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某石化公司裂解炉原料预热管线焊接接头因开裂引起了介质泄漏。通过宏观检查、化学成分分析、力学性能分析、金相分析、扫描电镜及能谱分析等手段,分析焊接接头发生开裂的原因。结果表明:原料预热管线焊接接头采用异种钢焊接连接,焊缝背面余高较高,焊缝与基体交界处存在几何结构突变,导致焊根处产生了较大的应力集中,同时两侧母材金属的线膨胀系数存在较大差异,且P11管侧熔合线处材料性能差,导致P11管侧焊根部位成为整个焊接接头的最薄弱部位。设备冷备工况下,管线内壁处于硫化物腐蚀介质环境,焊根处尖角部位在焊接残余应力、热应力和工作应力的共同作用下发生了硫化物应力腐蚀开裂,裂纹不断扩展,最终引起介质泄漏。 相似文献
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中石化金陵分公司制氢转化炉管在服役8900小时后上部法兰环焊缝发生泄露,对导致炉管与法兰焊接接头产生穿透性裂纹的成因作全面分析,找出泄露的根本原因,并提出了解决措施。 相似文献
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采用金相、断口扫描电镜等手段对投用4年的裂解炉管6m高度处的裂纹进行了分析。裂纹起源于外表面,呈多条平行分布沿周向扩展。分析表明,炉管微观组织正常,没有大量碳化物积聚和蠕变空洞,外表面有轻微的脱碳层,表明炉管没有超温迹象。炉管开裂是由热疲劳所致。热疲劳是由于炉管烧焦期间升降温产生的交变热应力和机械应力共同作用造成的。 相似文献
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描述合成辅锅炉管开裂的外观形貌,通过对炉管的材料进行化学成分分析、金相检查以及蠕胀检查,找出炉管失效的原因是管子外表面有裂纹,内表面结垢而导致局部过热,引起了管子蠕胀后开裂,直至穿透,提出工艺监护及管理措施. 相似文献
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通过对材质为35Cr45Ni+NbMA的乙烷裂解炉炉管进行宏观形貌、微观形貌、扫描电镜、金相、化学成分等方面的分析,分析了炉管失效的原因,提出了相应的预防措施和建议。结果发现:炉管长期高温服役,力学性能下降,炉管内形成的厚结焦层与炉管母材的热膨胀系数之间的差别,导致在停炉过程中产生超过常温断裂强度的高水平应力,是该乙烷裂解炉炉管断裂失效的主要原因。 相似文献
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采用宏观检查、金相组织、力学性能测试方法对某炼油厂制氢车间运行3.5万h即发生开裂的HP型制氢转化炉炉管进行了析。结果表明:炉管破裂失效的主要原因是高温蠕变破裂,长期超温运行是导致炉管提前失效的直接原因。 相似文献
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The transport properties of ionic liquids (ILs) are crucial properties in view of their applications in electrochem-ical devices. One of the most important advantages of ILs is that their chemical–physical properties and conse-quently their bulk performances can be well tuned by optimizing the chemical structures of their ions. This will require elucidating the structural features of the ions that fundamentally determine the characteristics of the nanostructures and the viscosities of ILs. Here we showed for the first time that the“rigidity”, the order, and the compactness of the three-dimensional ionic networks generated by the anions and the cation head groups determine the formation and the sizes of the nanostructures in the apolar domains of ILs. We also found that the properties of ionic networks are governed by the conformational flexibility and the symmetry of the anion and/or the cation head group. The thermal stability of the nanostructures of ILs was shown to be con-trolled by the sensitivity of the conformational equilibrium of the anion to the change of temperature. We showed that the viscosity of ILs is strongly related to the symmetry and the flexibility of the constitute ions rather than to the size of the nanostructures of ILs. Therefore, the characteristics of the nanostructures and the viscosities of ILs, especially the thermal stability of the nanostructures, can be fine-tuned by tailoring the symmetry and the conformational flexibility of the anion. 相似文献
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Investigation of the effects of fatty acids on the compressive strength of the concrete and the grindability of the cement 总被引:1,自引:0,他引:1
In cement industry, a great energy consumption has been observed during grinding of clinker. To reduce this consumption, some waste products have been used as grinding aids.In this investigation, the effects of sunflower oil (SO), oleic acid (OA), stearic acid (SA), myristic acid (MA) and lauric acid (LA) on the fineness and strength of the cement have been examined. These aids were added into clinker in certain ratios based on the cement clinker weight and the grinding has been done for a definite time at the same condition.All of the fatty acids used increased the fineness as compared with the cement without the grinding additives. SO and OA decreased the strength significantly, LA decreased it to a lesser extent and SA increased it definitely according to the common cement. But MA did not alter the strength of the cement as much as SA. In addition, the covering of the balls influences the grinding of cement clinker unfavourably. 相似文献
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Polyurethaneureas (PUU), which were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG), and 3,5-diaminobanzoic acid (DABA), were used as polyelectrolytes in this study. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to monitor the effect of the various kinds of PEG on the changes in morphology of PUU electrolytes corresponding to the concentration of lithium perchlorate (LiClO4) dopants. The results of DSC and FT-IR indicate the Li+ ions coordinate with the soft and hard segments. Additionally, the crystallinity of the PEG soft segment and the ordered hydrogen-bonded urea carbonyl groups decreased with increasing salt concentration. Impedance spectroscopy (IS) measurements show that the PUU electrolyte with the high phase separation degree has the high ionic conductivity. The hard-segment Tg and the soft-segment Tm influence the conductivity behavior of polyelectrolytes with increasing measurement temperature. 相似文献
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In spinning basalt fibres, the drafting force is in the same range as in spinning of glass fibres. The effect of the drafting
force can not be considered in the calculation for the strength and rigidity of the bottom of the spinneret.
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Translated from Khimicheskie Volokna, No. 5, pp. 47–50, September–October, 2007. 相似文献
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组合凹模的应力分析是一个非常复杂的问题,对其进行精确分析是解决模具寿命的关键。本文采用有限元分析软件Ansys对转子的组合凹模进行了分析,为转子组合凹模的优化设计提供了依据。 相似文献