动态轻压下在中碳钢铸坯中心偏析控制中的应用

介绍了某厂直弧型板坯连铸机生产中碳钢过程中,通过对动态轻压下技术参数进行优化,完善了动态连铸控制工艺,使中碳钢连铸坯中心偏析得到明显改善,B级偏析率平均由36．84％下降到15．91％。     

连铸工艺对中碳钢碳偏析的影响

通过试验连铸不同工艺对中碳钢的碳成分偏析的影响,对比了连铸坯形貌、轧材低倍和碳偏析指数等指标。     

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.     

大方坯连铸关键装备技术应用研究

简述了攀钢大方坯连铸结晶器电磁搅拌技术、二冷控制技术和凝固末端动态轻压下技术在重轨钢连铸中的应用效果。生产统计表明,铸坯表面无清理率达到100％,中心疏松≤1．0级,中心偏析≤1．0级,中心缩孔≤0．5级,中心碳偏析指数≤1．05,等轴晶率≥38％,为攀钢生产高速铁路用钢轨提供了合格铸坯。     

连铸中碳圆钢热锻后中心组织的研究

针对连铸方法生产的中碳钢经热锻后中心区域的金相组织进行观察、分析,研究中心偏析对圆钢热锻后中心区域金相组织的影响。     

结晶器电磁搅拌对中碳钢成分偏析的影响

就结晶器电磁搅拌强度对连铸中碳钢的碳成分均匀性的影响进行工业性试验研究,分析了正、负偏析产生的原因、区域,提出了合理的电磁搅拌工艺参数。     

西宁特钢连铸空心颗粒保护渣试验研究

西宁特钢连铸采用空心颗粒渣在连铸结晶器中进行保护浇注,经批量生产试验,成渣性能好,铸坯表面质量提高：高碳钢和中碳钢表面修磨率分别降低４．３１％和２．０６％。     

连铸方坯成份偏析研究

为了说明ML35、45、60、654N连铸方坯低倍检验缺陷造成的成份偏析对轧材性能的影响,在经低倍检验后的铜坯上,采用选点和定点取样方法,钻取不同位置的样品进行化学成份分析,结果表明连铸方坯中心部位缺陷中,单一出现的中心疏松或缩孔不与宏观上的成份偏析同时发生;当连铸方坯出现≥1．0级中心偏析时,连铸方坯中心部位的碳含量将比连铸方坯其它部位的碳含量高0．04％左右;中心偏析≤0．5级时对连铸方坯中心部位的化学成份无明显关系;中心偏析为1．0级以上级别时碳含量不会随之增加,但偏析面积随之增大。     

高级别管线钢连铸板坯动态轻压下最佳压下位置研究

介绍了不同动态轻压下压下位置对连铸板坯内部质量的影响。通过对连铸板坯横断面的低倍检验结果和沿连铸板坯厚度方向化学成分分析，发现动态轻压下对连铸板坯中心偏析的改善效果十分显著，高级别管线钢的最佳动态压下位置fa=0．5-0．8。     

420 mm特厚板坯大压下技术的应用

对新钢3#特厚板连铸机大压下工艺进行了细致的研究.在常规0.55 m/min的拉速条件下,确定了420 mm厚中碳钢时连铸坯大压下段为第9段和10段;通过不同压下量试验条件下连铸坯中心偏析程度对比确定了在第9段和10段分别采用压下量为7 mm和1.5 mm的大压下工艺,连铸坯中心偏析得到显著改善,满足了新钢高品质特厚钢板对连铸坯内部质量的严格要求.     

