基于Fluent对水平连铸结晶器温度场分布及传热的研究

以水平连铸圆坯连铸生产工艺为研究对象,采用Fluent数值模拟软件凝固传热模型并结合射钉试验共同研究了管坯在不同拉坯工艺条件下,结晶器内的温度场分布与凝固传热过程,并对不同拉坯参数下铸坯试样进行了检测分析。研究发现：水平连铸拉坯工艺参数：拉速V=2．13m／min,浇注温度T=1544℃,中间包过热度△T=40℃的拉坯参数下,结晶器内的温度场分布均匀稳定,铸坯质量好,产量高。研究表明,采用Fluent数值模拟软件凝固传热模型并结合射钉试验可以有效分析在不同拉坯工艺条件下水平连铸结晶器内的温度场分布及凝固传热过程,并进一步制定合理的拉坯工艺参数,降低管坯质量缺陷的发生,提高铸坯质量。     

水平连铸方坯的凝固传热

本文根据西德Technica Guss水平连铸工艺,采用计算机数值模拟的方法来研究水平连铸方坯的凝固传热。经试验验证表明,可利用该凝固传热模型来预报采用不同连铸工艺参数时的铸坯温度和坯壳厚度分布及液芯长度。浇铸温度Tp、拉坯速度V、结晶器冷却水量Q和冷却水温差ΔTw等主要连铸工艺参数均不同程度地影响铸坯的凝固特性,其中拉坯速度V和冷却水温差ΔTw的影响最为显著。     

高拉速下凝固进程的试验测量与模型预测

 根据京唐高拉速试验特点,结合板坯连铸机设备和洁净钢连铸工艺特点和要求,建立连铸板坯凝固传热模型并结合射钉法测量综合预测了1.9～2.4 m/min高拉速条件下铸坯的凝固坯壳厚度和凝固终点位置。综合研究表明,结合射钉试验和数值模拟能更精确跟踪铸坯的凝固进程,为高拉速试验提供准确的凝固信息,并能为评价连铸机综合冷却能力、优化二冷制度和轻压下工艺提供合理的参考信息。     

新钢板坯连铸工艺参数和动态轻压下工艺优化研究

针对新余钢铁公司板坯连铸生产的实际情况,通过检测不同拉速、比水量、过热度等工况条件下铸坯的内部品质,确定了合理的连铸工艺参数.通过射钉法对铸坯凝固末端位置进行测定,运用板坯温度场与配水软件计算出铸坯凝固的温度场以确定合适的轻压下区间,通过数值计算得出合适的轻压下量.     

水平连铸40Cr圆坯凝固特性的研究

以40Cr圆坯水平连铸工艺为研究对象,采用射钉试验、红外测温试验、硫印试验及酸浸低倍试验研究了40Cr圆坯的凝固传热过程.通过本研究得出40Cr圆坯在拉速V=1.99(m/min),浇注温度T=1544℃,中间包过热度AT=52℃的拉坯参数下,钢坯的液芯长度为L=17.47m,铸坯的中心疏松为1.5级,中心裂纹为1.5级.试验结果表明,射钉法可以有效分析连铸坯的凝固传热过程,为高效连铸生产提供可靠的理论参考.     

不同宽度H2结晶器流动、传热凝固行为对比

薄板坯连铸工艺的H2漏斗形结晶器可以生产宽度860～1 730mm的铸坯.对不同宽度H2结晶器内钢液流动、传热凝固行为进行研究,能加深了解H2结晶器内的冶金行为,并为H2薄板坯连铸设备制造及工艺参数优化提供指导.采用数值模拟技术研究拉速4.5 m/min时,宽度900、1 300、1 700mm结晶器内钢液流动、传热凝固行为.结果表明:结晶器宽度增加,流场变化显著,钢液自由液面近水口处波动加剧.不同宽度下,结晶器出口处铸坯坯壳厚度及其表面温度的差别主要体现在靠近铸坯窄边处.     

