低碳铝镇静钢中间包浇注过程夹杂物的行为

 通过对BOF-Ar站-CC炼钢流程生产低碳铝镇静钢的中间包不同浇注时间取样及正常坯的取样,采用氧氮化学分析、光学显微镜以及扫描电镜-能谱(SEM+EDS)等多种方法研究了中间包浇注过程夹杂物特征的变化。结果表明：每炉钢包开浇时与浇注末期,钢中T[O]含量均高于浇注中期的T[O]含量,这是由于换包过程中钢水被二次氧化;中间包钢水及正常坯中的夹杂物,按照其形貌与成分可以分为以下3类：Al2O3基夹杂物,MnS基夹杂物,来自中间包覆盖剂或者钢包下渣所卷入的外来夹杂物。中间包及铸坯中的夹杂物主要以1~4 μm的Al2O3为主,同时在铸坯中发现了大量的MnS夹杂物,使铸坯中夹杂物的数量密度升高。当钢液中硫含量较高时,铸坯中气泡+Al2O3类型的夹杂物增加。在当前的工艺条件下,交换钢包之后的开浇阶段与浇注末期,钢水的二次氧化对铸坯的洁净度产生重要影响,同时应合理控制钢中的硫含量,减少铸坯中气泡+Al2O3类型的夹杂物,避免钢液在凝固过程中析出大量的MnS夹杂物。     

车桥管用20Mn2钢的二次氧化行为

本文通过系统取样跟踪分析了BOF→LF→圆坯连铸工艺生产20Mn2钢的洁净度限制环节;结果表明,凤宝20Mn2钢洁净度的限制性环节是二次氧化。明显的二次氧化发生在三个位置：①喂Si-Ca线后;②LF结束到中间包过程;③中间包到结晶器的浇注过程;从入LF到浇注结束整个过程平均增N达40×10-6,累积二次氧化量达到109×10-6,夹杂物总去除量为198×10-6;大型夹杂物在喂Si-Ca线和中间包中均有明显增加,主要为Al-Si-Mn-Ti复合氧化物,是典型的二次氧化产物。因此,目前该厂改善洁净度的关键是保护浇注的控制。     

钢铁冶炼新技术讲座之十二连铸新技术(二)

2提高连铸坯洁净度技术连铸过程中生产洁净钢,一方面是去除液体钢中氧化物夹杂,进一步净化进入结晶器的钢水,另一方面是防止钢水的再污染。对于液体钢中夹杂物去除主要决定于夹杂物形成、夹杂物传输到钢——渣界面和渣相吸附夹杂物。对于防止连铸过程钢水再污染,主要决定于:(1)钢水二次氧化;(2)钢水与环境、钢水与空气、钢水与耐材相互作用;(3)钢液流动与液面稳定性(渣-钢界面紊流、涡流);(4)渣钢浮化卷渣。2.1生产洁净钢主要控制技术(1)保护浇注技术常用的钢水密封保护如:中间包密封、钢包→中间包采用注流长水口 吹氩保护,中间包→结晶器…     

45号钢冶炼过程中气体含量及其控制研究

对某厂LD转炉—LF精炼—连铸工艺生产的45号钢冶炼过程中氧、氮含量的变化进行了研究。实验结果表明：精炼后钢中夹杂物去除效果较好,T[O]含量降低了40.3％,而[N]含量变化并不明显;钢液转移至中间包过程中存在较严重的钢液二次氧化和中间包内衬氧化物的熔蚀,T[O]和[N]含量分别增加了73．7％和45．9％;浇注过程中同样存在较为严重的二次氧化现象,铸坯中[N]含量增加了21．6％,由于在浇注过程中去除了部分氧化物夹杂,T[O]含量降低了12．8％。由此可见,为了提高45号钢铸坯质量,现有生产工艺需要进一步防止钢液二次氧化。     

高碳钢线材中夹杂物形貌及控制研究

优质高碳钢中的夹杂物来源于脱氧产物、吹氩降温过程中的二次氧化、钢包到中间包浇注过程的二次氧化、钢包和中间包耐火材料的剥离等.指出夹杂物形貌和能谱特征,分析不同破裂指数的夹杂物对线材的影响,为了得到塑性的MnO-Al2O3-SiO2夹杂物,应该采用Si-Mn脱氧.提出生产高碳钢线材过程中减少夹杂物的关键措施.     

