Elektrodenauswahl für das WIG‐Unterwasser‐Schweißen

Selection of electrode for GTA‐Underwater Welding Reproducible good weld quality and economical benefit of underwater‐welding require a complete automation. For this purpose Gas Tungsten Arc‐welding (GTA or TIG) offers numerous advantages, especially for the root and the following hot pass run. Disadvantages of GTA‐welding are the low weld deposit rate and the limited lifetime of the tungsten electrode. Already small wear damages cause wide alterations of the arc under high surrounding pressure, so that a suited choice of the electrode enables to increase the productivity considerably. Therefore the influence of the electrode features on welding process, arc stability, arc ignition, weld geometry and electrode wear has been investigated. For quick and elementary selection of electrode an assessment catalogue was elaborated.     

Die Anwendung von Schallemission für die Schweißnahtkontrolle

The use of Acoustic Emission as a weld Quality Monitor . The results obtained from our experiments with spot welding, gas tungsten-arc welding, and submerged-arc welding demonstrate the potential of acoustic emission monitoring as a nondestructive test for welds. The real-time nature of the acoustic emission data sets this technique apart from other nondestructive methods used for weld inspection. Since the acoustic emission from weld defects is transient, empirical calibration is required for each application. Defects can be located approximately but the type of defekt cannot be determined.     

Neue Steuerprinzipien für das Reibschweißen

New adjustments for friction welding of different solids The article describes the laws of most favourable selection system by friction welding of different materials. The aim is the welding, with a minimum of energy, time and other burden world's around, when the retail trade is slightly for important and different materials in the industries productions. However, the terms Friction Moment and Temperature are significant for Action one the surfaces of the partners. The article shows the development of Friction Moment in the time and gives points for the estimation optimal parameters for friction welding. Most importent variables are the differential coefficient the Friction Moment, the Temperature, the waste and the efficiency. The last term is the area between funktion M and time axis. The author shows that the term $ \frac{{{\rm dM}}}{{{\rm dt}}}\,{\rm R}\,{\rm or}\,\frac{{{\rm dT}}}{{{\rm dt}}}\,{\rm R} $ are going through a maximum and then in a low material. The friction welding is perfect by optimal conditions.     

Schweißen von Hohlstrukturen und offenporösen Metallschäumen für den Einsatz in Kombi‐Kraftwerken

Welding of Hollow Structures and Open‐Porous Metal Foams for Application in Combined Cycle Power Plants For applications within the scope of novel cooling concepts joining technologies for sandwich composites and open‐porous metal foams are researched in the context of the Collaborative Research Centre 561 “Thermally highly loaded, porous and cooled multi‐layer systems for combined cycle power plants”. The research motivation and application fields of the different structures are defined. Welding processes and strategies for manufacturing these structures are specified as well as the joining technologies’ characteristics. Planned future works for enhancements of the processes and structures are listed.     

Untersuchung verschiedener Schweißverfahren für die Nickel-Basislegierung NiMo 16 Cr 16 Ti

Investigation of Different Welding Processes with Nickel-Alloy NiMo 16 Cr 16 TI The overall favourable corrosion resistance of the nickel-chromium-molybdenum alloy NiMo 16Cr 16 Ti against attack by powerful oxidizing acids ensures a wide field of applications for this material. The alloy is readily processable using encased rod electrodes and shielded are welding. However, shielded arc welding should be given preference, as there are considerable differences in the analytical results between smelted welded material from encased rod electrodes and bright rods and wires. The different welded materials influence the corrosion resistance and the possibilities of forging welded constructions.     

Messung der Schweißkraft,des Abbrandes und des Kontaktwiderstandes von Kontaktwerkstoffen für die Energietechnik

Measuring of welding force and contact resistance with a testing equipment to classify contact materials for power engineering . Knowledge regarding welding force, erosion and contact resistance is very essential to select and evaluate contact materials which are to be used in electric switchgear. Measuring systems and results which are found in the literature are mostly carried out under test conditions not close enaugh to practice. An automatic test switchgear with which the mentioned technological characteristics can be evaluated is described. Test conditions can be varied in a very wide range so that every condition can be selected suiting the switchgear. Data on welding force, erosion rate and contact resistance of the contact materials like Ag 1000, AgNi 10, AgCdO 12 and AgC3 are given. A statement on the quality of braze between contacts and carrying material can be given.     

Elektronenstrahlschweißen von Weichenherzen für den Gleisbau

Electron Beam Welding of Switch Points for Railway Tracks By means of computer simulation a temperature curve has been evaluated, which avoids formation of martensitic structures and subsequent hardening effects.     

