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The effect of hot plastic deformation on the transformation of the primary (cast) microstructure of ductile cast iron with globular graphite (ductile cast iron) has been investigated. The results of metallographic (with the use of light and scanning electron microscopes) and electron microprobe analyses of experimental cast iron samples in the cast and deformed states have been discussed. It has been shown that an increase in the degree of plastic deformation from 20 to 80% brings significant microstructural changes in both the pearlitic-ferritic matrix and graphite inclusions of cast iron. 相似文献
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镍-石墨高温自润滑材料的熔炼制备及其组织性能 总被引:8,自引:6,他引:8
采用真空中频感应熔炼、电弧熔炼和高频感应熔炼辅助3 m落管无容器快速凝固方法,制备出镍-石墨两相自润滑合金.研究表明:在石墨型中浇铸,石墨呈片状生长;在金属型中浇铸,石墨有球化趋势;在电弧炉中熔炼并凝固,石墨基本呈球状组织形态,在3 m落管中经深过冷快速凝固后石墨呈球状组织.从而得出,石墨在生长过程中,(1010)棱面与(0001)基面的再辉温度差是影响石墨生长形态的重要因素.该材料具有高的冲击韧性和较低的电阻率,与45#退火钢及GCr15轴承钢干摩擦磨损时,摩擦因数分别稳定在0.23和0.15. 相似文献
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D. A. Baranov 《Protection of Metals》2007,43(1):50-53
The mechanism of the effect of preliminary plastic deformation on the corrosion resistance of high-strength cast iron is analyzed.
Based on the experimental results, a scheme of the mechanism considering the contribution of the variation in the number and
shape of graphite inclusions to the anisotropy of corrosion rate of strained cast iron is proposed.
Original Russian Text ? D.A. Baranov, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 1, pp. 55–58. 相似文献
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石墨形态对铸铁热疲劳性能的影响 总被引:3,自引:0,他引:3
主要研究了石墨形态对铸铁热疲劳性能的影响,为高速列车制动盘的合理选材提供依据。试验结果表明:蠕墨铸铁的耐热疲劳性能最好,球墨铸铁次之,灰铸铁最差。 相似文献
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Special features of structure and properties of cast iron with globular graphite subjected to plastic deformation in quasi-static and high-speed upset forging are considered. The strain curve and the dependence “deforming force – degree of elongation (drawing)” are obtained for cast iron with the pearlite-ferrite matrix. The effect of plastic deformation on the morphology of graphite particles, impact toughness, and failure of test specimens is determined at deformation under the conditions of free upset forging and forging in a holder. 相似文献
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1.IntroductionTheapplicationofelectroslagremeltingprocess(ESR)tocastironcastingproductionhasbeendescribedbymanyauthors[ljZ],whoemphasizethatthecastingqualitiesareimprovedbyoverheatingandcleaningofmoltencastiron,andchangingthegraphiteformofcasting.Itisnecessarytoworkontheelectrochemicalaspectsoftheprocess,sincewehaveliquidmetalsurfaceactingaselectrodesincontactwithanionicliquidslag.IncontrastwithmostESRprocessesinwhichthechemicalcompositionchangesbetweenthemeltingelectrodeandingotproducedfro… 相似文献
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在汽车上使用轻质铝合金发动机可以有效减少燃油消耗和环境污染,但铝合金的耐磨损性能较差,从而造成发动机工作过程中气缸壁面容易磨损。利用表面改性技术对铝合金表面进行强化处理,可以满足其作为滑动部件在高载荷条件下的使用要求。灰铸铁较低的成本和其中石墨的自润滑作用,使其成为铝合金发动机气缸表面保护涂层材料的首选。等离子喷涂技术以其高效率和灵活性在表面强化领域受到广泛应用。因此,利用等离子喷涂制备灰铸铁涂层成为改善铝合金发动机气缸表面耐磨性的有效方法之一。但是,由于等离子喷涂过程中熔滴冷却速度极快,等离子喷涂很难得到含大量石墨组织的灰铸铁涂层。以调控灰铸铁涂层中的石墨含量为目的,总结了等离子喷涂灰铸铁涂层的研究现状,以及基体温度、颗粒尺寸、添加合金元素等对熔滴冷却速度的影响,并以此为基础,结合凝固理论分析了在涂层中保留灰铸铁粉末中的石墨组织的可行性,同时分析了在铸铁涂层中保留石墨所面临的主要问题,并提出了解决这些问题的主要措施。最后就在等离子喷涂灰铸铁涂层中保留石墨的研究方向进行了展望。 相似文献
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In general,during the production of compacted graphite iron (CGI),the active residual magnesium reduces and the effect of inoculation fades after magnesium treatment.In this paper,characteristics of the thermal analysis curve of CGI are compared with those of ductile iron and grey cast iron.The fading effect on the compacted graphite percentage and thermal analysis curve were also studied.Results indicate that the undercooling of CGI is as low as that of ductile iron,but CGI shows evident recalescence.In fading process,the magnesium element acts with oxygen.For a decrease in magnesium content,both the compacted graphite percentage and the austenitic liquidus temperature increase.The temperature of eutectic undercooling (TEu) decreases before the flake graphite appears.After that,TEu increases quickly,up to as high as 20 ℃,and then gradually decreases.The evolution of recalescence degree is opposite to that of TEU. 相似文献
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Chapter 3
Spheroidal Graphite Cast Iron(I)
Spheroidal Graphite Cast Iron, SG iron in short, refers to the cast iron in which graphite precipitates as spheroidal shape during solidification of liquid iron. The graphite in common commercial cast iron can only be changed from flake to spheroidal shape by spheroidising treatment. Since spheroidal graphite reduces the cutting effect of stress concentration, the metal matrix strength of SG iron can be applied around 70%-90%, thus the mechanical property of SG iron is significantly superior to other cast irons;even the tensile strength of SG iron is higher than that carbon steel. 相似文献
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《International Journal of Cast Metals Research》2013,26(1-4):81-85
