Shielding gas

About: Shielding gas is a research topic. Over the lifetime, 6697 publications have been published within this topic receiving 58668 citations.

Flux cored arc welding : arc signals, processing and metal transfer characterization

Abstract: Metal droplet transfer in flux cored arc welding (FCAW) was studied using electrical arc signals and droplets collected from the welding process. A large number of metal droplets from the FCAW experiments was collected. According to the size distribution of the droplets, several metal transfer modes could be identified amongst which spray transfer predominated. The electrical arc signals, in particular, voltage, were processed using the fast Fourier transform (FFT) technique. Characteristic spectral frequencies corresponding to different metal transfer modes were identified. The size distribution of the collected droplets correlated extremely well with these characteristic frequencies. The electrode melt rate, calculated using the characteristic frequencies identified from the FFT analysis, agreed closely with the measured melt rate. Results from the arc signal analysis and the FFT analysis showed that both arc voltage fluctuations (Δu) and characteristic frequencies of the FFT spectra were adequate to distinguish the different kinds of metal transfer modes in FCAW. Metal transfer mode maps, constructed using the two sets of results, were used to determine the optimal parameters for E71T-1, 1/16-in.-diameter electrode, and Ar-25%CO 2 shielding gas.

The Influence of Oxygen Additions on Argon-Shielded Gas Metal Arc Welding Processes

Abstract: It has been observed experi- mentally that small additions of oxygen to the argon shielding gas affect the gen- eral operation of GMAW processes. By theoretically modeling the arc column, it is shown that the addition of 2 to 5% oxy- gen to argon has an insignificant effect on the arc characteristics. This corresponds to the minor changes in the thermophys- ical transport and thermodynamic prop- erties caused by the oxygen addition. Therefore, it is concluded that the addi- tion of oxygen to the argon shielding gas mainly affects the anode and the cathode regions. From the literature, it was found that the formation of oxides initiates arc- ing at the cathode and decreases the movement of the cathode spots. These oxides can also improve the wetting conditions at the workpiece and the elec- trode. Finally, oxygen is found to affect the surface tension gradient and thereby the convective flow of liquid metal in the weld pool.

Method for monitoring laser weld quality via plasma light intensity measurements

Abstract: A method for monitoring the quality of a laser process such as a laser welding process includes monitoring the light emitted from the weld plasma above the surface of the workpiece irradiated by the laser beam The intensity of the light emitted from the plasma is compared to a predetermined value of the light emission as determined under process and workpiece conditions that produce welds of acceptable quality Variations of the monitored light intensity greater than a preselected value can be valuated as unacceptable welds Such variations can be caused by changes in the laser beam power, the workpiece speed, laser focusing problems, insufficient shield gas flow, workpiece deformation and weld contamination The process monitors the light emission for a selected range of wavelengths that correspond to the major emission peaks of the light spectrum The method enables in-process control of laser processes