Eigenschaften verschiedener Kontaktwerkstoffe für Schaltgeräte der elektrischen Energietechnik und deren Gefügeänderungen durch Lichtbogenbelastung

Properties of Different Contact Materials for Electrical Switchgear and Changes in Structure due to Arcing . Due to arcing during switching operations the microstructure of the material below the contact surface is converted. After the contacts have been used in switching their properties are determined to a great extent by the contact microstructure so formed. By means of a test switching apparatus the contact properties of the materials pure copper and pure silver produced by melting and of AgNi 10, W Ag 35 NiCuT, AgCdO 12 and AgC 3 produced by powder metallurgy were investigated during making operations and alternating making and breaking. Microsections from the used contacts were prepared perpendicular to the contact surface to evaluate the contact microstructure. Considerable differences occur in the contact microstructure depending on the type of material and switching. The contact properties welding force, contact erosion and contact resistance are affected so much by the breaking operation that it can result in a reversal of the tables of materials. In selecting a contact material with a test switching apparatus for use in a specific type of switchgear the contact properties must therefore be acquired simultaneously as a measurement series during test conditions related to the application.     

Einflußgrößen auf die Schweiß;kraft elektrischer Kontaktstücke in der Energietechnik

Parameters Influencing the Welding Force of Electric Contacts in Power Engineering . Main parameters influencing the accumulated frequency distribution of the welding force using bouncing contacts are: contact force, closing velocity, duration of bouncing, number of operations, testcurrent, phase displacement, frequency, moment of contact in relation to current zero at inductive load. The statistical distribution over a wide range of the values of the welding force is traced back on the relative position of the weldings on the surfaces of the contacts by means of a model. The influence of duration of bouncing, number of operations, contact force, opening velocity, value of test current and polarity on the welding force is described by accumulated frequency distribution plottings for various contact materials when making contact synchronous- and asynchronously.     

复合材料层合板准静态压痕实验研究

采用准静态压痕(QSI) 实验方法针对多种材料对集中准静态压痕力的损伤阻抗进行了测试。选取2 个特征载荷下的试样进行了超声C 扫描探伤和扫描电镜(SEM) 显微观察, 分析了QSI 实验中层合板的损伤过程, 针对初始分层接触力f₁和最大接触力f₂对材料的损伤阻抗特性进行了分析。测试了2 种材料体系层压板的最大接触力, 发现该值具有较好的可重复性。研究了测试条件(试样尺寸和支持条件) 和材料特性(不同纤维、基体种类和铺层方式) 对最大接触力的影响。实验结果表明, 试样尺寸和支持条件对最大接触力的影响较小, 在必要时可以采用非标试样测试最大接触力, 而最大接触力与树脂基体、纤维特性及铺层方式都有关, 最大接触力对应的凹坑深度d₂主要由纤维强度和延伸率决定, 树脂特性对d2有影响但影响程度较小。      

Failure analysis of CuW/CuCrZr contact materials in capacitor bank switch

The type test of CuW/CuCrZr arc contact used for ultra-high voltage system capacitor bank switch was conducted. Through the comparative analysis of morphologies, compositions, properties and microstructures of the contact materials before and after failure, it can be found that the abnormal open of moving arc contact and the arc erosion and mechanical wear of static arc contact are the major reasons affecting the arc contact failure. The failure mechanism and main affecting factors were investigated in detail. The results showed that arc erosion and mechanical wear are the two main factors that affect the service lifetime of arc contacts used for ultra-high voltage transmission lines and cannot be ignored. Therefore, improving the arc erosion resistance and mechanical wear resistance simultaneously is the key to prepare the arc contact materials with longer lifetime.     

Laserakustik für Schicht‐ und Oberflächenprüfung

Laser‐acoustics for Testing Coatings and Material Surfaces A laser‐acoustic test method is presented, which can be used for the non‐destructive characterization of coatings and material surfaces. The method measures the dispersion of surface acoustic waves induced by short laser pulses. The technique is based on the fact that the propagation velocity of the wave depends on the frequency in coated and surface modified materials. Measuring the dispersion of the surface acoustic wave enables to determine important properties of the material surface. Three examples demonstrate that the laser‐acoustic method can solve very different problems of surface engineering. The wear resistance of diamond‐like carbon film with a thickness of few nano‐meters was evaluated. The elastic modulus of thermally sprayed coatings which are typically some hundred micro‐meters thick was measured, which allows to conclude on the defect structure of the coatings. The depth of sub‐surface damage layers in semi‐conductor materials was determined, which are created when the wafer is sliced from the ingot.     