Zum Einfluss des Schweißens auf das Kriechverhalten moderner Stähle für die thermische Energieerzeugung

The influence of welding on creep behaviour of modern steels for thermal power generation Un‐ and low alloyed ferritic/bainitic Chromium steels as well as high alloyed ferritic/martensitic 9–12 % Chromium steels are widely used for high temperature components in thermal power generation. Welding in all its variety is the major repair and joining technology for such components. The weld thermal cycle has significant influence on the base material microstructure and its properties. The Heat Affected Zone is often regarded as the weakest link during high temperature service. While weldments of un‐ and low alloyed ferritic Chromium steels can show significant susceptibility to Reheat Cracking in the coarse grained heat affected zone, weldments of high alloyed ferritic Chromium steels generally fail by Type IV Cracking in the fine grained heat affected zone during long term service. In this paper the influence of the weld thermal cycle on the base material microstructure is described. Long‐term creep behaviour of weldments is directly related to the main failure mechanisms in creep exposed ferritic weldments and implications for industries using heat resistant ferritic steels are shown.     

Erfahrungen beim Schweißen gasempfindlicher hochreiner Werkstoffe

Experiences in Welding Highly Pure, Gas-Sensitive Materials Highly pure steels and non-ferrous react during processing, particularly welding, with atmospheric gases and change their service properties. Hence special measures are often necessary in forming and inert gas welding. Taking the specific example of a high pure chromium steel (superferritic), welding properties, processing data and selection of suitable inert gas torches are described. The possibility of applying this information to other materials such as titanium is discussed.     

Schweißen mit dem Laserstrahl im Vakuum

Welding with the Laser Beam in Vacuum In the vehicle industry, beam welding methods are successfully applied for the joining of high‐quality parts. Here, the focus is mainly put on drive section components. Especially in component manufacturing of couplings, toothed wheel – shaft joints and drive shafts, electron beam welding using small vacuum cycle chambers is applied. The application of powerful solid‐state lasers results, however, often in negative consequences, such as soiling by process emissions or increased tendency to spatter. The application of laser beam welding in vacuum allows for the reduction of these side effects and, at the same time, for the increase of penetration depth and weld quality. This article introduces first results gained from tests made with workpieces from the vehicle industry.     

Schwellwert für Ermüdungsrißausbreitung: Bestimmungsmethoden,Kennwerte, Einflußgrößen

Threshold for Fatigue Crack Propagation: Experimental Procedure, Characterizing and Influencing Parameters For the determination of a fatigue crack propagation threshold there exists no “Standard” or other generally accepted experimental procedure. The threshold behaviour of “long” cracks can be characterized by threshold ΔK_th determination as a function of R as well as a function of K_max. The experimental determination of ΔK_th with constant K_max is simpler and a plot of the results versus K_max represents the threshold behaviour of a material more accurate. The whole threshold behaviour is characterized by three parameters. These three parameters can be obtained with relatively little experimental expenditure. The influence of certain conditions, i. e. material, microstructure, environment, ect., on the threshold ΔK_th are discussed. It seems that for a particular material and environment only two of these parameters can be considered as material properties. Test results show that with large change of amplitude ΔK fatigue cracks can grow still at ΔK smaller than ΔK_th. But after some growth, fatigue crack propagation ceases.     

Empfehlungen zur Werkstoffauswahl und zu den Schweißdaten für NH3-Lagerbehälter und NH3-Kesselwagen

Recommendations for Selection of Material and welding Electrodes for NH₃-storage Vessel and NH₃-Transport Container In liquid ammonia mostly only weld seams show cracks. Extensive SEM-investigations have shown that these are hydrogen induced cracks. During weld tests with the base materials St E 335 and St E 460 in different charges high yield strengths were determined in the weld material. Very often the yield strength values increase after stress relieving. This is caused by precipitation, which leads to a bracing of the lattice, thus raising the yield point. To ensure one of the base material adapted yield strength in the weld it is only possible in very rare cases with suitable weld additives. In the St E 460 with nitrogen and vanadium the yield strength value in the weld is even by use of the wire S 1 and neutral powder over 600 N/mm². It was found out that hydrogen induced cracks in the weld above 550 N/mm² yield strength occur very likely below 550 N/mm² occur very little. In the base material St E 355 the yield strength was limited for this reason in the weld with 500 N/mm² in the base material St E 460 limited with 550 N/mm². Proof has to be furnished for all welding procedures, sheet charges and weld additives applicable by means of welding probes.     

Schweißen im Behälter- und Apparatebau

Welding in Tank and Plant Construction Since a relatively limited number of plastics types are used, the welding tasks involved in chemical apparatus engineering can be accomplished with just a few welding techniques are well-known and welding can be carried out efficiently, reliably and economically by this means. In this respect, however, a number of important principles have to be observed. The DVS guidelines provide vital information on questions relating to calculation, design, personnel, equipment, material and testing. Extrusion welding enjoys prime importance as regards quality and economic aspects.