Increasing Performance and Energy Efficiency of Gas Metal Arc Welding by a High Power Tandem Process

Standard Gas Metal Arc Welding (Standard GMAW) and a high power Tandem GMAW (TGMAW) process are evaluated with respect to energy efficiency. Current, voltage and overall equipment power are measured and energy consumption is determined. The new key performance indicator Electrical Deposition Efficiency is introduced to reflect the energy efficiency of GMAW processes. Additionally, wall-plug efficiency of the equipment is determined in order to identify the overall energy consumption. Results show that energy efficiency as well as economic process performance can be significantly increased by application of the TGMAW process. Furthermore findings indicate that wall-plug efficiency of the equipment is independent of power level and material transfer mode. A metal plate of 30 mm thick structural steel is joined by Standard GMAW and TGMAW to demonstrate the total energy savings for a real weld. Electricity consumption is reduced by more than 20% using the high power TGMAW process.DFG, 199828953, SFB 1026: Sustainable Manufacturing - Globale Wertschöpfung nachhaltig gestalte

Sustainable technologies for thick metal plate welding

Welding is the most important joining technology. In the steel construction industry, e.g. production of windmill sections, welding accounts for a main part of the manufacturing costs and resource consumption. Moreover, social issues attached to welding involve working in dangerous environments. This aspect has unfortunately been neglected so far, in light of a predominant focus on economics combined with a lack of suitable assessment methods. In this chapter, exemplary welding processes are presented that reduce the environmental and social impacts of thick metal plate welding. Social and environmental Life Cycle Assessments for a thick metal plate joint are conducted for the purpose of expressing and analysing the social and environmental impacts of welding. Furthermore, it is shown that state-of-the-art technologies like Gas Metal Arc Welding with modified spray arcs and Laser Arc-Hybrid Welding serve to increase social and environmental performance in contrast to common technologies, and therefore offer great potential for sustainable manufacturing

Assessing carbon dioxide emission reduction potentials of improved manufacturing processes using multiregional input output frameworks

Evaluating innovative process technologies has become highly important within the last decades. As standard tools different Life Cycle Assessment methods have been established, which are continuously improved. While those are designed for evaluating single processes they run into difficulties when it comes to assessing environmental impacts of process innovations at macroeconomic level. In this paper we develop a multi-step evaluation framework building on multi regional input–output data that allows estimating macroeconomic impacts of new process technologies, considering the network characteristics of the global economy. Our procedure is as follows: i) we measure differences in material usage of process alternatives, ii) we identify where the standard processes are located within economic networks and virtually replace those by innovative process technologies, iii) we account for changes within economic systems and evaluate impacts on emissions. Within this paper we exemplarily apply the methodology to two recently developed innovative technologies: longitudinal large diameter steel pipe welding and turning of high-temperature resistant materials. While we find the macroeconomic impacts of very specific process innovations to be small, its conclusions can significantly differ from traditional process based approaches. Furthermore, information gained from the methodology provides relevant additional insights for decision makers extending the picture gained from traditional process life cycle assessment.DFG, SFB 1026, Sustainable Manufacturing - Globale Wertschöpfung nachhaltig gestalte

Environmental and Social Life Cycle Assessment of welding technologies

Life Cycle Assessment (LCA) and Social Life Cycle Assessment (SLCA) are applied in evaluating possible social and environmental impacts of the state-of-art welding technologies, such as Manual Metal Arc Welding (MMAW), Manual Gas Metal Arc Welding (GMAW), Automatic GMAW and Automatic Laser-Arc Hybrid Welding (LAHW). The LCA results indicate that for 1 meter weld seam, MMAW consumes the largest amount of resources (like filler material and coating on electrodes) and energy, which contributes to comparatively higher environmental impacts in global warming potential, acidification, photochemical ozone creation potential and eutrophication than other chosen processes. With regard to social aspects, the health issues and fair salary are under survey to compare the relative potential risk on human health caused by fumes in different welding technologies, and to indicate the sufficiency of current salary of welders in Germany. The results reflect that the wage status of welders is still fair and sufficient. The manual processes bring much higher potential risk of welders’ health than the automatic processes, especially MMAW

Umweltbewertung und Ökoeffizienz beim Metall-Schutzgasschweißen von Dickblechverbindungen

