共查询到20条相似文献,搜索用时 78 毫秒
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高级别表面耐指纹家电板要求钢板表面近乎零缺陷。对于在生产过程中出现的表面黑点缺陷,采用扫描电镜(SEM)和电子探针(EPMA)进行分析。结果表明,黑点缺陷种类较多,不同的黑点缺陷产生于热镀锌机组不同部位,如后处理风箱、拉矫机等。通过对设备的调整和清洁等措施,可成功消除黑点缺陷。 相似文献
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粉末冶金产品缺陷与显微组织 总被引:2,自引:1,他引:1
论述了铁基粉末冶金结构零件某些缺陷,如:裂纹、尺寸失控、力学性能不合格、不易切削等的内在显微组织分析。通过显微组织分析,找出产生缺陷的原因,从而提高工艺水平。 相似文献
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《有色金属材料与工程》2019,(6)
电子束熔化成型技术(electron beam melting,EBM)是3D打印的代表性技术之一,特别适合传统工艺不易加工的Ti-6Al-4V合金(TC4钛合金)的快速成型,目前在航空航天、化工、生物医疗等领域展示出巨大的应用前景。从EBM的原理出发,综述了EBM制备TC4钛合金的显微组织、缺陷以及力学性能。分析了受成型工艺参数和成型件位置等因素影响的冷却速度的变化所导致的TC4钛合金的显微组织发生变化;并指出了导致TC4钛合金出现缺陷的主要原因。EBM成型TC4钛合金的拉伸性能已与锻造TC4钛合金相当,其较低的疲劳强度可以通过热等静压处理提高。 相似文献
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HOXD4 and regulation of the group 4 paralog genes 总被引:1,自引:0,他引:1
A Morrison L Ariza-McNaughton A Gould M Featherstone R Krumlauf 《Canadian Metallurgical Quarterly》1997,124(16):3135-3146
From an evolutionary perspective, it is important to understand the degree of conservation of cis-regulatory mechanisms between paralogous Hox genes. In this study, we have used transgenic analysis of the human HOXD4 locus to identify one neural and two mesodermal 3' enhancers that are capable of mediating the proper anterior limits of expression in the hindbrain and paraxial mesoderm (somites), respectively. In addition to directing expression in the central nervous system (CNS) up to the correct rhombomere 6/7 boundary in the hindbrain, the neural enhancer also mediates a three rhombomere anterior shift from this boundary in response to retinoic acid (RA), mimicking the endogenous Hoxd4 response. We have extended the transgenic analysis to Hoxa4 identifying mesodermal, neural and retinoid responsive components in the 3' flanking region of that gene, which reflect aspects of endogenous Hoxa4 expression. Comparative analysis of the retinoid responses of Hoxd4, Hoxa4 and Hoxb4 reveals that, while they can be rapidly induced by RA, there is a window of competence for this response, which is different to that of more 3' Hox genes. Mesodermal regulation involves multiple regions with overlapping or related activity and is complex, but with respect to neural regulation and response to RA, Hoxb4 and Hoxd4 appear to be more closely related to each other than Hoxa4. These results illustrate that much of the general positioning of 5' and 3' flanking regulatory regions has been conserved between three of the group 4 paralogs during vertebrate evolution, which most likely reflects the original positioning of regulatory regions in the ancestral Hox complex. 相似文献
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The emission spectrum of TiCl has been investigated in the 3000-12 000 cm-1 region at high resolution using a Fourier transform spectrometer. The bands were excited in a microwave discharge through a flowing mixture of TiCl4 and helium. The observed bands have been classified into three electronic transitions, C4Delta-X4Phi, G4Phi-X4Phi, and G4Phi-C4Delta. In the 3000-3500 cm-1 region, four bands with R heads at 3368.7, 3331.8, 3291.9, and 3243.4 cm-1 have been assigned as the 0-0 bands of the 1/2-3/2, 3/2-5/2, 5/2-7/2, and 7/2-9/2 subbands, respectively, of the C4Delta-X4Phi transition. To higher wavenumbers, four transitions with 0-0 R heads at 10 930.7, 10 921.3, 10 906.5, and 10 886.9 cm-1 have been assigned as the 3/2-3/2, 5/2-5/2, 7/2-7/2, and 9/2-9/2 subbands, respectively, of the G4Phi-X4Phi system of TiCl. Four additional bands with 0-0 R heads at 7568.8, 7596.4, 7622.2, and 7651.7 cm-1 have been identified as the 1/2-3/2, 3/2-5/2, 5/2-7/2, and 7/2-9/2 subbands of the G4Phi-C4Delta transition, respectively. A rotational analysis of a number of vibrational bands of these transitions has been obtained and molecular constants have been extracted. The lowest 4Phi state has been assigned as the ground state of TiCl, by analogy with our recent work on TiF (R. S. Ram and P. F. Bernath, J. Mol. Spectrosc., in press). The correspondence between the electronic states of TiCl, TiF, TiH, and Ti+ is also discussed. Copyright 1997 Academic Press. Copyright 1997Academic Press 相似文献
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R Mahmood M Lewis R Biggers V Surendranath D Johnson ME Neubert 《Canadian Metallurgical Quarterly》1986,33(1):519-524
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《Canadian Metallurgical Quarterly》2013,52(2):149-151
AbstractFluoride emissions especially hydrogen fluoride from the aluminium smelting process present the potential for significant environmental damage and the care is, therefore, taken to remove them from the gas stream that leaves the plant. While previous work has focused on improving the scrubbing efficiency, more recent research has investigated the generation of fluoride emissions during the reduction process, in part to understand seasonal changes in fluoride emissions (summer syndrome). Several models have been developed to estimate the amount of hydrogen fluoride generated, but these do not consider the individual sources of fluoride generation and cannot be easily used to assess the impact of changes in relative humidity. This paper presents a new model, still under development, which simulates the hydrolysis of pot gas from an open feeder hole. During the course of this research, it has become clear that the major sources of moisture for hydrogen fluoride generation appear to be alumina, in the form of structural hydroxides and the ambient humidity. It is thought that summer syndrome can be explained by the changes in the ambient humidity. Initial results suggest that, in an open feeder hole, a 3000–5000 ppm hydrogen fluoride (HF) background in pot gas presents, the ambient moisture could account for 30–55% maximum of total HF emission, varying with ambient humidity, CO flaming and bath chemistry. However, the anode hydrogen and adsorbed alumina moisture only have limited contribution to the gaseous fluoride. 相似文献
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Yasuhiro Awakura Toshiya Doi Hiroshi Majima 《Metallurgical and Materials Transactions B》1988,19(1):5-12
The diffusion coefficients of CuSO4, ZnSO4, and NiSO4 in the aqueous solution systems of MSO4 and MSO4-H2SO4 were measured at 298 K using a diaphragm-cell method, and are listed as a function of molar concentrations of MSO4 and H2SO4. It was found that the concentration dependencies of the diffusion coefficients for CuSO4, ZnSO4, and NiSO4 in each single metal sulfate solution are very similar. The presence of H2SO4 generally causes a less significant concentration dependency of the diffusion coefficients of MSO4. The concentration dependencies of the diffusion coefficients of CuSO4 in aqueous solutions of CuSO4 and CuSO4-H2SO4 are attributed to the changes in the mean activity coefficient of CuSO4 and the viscosity of the solutions.
formerly Graduate Student, Department of Metallurgy, Kyoto University, Kyoto, Japan 相似文献