Neue Entwicklungen auf dem Gebiet der Schweißtechnik

Recent Development in the Field of Welding Technique. Because of important advantages as soundness of gap, no overlapping and possibility of mechanization the welding procedure takes a considerable plave in the wide field of joint techniques. Often the mechanical properties of the weld metal exceed the values of the base metal. The following report describes recent welding techniques: welding with cored-wire electrodes, the narrow-gap-welding and electron-beam welding at atmosphere. This procedures are often used for the welding of new grades of materials.     

Schweißtechnik im Chemie-Anlagenbau. Beispiele zur Auswahl und schweißtechnischen Verarbeitung der Werkstoffe im Hinblick auf ihre Betriebsbewährung

Welding Engineering in Chemical Systems Construction – Examples for Selection and Welding Processing of Materials as to Their Operational Verification Welding manufacturing occupies undoubtedly a key position in the construction of chemical apparatus and systems. It is possible to application-specifically select out of a variety of structural materials and welding fillers. Corrosion resistance, thermal and mechanical characteristics, especially any differences in the time-history of loading are the crucial criteria. In addition, the effects of welding on the material properties must be considered. Below examples will be given as to material criteria concerning specifications and selection, but primarily with respect to the corrodibility of stainless CrNi(Mo) steels and the appropriate welding fillers.     

Innovative magnesiumgerechte Gießtechnik

Innovative Magnesium adepted Casting Technology A main reason for the relatively small use of magnesium alloys as construction material is the demanding casting technology. The reactivity with ambient atmosphere and several other materials, the low specific heat values like heat capacity and heat of fusion, the small melting range and comparatively high liquidus temperatures of alloys with improved properties demand the optimizing of excisting and development new casting processes. In the scope of the Thrust Research Program SFB 390 “Magnesium Technology” founded by the German Research Council (DFG) the project B10 “Casting Technology” is engaged in the development and optimisation of casting techniques for Mg‐alloys. The emphasis of the developments in the Institute of Materials Science (IW) of the Universtity of Hanover is set on reliable, low contaminated processes of melting, melt handling and mould filling for the production of low defect structural components, even dealing with alloys difficult to handle.     

Modellierung des Ermüdungsrisswachstums in Schweißverbindungen unter Berücksichtigung von Schweißeigenspannungen

The present paper contains research results determined within the framework of a project called IBESS (?Integrale Bruchmechanische Ermittlung der Schwingfestigkeit von Schweißverbindungen“) by the Materials Mechanics Group of the Technische Universität Darmstadt [1]. Aim is to calculate the fatigue life of welded joints by taking into account the effect of residual stresses and the influence of the weld toe geometry. Here, the fatigue life is regarded as period of short fatigue crack growth. Two and three dimensional finite element models, with cracks as initial defects, are constructed for this purpose. Fatigue crack growth analyses are performed by using the node release technique together with the finite element program ABAQUS. The welding residual stresses as well as the plasticity induced crack closure effects are considered. Structural calculations are performed in order to introduce residual stress fields in finite element models. The calculated compressive residual stress field matches the measured one especially in the weld notch area. The effective cyclic J‐integral (ΔJ_eff) is used as crack tip parameter in a relation similar to the Paris equation for the calculation of the fatigue life. For this purpose, a Python code was written for the determination of ΔJ_eff at every crack length phase. The calculated fatigue lives were compared with experimental data and a good accordance between both results was achieved. The impact of welding residual stresses on ΔJ_eff as well as on the fatigue life during short crack growth was investigated. As expected, results revealed that at lower stress amplitude, a compressive residual stress field is favorable to the fatigue life, whilst a tensile residual stress field is unfavorable. The influence of residual stresses can be neglected only for large load amplitudes.     

Neue Trends in der Vakuummeßtechnik

There are no spectacular and innovative changes with regard to the vacuum process control technique. It is rather about minor improvements and modifications produced by developments, standards, improvements in process etc. This statement applies for all pressure respectively working ranges between atmospheric pressure and XHV.     

Schwingfestigkeitseigenschaften von Schweißverbindungen hochfester,schweißgeeigneter Baustähle

Fatigue strength properties of welded joints of high-strength weldable structural steel. Particularly with regard to weld joints, high-strength and super high-strength structural steels under unfavourable boundary conditions is hardly superior to normal-strength characteristics of butt joint and cruciform joint samples can be improved by optimizing the weld seam geometry and by subsequent mechanical treatment by shot peening with ceramic balls or with steel scraps, and at determining which difficulties may occur during this process. The practical tests were supported and completed by theoretical calculations according to the FE-method. A final comparison with the standards will illustrate the difficulties in determining admissible fatigue strength values of weld joints.     

Herstellung metallischer Turbinenbauteile nach der PM-Spritzgießtechnik

P/M Injection Moulding of Metallic Turbine Ports The well known injection moulding technique of ceramic components has been modified for the fabrication of metallic turbine parts. Commercially available super alloy powders, mainly Merl-76 and Udimet-700 were used. The following results have been obtained. Super alloy powder <45 µm can be used with PM injection moulding. After containerless HIP-treatment densities near 100% have been achieved. The tensile strength of the parts meet the requirements, when the surface roughness is reduced by mechanical treatment. The oxygen and carbon content in the finally produced parts is relatively high. But the distribution of the non-metallic inclusions is fine and uniform. So high strength values could be obtained.