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An electromagnetic system was used to reduce the porosity in laser beam welding of aluminum die casting. The difference of electrical conductivities between gases and molten aluminum is used by an electromagnetic system to displace the included gases to the top during a laser beam welding process. It bases on generating Lorentz forces within the weld pool via an oscillating magnetic field. A partial penetration laser beam welding of standard die-cast aluminum alloy AC-AlSi9MnMg in flat position is used. An optimized laser beam process was taken to investigate the porosity content and the surface smoothing by applying an electromagnetic field. The produced weld seams were analyzed in cross section views, by x-ray imaging and by computer tomography (CT). Depending on the magnetic flux density, a significantly reduction of the porosity down to 75% can be achieved. Especially big pores can be removed successfully. A surface smoothing of up to 75% can also be reached by using this system.

High-pressure die cast (HPDC) aluminum components are increasingly integrated into the assembly of vehicles for weight-reduction. Adhesive bonding of HPDC aluminum alloys with other structural parts has been ever challenging in the hybrid construction of automobiles due to the inherent contamination of casting surfaces by die lubricants. In this study, the residual lubricant on HPDC AlSi10MnMg plates was quantitatively measured using surface sensitive techniques. Chemical pretreatment processes were designed and the effectiveness of pretreatment processes was evaluated by comparison of surface morphologies and chemical compositions, as well as adhesion properties before and after aging. It is found that the initial single lap-shear strength of the as-cast AlSi10MnMg plates shows a location-dependence and is influenced by casting parameters, particularly in the regions away from the melt-ingate of the die, where a high amount of residual lubricants is often measured. Chemical pretreatments including degreasing, deoxidation and deposition of titanium-oxide conversion coatings can improve the surface homogeneity through removal of residual lubricants from and replacement of oxide layers at the surface of HPDC AlSi10MnMg alloys. The chemical treatment process consisting of degreasing in alkaline solutions, deoxidation in fluoride-containing sulfuric acid solutions and dipping in hexafluorotitanic acid solutions has been identified to be the most effective pretreatment procedure by generating a rough surface in a micro-scale, and removing residual lubricants to a large extent from as well as inhibiting corrosion at the surface of HPDC AlSi10MnMg plates. The effectiveness of this pretreatment process was also confirmed by durability assessment of epoxy-bonded single lap-shear joints and wedge specimens after environment exposure to 70 °C, 100% R. H. for 4 weeks.

The main problem of electron beam welding of duplex stainless steels (DSS) is the degradation of the mechanical properties and the corrosion resistance due to an unfavourable ferrite content in the weld metal. This occurs because of the high cooling rate and the effusion of nitrogen from the weld pool, which is characteristic for this welding process. To guarantee the necessary mechanical and technological properties and the corrosion resistance, the DSS are welded with filler material and afterwards undergo a post-weld heat treatment. The present work shows the results of investigations concerning the development of an electron multi-beam technology for welding the thick-walled components of DSS without a filler material and post-weld heat treatment. The electron multi-beam technique allows the formation of many weld pools at the same time, which might achieve slower cooling rates and influence the austenite–ferrite formation of the DSS welds. Based on the results of previous studies, in which the optimum cooling rate and number of weld pools were determined, different electron multi-beam techniques were developed and applied to produce the bead on plates of these steels. The studies were performed on standard duplex stainless steel of type X2CrNiMoN22-5-3 and on lean duplex stainless steel of type X2CrNiN23-4. The resulting austenite formation, mechanical properties and the corrosion resistance of the electron multi-beam welds were investigated and are presented in this work.

Thick-walled components made of duplex stainless steels are used in the semi-finished products as well as in machinery, apparatus and plant construction. Electron beam welding (EBW) of these components may be recommended for economic and quality reasons. To guarantee the necessary mechanical and technological properties and the corrosion resistance, the duplex stainless steels are welded with filler material and afterwards undergo a post-weld heat treatment. The present work shows interim results of investigations concerning the development of an electron beam multi-process technology for welding these steels without filler material and post-weld heat treatment. The studies were performed on standard duplex stainless steel of type 1.4462 (X2CrNiMoN22-5-3). When welding duplex stainless steels, the cooling rate and the chemical composition have a crucial influence on the final result. Based on fundamental investigations relating to the influence of the process parameters on the effusion of nitrogen and the cooling rates, the resulting austenite formation, mechanical properties and the corrosion resistance were taken into account to develop appropriate electron beam multi-process techniques. The ferrite content was measured metallographically and by magnetic induction, the impact toughness was measured at −40 °C and the determination of critical pitting temperatures was performed using electrochemical noise measurements.

