二冷喷淋强度对连铸坯凝固组织的影响

 推导了连铸过程中二冷喷淋强度与连铸参数之间的关系,比较了喷淋强度对2种断面连铸坯凝固组织的影响。结果表明,喷淋强度能更精确地反映铸坯凝固组织与冷却参数间的关系;铸坯表面的枝晶间距为20 μm左右,而中心区为200～350 μm;距表面相同距离,对角线区的枝晶比横向细小。喷淋强度相近时铸坯的凝固规律为：200 mm×200 mm断面中心区组织较细小,150 mm×150 mm断面近中心区组织较细小。从铸坯表面到中心整体上符合凝固曲线左侧规律,但断面大于200 mm×200 mm的连铸坯,中心和近中心区凝固时符合凝固曲线右侧规律。     

间歇式变向复合电磁搅拌作用下60Si2CrVAT钢的凝固组织

研究了间歇式变向复合电磁搅拌作用下60Si2CrVAT弹簧钢连铸坯的凝固组织.结果表明,间歇式变向复合电磁搅拌工艺可以显著减少60Si2CrVAT弹簧钢铸坯断面中心疏松和缩孔,提高铸坯凝固组织的致密度.铸坯中二次枝晶臂间距为30～250 μm,中心等轴区由铸坯断面面积的19.6%增加到25%,铸坯内部质量得到了极大的改善.     

1650板坯压下过程热/力学行为及压下工艺优化

为了控制梅钢1 650板坯连铸包晶钢过程铸坯内裂纹发生,基于梅钢1 650板坯连铸机生产实际,建立了1 560mm×230mm断面包晶钢铸坯凝固过程三维热/力耦合有限元模型,揭示了铸坯凝固过程各冷却区内的温度场分布规律和铸坯压下过程应力与变形行为演变规律。结果表明,铸坯在结晶器及零段内冷却强度大,沿拉坯及其垂直方向的温度分布梯度大;在实施铸坯凝固末端压下过程中,铸坯宽面中心与宽向1/4处的表面变形及应力变化较为同步,且靠近铸坯内弧侧凝固前沿的塑性应变最大,铸坯应力最大值集中在角部区域;目前梅钢包晶钢连铸压下区间设置不当,易引发铸坯产生内部裂纹。     

连铸板坯二冷高温区传热均匀性研究与优化

在板坯连铸过程中,二冷区传热的均匀性对铸坯表面与内部质量均有重要的影响.首先对国内某钢厂二冷各区的喷嘴进行了喷淋性能测试,根据各冷却区喷嘴的布局及2 000 mm×250 mm断面包晶桥梁钢板坯连铸生产过程的各区水量分布,建立了铸坯三维凝固传热有限元计算模型,模拟分析了铸坯在二冷区内的动态凝固传热行为.在此基础上,优化...     

“有限元—移动热源”法模拟连铸凝固过程

本文建立了连铸坯凝固传热的数学模型,阐述了“有限元-移动热源”法模拟连铸坯凝固过程的方法和编制计算程序。分析了在数值计算过程中将铸坯的凝固潜热算入比热会产生的误差,而采用“有限元-移动热源”法能消除这一误差,采用本法模拟计算了连铸坯的凝固过程,取得模拟与实测值基本吻合的好结果,本研究为模拟铸坯凝固过程提供了更为有效的新方法。     

高效连铸抛物线锥度结晶器的研究与设计

应用凝固理论对高效连铸条件下结晶器内初生坯壳生长规律、铸坯的凝固收缩特性进行了系统研究。利用结晶器锥度设计的最小气隙原则,建立结晶器设计计算模型,开发出高效连铸抛物线锥度结晶器设计系统。该系统可依据工艺条件设计出满足不同钢种和拉速条件的结晶器锥度、内腔曲线方程、上下口以及任意间位置的内腔尺寸,为结晶器的生产提供操作数据和理论依据。最后分别讨论了钢种、结晶器长度、拽坯速度、铸坯断面尺寸与结晶器锥度、凝固收缩系数的关系。     

基于有限元的板坯连铸凝固过程数值模拟

利用有限元分析软件Marc2003建立了板坯连铸凝固过程的二维数学模型.通过计算,可以得到连铸坯在任意段截面的温度场分布、凝固坯壳的厚度和相应的冶金参数.拉坯速度、过热度等工艺参数对温度场分布和凝固坯壳的生成影响很大,可以利用模型对工艺参数进行优化配置.     

气隙对连铸坯凝固影响的有限元数值模拟

以连铸坯凝固传热有限元数学模型研究了铸坯角部形状和气隙对坯壳凝固行为的影响研究结果表明：采用有限元法离散铸坯圆角能更合理地反映铸坯角部的几何和换热条件，从而可以更准确地研究角部换热条件对铸坯凝固行为的影响。角部气隙显著地降低了坯壳表面的换热，使铸坯偏角区成为热节区。此热节区是铸坯凹陷、皮下裂纹等缺陷和漏钢事故发生的诱因。     

高碳耐磨球钢大方坯凝固及坯壳生长规律研究

基于ANSYS软件建立了310mm×360mm断面大方坯连铸过程二维凝固传热数学模型,通过窄面射钉试验及铸坯表面测温对模型的准确性进行了验证,模拟了不同碳含量的高碳耐磨球钢大方坯宽面和窄面凝固坯壳的生长。结果表明模型能精确地获得不同工况下任意位置凝固坯壳的厚度分布、凝固终点位置及铸坯中心固相率;发现不同碳含量的高碳耐磨球钢具有相同的凝固规律:结晶器弯月面至二冷区出口,相应的铸坯柱状晶区凝固坯壳厚度与凝固时间的平方根呈线性关系,符合平方根定律,并对平方根定律进行了修正,修正项与过热度有关;二冷区出口至凝固终点,相应的铸坯等轴晶区凝固坯壳厚度与凝固时间的平方根呈非线性关系,不再符合平方根定律。     

连铸应用凝固传热计算的几个问题

1.连铸坯在结晶器内的凝固传热计算 通过对连铸坯凝固传热过程的研究,可以得到铸坯在冷却凝固过程中的温度场、坯     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.     

Quality of life of relatives of mental patients

Usage of quality of life of psychiatric patients' relatives as the parameter of estimation of the quality of psychiatric care is considered. By means of standard questionnaire elaborated by the authors as well as by means of both individual and group conversations the quality of life was analyzed in 40 relatives which lived together with psychiatric patients. Different spheres of their life and difficulties (financial, social-psychologic, production) were examined in families with such patients. The defects of psychiatric care that had direct influence on the quality of life of the psychiatric patients' relatives are outlined.