Grundlagen der Werkstoffauswahl bei der Bekämpfung des Strahlverschleißes

Fundamentals of Material Selection in the Conditions of Erosive Wear Problems of proper selection of materials for parts subjected to wear by a stream of abrasive particles are discussed. Considering the main laws governing such kind of wear, the author concludes that target material selection in the case of erosion, like in any other case of abrasive wear, will depend on the ratio of abrasive grain hardness to material hardness. Special attention should be given to hard components in the abrasive. It has been established that a 10-15% content of quartz particles in the abrasive is enough to cause an abrupt fall in the wear resistance of chilled steels, white iron and hard surfacing alloys, thus making their use questionable. Finegrained WC-Co-type sintered carbides have shown the highest wear resistance in such conditions. The conclusions drawn in this paper are borne cut by a considerable body of experimental data.     

Laserstrahlschweißen von Titanwerkstoffen unter Berücksichtigung des Einflusses des Sauerstoffes

Influence of the oxygen content in the shielding gas on microstructure and mechanical properties of laser welds of titanium and titanium alloys In the present work, a new tool concept for laser welding of titanium in high volume production has been presented and evaluated. Through the innovative application of a six‐layer metal web it is possible to calm the argon gas flow and avoid pernicious turbulences during welding. The integration of the mentioned metal web at the base of an open welding chamber allows the automated welding of highly reactive materials, such as titanium, under atmospheric pressure and inert shielding conditions. The higher density of argon relative to air offers the unique possibility to leave the chamber open on the top, so that a higher degree of flexibility than gas shielding devices for TIG welding, especially for industrial robots, is attained and can be successfully used for industrial mass production. Furthermore this device is important for welding three‐dimensional contours or to shield the regions of overlap (in overlapped joints) where shielding gas trailers are unsuccessful. By means of the presented gas shielding procedure and a modern laser welding process such as Nd:YAG laser welding, systematic investigations on the effect of oxygen on the microstructure as well as on the mechanical properties of reference bead‐on‐plate weldments could be performed for the first time. As a result of these welding trials it can be concluded that in order to avoid discolorations and hardness increase, lower restrictions to the purity of the shielding gas, in comparison to TIG welding condition, can be allowed. The maximum tolerable value of oxygen in the welding atmosphere was found to be approximately 1000 ppm for laser welding. On the contrary the maximum value for TIG welding is about 30 ppm. Further investigations on the microstructural and mechanical properties of the joints confirm that the optical quality assurance criteria for TIG welding due to the standards of aircraft construction transferable to Nd:YAG welding are.     

Ultraschallschweißen von Kontaktwerkstoffen

Ultrasonic Welding of Contact Materials . Ultrasonic welding of metals has found only a few industrial applications until now. Today however ultrasonic welding equipments with high power output for the welding of thicker parts are available. Contact materials have been welded ultrasonically on various base materials, e. g. silver and silver alloys on copper and copper alloys and aluminium. Bond quality was determined by shearing off the contact plates from the base material. Metallographic investigations and microhardness measurements were made to examine the bonding mechanisme. Ultrasonic welding will be a very good supplementary method in contact technology mainly for the welding of hardly weldable components like AgCdO or Al.     

复相增强AgMeO电触头材料的研究进展

由于良好的抗电弧侵蚀性、抗熔焊性及耐电磨损性,AgMeO电触头材料在电器工业中得到了广泛应用。目前,单一强化相增强银基电触头材料的研究已经基本成熟,但很难提高其综合性能;虽然复相增强银基电触头材料的研究尚不够深入,但已经表现出巨大的研究潜力,因此复相增强银基电触头材料成为研究热点。本文概述了复相增强银基电触头材料的研究现状与成果,同时对复相增强电触头材料的发展方向进行了展望。     

Problemlösungen durch Schichtverbundwerkstoffe in der Elektrotechnik

Clad Metals for Electrical Engineering . Materials with optimum properties for conducting springs can be produced by cladding a metallic sheat of high electrical conductivity between two sheats of a metal with high stiffness. Using suitable cladding components, thermo bi metals with different electrical resistance can be produced without essential variation of deflection and force. With this it is possible, to use groups of devices with uniform mechanical construction for different currents, which means a good technical as well as economic solution. High prices of noble metal based contact materials have led to the production of contact bimetals some years ago. Inspite of higher production costs these materials can be used very economically.     