连铸坯夹杂物产生原因分析及改进措施

造成连铸坯中非金属夹杂物的主要原因:浇注过程卷渣及中间包排渣不及时等人员操作问题;保护浇注密封效果差、水口浸入深度不合理、水口偏斜等增加了钢水二次氧化;钢水过热度高及挡渣墙寿命低、水口渣线设计不合理等。通过规范操作、防止钢水二次氧化、中间包过热度由30~50℃降低至20~35℃、促进夹杂物上浮等改进措施,普碳钢内部夹杂比率从万吨钢5.2次降低到0.3次。     

减少冷轧IF钢表面夹杂物的生产实践

通过对鞍钢第二炼钢厂复吹转炉、RH精炼处理、中间包及铸坯取样分析,结果表明冷轧IF钢表面夹杂物主要来自中间包二次氧化产生的大于100μm的簇群状、块状的A12O3夹杂物,并且主要分布在铸坯表面层或上1／4层厚度。优化结晶器浸入式水口几何参数,加强保护浇铸措施,开发中间包湍流控制器新技术,可以有效地防止钢液的二次氧化。大批量生产IF钢板过程中,夹杂物废品率由10,37％降低到0．61％。     

板坯连铸机保护浇注研究

通过对板坯连铸机保护浇注工艺技术研究,针对钢包钢流、中间包冲击区、钢包开浇初期钢水、中间包注流等与空气接触的部位保护浇注措施优化改进,有效地防止了钢水二次氧化,提高了铸坯质量。     

IF钢非稳态连铸坯洁净度定量分析

通过氧氮分析、定量金相分析及大型夹杂物分析等试验方法,对某钢厂IF钢生产稳态及非稳态浇注的连铸坯进行了对比研究。结果表明,稳态坯w(T[O])和w(N)的平均含量分别为11×10-6和18×10-6,显微夹杂物含量平均为4.0个/mm2,大型夹杂物含量为2.10 mg/kg,洁净度较高。非稳态浇注对连铸坯洁净度有较大程度的危害。中间包开浇头坯受到较为严重的空气二次氧化,洁净度最差;钢包交换和更换浸入式水口时受到的空气二次氧化较小,但是钢渣反应和卷渣行为较为严重;尾坯洁净度受到空气二次氧化和卷渣的共同影响。连铸坯显微夹杂物含量分布,沿铸坯宽度方向一般1/4处最多,1/2处最少;沿铸坯厚度方向内外弧附近明显高于连铸坯中心部位。     

中碳铝镇静钢开浇阶段中间包钢水洁净度的变化规律研究

对中碳铝镇静钢单开第一炉浇注过程中的中间包钢水系统取样,用ASPEX扫描电镜分析了钢中夹杂物数量、成分等特征的变化规律。结果表明,开浇初期,中间包钢水的二次氧化现象严重。与RH终点的钢水相比,开浇初期中间包钢水的T.O含量增加了160%,N含量增加了39.7%,夹杂物的数量密度增加了118%,大颗粒夹杂物的数量密度增加了185%。随着浇注的进行,氧氮含量和夹杂物的数量密度下降;夹杂物成分向Al2O3含量增加的方向移动,且分布逐渐集中。开浇过程中钢水不仅受空气的氧化作用,还受中包耐材、卷渣等因素的影响。开浇初期钢液二次氧化生成的固态夹杂物更易聚合为大颗粒夹杂物。     

CSP中间包夹杂物去除效果的试验研究

 夹杂物对钢的性能有很大影响,尤其是对钢水纯净度要求较高的硅钢,因此在硅钢生产过程要采取措施严格控制夹杂物的含量。本文研究了马钢薄板坯连铸连轧生产硅钢时中间包内夹杂物的种类、含量及粒度组成等,分析中间包内夹杂物的分布,从而评价中间包去除夹杂物的能力。试验结果表明：改造优化以后的中间包基本能够去除>40m的大型夹杂物,也为<30m的小型夹杂物提供了聚集、长大的动力学条件,中间包去除夹杂物的能力较强,为生产高品质的硅钢提供了有力保障。     

CSP中间包夹杂物去除效果的试验研究

夹杂物对钢的性能有很大影响,尤其是对钢水纯净度要求较高的电工钢,因此在电工钢生产过程要采取措施严格控制夹杂物的含量。研究了马钢薄板坯连铸连轧生产电工钢时中间包内夹杂物的种类、含量及粒度组成等,分析中间包内夹杂物的分布,从而评价中间包去除夹杂物的能力。试验结果表明:改造优化以后的中间包基本能够去除40μm的大型夹杂物,也为30μm的小型夹杂物提供了聚集、长大的动力学条件,中间包去除夹杂物的能力较强,为生产高品质的电工钢提供了有力保障。     

Modeling Study of the Vortex and Short Circuit Flow Effect on Inclusion Removal in a Slab Tundish

A mathematical model was developed to study effects of the vortex and the short circuit flow phenomena during tundish operation on the inclusion removal for a wide range of particle diameters. The model was solved using FLUENT® commercial software; for the particle tracking the Lagrangian discrete phase model was employed. Even when the vortexes drag about 50% of the inclusions, the most detrimental phenomenon for inclusion removal is the short circuit flow. It is important to stress that for the global inclusion behavior the removal rate decreases as the tundish level increases. It can be concluded that when increasing the tundish capacity without any flow control device adjustment, the steel cleanliness is deteriorated significantly.     