Der globale Wettbewerb fordert von schweißtechnischen Fertigungsverfahren und Verfahrensentwicklungen eine starke Konzentration auf die Leistungsfähigkeit und die Wirtschaftlichkeit. Beim Metall-Schutzgasschweißen (MSG-Schweißen) kommen deshalb zunehmend MSG-Hochleistungsverfahren zum Einsatz. Parallel zu dem wirtschaftlichen Druck steigt das Bewusstsein für die planetarischen Grenzen der Erde und rückt Themen wie den Klimawandel in den Fokus der Öffentlichkeit. Ziel der vorliegenden Arbeit ist ein Beitrag zur Lösung der Umweltprobleme, welche auf das MSG-Schweißen zurückgeführt werden können. Um die wirtschaftlichen Rahmenbedingungen zu berücksichtigen werden sowohl Prozesse im konventionellen als auch im Hochleistungsbereich betrachtet. Zunächst wird der Energiebedarf in Abhängigkeit von Verfahrensvariante, Lichtbogenart und Leistungsbereich charakterisiert. Mit Hilfe von Ökobilanzen erfolgt eine detaillierte Analyse der Umweltwirkungen in den Kategorien Klimawandel, Versauerung, Eutrophierung, Photooxidantien und stratosphärischer Ozonabbau. Anschließend werden die Verbesserungsstrategien "Energieeffizienz" und "Fugenvorbereitung" in einer Ökoeffizienzbetrachtung bewertet

Eco-efficiency and environmental assessment of gas metal arc welding of thick metal plates