Study on Mitigating Center Macro‐Segregation During Steel Continuous Casting Process

In the current paper, Methods of enlarging the area for the distribution of segregation solutes were introduced to mitigate center macro‐segregation in steel billets and steel slabs during continuous casting process, which cost less and have significant effect. The location of center macro‐segregation is relative to the shape of liquid‐core at the solidification end during steel continuous casting. A method of dissymmetrical cooling on different surfaces, by which the area for the precipitation of segregation solutes was enlarged, was introduced to mitigate the center macro‐segregation in billets during continuous casting process. Method of optimizing the uniformity of solidified shell in the transverse direction was introduced to mitigate the center macro‐segregation in steel slabs. The uniform cooling intensity along the transverse direction guaranteed a regular solidification end in the continuous casting slab, which aided in the effective application of dynamic soft reduction technology. A relevant 2‐D heat transfer model was developed for the optimization of uniform solidification. The current method was applied to the industrial slab continuous casting using the heat transfer model. The results indicated a better industrial slab quality with much less center macro‐segregation after the use of the method.     

Dynamic Soft Reduction for Continuously Cast Rail Bloom

  Center porosity and centerline segregation in continuously cast bloom can be minimized by the well known method of dynamic soft reduction. Metallurgical results of soft reduction previously employed in continuous bloom casting for heavy rail steel in Panzhihua Iron and Steel Group were not fully achieved because of the improper soft reduction process. Therefore, experiments for optimizing the process parameters of soft reduction for bloom were carried out. The results show that the proportion of the center porosity, which is less than 10, increases from 2841% to 9981%, while the proportion of the centerline segregation class increases from 4091% to 100%, and the proportion of the central cavity increases from 9205% to 100%, whereas the center carbon segregation index decreases from 117 to 105. The internal quality and the mechanical performance of the rails produced from continuously cast blooms meet the requirement of high speed tracks of 350 km/h.     

连铸坯轧制厚钢板极限规格缺陷分析与改进

针对连铸坯轧制特厚板超声波探伤不合格的问题,对连铸坯及钢板取样进行热酸浸低倍组织检验,并对钢板样进行金相分析。结果表明,连铸坯本身有较严重的中心疏松和中心偏析,钢板有疏松残留,偏析严重处伴生微裂纹。通过提高钢液纯净度,投用连铸电磁搅拌(S-EMS),优化轻压下工艺,增加单道次压下量等措施,保证了特厚板质量,探伤合格率达到98.97%。     

中心偏析控制对型钢低温韧性的影响

 为了研究不同凝固组织形态(等轴晶比例)对连铸方坯宏观偏析及型钢力学性能的影响,通过工业试验改进连铸工艺改变连铸坯凝固组织结构。结果表明,大幅提高柱状晶比例可以有效控制连铸坯中心偏析并降低中心偏析影响区域面积,同时明显减少轧材中珠光体体积分数,提高组织均匀性,断后伸长率提高10%,韧脆转变温度从0降低到-40 ℃,因此,控制连铸坯偏析程度可实现优良低温韧性,这表明通过控制铸坯均匀性发展E级或更高韧性级别的技术可行。     

320 mm×410 mm大方坯连铸重轨钢质量改进与应用

为了提高大断面重轨钢连铸坯内部质量,满足钢轨探伤要求,针对大断面生产重轨钢铸坯宏观偏析及中心疏松较难控制的难点,采用合适的二冷制度、凝固末端电磁搅拌技术、动态轻压下控制技术、钢水过热度控制以及拉速控制等技术措施,开发了攀钢320 mm×410 mm大方坯连铸重轨钢生产工艺。生产的大方坯重轨钢连铸坯中心等轴晶率稳定控制在40%以上,中心疏松控制在不大于0.5的比例为91%以上,中心偏析在0.5级的比例为87%以上,等柱晶率不小于40%的比例为100%,碳偏析指数控制在0.95~1.07,铸坯及钢轨质量较好,满足了标准要求并通过了CRCC认证。     

