m/min for Q235 steel, the maximum ratios of ultimate broadening were 1.52%, 1.59%, and 1.81%, respectively, and the average ratios of ultimate broadening at the exit of the caster were 1.00%, 1.27%, and 1.48%, respectively; for SPHC steel, the maximum ratios of ultimate broadening were 1.34%, 1.44%, and 1.69%, respectively, and the average ratios of ultimate broadening at the exit of the caster were 0.64%, 0.76%, and 0.95%, respectively. The simulation results were verified by measurements on an SMS‐Demag continuous caster of Maanshan Iron and Steel Co. Ltd.; the measurement results agree with the simulation results. The mechanism of the effect of casting speed on slab broadening was also analyzed.     

日本高速连铸技术的开发

通过对连铸结晶器内的钢液流动、润滑技术、热流与冷却、振动与凝固以及实机操作等的研究,证实中碳钢采用2m/min,低碳钢用5m/min 的铸速,可进行稳定的高速连铸。     

高拉速板坯连铸结晶器液面波动影响因素研究

应用CFX软件,模拟高拉速板坯连铸结晶器流场和液面波动,计算F数,研究了拉速、结晶器规格、水口参数、结晶器吹氩等因素对结晶器液面波动的影响。通过与F数对比,各因素对结晶器液面波动影响态势与F数基本一致。高拉速下,最佳F数值为3～5,此时结晶器液面波动小且平稳,结晶器液面钢液中心线流速为0．05～0．1m／s。     

中碳钢板坯保护渣性能优化及提高拉速工业试验研究

 通过提高保护渣碱度以及渣中CaF2和Li2O含量,对中碳钢板坯用保护渣进行了优化,并采用优化的保护渣进行了提高拉速工业试验。结果表明：优化的保护渣具有较高结晶温度、较低的粘度和熔点;试验过程中,采用优化的保护渣液渣层厚度平均增加约2 mm,单耗增加0.03 kg/m2;采用优化的保护渣在1.5 m/min拉速下和采用原渣在1.3 m/min拉速下浇铸时,结晶器传热强度、传热的稳定性以及浇铸出的铸坯质量等项目水平相当。     

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。     

Simulation of thermal behavior during peritectic steel solidification in slab continuous casting mold

Thermal behavior of the solidifying shell in continuous casting mold is very important to final steel products.In the present work,one two-dimension transient thermal-mechanical finite element model was developed to simulate the thermal behavior of peritectic steel solidifying in slab continuous casting mold by using the sequential coupling method.In this model,the steel physical properties at high temperature was gotten from the micro-segregation model withδ/γtransformation in mushy zone,and the heat flux was obtained according to the displacement between the surface of solidifying shell and the hot face of mold as solidification contraction,the liquid-solid structure and distribution of mold flux,and the temperature distribution of slab surface and mold hot face,in addition,the rate-dependent elastic-viscoplastic constitutive equation was applied to account for the evolution of shell stress in the mold.With this model,the variation characteristics of surface temperature,heat flux, and growth of the solidifying shell corner,as well as the thickness distribution of the liquid flux,solidified flux,air gap and the corresponding thermal resistance were described.     

Numerical Simulation of Influence of Casting Speed Variation on Surface Fluctuation of Molten Steel in Mold

The influences of casting speed variation on surface fluctuation of the molten steel in mold during continuous casting were investigated with numerical simulation method.It was found that when the casting speed was evenly decreased from 1.4 m·min-1 to 0.6 m·min-1,the increase of the surface fluctuation of the molten steel in mold was observed only on time that was at the start of casting speed change.While,in experiment of increasing casting speed evenly from 0.6 m·min-1 to 1.4 m·min-1,the increase of the surface fluctuation of the molten steel in mold was observed only at the time when the casting speed was stopped to increase after it had been increased to 1.4 m·min-1.For surface fluctuation of the molten steel in mold which was produced during the casting speed evenly increasing or decreasing period and at the time when increasing or decreasing the casting speed at low casting speed level(0.6 m·min-1),the influence of casting speed change is very small.In addition,it is found that,at high casting speed level(1.4 m·min-1),even a little change of casting speed could result in remarkable increase of the surface fluctuation.Thus,at high casting speed,changing casting speed should be avoided or much slower speed changing rate should be used.     

低碳钢薄板坯高速连铸保护渣研究与优化

 针对低碳钢薄板坯高速连铸过程中保护渣液渣层过薄、黏结报警频发、铸坯表面纵裂纹过多等问题,在充分考虑高拉速下低碳钢凝固收缩特性的基础上,确定了保护渣润滑与传热性能的优化方向并开展了工业试验。将保护渣碱度从1.10提高到1.30,Li₂O质量分数从0.57%提高到1.06%,Na₂O质量分数从5.48%提高到8.16%,碳质量分数由7.71%降低到6.72%。对2种保护渣的流变性能和渣膜3层结构进行了深入研究,发现优化后保护渣渣膜中的液渣层比例增加,渣膜润滑系数α增大;同时,渣膜中的结晶层比例也有一定程度的提高,渣膜热阻系数β增大,从而使保护渣的润滑性能和控制传热能力均得到改善。从矿相分析结果看出,保护渣碱度的提高在一定程度上会促进硅灰石的析出,导致渣膜结晶率提高、热阻增大,进而起到控制传热的目的。生产实践表明,在拉速提高后,使用新型保护渣基本避免了黏结和裂纹的产生,生产效率和铸坯质量均得到显著提高。     

304不锈钢连铸过程中结晶器渣圈形成机制

 在连铸过程中,结晶器易结渣圈是造成铸坯产生缺陷的主要原因之一。对304不锈钢板坯连铸过程中结晶器保护渣原渣、距开浇60 min时的液渣和渣圈的化学组成、理化性能、结晶矿相以及渣圈形貌结构进行对比分析。结果表明,连铸过程中TiO2和Cr2O3从钢液进入液渣生成高熔点氧化物,使液渣和渣圈的完全熔化温度和黏度显著增大,碱度、转折温度降低。液渣与渣圈的物相以枪晶石和钙铝黄长石为主。高熔点相钙铝黄长石的大量析出以及TiO2和Cr2O3进入液渣使液渣黏度增大是渣圈形成并长大的重要原因。     

拉速对结晶器平均热流的影响

通过计算8088块板坯的平均热汉研究了拉速对板坯结晶器平均热流的影响结果表明：拉速对结晶器宽边的平均热流有显的影响,拉速在0．6－1．2m/min范围内,结晶器宽边平均热流随拉速提高而增加,当拉速超过1．2m/min后,结晶器宽边平均热流随拉速增加而提高的幅度变得很小;结晶器窄边的平均热流较宽边的热流约低0．2MW／m^2,当拉速超过1．2m/min后,结晶器窄边的平均热流仍可随拉速的进一步提高而增加。