Shielding gas

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

Dilution in single pass arc welds

Abstract: A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged are welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

Vapor-plasma plume investigation during high-power fiber laser welding

Abstract: This work is devoted to the investigation of the laser–matter interaction during up to 20 kW ytterbium fiber laser welding of thick mild steel plates. The plume attenuation of a probe 1.3 μm wavelength diode laser beam as well as of continuous radiation in the 250–600 nm wavelength range was measured during welding with and without Ar shielding gas supply. The measured results allow the calculation of the average size and concentration of fine condensed metal particles in different plume areas using the multi-wavelength method and the Mie scattering theory. The plume temperature, which determines the condensation conditions, was measured by means of Fe I atom spectral line emission registration. The spatial distribution of the extinction coefficient in the welding plume was measured and the plume attenuation of the high-power fiber laser beam during the welding process was estimated.

Study for TIG–MIG hybrid welding process

Abstract: Tungsten inert gas (TIG) and metal inert gas (MIG) welding are the most popular gas-shielded arc-welding processes used in many industrial fields. MIG welding is a high-efficiency process compared to TIG welding. However, improvements are needed to reduce spatter and improve weld metal toughness. Although pure argon shielding gas is desirable for weld metal toughness, MIG arcs are unstable in pure Ar to the extent that executing welding is difficult. We have found that MIG arcs become stable even using pure argon by simply using a hybrid TIG and MIG system. This process has the possibility of becoming a new welding process giving high quality and efficiency. In this study, we investigate the influence of the balance of current between the TIG and MIG arcs, which is most important in determining arc stability and arc penetration. We have confirmed the suitable range of conditions both experimentally and through numerical simulation and have applied this process for butt and fillet joints. We show that the welding time can be reduced to 17 ~ 44 % of the time required using a conventional TIG process.

The Investigation of Gravity-Driven Metal Powder Flow in Coaxial Nozzle for Laser-Aided Direct Metal Deposition Process

Abstract: The quality and efficiency of laser-aided direct metal deposition largely depends on the powder stream structure below the nozzle. Numerical modeling of the powder concentration distribution is complex due to the complex phenomena involved in the two-phase turbulence flow. In this paper, the gravity-driven powder flow is studied along with powder properties, nozzle geometries, and shielding gas settings. A 3-D numerical model is introduced to quantitatively predict the powder stream concentration variation in order to facilitate coaxial nozzle design optimizations. Effects of outer shielding gas directions, inner/outer shielding gas flow rate, powder passage directions, and opening width on the structure of the powder stream are systematically studied. An experimental setup is designed to quantitatively measure the particle concentration directly for this process. The numerical simulation results are compared with the experimental data using prototyped coaxial nozzles. The results are found to match and then validate the simulation. This study shows that the particle concentration mode is influenced significantly by nozzle geometries and gas settings.