连铸坯拉速对结晶器卷渣现象的影响

高拉速连铸具有高效、低成本的特点,是未来连铸的发展方向。以常规板坯结晶器为研究对象,采用大涡模拟方法对结晶器内的卷渣现象深入分析。结果表明,在连铸坯拉速较低的情况下,结晶器流场较为稳定,钢液冲击速度较小,上返流速度较小,界面波动幅度不大。在高拉速的情况下,钢液冲击速度增加,渣金界面速度及卷渣数量明显提高。通过界面最大速度分析,建立了一个临界卷渣速度的计算准则,发现不同拉速情况下的临界卷渣速度是不一样的,造成这种现象的原因在于卷渣机理的不同。本模型对控制常规板坯高拉速连铸生产具有一定指导意义。     

Estimation of life vulnerability inside buildings during earthquakes

A methodology is presented for assessing the expected loss of human lives due to the structural damage, failure of contents and non-structural components inside buildings during earthquakes. This approach estimates human life losses considering whether the structure collapses (partial or totally) or not. Entrapment and entrapment fatality rates are calculated using available data from worldwide literature and newspapers of 50 collapsed buildings, which information is reasonably reliable. We apply this methodology to one example of a five-floor RC frame building of typical office occupancy. Vulnerability functions are presented relating the intensity of the earthquake to the loss of human lives inside buildings, considering different times of occurrence of the earthquakes: daytime, commuting time and nighttime. Uncertainties in all parts of the process are very large, but they are formally addressed and taken into account. This methodology may improve the risk assessment for insurances purposes, optimisation of the cycle of life, mitigation strategies, risk control and tolerable risk.     

食品级水包油型月见草油微乳的稳定性研究

以月见草油为油相,吐温80、月桂酸为表面活性剂制备水包油型的食品级微乳并对其稳定性进行考察。通过透射电镜观察微乳形态,动态光散射仪测定微乳的粒径,紫外分光光度法测定苏丹Ⅱ含量,考察pH、贮藏温度、贮藏时间对稳定性的影响。结果表明,微乳液外观澄清透明,透射电镜观察为均匀球状液滴。微乳液在pH5~7时稳定性较好。在4℃和20℃贮藏条件下的稳定性较好,放置30d微乳液的粒径变化较小,微乳的包封率可达92.21%、91.89%,放置期间未出现分层、破乳现象。而在60℃下放置30d后微乳出现浑浊,包封率下降较大。      

羧甲基壳聚糖包裹椰子油脂质体制备的工艺优化

通过薄膜-超声分散法制备羧甲基壳聚糖包裹的椰子油脂质体,以大豆卵磷脂和氢化大豆卵磷脂为膜材,包封率为主要评价指标,采用单因素和正交实验对薄膜-超声分散法制备羧甲基壳聚糖包裹的椰子油脂质体的工艺和配方进行优化,并对所制备脂质体的微观形态、包封率、丙二醛(malondialdehyde,MDA)含量和体外释放度进行分析。结果表明:最佳制备条件为羧甲基壳聚糖与磷脂比为1：16,磷脂与胆固醇比为8：1,椰子油与磷脂比为3：1,pH为4.5,超声强度750 W,超声时间20 min,此条件下实际包封率为96.94%±0.20％。羧甲基壳聚糖包裹椰子油脂质体在0.9%氯化钠中,24 h的释放度为41.28%±0.30%。椰子油脂质体的包封率高和累积释放度高,稳定性好,可实现延缓释放和靶向给药。     

沙棘籽油微胶囊的制备及氧化稳定性评价

沙棘籽油是一种富含不饱和脂肪酸的功能性油脂,容易氧化变质。本文将添加天然抗氧化剂与微胶囊制备技术相结合,改善沙棘籽油的氧化稳定性,延长货架期。首先测定了沙棘籽油的组成成分,然后以沙棘籽油为芯材,添加经过筛选的天然抗氧化剂L-AP,以辛烯基琥珀酸淀粉钠,酪蛋白酸钠及麦芽糊精等为壁材制备沙棘油微胶囊,并通过65 ℃烘箱加速保藏实验评价其氧化稳定性。结果表明:沙棘籽油中不饱和脂肪酸含量占总脂肪酸的80.6%±2.10%;制备沙棘籽油微胶囊的最佳配方为辛烯基琥珀酸淀粉钠15%、酪蛋白酸钠5%、麦芽糊精5%、抗性糊精30%、甘蔗浓缩汁10%、沙棘籽油30%、异麦芽酮糖5%,并添加3 g/L三聚磷酸钠,包埋率高达91.8%±1.59%;65 ℃烘箱加速保藏实验结果表明,添加抗氧化剂并制备微胶囊能有效提高沙棘籽油的氧化稳定性。     

Mathematical modelling of inclusion motion and entrapment in billet mould with effect of electromagnetic stirring

ABSTRACT

In-mould electromagnetic stirring (M-EMS) is a widely used technique during continuously casting (CC). To investigate the M-EMS effect on the inclusion motion and entrapment in a billet CC mould, a coupling mathematical model was developed. The result indicates that the M-EMS changes molten steel flow pattern and transient inclusion distributions in the mould. Inclusions have a tendency to move close to the mould centre under M-EMS. When the M-EMS is off, the distributions of inclusions in the solidified shell is relatively uniform. When the M-EMS is applied, many inclusions are entrapped near the stirrer mid-plane. Furthermore, distances of captured inclusions below the billet surface become larger. Additionally, the M-EMS has a significant effect on the overall removal fraction of inclusions. At last, detection of inclusions in samples obtained from a plant has been performed. A similar tendency can be found between the predicted and experimental results.     

板坯连铸结晶器钢液卷渣现象研究

利用水模型研究安钢板坯结晶器内钢液的卷渣机理，得出其主要卷渣方式，并考察了水口结构参数及操作参数对卷渣的影响，提出避免卷渣的的改进措施。     

多模式全连续铸轧产线卷渣缺陷分析及控制

通过扫描电镜和能谱分析仪对低碳低硅铝镇静钢表面卷渣缺陷微观形貌进行观察和能谱分析。结果表明,低碳低硅铝镇静钢表面较短条状卷渣缺陷的主要成分为钙、铝和氧,为典型的钙铝酸盐夹杂物;较长条状卷渣缺陷的主要成分为钙、硅、氟、钠和氧,为典型的保护渣成分。针对不同类型的卷渣缺陷及其成因,分别在炼钢工艺的挡渣出钢、精炼工艺的升温时间和钙含量以及连铸工艺的中间包控流装置、中间包保护气氛、结晶器液面波动、钢包下渣和结晶器保护渣等方面进行改造、控制和优化。采取上述措施后,因低碳低硅铝镇静钢表面卷渣缺陷造成的产品降级率由大于10.0%降至1.5%以下,产品质量得到明显提升。