This chapter describes the impact of the development of the gas-shielded arc welding (MAG) process. Due to its high operating factor and deposition rate, GMAW has the potential to improve productivity compared to GTAW and SMAW processes.
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While the need to realize the economic benefits of the process has led to a clear trend towards wider use of GMAW worldwide, reliable quality has historically been difficult to achieve. Therefore, the main development direction of the
was to improve control and achieve more consistent quality. The way material is transferred from the consumable electrode tip to the weld pool has a significant impact on the overall performance of the MSG process: process stability, spatter formation, weld quality and process positioning capabilities.The different types of natural transfers have been divided into groups. This chapter presents a simplified basic classification of metal transfer in GMA welding. It also covers spherical droplet transfer, repellent droplet transfer, spray droplet transfer, immersion transfer and several variations on normal transfer.
Health, Safety and Environmental Issues
Gas Metal Arc Welding (GMAW) is a fast and inexpensive process that is sometimes called Gas Arc Welding (MIG) (Figure 1). In this process, an arc is ignited between the base material and a continuously excited melting electrode, which supplies the filler material to the weld seam (2).The electrode is bare with no coating or core. The shield, which protects the molten metal from reacting with the atmosphere, is powered by an external gas, usually containing one of the following mixtures: helium, argon, or carbon dioxide. Significant amounts of fumes can be generated during welding with this process. Most of the fumes from MIG welding are caused by electrode wear and not the base metal.
Welding Processes
Mechanized Pulsed Arc Welding (GMAW) is used successfully for field welding of large diameter pipelines16 such as As oil and gas transport lines used. In any case, GMAW still has a reputation for not melting and its use for critical applications is banned by most engineering firms and operators. The GMAW uses the same wire as the GTAW but does not appear to be as sensitive to nitrogen loss and often offers better corrosion properties.
There is evidence that the GMAW pulse welding process is not as readily applicable to position welding duplex stainless steels as it is to austenitic stainless steels.17 Good weld profiles have been achieved with the proprietary 11% He gas mixture 0.4% CO2, balance Ar. In addition, helium-containing gases have been developed and have also shown good results.19
