吹气孔直径对RH精炼过程钢液流动和混合特性的影响

针对90t RH精炼装置,以水力学模拟研究了吹气孔直径对真空循环精炼过程中钢液流动和混合特性的影响.模型和原型的相似比为1:5.模型吹气孔直径分别为0.8 mm和1.2 mm.结果表明,1.2 mm孔径下环流量和主要工艺参数间的关系为Ql Q80.26Du0.69Dd0.80;在给定的吹气量和插入管内径下,增大吹气孔直径并不显著改变精炼过程中钢液流动特征,环流量随吹气孔直径的增大而略有增大,其关系式为Ql=2.40Q 0.23gD0.72u D0.88d d0.13in;相应地,混合时间稍有缩短;0.8和1.2 mm孔径下,τm与搅拌能密度的关系分别为τm ε5和τm ε0.49.

ERT Imaging of Gas-Liquid Mixing in Agitated Vessel

An investigation using Electrical Resistance Tomography （ERT） was carried out in order to characterize gas-liquid mixing in an agitated vessel. The experimental work was carried out in a 400 mm diameter agitated vessel that was fitted with four planes, 16 stainless steel electrodes. Agitation was carried out using the Lightnin Labmaster and Rushton turbine while conductivity data acquisition was carried out using the ITS P2000 ERT system. A Mathlab code was developed to construct a surface plot for gas hold-up from the ERT data. Various gas dispersion conditions such as flooded, loaded and fully dispersed were successfully characterized using the ERT technique.

薄规格高品质汽车板交接坯降级策略的优化

近年来在汽车轻量化大趋势及成本控制的压力下,诸多车企将汽车板减薄至0.65 mm左右后,加工制作冲压变形大部件时钢板冲压开裂缺陷(俗称“针眼”)显著增加,其主要发生于连铸交接坯轧制的钢板。对薄规格高品质汽车钢板冲压开裂问题开展了研究,通过采用扫描电镜和能谱分析分别对开裂缺陷部位进行高倍观察和成分分析,同时运用数值模拟方法研究了炉炉连浇过程接续炉次钢水进入中间包后的流动和混合特征。研究发现造成汽车板冲压开裂的夹杂物主要分为2类,一类为条、块状Al_(2)O_(3)夹杂物,另一类为CaO·2Al_(2)O_(3)、CaO·6Al_(2)O_(3)类钙铝酸盐夹杂物。交接坯轧制的汽车板中Al_(2)O_(3)夹杂物和钙铝酸盐类夹杂物较正常坯多,主要原因为接续炉次开浇时刻中间包内少量钢水裸露被氧化和少量覆盖渣混入钢液。开发了板坯连铸炉炉连浇过程交接坯长度预测模型,并通过对混浇过程产生的铸坯取样分析验证了模型的适用性。钢板轧制发生冲压开裂的交接坯主要是中间包出口处接续炉次钢水质量分数达到20%~80%时间段内所浇铸形成的铸坯,采用“双挡墙+双挡坝”控流结构的中间包产生交接坯时间最短,为7.33 min。根据以上研究结果进行了工业试验,并且对30个浇次的实际生产数据进行了跟踪和统计,按照之前的交接坯降级策略需要降级84块铸坯,通过策略优化,仅降级了38块铸坯,降级量由之前的41.38%减少至18.72%,而所生产薄规格汽车板的“针眼”状冲压开裂发生率没有增加,仍保持在每万件2.5起以下的先进控制水平。