High-Mn austenitic steels with TWIP and TRIP effect are characterized by an exceptional combination of high plasticity and high strength making them ideal for use in crash-relevant automobile components. At this point, European and international steel producers are facing the market launch of these steels, without detailed information regarding their weldability. This paper presents results from a publicly funded research project concerning the weldability of different systems of uncoated Fe-Mn alloys for gas metal arc welding. The different alloying concepts were produced by the Max Planck Institute for Iron Research GmbH in Dusseldorf specifically for this research project. For gas metal arc welding some newly developed metal cored wires were used and the heat input was varied by using different arc welding processes (short arc, cold metal transfer, cold metal transfer + pulsed arc). In addition to the metallurgical characteristics of the base metals and welds (segregation behaviour, grain size) the paper presents results on the quality of the welds depending on welding process and filler material.

The process of aluminum die-casting produces near-net-shape, complex and thin-walled prefabricated parts of aluminum that is more widely applied in all areas of the industry because it has economic advantages compared to other processes in productivity. The technique mostly used in the molding process of aluminum die-casting products is fusion welding, which shows multiple problems: The safe production of pore free welding seams requires an expensive optimization all over the die-casting process as well as the choice of a qualified welding process.Compared to arc welding, the beam welding processes are characterized by high welding speeds, low heat input and consequently by small heat-affected zones and minimal distortion. Thus, the beam procedures are suitable in particular for components in which narrow and deep weld seams are required. Exemplary, aluminum die cast housings are such parts. However, the welds have to meet the desired requirements on the tightness there. This is a great challenge because aluminum die cast tends to pore formation and melt ejection due to its production-related gas content.Respect to the achievable weld seam quality, in particular, electron beam welding exhibits best results. This is due to the process management under vacuum in the range of p=10−3 hPa, which makes it possible to eliminate atmospheric influences and generally contributes to better degassing.An alternative beam welding procedure is laser beam welding. Compared to the EB welding, however, laser beam weldings of aluminium die cast have an increased porosity. In this paper, different possibilities are presented by which an improvement of weld seam quality in laser beam welding of aluminum die casting can be achieved. Experiments with different laser optical configurations, as well as varying process parameters influence the formation of pores in a considerable extent. In addition, the ambient pressure is a decisive parameter to improve the weld quality. The welding process is more and more stable and the formation of pores is clearly suppressed by decreasing pressure.The process of aluminum die-casting produces near-net-shape, complex and thin-walled prefabricated parts of aluminum that is more widely applied in all areas of the industry because it has economic advantages compared to other processes in productivity. The technique mostly used in the molding process of aluminum die-casting products is fusion welding, which shows multiple problems: The safe production of pore free welding seams requires an expensive optimization all over the die-casting process as well as the choice of a qualified welding process.Compared to arc welding, the beam welding processes are characterized by high welding speeds, low heat input and consequently by small heat-affected zones and minimal distortion. Thus, the beam procedures are suitable in particular for components in which narrow and deep weld seams are required. Exemplary, aluminum die cast housings are such parts. However, the welds have to meet the desired requirements on the tightness there. This is a great challenge because ...

Der Druckgussprozess und die giesereiinterne Prozesskette sind von einer hohen Dynamik gekennzeichnet und komplexen Energie- und Ressourcenverbrauchen gekennzeichnet. Um diese Optimieren zu konnen, werden sowohl die Produktionsprozesskette Aluminiumdruckguss und ihre Historie sowie die Handlungsfelder entlang der Prozesskette und im Kernprozess selbst im Kontext Energie- und Ressourceneffizienz vorgestellt.

