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1.
In this paper, forging of helical gears has been investigated. The forging process of helical gears has been classified into
two types of operations: guiding and clamping. The two types of forging of helical gears have been analyzed by using the upper-bound
method. Kinematically admissible velocity fields have been developed in which an involute curve has been introduced to represent
the tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters
such as module, number of teeth, helix angle and friction factors on the forging of helical gears. Some forging experiments
were carried out with commercial aluminum alloy to show the validity of the analysis. Good agreements were found between the
predicted values of the forging load and those obtained from the experimental results. 相似文献
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目的研究稀土含量对Ti6Al4V钛合金表面等离子体渗氮层结构和性能的影响。方法运用等离子表面改性技术对Ti6Al4V(TC4)钛合金进行等离子渗氮处理,渗氮过程中通入不同含量的稀土作为催渗剂,以获得钛合金表面强化层。利用金相显微镜和扫描电子显微镜(SEM)观察渗氮层组织,用X射线衍射仪(XRD)分析渗层相组成,用能谱仪(EDS)检测渗层的化学成分,用维氏显微硬度计测量渗层的显微硬度,用球-盘式摩擦磨损试验机和三维轮廓仪检测渗层的摩擦磨损性能。结果TC4钛合金表面等离子渗氮层结构包括表面化合物层(主要成分为δ-TiN)和扩散层(主要为N原子扩散形成的N-Ti固溶体),加入稀土可以促进N原子向基体的扩散,提高渗氮速度。渗层厚度增加,硬度和耐磨性能提高,扩散层使钛合金基体与化合物层之间的硬度梯度更加平缓。当稀土通入速率为60 mL/min时,渗层厚度可达155μm,表面硬度为1275HV0.05,摩擦系数降到0.27,磨损率明显降低。结论钛合金等离子渗氮过程中加入稀土可以有效提高渗速,改善渗氮层硬度,提高材料表面的耐磨性能。 相似文献
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Dong-Cherng Wen 《Surface & coatings technology》2009,204(4):511-519
In this study, the wear- and corrosion resistance of the layers formed on the surface of a precipitation hardenable plastic mold steel (NAK55) by plasma nitriding were investigated. Plasma nitriding experiments were carried out at an industrial nitriding facility in an atmosphere of 25% N2 + 75% H2 at 475 °C, 500 °C, and 525 °C for 10 h. The microstructures of the nitrided layers were examined, and various phases present were determined by X-ray diffraction. Wear tests were carried out on a block-on-ring wear tester under unlubricated conditions. The corrosion behaviors were evaluated using anodic polarization tests in 3.5% NaCl solution.The findings had shown that plasma nitriding does not cause the core to soften by overaging. Nitriding and aging could be achieved simultaneously in the same treatment cycle. Plasma nitriding of NAK55 mold steel produced a nitrided layer consisted of a compound layer rich in ε-nitride and an adjacent nitrogen diffusion layer on the steel surface. Increasing the nitriding temperature could bring about increase in the thickness of the nitrided layer and the nitride volume fraction. Plasma nitriding improved not only surface hardness but also wear resistance. The anti-wear property of the steel was found to relate to the increase in the thickness of the diffusion layer. Corrosion study revealed that plasma nitriding significantly improved corrosion resistance in terms of corrosion potential and corrosion rate. Improvement in corrosion resistance was found to be directly related to the increase in the nitride volume fraction at the steel surface. 相似文献
4.
Gears are integral and vital machine elements in the field of drive and transmission technology. With regard to economic and ecological aspects, cold forging represents a promising approach compared to conventional cutting processes for producing highly-loadable gears. A possible extrusion process for manufacturing helical gears is the so-called “Samanta”-process. In comparison to conventional extrusion processes, an additional ejector system is avoidable. Thus, in particular for helical gears, a negative impact on the gear quality by the ejector operation is prevented. Furthermore, the process chain during the component production cycle is shortened which leads to a more efficient production. The achievable gear accuracy as well as insufficient tool life are major challenges while establishing the “Samanta”-process in industry. To enable an industrial application, basic process understanding as well as knowledge about the influences on the process results is required. For influencing component and process properties within cold forging, approaches from the tribological system can be generally used. The aim of this study is to analyze the influence of the friction conditions on selected component and process properties within cold forging of gears by the “Samanta”-process. For adjusting the occurring friction, various lubrication systems were applied, which have been qualified using a double cup extrusion test (DCE-test). The results reveal that the lubrication system determines the friction conditions during forming. Within cold forging of helical gears by the “Samanta”-process, the friction influences the resulting strain hardening of the components and the required maximum forming force as well as the energy amount. 相似文献
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《CIRP Annals》2022,71(1):89-92
Gear hobbing is widely employed to manufacture automotive gears, where the productivity depends on the cutting speed. Currently, gear hobbing is performed at ~300 m/min using high-speed steel hob cutters. In this study, ultra-high-speed gear hobbing was attempted using a large-diameter cemented carbide hob cutter on a gear grinder. This enabled a cutting speed up to 2450 m/min. Many interesting phenomena were acquired in this speed range. Chips were severely oxidized, whereas the gear surface was not affected. Compressive residual stress was generated at the gear surfaces with low surface roughness and high hardness, while the wear of hob cutter was insignificant. 相似文献
6.
