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对钼板材正弦廓形轧辊轧制工艺进行数值模拟,并通过正交试验优化轧制工艺参数。创建了轧辊和钼板的三维实体模型,建立了优化试验的目标函数即钼板材破坏值。正交模拟轧制试验结果表明,生产4mm厚钼板材的最佳轧制方案为:开坯轧制加热温度1 200℃,变形程度37.5%;二火一轧加热温度1 150℃,变形程度24%;二火二轧变形程度23%;三火一轧加热温度1 100℃,变形程度20%;三火二轧直接轧至4mm板厚。在此轧制工艺条件下,钼板材的破坏值可能最小。 相似文献
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易切削奥氏体不锈钢(%:0.09~0.10C、0.80~0.82Si、0.40~0.43Mn、0.08~0.09P、0.10~0.11S、9.14~9.20Ni、18.12~18.30Cr、0.73~0.78Ti)由30 kg真空感应炉冶炼,Φ450 mm轧机经8道次开坯成75 mm×75 mm坯。当钢锭加热温度1200℃,1~4道次(1150~1060℃)轧制未出现开裂,5~8道次(950~770℃)轧制钢坯出现严重表面裂纹。扫描电镜与能谱分析表明,钢中夹杂物为硫化锰-硫化铁复合夹杂物。通过将1~8道次开坯温度控制在1150~1060℃时,有效地避免了钢坯表面开裂的发生。 相似文献
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研究了粉冶TZM钼合金薄板轧制工艺,通过850~1000℃低温开坯、横轧、叠轧等工艺试验结果表明,不用传统轧制工艺.可生产出0.25mm×310mm×420mm高质量的TZM合金薄板,满足用户的高性能和高精度的技术要求。为改进钼合金板材轧制工艺提供了科学数据。 相似文献
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研究了轧制开坯温度、初道次变形率、热轧终轧温度等对钼板组织和性能的影响,得出合适的轧制工艺可使钼板的组织均匀、细小,抗拉强度、屈服强度、延伸率等性能提高。通过研究,确定了钼板坯的最优轧制工艺。 相似文献
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特厚模具钢因具有卓越的性能和可靠的使用寿命,在制造大型模具中起着不可替代的作用。然而,在连铸过程中,铸坯内部可能形成的缺陷对模具钢的力学性能和使用寿命造成严重影响。设计合理轧制工艺提高芯部变形是改善芯部缺陷的重要途经之一。针对大直径椭圆连铸坯轧制成特厚钢板的开坯粗轧、平整成型及精轧3个过程,采用有限元数值模拟的方法研究了不同轧制工艺对42CrMo特厚钢板不同位置的累积变形量、单道次变形量以及钢板成材率的影响。利用材料性能计算软件JMatPro计算了42CrMo钢的高温变形行为和热导率、比热容、密度、弹性模量、泊松比等物理参数,采用ABAQUS软件进行轧制有限元模拟分析了轧制道次压下量对椭圆坯内部疏松压合的影响规律。结果表明,开坯粗轧的前3道次压下量变化对芯部变形影响不大,芯部变形量主要取决于精轧阶段单道次压下量。采用前3道次较小压下量开坯加后5道次较大压下量精轧,芯部累积变形量最大,达1.5,且最后5道次中每道次的应变量均大于0.14,可以有效提高大规格椭圆坯轧制的特厚板芯部变形渗透率,有利于芯部裂纹和疏松等铸坯缺陷的改善。 相似文献
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对325 mm×280 mm大方坯在开坯、加热炉加热、堆垛缓冷和水除鳞等生产流程的温度变化规律进行了研究。结果表明:开坯到160 mm×160 mm热轧坯时,角部温度已经下降到990℃,表面中心温度下降到1 012℃。冷装热轧坯经过50 min的加热后温度基本达到1 000℃,热轧坯开坯后直接入炉经过40 min的加热后热轧坯温度已经达到1 060℃以上,基本满足了轧制的要求。铸坯经过堆垛冷却48 h后,堆垛表层的铸坯中心温度下降到20℃左右,堆垛中心的铸坯中心温度下降到80℃左右。冷却速率自顶向下逐渐减慢,堆冷铸坯的冷却速率为8.3~15.3℃/h,铸坯的平均冷却速率为10.44℃/h。热轧坯在经过水除鳞段后,铸坯角部温度下降到1 053℃,边部中心温度下降到1 055℃,整个水除鳞阶段热轧坯的温降幅度在15℃左右。 相似文献
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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. 相似文献
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TA Solokhina LS Shevchenko IuV Se?ku EG Rytik LV Besedina TS Veshchugina 《Canadian Metallurgical Quarterly》1998,98(6):42-46
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. 相似文献
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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) 相似文献
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The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies. 相似文献
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鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美". 相似文献
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针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。 相似文献