This paper presents extensive investigations about the influence of He-additions to argon TIG-arc properties. Results of diagnostic methods, numerical simulations and welding trials are combined to improve the comprehension about the mode of action of gas mixtures. Additionally, selected results of the investigation with H2- and N2-additions are summarized. The investigations show that all gas additions cause an increase of the heat input into the workpiece. However, the stagnation pressure depends on the gas composition: He-additions result in a decrease of the stagnation pressure which depends on the arc length, whereas H2-and N2-additions increase the pressure. By a systematic choice of the gas mixture the weld depth and also the maximum feed speed can be influenced.

Numerical and Experimental Studies of the Influence of Process Gases in Tig Welding

A numerical model of a three-dimensional transient weld pool was conducted to analyze the hump formation mechanism in high-speed single-wire gas metal arc welding (GMAW) and the hump suppression in triple-wire GMAW. The effect of heat convection, radiation, and vaporization on temperature field and the impact of arc pressure, surface tension, Lorentz force, buoyancy force, and droplet impinging force on the fluid flow field were considered during simulations. In good agreement with the experimental beads and images recorded by high-speed camera, the simulated results are shown: during the hump formation in single-wire GMAW, the liquid channel was formed, elongated, pinched, and solidified due to the strong backward molten metal flow and the normal surface tension. However, in the same line energy, humps were suppressed in triple-wire GMAW. The “pull-push” flow in the triple-wire GMAW weld pool could dramatically slow down the backward trend, which reduced the solidification rate. Consequently, the liquid channel disappears and the humps could not be formed any more.

Numerical simulation of hump suppression in high-speed triple-wire GMAW

Twin Wire Gas Tungsten Arc Cladding

In the gas metal arc welding (GMAW) process, when the welding speed reaches a certain threshold, there will be an onset of weld bead undercut defects which limit the further increase of the welding speed. Establishing a mathematical model for high-speedGMAWto predict the tendency of bead undercuts is of great significance to prevent such defects. Under the action of various forces, the transferred metal from filler wire to the weld pool, and the geometry and dimension of the pool itself decide if the bead undercut occurs or not. The previous model simplified the pool shape too much. In this paper, based on the actual weld pool geometry and dimension calculated from a numerical model, a hydrostatic model for liquid metal surface is used to study the onset of bead undercut defects in the high-speed welding process and the effects of different welding parameters on the bead undercut tendency.

Predicting of bead undercut defects in high-speed gas metal arc welding (GMAW)

The current research work is based on combine effect of TIG & MIG welding to achieve desirable mechanical properties. The stainless steel 304L plates were selected for welding. Current, Voltage and gas flow rate were taken as input parameters to study the response (hardness and width of weld bead). The experiments were conducted with the help of a full factorial design. The increase in gas flow rate decreases the hardness of the weld bead as well as increases the bead width to some extent. Non-dominated Sorting Genetic Algorithm was used to optimize the responses. Sixteen non-dominated solutions were obtained. The welding current, voltage and gas flow rate should be maintained at approximately 200A, 24V and 15-17 l/min respectively for the best hardness and bead width value.

https://iopscience.iop.org/article/10.1088/1757-899X/377/1/012067/pdf

B. Lucas

Papers

Fcaw, multiwire& gas selection : techniques to enhance mig productivity