Der Druckgiesprozess ist im Hinblick auf eine Ressourceneffizienz ein sehr relevantes Handlungsfeld in der gesamten Prozesskette. In der Gieszelle werden uber die Parameter der Giesmaschine und des Spruhprozesses sowie uber die eingesetzte Schmelzequalitat und die Auslegung der Form sowie ihren Verschleiszustand die Qualitatseigenschaften des gegossenen Bauteils eingestellt. Fehler, die in diesem Prozessschritt gemacht werden, fuhren unweigerlich zu einem Ausschuss der Bauteile. Schwerpunkt in diesem Kapitel ist daher eine detaillierte Betrachtung der Masnahmen zur energieorientierten Maschinenoptimierung und des Einflusses der Prozessparameter auf die Bauteilqualitat.

Der Druckgiesprozess ist ohne Trenn- und Hilfsstoffe technisch nicht durchfuhrbar. Insbesondere die Trennstoffe und ihre Applikation uber den Spruhprozess beeinflussen nicht nur den Prozessablauf, sondern auch die Bauteilqualitat im Hinblick auf ihre Weiterverarbeitung. Ein Schwerpunkt im Verbundprojekt war daher der Themenkomplex der Trennstoffe, deren Wechselwirkungen mit der Giesform und der Einfluss auf die Bauteilqualitat. In den folgenden Kapiteln werden, ausgehend von den Grundlagen der Trennstoffanwendung, die Trennstoffentwicklungen sowie ein im Hinblick auf die Formenstandzeit und Ausschussreduzierung optimierter Spruhprozess vorgestellt. Auserdem wird das Potenzial einer Minimalmengenschmierung des Kolbens betrachtet und eine Bewertung der Entwicklungsarbeiten im Hinblick auf die Weiterverarbeitung der Bauteile vorgenommen.

Increasing demands on safety and environment require the production of complex components with high strength and reduced weight. To this purpose, a great variety of steel concepts was developed in the past 30 years. Novel austenitic Fe-Mn-steels with high manganese levels ranging from 15 to 25%, which are characterised by an exceptional combination of high plasticity and high strength, show a great potential for innovative lightweight designs. The excellent mechanical properties of these steels are based on the TWIP-effect (twinning induced plasticity), generating a high energy absorption capability through work hardening. At this point, European and international steel producers are facing the market launch of these steels without statements regarding their weldability. While the newly developed materials offer a high potential for use in car bodies, they also demand high production technology standards. This paper introduces the first fundamental investigations on the hot cracking behaviour of four different high manganese TWIP-Steels. The TWIP-steels were produced by the Max-Planck Institut fur Eisenforschung GmbH (MPIE) Dusseldorf especially for this project and are characterized by different alloying concepts concerning the contents of carbon, manganese, silicon and aluminium. The investigations include the measurement of the thermo-physical properties (solidification temperature range, thermal expansion, thermal diffusivity, specific heat capacity) of the TWIP-steels. Hot cracking tests are performed by PVR-test (deformation crack test), using TIG-welded externally loaded specimens to rank the hot cracking sensitivity with respect to other already assessed Cr-Ni-Steels and Ni-Base Alloys. Furthermore, a special self-restraint testing procedure for arc welding processes tailored to a real weldment geometry was investigated and the results were compared to those of the PVR-test. In order to gain further knowledge regarding formation and propagation of the hot cracks, optical microscopy, SEM-microscopy and EDX-analyses were performed. In conclusion, the experimental results are discussed with respect to their significance for the welding suitability of these TWIP-steels.

The lifetime and economic methods of improving the lifetime of a die-casting die are key factors for the die-casting industry since the global competition and the competition with other production techniques have increased significantly. The article depicts the approach, technical realization, latest results and process limitations of the INNOGRAD research project. Here, powder-based laser-cladding is applied to combine two materials as a functionally graded material. By applying gradient structures it is possible to fit the material to the predominant type of exposure, resulting in an increase in the lifetime of die-casting dies.

Description d'une technique analytique pour identifier et quantifier l'azote dans les aciers allies. Utilisation de la spectrometrie Auger