X80管线钢238 mm x 1 650 mm连铸坯温度场及凝固末端位置的数学模拟

用二维切片跟踪铸坯凝固传热的方法建立了X80管线钢（/%:0.04C,1.85Mn,0.25Si,0.006P,0.003S,0.30Ni,0.21Mo,0.06Nb,0.02V）238 mm×1650 mm板坯连铸过程中垂直拉坯方向传热的数学模型,通过ANSYS对X80管线钢连铸过程中温度场及坯壳厚度的渐变进行计算,得出拉速1.2mm/min时,出结晶器坯壳厚为18.14 mm,铸坯液芯长22.58 m。凝固壳厚度计算值射钉测试结果的相对误差≤2.5%,凝固末端位置的相对误差为0.68%。分析了过热度（25~55℃）,拉速（1.2~1.3m/min）和二冷水量（79.2~96.8 m³/h）对切片各点温度和凝固末端位置的影响。结果表明,增大拉速、减小二冷配水量,连铸坯表面温降变慢,凝固末端位置距离结晶器液面越远,凝固时间变长;该X80管线钢板坯连铸最佳工艺参数为钢水过热度35℃,拉速1.2 m/min和二冷配水量88m³/h。     

Ⅹ80管线钢238mm×1650mm连铸坯温度场及凝固末端位置的数学模拟

用二维切片跟踪铸坯凝固传热的方法建立了X80管线钢(/%:0.04C,1.85Mn,0.25Si,0.006P,0.003S,0.30Ni,0.21Mo,0.06Nb,0.02V)238 mm×1650 mm板坯连铸过程中垂直拉坯方向传热的数学模型,通过ANSYS对X80管线钢连铸过程中温度场及坯壳厚度的渐变进行计算,得出拉速1.2mm/min时,出结晶器坯壳厚为18.14 mm,铸坯液芯长22.58 m。凝固壳厚度计算值射钉测试结果的相对误差≤2.5%,凝固末端位置的相对误差为0.68%。分析了过热度(25~55℃),拉速(1.2~1.3m/min)和二冷水量(79.2~96.8 m~3/h)对切片各点温度和凝固末端位置的影响。结果表明,增大拉速、减小二冷配水量,连铸坯表面温降变慢,凝固末端位置距离结晶器液面越远,凝固时间变长;该X80管线钢板坯连铸最佳工艺参数为钢水过热度35℃,拉速1.2 m/min和二冷配水量88m~3/h。     

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     

高拉速下37Mn5钢连铸圆坯内部质量控制研究

针对Φ200 mm 37Mn5钢圆坯高拉速下铸坯存在的内部裂纹、中心缩孔与中心疏松等缺陷,结合生产实际分析得出过热度高、结晶器电磁搅拌强度偏小、二冷工艺及喷嘴布置不合适是引起铸坯质量问题的主要原因。通过建立经射钉及测温试验验证的凝固传热模型与采用高斯计测量电磁搅拌磁场的分布特征分别对二冷工艺制度和结晶器电磁搅拌参数进行优化,同时对二冷区喷嘴布置进行改进。结果表明:对于Φ200 mm断面37Mn5钢连铸拉速从1.4 m/min提高到1.8 m/min,铸坯内部质量明显改善,内部裂纹消失,中心缩孔和中心疏松均为0.5级,若过热度大于30℃,仍存在比较严重的中心缩孔。     

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。     

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)     

Comparison of rates of infection of two methods of emergency ventricular drainage

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.     

浅析《野草》的版画特征

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".     

四辊破碎机车刀架的改造

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。     

显微维氏硬度测量不确定度评定

对显微维氏硬度测量不确定度进行评定，建立了不确定度计算的数学模型，确定了影响实验结果的各项因素，计算出了各因素的标准不确定度，得出结果的扩展不确定度，并给出最终测量结果的表达式。     

Concept of freedom of infection of animal flocks

Totally negative results of epidemiological investigation of random samples do not prove the absence of the infection as the pathogen may be restricted to only a few animals in the herd for a long time. The statement "absence of infection" is critical for such situations. The question is raised, whether the statement "absence of infection" should be generally avoided. Classification of herds and flocks according to the prevalence of the pathogen would be more valid for the implementation of control measures.     

Comparison of the results of surgical and conservative treatment of fractures of the diaphysis of the tibia

In this paper is treated the fundamental problematic of the fracture of the diaphysis of the tibia and the therapeutic results after the conservative and operative treatment are confronted. Among 518 patients with 433 open fractures and 35 with closed fractures of the diaphysis of the tibia, successful treatment of more 2/3 was obtained in the period from 1968 to 1972. Following our casuistics and literature, whose results are similar, we find out that the average total treatment of the osteosynthesis of the fracture of the diaphysis was shortened for 2,5 months depending upon the type and the localisation of the fracture. Apolied methods of the operative and conservative and conservative treatment in relation to the velocity of the medical cure as well as to the extreme anatomical-functional results are analised. We noticed that osteosynthesis, made by the intermedullary nail and the extension of the canals or by a small AO table, by the achieved stability makes conditions of immediate motions and an early rehabilitation. Because of that it gives the best functional results.