Untersuchung des Erosionsverhaltens von silberbasierten Kontaktwerkstoffen mittels FIB‐Techniken

Microstructure investigations and arc erosion behaviour of silver‐based contact materials by focused ion beam technique The understanding of the degradation mechanisms of contact materials is a key issue for the development of new materials with enhanced durability. This can be achieved through the investigation of the microstructure modification caused by electrical arcs on the surface of contacts. In this work, the erosion behaviour of pure silver and silver based composites as well as the characterization in two or three dimensions is presented. Single breaking operations were performed with direct current. Using white light interferometry, the size of the craters on the surface as well as the volume of eroded material has been measured. By means of dual beam techniques, the microstructural modifications in the crater have been investigated and reconstructed in three dimensions.     

银钨触头材料的制备工艺及使用性能

银钨触头材料目前应用较为广泛,具有良好的导热和导电性能、耐电磨损性能、抗熔焊性能、抗氧化能力等优点.详细叙述了制备银钨触头的熔渗法和机械合金化法,并对两种方法作了一些理论上的分析.对银钨触头的熔焊特性、电弧侵蚀机理以及腐蚀机理进行了探讨.     

Welding of dense alumina and aluminium by plastic deformation and diffusion

The development of a welding system which makes it possible to obtain a close joining of two very different materials is described: high density (low porosity) alumina and aluminium alloy. To determine the characteristics of the contact area, optical microscopy was used, whereas energy dispersive spectroscopic (EDX) microanalysis was employed in the study of the atom diffusion that may take place through the metal-ceramics interface. The Hopkinson bar was used to test the joint resistance in an impact test.     

Investigating the temperatures of contact elements on separation

Solutions are presented for the heat-conduction equations of the liquid-bridge-solid system which is set up on separation of electrical contacts. The conditions are given for the selection of contact materials to ensure minimum erosion of one of the electrodes.     

Prediction and optimization of friction welding parameters for super duplex stainless steel (UNS S32760) joints

Friction welding finds widespread industrial use as a mass production process for joining materials. Friction welding process allows welding of several materials that are extremely difficult to fusion weld. Friction welding process parameters play a significant role in making good quality joints. To produce a good quality joint it is important to set up proper welding process parameters. This can be done by employing optimization techniques. This paper presents a multi objective optimization method for optimizing the process parameters during friction welding process. The proposed method combines the response surface methodology (RSM) with an intelligent optimization algorithm, i.e. genetic algorithm (GA). Corrosion resistance and impact strength of friction welded super duplex stainless steel (SDSS) (UNS S32760) joints were investigated considering three process parameters: friction force (F), upset force (U) and burn off length (B). Mathematical models were developed and the responses were adequately predicted. Direct and interaction effects of process parameters on responses were studied by plotting graphs. Burn off length has high significance on corrosion current followed by upset force and friction force. In the case of impact strength, friction force has high significance followed by upset force and burn off length. Multi objective optimization for maximizing the impact strength and minimizing the corrosion current (maximizing corrosion resistance) was carried out using GA with the RSM model. The optimization procedure resulted in the creation of nondominated optimal points which can aid the process operator to fix the input control variables. The selection of a point from the Pareto front will always be a trade-off between the corrosion resistance and impact strength of the weld depending on the application.     

Entwicklung,Eigenschaften, Verarbeitung und Einsatz des hochsiliciumhaltigen austenitischen Stahls X2 CrNiSi 18 15

Development, Properties, Processing and Applications of High-Silicon Steel Grade X2 CrNiSi 18 15 Production, storage and transportation of highly concentrated nitric acid (approximately 98%) frequently occur in containers and vessels made of pure aluminium. In many cases, however, their service life is restricted by the insufficient corrosion resistance of the welds. Though tantalum exhibits a superior resistance to corrosion, it is only used in very specific occasions for cost considerations. Commercial grade austenitic chromium-nickel steels as well as ferritic chromium steels assume a transpassive state under such service conditions, and suffer from intergranular attack even if the structure is free of precipitates. A significant corrosion resistance to highly concentrated nitric acid in combination with good workability and weldability can be achieved by an austenitic chromium-nickel steel alloyed with silicon. For corrosion considerations a silicon contents of at least 3,7 wt. % has to be aimed at. Since the silicon is held in solid solution in the austenitic matrix, the mechanical properties of the special grade X 2 CrNiSi 18 15 are not very different from those of commercial chromium-nickel steel grades. Welding materials of the same kind are available for manual are welding as well as for TIG welding. The corrosion resultance of the weld deposit is similar to that of the base metal. However, the tendency of this steel to precipitate intermetallic phases is increased by the silicon addition. There, a proper heat control during welding is a necessary prerequisite in order to avoid intercrystalline attack in the heat-affected zones on both sides of the weld. A silicon contents of approximately 4 wt. % not only improves the corrosion resistance against highly concentrated nitric acid but also results in a considerable improvement when this special steel is used in chromic acid solutions and hot concentrated sulfuric acid. Also the high temperature corrosion, resistance of this material is remarkable. Several piping systems, chemical equipment, pumps, and fittings have been in successfull service for several years and proved the excellent properties of the X 2 CrNiSi 18 15 specially steel.     