D. Shahriari A. Amiri M. H. Sadeghi 《Journal of Materials Engineering and Performance》2010,19(5):633-642
In hot forging of Nimonic 115, it is desirable to determine friction coefficients. Changing magnitudes of temperature and
type of lubricant at the surface of the workpiece and dies influence friction coefficient. This paper describes an experimental
investigation of friction under hot forging conditions using the ring compression test. The 3D FEM simulations were used to
derive the friction calibration curves and to evaluate material deformation, geometric changes, and load-displacement results.
A series of ring compression tests were carried out to obtain friction coefficients for a number of lubricants including mica
plate, glass powder, graphite powder, and dry condition. The experiments show how the variations in temperature at the interface
affected frictional behavior. On the basis of these results, mica is recommended for hot forging of Nimonic 115 and its friction
coefficient is approximately 0.3. 相似文献
7.
The effect of technological conditions of nitriding such as process time duration and chemical composition of saturating medium, on the corrosion behaviour of nitrided coatings in 14 M solution of sulphuric acid was analyzed. The investigations were done on the alloy Ti‐5,0 Al‐2,0 Mn. The nitriding was carried out in nitrogen both at atmospheric pressure and rarefied nitrogen pressure (1 Pa) at the temperature 850°C and time processing in the range from 5 to 20 h in nitrogen‐containing gas only, and in powder electrode graphite and nitrogen‐containing gas. It was shown that technological conditions of nitriding determine the protective properties of nitrided coatings. It was indicated that the optimal structure of the nitride layer for best corrosion protection is the thin nitride TiNx with high surface quality and a gas‐saturated layer. Nitriding in graphite powder effects positively the protective properties of nitride coatings due to reducing the nitride‐forming process. 相似文献
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目前重载齿轮常用的表面热处理工艺有渗碳淬火、感应淬火以及渗氮处理等,渗氮处理由于畸变小、工序简单等优点在工业生产上具有很大的优势和广阔的应用前景。通过增加渗层深度以及提高基体硬度能够有效提高渗氮齿轮的承载能力,从而扩大渗氮处理在重载齿轮上的应用。介绍了渗氮处理对齿轮的接触疲劳强度和弯曲疲劳强度的影响,以及基体性能对渗氮工艺的影响,回顾了渗氮齿轮的研究进展,如渗层可控离子渗氮、稀土催渗、时效硬化渗氮钢等,指出提高渗氮齿轮承载能力的途径为,深入进行渗氮齿轮的基础性研究,提高渗氮过程控制水平以及积极开发新工艺等。 相似文献
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In this study, the forging processes of spur gears have been investigated. The forging processes of spur gears have been classified into two types of operations, guiding one and clamping one in this investigation. Two types of forging have been analyzed by using upper bound method. The relative average punch pressure have been calculated and compared with each others for various modules and numbers of teeth on the forging of spur gears. The forging experiments were carried out with a commercial aluminum alloy. The predicted forging loads obtained by the present upper bound methods are shown to approximate to the experimental results at final filling-up stage. The forged parts obtained through the guiding type forging were compared with those obtained through the clamping type forging. 相似文献
13.
