共查询到20条相似文献,搜索用时 78 毫秒
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连铸坯热装炉改善钢的组织性能鞠幼华鞍钢钢研所我国连铸工业的发展与国际发达国家有许多不同之处,随着连铸坯短流程直送热装工艺的推广应用与连铸连轧新工艺的开发,将形成连铸坯冷装、温装、热装、在线补热直接轧制和薄板坯连铸连轧等多种工艺。装炉坯温(表面形心温度... 相似文献
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一、引 言 产品质量很大程度上取决于锻坯质量,提高锻坯质量对于提高产品质量至关重要。 本厂的气门锻坯质量长期不够稳定,除了一些其它类型的缺陷以外,其中盘部端面上产生“环形圈”(实际是环形折叠纹)是一种常见缺陷。由于“环形圈”是以折叠的外形出现,其深度常常不易判断和检测。要想了解缺陷的深度,必须通过破坏性纵向剖切后观察。“环形圈”深度若超过机加工尺寸余量(本厂气门端面机加工余量一般定在1~1.5mm),机加工后的成品就会因不符合图纸要求而报废,即造成原材料、工时等方面的浪费。 为了避免或减少上述浪费,对气门锻坯“环形圈”缺陷产生的原因、过程等进行理论分析,从而达到锻坯质量的早期判定,甚至彻底避免该缺陷的产生,无疑是具有一定意义和价值的。 本文试图从气门锻坯的电镦加热,锻造成形中与质量有关的一系列因素的影响入手,通过对锻坯的整个变形形式、过程及其应力状态进行理论分析,判明“环形圈”产生的原因和过程,以便找出预防该缺陷的途径。 相似文献
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文章回顾了国内外连铸坯热送热装的发展概况,介绍了连铸坯热装的工艺特点和实行连铸坯热送热装的技术条件及我国连铸坯热送热装的发展方向。 相似文献
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在考虑炽热炉底的辐射加热和导热加热的基础上,建立了环形炉内管坯二维加热模型。计算结果表明,管坯表面热流密度沿周向分布的不均匀性造成了管坯温度沿周向分布不均。炽热炉管对管坯下部表面的导热及辐射加热对其加热至关重要。 相似文献
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管坯在环形加热炉内加热时,其表面辐射热流的分布是很不均匀的,靠近炉底的管坯表面的辐射热流比上部的小得多,因而造成管坯表面自下向上温度分布不均匀。适当增加管坯间距与其半径比(一般在3~4较为适宜),以及提高炉底反射率,可提高管坯表面热流分布的均匀性,改善加热质量。 相似文献
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目前中国的钢管业正处在一个新的发展转折点和平衡点,尤其是无缝管和焊管的争论已成为近几年的焦点。从无缝管与焊管的发展过程、国内外的现状、以及各自的特点等方面就其发展的趋势与前景,进行了客观地分析和科学的论证。 相似文献
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Xiao-Ze Du Shao-Rong WuSheng-Yao Jiang 《International Journal of Heat and Mass Transfer》2002,45(9):1889-1893
The Kelvin-Helmholtz instability of evaporating thin falling film flow in vertical tube is studied by method of energy analysis. Based on the rules that the interfacial capillary waves come from the balance of works done by inertial force, surface tension on phase-change interface, and also capillary force on tube wall, the stability behaviors of falling film with different Reynolds number and different perturbation wavelength are explored in detail. The analysis indicates that the main reason of film breakup by increasing tube wall heat flux is that, the stability effect of capillary adsorbability on tube wall is weakened as surface tension waving is enhanced by improving tube wall temperature. 相似文献
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Mohamed M. Mahmoud Tassos G. Karayiannis David B.R. Kenning 《International Journal of Heat and Mass Transfer》2011,54(15-16):3334-3346
The inner surfaces of microtubes may be influenced strongly by the process of making them due to manufacturing difficulties at these scales compared to larger ones, e.g. the surface characteristics of a seamless cold drawn tube may differ from those of a welded tube. Accordingly, flow boiling heat transfer characteristics may vary. In addition, there is no common agreement between researchers on the criteria of selecting tubes for flow boiling experiments. Instead, tubes are usually ordered from commercial suppliers, in many cases without taking into consideration the manufacturing method and its effect on the heat transfer process. This may explain some of the discrepancies in heat transfer characteristics which are found in the open literature. This paper presents a comparison between experimental flow boiling heat transfer results obtained using two different metallic tubes. The first one is a seamless cold drawn stainless steel tube of 1.1 mm inner diameter while the second is a welded stainless steel tube of 1.16 mm inner diameter. Both tubes have a heated length of 150 mm and the flow direction is vertically upwards. The tubes were heated using DC current. Other experimental conditions include: 8 bar system pressure, 300 kg/m2 s mass flux, about 5 K inlet sub-cooling and up to 0.9 exit quality. The results are presented in the form of local heat transfer coefficient versus local quality and axial distance. Also, the boiling curves of the two tubes are discussed. The results show a significant effect of tube inner surface morphology on the heat transfer characteristics. 相似文献
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大容积无缝钢瓶、管柬式集装箱和长管拖车作为专用气体储运装备在我国使用和制造已有10年时间,在检验检测和安全监管方面已基本形成相应的安全规范,但设计制造缺乏标准支撑。本文对管柬式集装箱的设计制造资质、组装工艺和型式试验要求进行简要介绍,包括大容积无缝钢瓶和长管拖车的相应要求。 相似文献
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炼油化工加热炉用高频电阻螺旋焊翅片管常见的11种缺陷,包括炉管光管表面原始缺陷、基管的直线度、翅顶撕裂、翅片倾伏、翅厚减薄、翅根松脱、翅根飞溅、翅根焊渣、翅根焊瘤、翅根皱折等,对各种缺陷的表现特点及其成因进行了简单的分析。 相似文献
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