汽车钢DC03夹杂物产生原因分析及改进措施

通过采用扫描电镜、金相分析等手段,结合现场实际生产过程探讨了邯宝炼钢厂生产汽车钢DC03产生夹杂的原因分析,并针对其原因提出了改进措施。研究结果表明：DC03钢板产生的夹杂有两类：一类是钙铝酸盐夹杂,主要原因是来源于炼钢过程中大颗粒耐火材料脱落物或中间包卷渣;另一类是伴有钠、氟元素氧化铝夹杂,主要原因是保护渣卷入。为此,采取了优化保护渣成分、增加浇次开浇中间包质量、改进中间包包盖的吹氩管路、优化中间包覆盖剂成分和中间包吹氩量等措施,取得了良好的效果,低碳钢平均夹杂率由改进前的0.47%减少至0.32%。     

Water Modeling of Swirling Flow Tundish for Steel Continuous Casting

A conventional turbulence inhibitor is compared with a swirling chamber from the points of view of fluid flow and removal rate of inclusion in the tundish. Comparing the RTD curves, inclusion removals, and the stream-lines in water model experiments, it can be found that the tundish equipped with a swirling chamber has a great effect on improving the flow field, and the floatation rate of inclusion is higher than the tundish with a turbulence inhibitor. Because of the introduction of the swirling chamber, the flow field and inclusion removal in a two-strand swirling flow tundish are asymmetrical. Rotating the inlet direction of swirling chamber 60 degree is a good strategy to improve the asymmetrical flow field.     

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。     

Aggregation Kinetics of Inclusions in Swirling Flow Tundish for Continuous Casting

 The mechanism of inclusion aggregation in liquid steel in swirling flow tundish is analyzed by applying the theory of flocculation which was developed in the field of colloid engineering. The gas bridge forces due to the micro bubbles on hydrophobic inclusion surfaces were considered responsible for the inclusion collision and agglomeration, which can avoid the aggregation to breakup. The quantity of micro bubbles on hydrophobic inclusion particle is more than that on hydrophilic one. The trend of forming gas bridges between micro bubbles on particles is strong in the course of collision. The liquid film on hydrophobic particles is easy to break during collision process. Hydrophobic particles are liable to aggregate in collision. According to the analysis of forces on a non-metallic inclusion particle in swirling chamber, the chance of inclusion collision and aggregation can be improved by the centripetal force. Hydrophobic particles in water are liable to aggregate in collision. Hydrophilic particles in water are dispersed although collision happens. The wettabiliy can be changed by changing solid-liquid interface tension. The non-metallic inclusion removal in swirling flow tundish is studied. It shows that, under certain turbulent conditions, the particle concentration and the wettability between particles and liquid steel are the main factors to induce collision and aggregation.     

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。     

Experimental investigation of flow control devices effect on inclusion separation in a four strand tundish

In continuous casting, molten steel often contains non-metallic inclusions that have a very high melting temperature and thus remain suspended in the molten flow. Given the lower density of these substances compared to the melt, they can be filtered in the form of top slag by proper use of buoyancy forces. Thus, providing a desirable flow pattern, reduced flow turbulence, and adequate residence time for inclusions in the tundish will improve the inclusion separation performance and therefore the product quality. In this study, a reduced-scale water model of a tundish was used to evaluate the effect of melt level in the tundish on the flow pattern and inclusion separation performance. Then, the flow control devices are added to this simple tundish model to examine the effect of them on the flow behaviour and inclusion separation. Experimental investigation showed that raising the water level in the model tundish has desirable effects on inclusion separation and the use of the dam at the inlet with tall dam improves the flow pattern and inclusion separation almost 20% in the form of top slag.     

Water Modeling of a Swirling Flow Tundish for Steel Continuous Casting

 A conventional turbulence inhibitor is compared with a swirling chamber from the points of view of fluid flow and removal rate of inclusion in the tundish. Comparing the RTD curves, inclusion removals, and the streamlines in water model experiments, it can be found that the tundish equipped with a swirling chamber has a great effect on improving the flow field, and the floatation rate of inclusion is higher than the tundish with a turbulence inhibitor. Because of the introduction of the swirling chamber, the flow field and inclusion removal in a two-strand swirling flow tundish is asymmetrical. Rotating the inlet direction of swirling chamber 60 degree is a good strategy to improve the asymmetrical flow field.