Forging tools are often showing short lifetimes compared to cold forming tools e.g. for sheet metal forming. This is based on the process conditions where high local surface temperatures are alternating with chilling conditions due to the spray cooling with water based cooling lubricants. The resulting thermal shock is provoking fatigue of the tool material in the near surface regions. Crack initiation and crack growth due to thermal shock exposure then causes chipping of the tool steel material in the surface regions. These are starting points for extensive wear.Hardness and wear resistance of tool surfaces at elevated temperatures can be dramatically enhanced with nitriding pretreatments. This has become state-of-the-art for hot forming tool steels in many forging applications. With inappropriate adjustments of the nitriding parameters a decrease of the ductility can occur and will reduce the crack resistance of the tool surface especially under thermal shock conditions.The hot working steel DIN-1.2367 (X38CrMoV5) is currently one of the most often used chromium-molybdenum tool steels in the field of forging. Exemplary for this material is the influence of the nitriding parameters like temperature, nitrogen supply and plasma parameters on the nitriding depth, the maximum hardness and the crack sensitivity will be discussed.Nitrided samples will be investigated with methods developed for the adhesion measurement of hard coatings. It could be shown that this is also appropriate for a qualification of the crack sensitivity of tools. Comparative application tests in the production of automotive components show the influence on the wear behavior and lifetime of forging tools in an industrial environment. 相似文献
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The effect of severe plastic deformation under dry sliding friction on the structure, microhardness, and wear rate of the VT1-0 titanium subjected to gas nitriding has been studied. It has been shown that this deformation leads to the formation of a nanocrystalline structure with an α-crystal size of 10–100 nm and a microhardness of ~3.1 GPa in a surface layer up to 10 μm thick. The presence of this structure intensifies the saturation of the surface of the titanium with nitrogen in the course of subsequent gas nitriding at temperatures of 650–750°C. The formation of the nitride nanocrystalline TiN phase in the deformed titanium occurs at a relatively low nitriding temperature (700°C) and a short-term holding (2 h). The volume fraction of the nitride phase, which is formed in the layer up to 10 μm thick, reaches a few tens of percent, which leads to an increase in the microhardness of the nitrided surface of the titanium deformed by friction. Preliminary severe plastic deformation has a negative effect on the fatigue wear resistance of the nitrided titanium due to an increased brittleness of the deformed and subsequently nitrided surface layer of this material. 相似文献
17.
Friction plays an important role in metal forming, and numerical simulation of forging processes requires precise informations about the material properties and the value of the friction factor m or coefficient μ. This paper describes the T-shape compression, a new friction testing method by combined compression and extrusion of a cylinder between a flat punch and a V-grooved die. It can realize actual cold forging condition and allows measuring the friction on the cylindrical surface of the billet during forging process. The results of experiments and simulations show that the stroke–load curve and the height of the extruded part are both sensitive to friction. In order to obtain the highest sensitivity to friction, a FE parametric study of this test has been performed: it indicates that small corner radius and V-groove angle in the die should be chosen. Two commercial FE codes, FORGE 3D and ABAQUS, were used and provided very similar results for a given friction condition. Low carbon steel drawn bar with phosphate and soap coating was chosen as specimens. Friction tests with three different lubrication conditions (solid coating, oil and oil + solid coating) were carried out, and then friction factor m and friction coefficient μ were determined by using experimental results and the calibration by numerical simulation of T-shape compression test. 相似文献
18.
D.J. Politis J. Lin T.A. Dean D.S. Balint 《Journal of Materials Processing Technology》2014,214(11):2248-2260
This paper introduces a method for the production of bi-metal gears using the forging technique. To study the process, model materials of copper (tooth ring material) and lead (core material), were used for both experimentation and simulation. Firstly, experimental setup and test procedures are introduced and the bi-metal gears are forged with different thicknesses of the outer ring material. A simplified FE model is established based on the symmetry of a gear forging process, which enables the 3D FE analysis to be carried out in an efficient manner. The material flow and thickness distribution of the experimentally forged bi-metal gears are analysed and compared with FE predictions. The effect of friction on the axial lock caused by the material flow of the forged gears is also studied. Finally, simulations of different combinations of the inner core and outer ring materials, specifically steel (ring material), copper (ring and core material) and lead (core material) are performed. The numerical and experimental data showed that: thin rings can deform excessively, affecting the structure of the gear; and that both tooling friction and flow stress can significantly affect the relative material flow between the core and the ring. 相似文献
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Friction welding of cast Fe-28Al alloy carried out for different times under constant friction pressure, forging pressure, forging time, rotational speeds. Shear strengths and hardness values of weld interface identified and microstructure properties of the welded samples were investigated by optical and scanning electron microscopy (SEM). Experiments results demonstrated that the shear strengths of the welds were higher than the base metal, very close to each other and independent of the process time. 相似文献