不同喂入位置条件下稀土在连铸板坯中分布及其对性能影响

通过化学分析、金相观察及冲击试验,分析了结晶器喂稀土及中间包喂稀土的连铸坯中夹杂物形态、分布,并测试了横断面上的冲击韧性.研究表明与结晶器喂稀土相比,中间包喂稀土的连铸坯中,稀土及夹杂物分布更均匀,夹杂物球化效果更好、尺寸更小、总数更少;冲击韧性明显高于未喂稀土,尤其是克服了连铸坯内弧侧四分之一范围冲击韧性的大幅降低的缺陷.因此,中间包喂稀土比结晶器喂稀土具有更大的优越性.     

中间包喂稀土消除连铸坯内弧侧卷渣缺陷原因研究

通过硫印试验、金相观察及冲击试验,比较了未喂稀土、结晶器喂稀土及中间包加稀土连铸坯内弧侧四分之一处夹杂物形态及分布及连铸坯横断面上的冲击韧性,发现结晶器喂稀土的连铸坯内弧侧卷渣缺陷形态及分布与未喂稀土的相近,冲击韧性变化也相同,而中间包加稀土基本消除了内弧侧四分之一处的卷渣缺陷,冲击韧性明显提高;并分析了中间包加稀土消除内弧侧卷渣原因.     

开发结晶器喂稀土丝方法扩大稀土处理钢品种

本文总结了武钢第二炼钢厂开发的板坯连铸结晶器喂稀土丝方法的研究。试验结果表明:结晶器喂稀土丝工艺是可行的,这种稀土加入方法避免了钢包或中间包水口结瘤的缺点,稀土回收率达80％左右,并在钢中分布基本均匀;钢中添加稀土有利于促进钢液的凝固,改善铸坯凝固组织,使等轴晶率提高10～15％,钢中夹杂物偏析线得到明显改善;钢中添加稀土后,有效地改善了铸坯中夹杂物的形态、大小及分布,致使钢材的塑性、韧性及各向异性得到明显改善。     

稀土加入工艺及其在石油专用管钢中的应用研究

本文着重介绍稀土处理对控制石油专用管钢夹杂形态，降低钢中总氧量，改善铸坯组织与低温横向切口冲击韧性的作用及其主要影响。试验结果表明，对石油专用管钢连铸结晶器喂稀土丝，在大型铸坯上稀土颁基本均匀，夹杂物呈球状与椭圆状，生成的稀土夹杂细小，分布均匀，钢板与钢管的强度和延伸率与常规ＲＨ处理同炉钢相当，都达到了ＡＰＩ标准要求。稀土试验管线钢的热轧板－１０℃低温横向切口冲击值（[S]＜０．０１２％）都超过了９     

稀土在连铸结晶器内的加入方法及作用规律

采用喂丝法将混合稀土金属丝添加到连铸结晶器内,达到了降低硫、氧含量,净化钢液,控制钢中夹杂物大小、分布及形态,消除中心偏析、改善铸坯质量的效果。使钢材低温冲击韧性和弯曲塑性明显提高。     

稀土元素在钢水中的作用机理及加入技术研究

介绍了稀土元素的性质及稀土在钢水中脱氧、脱硫及夹杂物变性处理的作用机理,着重介绍了结晶器喂稀土丝工艺及相关的稀土丝加入量、喂丝速度、喂丝位置的确定方法。比较认为,双侧喂丝工艺比单侧喂丝工艺铸坯中稀土元素分布更加均匀。介绍了结晶器喂稀土丝技术对连铸保护渣的影响和要求。     

大管坯连铸中间包钢液内夹杂物去除的研究

通过中间包水模型试验和工业试验研究了U型挡墙中间包和Y型挡墙中间包对夹杂物去除的影响.结果表明:Y型挡墙中间包能提高夹杂物的去除率.与U型挡墙中间包相比,从中间包到铸坯,钢中平均总氧去除率显著提高,铸坯中大于50μm的夹杂物显著减少,而显微夹杂数目变化不大;同时Y型挡墙中间包内各流夹杂物分布较均匀.使用U型挡墙中间包时,中间包到铸坯过程吸氮较少.     