The present thesis analyzes the environmental impacts of Gas Metal Arc Welding (GMAW) of thick metal plates. This is done by characterizing the process-specific energy consumption and Life Cycle Assessments (LCA). Furthermore, the effect of both energy efficiency and joint preparation on eco-efficiency is evaluated. The experiments are conducted with single wire GMAW and tandem GMAW processes. The energy consumption of GMAW is characterized by evaluating various material transfer modes with the indicators Electrical Deposition Efficiency (EDE) and the wall-plug efficiency of the welding power source. The results for the wall-plug efficiency show values between 80% and 85% independent of the applied process. In single wire GMAW, the EDE depends on the material transfer mode and the setup of the welding power source characteristic. Under optimum conditions, the pulsed arc transfer achieves the highest energy efficiency. In tandem GMAW, the modified dip transfer and the pulsed arc transfer without synchronization show the highest EDE values. In contrast to single wire GMAW, tandem GMAW reaches significantly higher energy efficiency values. The influences of energy efficiency and the joint preparation on the environmental impacts are investigated by means of LCA studies for weld seams produced by single wire and tandem GMAW. The eco-efficiency is evaluated by comparing the mechanical properties as well as the environmental impacts of the weld seams. In the experiments with regard to the influence of energy efficiency, the high EDE of tandem GMAW reduces the electrical energy consumption by 24% compared to single wire GMAW. This leads to reduced environmental impacts, which are mainly dominated by the electrical energy for welding and by the filler material. The weld seams of both process variants – single wire and tandem GMAW – fulfill the requirements of the welding procedure test and produce weld seams with an equivalent quality. The eco-efficiency is enhanced up to 11% by application of an energy efficient tandem GMAW process. The investigation concerning the influence of the joint preparation adopts different groove geometries for single wire and tandem GMAW. For tandem GMAW, the opening angle is reduced which leads to 35% less filler material consumption. The impact assessment reveals a significant decline of the environmental impacts by the altered joint preparation. Besides the electrical energy for welding and the filler material, the electrical energy for milling the joint preparation accounts for major shares of the environmental impacts. In the welding procedure test, the weld seams of both process variants fulfill the quality requirements. In total, the varied joint preparation results in an increased eco-efficiency of up to 38%. In order to make a comparison between the influences of energy efficiency and joint preparation, the results of the eco-efficiency studies are normalized. The joint preparation shows a significantly higher normalized eco-efficiency increase than energy efficiency. Consequently, the following suggestions for eco-efficient GMAW are derived: The cross-section area of the weld seam which is controlled by the joint preparation should be kept as small as possible. In case this is not possible, a high EDE of the process should be pursued.Die vorliegende Arbeit analysiert die Umweltwirkungen beim MSG-Schweißen von Dickblechverbindungen. Sie charakterisiert den Energiebedarf, erstellt Ökobilanzen und bewertet den Einfluss von Energieeffizienz und Fugenvorbereitung auf die Ökoeffizienz. Die Experimente werden mit MSG-Verfahren im Eindraht- und im Tandembetrieb durchgeführt. Der Energiebedarf wird über die Kennzahlen Abschmelzeffizienz und Anlagenwirkungsgrad für verschiedene Betriebs- und Lichtbogenarten charakterisiert. Der Anlagenwirkungsgrad der Schweißstromquellen beträgt einheitlich 80-85%. Im Eindrahtbetrieb zeigen die Abschmelzeffizienzen des Impulslichtbogens, des Sprühlichtbogens und des modifizierten Sprühlichtbogens eine Abhängigkeit sowohl von der Lichtbogenart als auch von der Kennlinieneinstellung. Unter der Voraussetzung optimaler Einstellungen erreicht der Impulslichtbogen die höchste Energieeffizienz. Die höchsten Abschmelzeffizienzen im Tandembetrieb erzielen modifizierte Kurzlichtbögen und asynchron gesteuerte Impulslichtbögen. Im Vergleich zum Eindrahtschweißen haben die Tandemprozesse eine deutlich höhere Energieeffizienz. Zur Einflussanalyse energieeffizienter Schweißprozesse und der Fugenvorbereitung werden Ökobilanzen für Schweißnähte mit Eindraht und Tandemverfahren erstellt. Zur Bewertung der Ökoeffizienz werden die mechanisch-technologischen Eigenschaften und die Umweltwirkungen der Verfahrensvarianten verglichen. In den Experimenten zum Einfluss der Energieeffizienz wird beim Tandemschweißen durch die höhere Abschmelzeffizienz der Bedarf an elektrischer Energie um 24% gegenüber der Eindrahtvariante gesenkt. In der Wirkungsabschätzung führt dies zu geringeren Umweltwirkungen, welche maßgeblich von der elektrischen Energie für das Schweißen und dem Zusatzwerkstoff bestimmt sind. Die Schweißnähte beider Verfahrensvarianten bestehen die mechanisch-technologische Prüfung und können als gleichwertig betrachtet werden. Die Ökoeffizienzsteigerung durch die erhöhte Energieeffizienz des Tandemverfahrens beträgt bis zu 11%. Für den Einfluss der Fugenvorbereitung wird der Öffnungswinkel beim Tandemschweißen variiert und so der Zusatzwerkstoffbedarf um 35% gesenkt. Dies führt in der Wirkungsabschätzung zu erheblich geringeren Umweltwirkungen. Neben der elektrischen Energie für das Schweißen und dem Zusatzwerkstoff hat die elektrische Energie für das Fräsen der Fugenvorbereitung einen dominanten Einfluss auf die Umweltwirkungen. In der mechanisch-technologischen Prüfung erfüllen die Schweißnähte beider Verfahrensvarianten die Anforderungen. Die Ökoeffizienzsteigerung durch Variation der Fugenvorbereitung beträgt bis zu 38%. Zum Vergleich der Einflüsse von Energieeffizienz und Fugenvorbereitung werden die Ökoeffizienzsteigerungen normiert. Aus der erheblich größeren normierten Ökoeffizienzsteigerung der Fugenvorbereitung folgen die Handlungsempfehlungen für ein ökologieorientiertes MSGSchweißen: Der von der Fugenvorbereitung vorgegebene Schweißnahtquerschnitt ist so klein wie möglich zu gestalten. Ist dies nicht möglich, sollte eine möglichst hohe Abschmelzeffizienz angestrebt werden

Sustainable Welding Process Selection Based on Weight Space Partitions

AbstractSelecting a welding process for a given application is crucial with respect to the sustainability of part manufacturing. Unfortunately, since welding processes are evaluated by a number of criteria, preferences for one or the other process can be contradictory. However, the prevalent procedure of weight assignment for each criterion is subjective and does not provide information about the entire solution space. From the perspective of a decision maker it is important to be able to assess the entire set of possible weightings and answer the question which welding process is optimal for which set of weights. This issue is investigated by means of a weight space partitioning approach. Two welding processes are considered with respect to three criteria that reflect their economic and environmental performance. In order to find the most sustainable welding process the underlying weight space partition is evaluated