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The method of experimental evaluation of the temperature in the penetration channel in electron beam welding is described. The method is based on measuring the concentration of vapours above the zone of interaction of the electron beam with the metal by chemical analysis of a metal layer sprayed on a substrate. The experimental values of temperature are compared with the results of calculations carried out using the model based on the examination of the equilibrium of an element of the wall of the penetration channel. 相似文献
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The problem of producing multi-seam components by electron beam welding is investigated. It is shown that if the variation of temperature after welding the first joints is not taken into account and subsequent welded joints are produced in the same conditions, the depth of penetration increases. This has been confirmed by experimental results. To ensure the same depth of penetration in producing several welded joints in the same component, the second and subsequent welded joints should be produced in the corrected conditions after equalizing the temperature throughout the entire volume of the component. A method is proposed for calculating the electron beam welding conditions of consecutively produced welded joints and the holding time of the component to ensure equalization of temperature. 相似文献
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Modelling and simulation of electron beam melting 总被引:1,自引:0,他引:1
In recent years, the scientific and industrial relevance of additive layer manufacturing (ALM) has grown. In the metal area
of ALM, the capacity of laser technologies is noticeably limited. This is mainly due to an inertial beam deflection device,
which is also referred to as a mirror galvanometer. In contrast, the electron beam technology offers high power density as
well as considerable scanning rates. Therefore, electron beam melting (EBM) seems to be suitable for processing a broad variety
of alloys in an economic way. In particular, the enormous scanning rates which can be realized by use of an electron beam
enable an economic manufacture of high quality parts. However, profound expertise is required in order to establish EBM as
an industrial production technology. By means of mathematical–physical modelling, process stability of the melting step is
being increased. Moreover, by solving a detailed thermal model using the finite element method (FEM), substantial knowledge
of adequate parameter settings in dependence of the utilised material is developed. Finally, a process window as a function
of scan speed and beam power is developed based on experimental results. 相似文献
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Conformation and oxidation transformations in cis-polyacetylene films irradiated by an electron beam
《Synthetic Metals》1997,90(2):89-92
The effect of an electron beam irradiation on cis—trans isomerization and oxidation in polyacetylene films is studied by IR spectroscopy. It is found that the irradiation treatment of the films results in the stabilization of the initial cis-conformation of polyacetylene and the decrease of the oxidation destruction of polymer chains. The effect of the conformation stabilization is most clearly seen in a long-duration storage of irradiated films under inert atmosphere at low temperatures. This effect is significantly less pronounced at high temperatures. The increase of the conformational stability of the irradiated polyacetylene films is supposed to be caused by the formation of transverse crosslinkages between the chains under irradiation. 相似文献
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针对电子束焦点难以直接测量的问题,提出一种利用电子束流与金属粉末相互作用产生的熔池温度极值效应测量电子束流焦点的方法.文中分析讨论了电子束流焦点位置的影响因素,通过试验研究了电子束加热过程中粉末熔池温度与聚焦电流的函数规律,发现温度—聚焦电流关系函数的极大值即为聚焦电子束能量密度分布状态的临界转变点.基于扫描电子束粉末烧结过程的这种临界温度特性,提出了一种测量电子束加工过程动态焦点的方法,即变焦-临界温度极值检测的焦点测量法.结果表明,这种方法可以实现电子束焦点位置的快速、高效地检测与定位控制. 相似文献
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《Science & Technology of Welding & Joining》2013,18(7):614-619
AbstractElectron beam welding (EBW), as a high performance welding method, is also subject to requirements of high integrity welds which particularly include residual stresses affecting distortion and fatigue behaviour. In this context multiple beam technique may provide new applications of specific thermal weld treatment. The present work introduces a promising method of local post-heating in a certain distance to the current welding location applying multiple beams for the reduction in residual stresses in EB welded sheet metals. The conducted investigations include finite element analysis (FEA) and stress measurements in the weld seam area. Using a systematic approach within the FEA decisive process parameters are optimised with reference to the achievable reduction in residual stress. All simulation results are validated by experiments applying strain gauges for the stress measurement. Both simulations and experiments revealed a considerable decrease in residual stress achievable by appropriate positioning of additional heat sources combined with the right power input and beam focusing. 相似文献