82B中心网状渗碳体产生原因及改善方法

高碳钢连铸生产技术工艺优化是当前连铸技术研究的主要内容之一。针对国内某钢厂SWRH82B高碳钢生产过程中出现碳偏析、网状渗碳体组织缺陷的问题,采用数值模拟与实验相结合的方法,利用Fluent软件建立了八机八流连铸机凝固传热模型,数值模拟计算凝固传热特征;研究了八机八流连铸机在不同浇注速度、过热度和末端电磁搅拌参数条件下对SWRH82B高碳钢铸坯碳偏析和夹杂物的影响;分析了SWRH82B高碳钢连铸过程中的主要要素与组织性能之间的关系。研究结果表明：铸坯中心碳偏析是网状渗碳体主要诱导因素,通过调整过热度和浇注速度有利于促进钢液成分的均匀化,降低夹杂物含量;当过热度降低至25 ℃,浇注速度提高至2 m·min⁻¹,铸坯中心平均碳偏析指数由1.17降低为1.11,索氏体化率达到89%,网状渗碳体级别由四级下降到一级,基本消除C类夹杂物;通过设置末端电磁搅拌参数为电流370 A、频率7 Hz时,碳偏析指数最低值下降到1.04。通过优化连铸生产工艺参数,解决了企业SWRH82B高碳钢生产过程中的缺陷,为高碳钢的高质量生产提供理论与实践支撑。     

降低SWRH82B铸坯中心偏析的探索与实践

通过大量的现场取样,结合实验室研究手段,系统的研究钢水过热度、拉速、二次冷却强度等工艺参数对高碳连铸坯中心偏析的影响,从而得出最佳的生产参数控制范围,改善swRH82B高碳钢连铸坯的中心偏析,提高铸坯质量和加工性能。     

原位统计分布分析技术分析不同中低合金钢连铸板坯横截面上碳、硅、锰、磷、硫、铌、钛、钒

采用金属原位统计分布分析（OPA）技术考察了不同生产工艺条件下不同厚度的中低合金钢连铸板坯横截面上C、Si、Mn、P、S、Nb、Ti、V等元素的分布、富集及中心偏析形态。观察并描述了几种典型的中心偏析形式,如断续的、连续的以及正负偏析呈交错分布状等;发现大多元素的中心偏析模式相对固定,即在沿拉速方向一定厚度范围内具有稳定性;给出了最大偏析度、统计偏析度等定量表征元素分布状态的原位技术特征值;讨论了各元素在板坯中形成偏析的难易程度及常见的分布模式。硫元素的偏析分析结果和传统分析硫偏析的方法-硫印也基本一致。研究表明,原位统计分布分析技术能有效地应用于较宽含量范围内、不同厚度尺寸的中低合金钢板坯的成分分布分析和偏析分析,且其分析结果具有很好的重复性和可靠性。     

Modeling and control of dynamic soft reduction in continuous slab casting

The centerline segregation in continuous casting steel is known to be formed by the interdendritic enriched liquid flow at the solidification end in strand.At present,several methods,such as thermal soft reduction, electromagnetic stirring and dynamic soft reduction,are available to reduce the center segregation and to improve the internal quality.Although some methods could alleviate center segregation to some extent,they can also give rise to new problems.For instance,thermal soft reduction can lead to surface cracking during casting of some steels and electromagnetic stirring can result in white band.Dynamic soft reduction is an effective technology for the improvement of strand quality in continuous slab casting.In this paper,the key parameters of dynamic soft reduction technology,such as soft reduction region,the total reduction amount,for low carbon steel have been studied based on experimental and theoretical analysis.The soft reduction region was related to the segregation of chemical composition,slab bulging of narrow side and avoiding internal crack of slab.The total reduction amount was composed of natural thermal shrinkage and actual reduction amount depending on critical strain.For low carbon steel with slab dimension of(950 - 1 950) mm×170 mm,the solid fraction range in soft reduction region was recommended from 0.4 to 0.8,the total reduction amount was 2.0 -2.8 mm,and the optimized reduction rate was 0.4 - 1.2 mm/min,respectively.Furthermore,a dynamic soft reduction system in continuous slab casting, Visual Cast-Dynamic,has been developed by multithreading method.It demonstrated that the dynamic soft reduction model in this study was correct with the ability of online control.