Shielded metal arc welding

About: Shielded metal arc welding is a research topic. Over the lifetime, 4462 publications have been published within this topic receiving 40560 citations. The topic is also known as: manual metal arc welding & flux shielded arc welding.

Exposure of welders and other metal workers to ELF magnetic fields.

Abstract: This study assessed exposure to extremely low frequency (ELF) magnetic fields of welders and other metal workers and compared exposure from different welding processes. Exposure to ELF magnetic fields was measured for 50 workers selected from a nationwide cohort of metal workers and 15 nonrandomly selected full-time welders in a shipyard. The measurements were carried out with personal exposure meters during 3 days of work for the metal workers and 1 day of work for the shipyard welders. To record a large dynamic range of ELF magnetic field values, the measurements were carried out with ‘‘high/low’’ pairs of personal exposure meters. Additional measurements of static magnetic fields at fixed positions close to welding installations were done with a Hall-effect fluxmeter. The total time of measurement was 1273 hours. The metal workers reported welding activity for 5.8% of the time, and the median of the work-period mean exposure to ELF magnetic fields was 0.18mT. DC metal inert or active gas welding (MIG/MAG) was used 80% of the time for welding, and AC manual metal arc welding (MMA) was used 10% of the time. The shipyard welders reported welding activity for 56% of the time, and the median and maximum of the workday mean exposure to ELF magnetic fields was 4.70 and 27.5mT, respectively. For full-shift welders the average workday mean was 21.2 mT for MMA welders and 2.3 mT for MIG/MAG welders. The average exposure during the effective time of welding was estimated to be 65 mT for the MMA welding process and 7 mT for the MIG/MAG welding process. The time of exposure above 1mT was found to be a useful measure of the effective time of welding. Large differences in exposure to ELF magnetic fields were found between different groups of welders, depending on the welding process and effective time of welding. MMA (AC) welding caused roughly 10 times higher exposure to ELF magnetic fields compared with MIG/MAG (DC) welding. The measurements of static fields suggest that the combined exposure to static and ELF fields of MIG/MAG (DC) welders and the exposure to ELF fields of MMA (AC) welders are roughly of the same level.Bioelectromagnetics 18:470-477, 1997. q 1997 Wiley-Liss, Inc.

Adaptive control for arc welding

Abstract: A semiconductor electronic chopper precisely controls the current to a welding arc in response to arc length as represented by arc voltage. The actual arc current is compared with a reference current to generate a switching signal which adaptively controls electronic switches in order to meet arc requirements. For manual welding with covered electrodes (SMAW), frequently referred to as ''''stick welding,'''' a slope control potentiometer is used to vary the value of the reference current when the arc length (voltage) deviates from a preset normal operating length (voltage). This creates a family of volt-ampere characteristic curves all passing through the preset voltage and current operating point. A digging characteristic is obtained by increasing the reference current rapidly when the arc voltage (length) goes below a preset value. An intermittent spray transfer welding process, particularly applicable to continuous wire feed electrode systems, is created by maintaining the welding current at a high constant value until the electrode wire burns back to a maximum desired length (voltage) and then automatically reducing the current to a low constant value until the electrode is advanced sufficiently to shorten the arc and signal the system to change to a high current, etc.

The effect of shielding gas composition in CO2 laser—gas metal arc hybrid welding

Abstract: In carbon dioxide (CO2) laser—gas metal arc hybrid welding, a shielding gas is supplied to isolate the molten metal from the ambient air, suppress the laser-induced plasma, remove the plume out of the keyhole, and stabilize the metal transfer. In this study, a shielding gas consisting of helium, argon, and CO2 was used, and its effects on the composition of the welding phenomena, such as behaviours of laser-induced plasma generation, molten pool flow, and droplet transfer in gas metal arc welding, were investigated. High-speed video observation was used to investigate the welding phenomena inside the arc regime. Consequently, helium was found to have a dominant role in suppressing laser-induced plasma; minimum helium content at a laser power of 8 kW was suggested for laser autogenous and hybrid welding. Argon and CO2 govern the droplet transfer and arc stability. A 12 per cent addition of CO2 stabilizes the metal transfer and eliminates undercut caused by insufficient wetting of molten metal.

Influence of Pulse Parameters on Characteristics of Bead-on-Plate Weld Deposits of Aluminum and Its Alloy in the Pulsed Gas Metal Arc Welding Process

Abstract: A summarized influence of pulse parameters have been studied; these parameters are defined by a hypothetically derived factor ϕ = [(I b /I p )ft b ] on the characteristics of bead-on-plate weld deposits of aluminum and Al-Mg alloy, with respect to their geometry and microstructure. The weld geometry has been studied in reference to the depth, width, and area of fusion of the base plate, and the bead height, bead width, toe angle, form factor, area of weld deposit, fraction of base metal fusion per unit mass of weld deposition, and dilution. It is found that these aspects of geometry and the microstructure of the weld metal and heat-affected zone (HAZ) vary significantly with a change in the factor ϕ. The value of the factor ϕ at approximately 0.1 has been seen as critical to the change in the different aspects of the pulsed–gas metal arc (P-GMA) weld. It is also found that, at a given ϕ, the variation in mean current and heat input significantly affects the geometry and microstructure of the weld deposit.