Entwicklung,Eigenschaften, Verarbeitung und Einsatz des hochsiliciumhaltigen austenitischen Stahls X2CrNiSi1815

Development, Properties, Processing and Applications of High-Silicon Steel Grade X2CrNiSi1815 Production, storage and transportation of highly concentrated nitric acid (approximately 98%) frequently occur in containers and vessels made of pure aluminium. In many cases, however, their service life is restricted by the insufficient corrosion resistance of the welds. Though tantalum exhibits a superior resistance to corrosion, it is only used in very specific occasions for cost considerations. Commercial grade austenitic chromium-nickel steels as well as ferritic chromium steels assume a transpassive state under such service conditions, and suffer from intergranular attack even if the structure is free of precipitates. A significant corrosion resistance to highly concentrated nitric acid in combination with good workability and weldability can be achieved by an austenitic chromium-nickel steel alloyed with silicon. For corrosion considerations a silicon contents of at least 3,7 wt. % has to be aimed at. Since the silicon is held in solid solution in the austenitic matrix, the mechanical properties of the special grade X2CrNiSi 18 15 are not very different from those of commercial chromium-nickel steel grades. Welding materials of the same kind are available for manual arc welding as well as for TIG welding. The corrosion resultance of the weld deposit is similar to that of the base metal. However, the tendency of this steel to precipitate intermetallic phases is increased by the silicon addition. There, a proper heat control during welding is a necessary prerequisite in order to avoid intercrystalline attack in the heat-affected zones on both sides of the weld. A silicon contents of approximately 4 wt. % not only improves the corrosion resistance against highly concentrated nitric acid but also results in a considerable improvement when this special steel is used in chromic acid solutions and hot concentrated sulfuric acid. Also the high temperature corrosion resistance of this material is remarkable. Several piping systems, chemical equipment, pumps, and fittings have been in successfull service for several years and proved the excellent properties of the X 2CrNiSi 18 15 specially steel.     

3D Direct Laser Writing of Nano‐ and Microstructured Hierarchical Gecko‐Mimicking Surfaces

Applying 3D direct laser writing, artificial hierarchical gecko‐type structures are designed and fabricated down to nanometer dimensions. In this way, the elastic modulus and the length scale of the gecko's setae are very closely matched. Direct laser writing is a very flexible rapid prototyping method allowing the fabrication of arbitrary nanostructures. Since the parameters of the structures can be easily changed, this technique is perfect for design studies of dry adhesives. Measuring the adhesional forces by atomic force microscopy, the influence of several design parameters like density, aspect ratio, and tip‐shape on dry adhesion performance are systematically examined. In this way, it is revealed that hierarchy is favorable for artificial gecko‐inspired dry adhesives made of stiff materials on the nanometer scale.     

Zerstörungsfreie Prüfung von Tiefspaltschweißnähten mittels Durchstrahlung und Ultraschall

Non destructive testing of Narrow-Gap welded joints using radiographic and ultrasonic methods . The intensified demand for economical sources of electrical energy has led to nuclear power plants with increasingly larger pressure vessels, particularly for BWR and PWR installations. The wall thicknesses of these vessels now exceeds 200 mm. The fabrication of these heavy structural components to close construction tolerances has required the development of economic welding processes, which in general are fully mechanised. One such process which has been successfully applied to the joining of heavy sections is Narrow-Gap welding. Investigations on Narrow-Gap welded joints using conventional nondestructive testing methods, such as radiographic and ultrasonic methods, have revealed that weld defects in these weld seams can be readily determined since for this process, the possible zones of weld failures are clearly defined over a very small region. The assessment of the test results according to accepted standards for pressure vessel construction has revealed, that providing the welding conditions are carefully controlled, acceptable weld quality is ensured.     

常用电接触材料耐腐蚀性能研究

本文用人工尘土颗粒无水亚硫酸钠对常用电接触材料的实验样片：镀金样片、镀镍样片、铜样片进行一定温湿度条件下的腐蚀实验。通过对单一实验样片的实验数据分析以及对各实验样片腐蚀后的结果对比,研究特定温湿环境下的常用电接触材料耐腐蚀性能。