AbstractAlthough it is known that the addition of bismuth refines the graphite nodule in spheroidal graphite cast iron, the refinement mechanism has not yet been clarified. In this research, the effect of bismuth on the refinement has been investigated by examining the microstructure of the spheroidal graphite cast iron containing a small amount of bismuth. Bismuth was added at 0˙01 mass% to the spheroidal graphite cast iron melt containing 3˙5–3˙7 mass% carbon and 2˙0– 2˙8 mass% silicon, then the melt was poured into the mould to obtain the stepped test bar with 2, 3, 5 and 10 mm thicknesses. The graphite nodule increased as the bismuth content increased. The diameter of the graphite nodule decreased as the thickness decreased, namely, as the cooling rate increased. The graphite nodule was further refined by the addition of bismuth. The increase in silicon content increased the graphite nodule count and the ferrite in the matrix. It postulated that bismuth exists as simple substance or a compound in the vicinity of the nucleus of the graphite. 相似文献
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Flake and spheroidal graphite cast irons with similar composition were subjected to high temperature oxidation to investigate graphite morphology and distribution effects on the oxidation behavior. High temperature oxidation tests were conducted between 400 and 750 °C in air. For comparison low carbon steel was also tested.Graphite morphology obviously affected high-temperature oxidation resistance. The flake graphite cast iron exhibited the worst high-temperature oxidation resistance compared with spheroidal graphite cast iron. Since graphite flakes provide suitable sites for the iron oxide growth and are almost interconnected, the iron oxide grows faster and penetrates along the graphite flakes boundaries resulting in the subsurface oxidation. Due to the severe subsurface oxidation flake graphite cast iron parabolic rate constants are five times higher than that of the spheroidal graphite cast iron. However, spheroidal graphite cast iron parabolic rate constants and oxide layer thickness are similar to those of the low carbon steel. Therefore, graphite flakes have negative effect on the cast iron high temperature oxidation resistance. 相似文献
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The interfacial adsorpton behaviour of some minor elements contained in inoculants used in the manufacture of spheroidal-graphite cast iron have been studied by using a scanning auger microprobe at the fracture surfaces of specially-prepared specimens. It is shown that bismuth, boron and sometimes aluminium are adsorbed at the graphite/ melt interfaces, while neither calcium, zirconium, strontium, barium nor the nodularising element magnesium are detected at the interfaces during solidification of s.-g. iron. It is evident that the inoculation mechanism of Bi and B is mainly related to the interfacial adsorption behaviour during solidification, while Ca, Zr, Sr and Ba mainly act as heterogeneous substrates for graphite nucleation. Based on the results, some more powerful Bi or B containing inoculants for s.-g. cast iron have been developed. 相似文献
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Note:This book consists of five sections: Chapter 1 Introduction, Chapter 2 Grey Iron,Chapter 3 Spheroidal GraphiteCast Iron,Chapter 4 Vermicular Graphite Cast Iron,and Chapter 5 White Cast Iron.CHINA FOUNDRY publishes thisbook in several parts serially,starting from the first issue of 2009. 相似文献
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The shape of the graphite nodules in ferritic spheroidal graphite (SG) cast iron is changed by hot-swaging and hot-rolling, when symmetric ellipsoidal graphite and asymmetric ellipsoidal graphite can be obtained, respectively. For the symmetric ellipsoidal graphite, the graphite shape ratio tends to decrease with increasing reduction ratio. The increase of flow stress with increasing reduction ratio can be explained by the decrease in the stress concentration induced by the graphite with increasing reduction ratio. On the other hand, the graphite shape ratio is more complex for the asymmetric ellipsoidal graphite than the symmetric ellipsoidal graphite specimens. The graphite shape ratio tends to increase and decrease with increasing reduction ratio in two transverse directions. As a result, a balance exists in the specimen between increasing and decreasing stress concentration, showing that the tensile flow stress is independent of reduction ratio.To understand the effect of the graphite shape ratio on the tensile flow stress during tensile deformation, specimens with different carbon contents and graphite shape ratios were used in this study. Furthermore, the triaxial parameter (k1) has been defined such that the larger stress concentration effect will have the larger k1 value. Based on the present experimental results, the graphite shape ratio tends to decrease with increasing reduction ratio or tensile strain, so that the stress concentration effect and triaxial parameter (K1) tend to decrease with increasing reduction ratio and tensile strain. Therefore, the effect of the graphite nodules in ferritic SG cast iron on the tensile flow stress is not only reduction of the effective area fraction of the matrix but also development of an uneven triaxial stress field. 相似文献
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