连铸中间包内夹杂物去除的水模拟试验与工业实践

通过中间包水模型试验和工业试验,研究了U型挡墙中间包和Y型挡墙中间包对夹杂物去除的影响。结果表明：Y型挡墙中间包能提高夹杂物的去除率。与U型挡墙中间包相比,从中间包到铸坯过程钢中平均总氧去除率显著提高,铸坯中大型夹杂物含量显著减少,而显微夹杂数目变化不大;同时Y型挡墙中间包内各流夹杂物分布较均匀。使用U型挡墙中间包时,中间包到铸坯过程吸氮较少。     

连铸稀土加入工艺试验

对多流大方坯连铸机生产稀土钢的稀土加入工艺进行了试验,分析了钢包、中间包、结晶器喂稀土丝的优缺点,并进行了对比。根据包钢大方坯连铸工艺的特点和实际情况,选出了大方坯连铸稀土钢的稀土加入工艺。     

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。     

Formation and evolution of macro inclusions in IF steels during continuous casting

The evolution of macro inclusions during continuous casting was investigated by large-area inclusion characterization using ASPEX and analysis of nozzle blockage deposits. Six kinds of inclusions over 5?μm were observed in samples taken from the tundish and the slabs: single alumina particles, alumina dendrites, refractory-related alumina, alumina associated with bubbles, alumina clusters and Al–Ti complex oxides. By examining the morphology of the nozzle blockage deposit, it was concluded that the refractory-related alumina in the slabs came from the decarburization layer washed away by the steel stream. Some of the alumina clusters that came from the nozzle blockage deposit dislodged by the steel flow, were formed by the agglomeration and sintering of 5–20?μm inclusions that were carried over from the tundish. Two kinds of Al–Ti oxides were found in the tundish, and their evolution mechanisms during the casting process were proposed.     

管线钢浇次头坯夹杂物控制

研究了管线钢浇次头坯夹杂物的主要来源及控制措施。采取将浇次头坯轧制成热轧板和在热轧板取样分析的试验方案,得出热轧板和铸坯夹杂物分布。结果表明开浇初期4 m以内的头坯存在2级以上的B类夹杂物和保护渣卷渣。开浇初期钢水注流的二次氧化是导致头坯夹杂物超标的主要因素。提出开浇初期增加吹氩量和适当延长吹氩时间能够较好的排除中包空气,对降低注流二次氧化起到很好作用。     

稀土钢连铸板坯纵裂研究

研究分析了影响稀土钢连铸板坯纵裂的多种工艺因素，包括钢中化学成分、结晶器保护渣、结晶器拔热量、二冷水、拉速和中间包过热度等。据此采取了有效措施，彻底消除了稀土钢板坯纵裂。     

Influence of Rare Earths on Improve Impact Property of Structural Alloy Steel with Extra Low Sulfur and Oxygen

The influence of rare earth lanthanum and cerium on impact property of structural alloy steel with extra low sulfur and oxygen was studied by impact test and microanalysis. The results showed that rare earths increased impact power of the steel when their contents were about 0.005%. Proper addition of rare earths could purify grain boundaries and decrease amount of inclusions, and reduced the possibility of crack growth along grain boundaries and through inclusions. Therefore, such steel could absorb more crack growth energy while it was impacted. However, if the content of rare earths is excessive, the grain boundary would be weakened and brittle-hard phosphates and Fe-RE intermetallic would be formed, which worsened impact toughness of steel.     

Simulation of coagulation of non-metallic inclusions in tundish and their trapping into solidified shell in continuous casting mould

Abstract

A mathematical model simulating the coagulation and flotation of non-metallic inclusions in the tundish and continuous casting mould was developed based on turbulence coagulation and Stokes coagulation. From the simulation in the tundish, it was found that Stokes coagulation is dominant in the tundish. In the mould, the simulation result was that argon bubbles become the desirable sites where alumina inclusions are gathered and form large alumina clusters. The influence of the liquid steel flow in the mould applied by an in-mould electromagnetic stirring technique on the trapping rate of non-metallic inclusions into the solidified shell was examined. The horizontal flow in front of the shell was found to be effective for disturbing the trapping and decreasing the population of large non-metallic inclusions in the shallow surface layer of cast slabs. This effect was interpreted by the lift force applied to non-metallic inclusions in the velocity boundary layer formulated.     

Mathematical modeling of tundish operation and flow control to reduce transition slabs

Minimization of transition slabs in continuous casting operations is critical for optimum quality and productivity. The number of these slabs is closely related to the tundish geometry and operating practice. Therefore, tundish flow and mixing with various tundish configurations and different tundish operating levels are investigated through computer simulation. Residence time distributions and transitional concentration profiles are predicted. Finally, practical operations for a grade change to reduce transition slabs are assessed.     

俄马钢连铸中间包吹氩保护工艺

由于中间包采用透气水口、长水口、塞棒及挡渣墙吹氩保护工艺,钢中点状不均匀类缺陷率减少了0.000 3%,钢中夹渣类缺陷率减少了0.020%,粗大颗粒夹杂类缺陷造成的板坯废品率减少了0.003 2%,有效地降低了钢水连铸中的板坯缺陷,创造了可观的经济价值.