Selection of parameters of pulsed current gas metal arc welding

Optimization of weld bead geometry for stainless steel claddings deposited by FCAW

The weld quality comprises bead geometry and its microstructure, which influence the mechanical properties of the weld. The coarse-grained weld microstructure, higher heat-affected zone, and lower penetration together with higher reinforcement reduce the weld service life in continuous mode gas metal arc welding (GMAW). Pulsed GMAW (P-GMAW) is an alternative method providing a better way for overcoming these afore mentioned problems. It uses a higher peak current to allow one molten droplet per pulse, and a lower background current to maintain the arc stability. Current pulsing refines the grains in weld fusion zone with increasing depth of penetration due to arc oscillations. Optimum weld joint characteristics can be achieved by controlling the pulse parameters. The process is versatile and easily automated. This brief review illustrates the effect of pulse parameters on weld quality.

Effect of Pulse Parameters on Weld Quality in Pulsed Gas Metal Arc Welding: A Review

While metal vapours have an important impact on the efficiency of the pulsed gas metal arc welding process, only a few papers are focused on this effect. In this paper, methods based on emission spectroscopy are performed to improve the understanding of the physical phenomena occurring during the high-current pulse. Boltzmann plots applied to iron lines, the Stark broadening of the 696.5 nm argon line and composition calculations assuming local thermodynamic equilibrium are used to determine characteristic parameters of the plasma. It is observed that the central part of the arc is composed mainly of iron. The percentage of iron increases quickly at the beginning of the high-current pulse, and slowly decreases when the central part broadens. During the high-current phase the temperature profile has a minimum value of around 8000 K at the axis of the arc while the argon envelope of the central part reaches temperatures of approximately 13.000 K. The high percentage of iron and the high radiation of the plasma at the centre can explain the measured shape of the temperature profile.

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Spectroscopic investigation of the high-current phase of a pulsed GMAW process

The application of response surface methodology was highlighted to predict and optimize the percentage of dilution of iron-based hardfaced surface produced by the PTA (plasma transferred arc welding) process. The experiments were conducted based on five-factor five-level central composite rotatable design with full replication technique and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was also used to optimize the process parameters that yielded the lowest percentage of dilution.

Application of Response Surface Methodolody to Prediction of Dilution in Plasma Transferred Arc Hardfacing of Stainless Steel on Carbon Steel

An efficient method of iden- tifying power supply pulsing parameters for pulsed gas metal arc welding based on statistical experimental design is pre- sented. Fractional factorial screening ex- periments are combined with D-optimal experimental designs to allow the user to develop an accurate wire feed rate model for varying pulsing conditions and to characterize the desirable one droplet per pulse (ODPP) operating region for a given wire type and diameter. Equations defining the wire feed rates and time at a given peak current required for ODPP transfer are presented. Compared to con- ventional techniques, a very small num- ber of experiments is required. A power- supply-dependent approach and a more generic method employing measured rather than nominal current values are presented. Joints produced using this ap- proach are evaluated and found to meet applicable bead geometry standards.

Experimental approach to selection of pulsing parameters in pulsed GMAW

The droplet transfer mode is a critical element in the arc welding process. Multiple transfer modes have been identified, and the conditions under which they occur have been characterized. In the pulsed gas metal arc welding (GMAW-P) process, droplet transfer mode is affected not only by welding voltage and current, but also by the pulsing parameters. In this work, experimental techniques were used to investigate the transitions from pulsed globular to pulsed spray to pulsed streaming transfer in GMAW-P of 1.2-mm 4047 aluminum welding wire. A new method for characterizing one-droplet-per-pulse (ODPP) operating conditions is described and the transition from pulsed globular to pulsed spray transfer is characterized. The roles of pulse frequency and duty cycle on droplet transfer are explained.

Droplet transfer in pulsed gas metal arc welding of aluminum

The use of readily acquired weld arc data such as voltage, current, or light emissions to identify droplet transfer events or transfer mode, or for quality purposes such as seam tracking is of interest for thin section applications in arc welding of aluminium. In the present study, voltage, current, and light emission signals are acquired at high rates, and synchronised with high speed shadowgraphing. The usefulness of the various signals for identifying droplet detachment events and transfer modes during pulsed gas metal arc welding of aluminium is compared. It is found that individual droplet detachments are consistently identifiable during globular, spray, and streaming transfer, and during peak and background current detachment, using the voltage signal. Although the arc light signal also contains droplet detachment data, it is difficult to identify droplet detachments occurring during the background phase at low background current levels. Preliminary measurements show that these signals can a...

Analysis of arc voltage, current, and light signals in pulsed gas metal arc welding of aluminium

Experimental Approach to Selection of Pulsing Parameters in Pulsed GMAW A method for selection of process parameters in pulsed GMAW helps to efficiently develop welding procedures

D. W. Lyons

Papers

Experimental approach to selection of pulsing parameters in pulsed GMAW

Droplet transfer in pulsed gas metal arc welding of aluminum

Analysis of arc voltage, current, and light signals in pulsed gas metal arc welding of aluminium

Experimental Approach to Selection of Pulsing Parameters in Pulsed GMAW A method for selection of process parameters in pulsed GMAW helps to efficiently develop welding procedures