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进行了Ti80大厚板电子束焊接试验,实现了56 mmTi80无缺陷焊接.分析焊缝和热影响区精细组织,结果表明,焊缝上部为柱状晶粒,下部为柱状晶和等轴晶,晶粒内组织为马氏体α相和残余β相.焊缝由上至下高温停留时间逐渐减小、冷却速度逐渐加快,马氏体α相呈长大趋势.热影响区分为靠近焊缝区的Ⅰ区和靠近母材的Ⅱ区.热影响Ⅰ区组织为马氏体α相、初生α相和β相;Ⅱ区组织为初生α相、次生α相和转变β组织.Ⅰ区由于受热影响作用大,其组织更接近于焊缝;Ⅱ区组织则更接近于母材组织. 相似文献
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I. M. Poletika T. A. Krylova Yu. F. Ivanov M. G. Golkovskiy V. D. Kitler A. D. Teresov S. A. Makarov 《Protection of Metals and Physical Chemistry of Surfaces》2012,48(2):221-232
In this work, electron beam welding by electron accelerator of tungsten and chromium carbides and subsequent pulse processing
by low-energy electrons has been applied for fabrication of nano- and ultradisperse grain structures penetrated by the system
of nanosized pores. It has been demonstrated that, in the region of secondary pulse exposure, the nanohardness and elasticity
modulus achieve high values. The wear resistance of the modified structure depends on the value of the specific load in the
vicinity of contact with indentor. 相似文献
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针对电子束选区熔化成形技术中存在的真空辐射环境及表面不允许破坏的情况,提出热电偶测温和数值模拟相结合测温的方法对经电子束预热处理的底板表面温度进行测量.热电偶测温为数值模拟中电子束热效率、电子束作用深度和底板厚度三个因素的水平进行优化,从而得到合理的数值模拟程序,并利用该数值模拟程序和优化的因素水平对底板表面温度进行合理的预报.结果表明,采用数值模拟及热电偶底面测温相结合可以得到精确度较高的表面温度,底板表面温度达到钛合金粉末烧结温度800℃时的电子束预热时间为1 600 s. 相似文献
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Electron beam welding experiments on 2.5-mm-thick as-forged Ti–43Al–9V–0.3Y intermetallic plates were carried out. Cold cracking occurred in the direct electron beam welding joints because of the brittleness of the microstructure and the residual stress. A crack-free electron beam welding joint was obtained by a new composite control method. This process can prolong the high temperature stage to promote the phase transformation and to give the expected microstructure of the joint. The microstructures and tensile strengths of the joints were examined by TEM, X-ray diffraction, electron back scattering diffraction and universal test machine. The weld obtained by the composite control method was characterized by an analysis of the combined phase structure of the γm grain and the γ/α2 colony microstructure. The tensile strength of the joint that was obtained by the composite control method was found to be 411.3 MPa, which is 20% higher than the direct welding joint. 相似文献
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应用自主开发的基于虚拟仪器的电子束钎焊系统,成功实现了不锈钢毛细管板接头的电子束钎焊。研究了电子束束流、加热时间、聚焦电流和扫描幅值等电子束钎焊工艺参数对钎焊接头质量的影响规律。试验结果表明,随着电子束输入功率密度的增加,钎角高度和BNi-2钎料向毛细管壁的扩散深度都逐渐增大。在优化的电子束钎焊规范下,不锈钢管板接头钎透率100%,毛细管无溶蚀产生。通过电子探针显微分析仪研究了电子束钎焊接头中各相的化学组成,钎焊接头主要由硼化镍相、硼化镍和硅化镍相、硼化铬相以及镍的固溶体组成。 相似文献
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The electron beam welding-brazing being used to join 5A06 Al alloy to TC4 Ti alloy decreases the formation of brittle intermetallic compound. Experiments were carried out to study the influence of electron beam welding parameters on the tensile strength of welds, based on an orthogonal test and analysis method. The welding parameters include beam current, welding speed, scanning figure, scanning frequency, figure size, beam offset and focus current. The optimum parameters for 3 mm 5A06 Al alloy and 2 mm TC4 alloy were as follows: acceleration voltage was 60 kV, beam current was 11 mA, welding speed was 600 mm/min, focus current was 0 mA, scan figure was ○, scanning frequency was 1 000 Hz and beam offset was 0.5 mm. The results show that the joints were with good appearance and quality welded by the optimum parameters. The successful joints could be gained and the maximum tensile strength of Al/Ti dissimilar alloy joints could be up to 222.61 MPa using electron beam welding-brazing. 相似文献
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Surface finishing of stainless steels for orthopedic surgical tools by large-area electron beam irradiation 总被引:1,自引:0,他引:1
Surgical tools and jigs are initially machined by multi-axis milling. Then surface finishing is carried out mainly by hand lapping. As these tools undergo repeated use, the removal of burrs, scratches and rust from the surfaces is also performed manually after each operation. These finishing processes are time-consuming and costly. In this study, a new finishing method by large-area electron beam irradiation is proposed. Electron beam (EB) with high energy density can be obtained without focusing the beam, and large-area EB can be used for instantly melting or evaporating the metal surface. Stainless steel for surgical tools and jigs was treated by the large-area EB irradiation method. The experimental results show that highly efficient surface smoothing of stainless steels by large-area EB irradiation may be achieved. In addition, the resistance to corrosion and blood repellency can be improved simultaneously with surface smoothing. 相似文献
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对5种不同丝束空间位向关系下的焊接稳定性及焊缝成形特点进行了研究.结果表明,丝束空间位向关系通过影响焊接过程热量分配及焊丝熔化过渡特性,进而影响焊缝成形.自熔焊、丝束分离及丝束部分相交时,焊接过程稳定,焊缝成形良好,而丝遮挡束与非接触过渡条件下焊接过程不稳定,焊缝成形较差.熔深从大到小规律为自熔焊,丝束分离,丝束部分相交,丝遮挡束,非接触过渡丝束关系;除非接触过渡下的熔宽最小之外,其它关系下熔宽相当;余高从高到低规律为非接触过渡丝束关系,丝遮挡束,丝束分离,丝束部分相交,自熔焊. 相似文献
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