Effects Of Various Welding Parameters Research Articles

Study and prevention of cracking during weld-repair of heat-resistant cast steels

Heat-resistant cast steels are highly sensitive to cracking as they are weld-repaired because of their very low ductility. To prevent weld-repair cracking of three different heat-resistant cast steels used for the manufacturing of superplastic forming (SPF) dies, the effect of various welding parameters, such as the choice of the filler material, the number of weld passes and the pre-heating temperature has been investigated. The choice of an appropriate filler metal and the pre-heating to 400 °C of the material prior to welding drastically lower the propensity to cracking, but remain unable to eliminate cracks entirely. To further reduce weld-repair cracking and hopefully prevent it completely, a buttering technique has been developed. Buttering of the base metal surface with nickel alloys before weld-repair has been shown to prevent cracking of the base metal, but results in some hot-cracking of the buttering layer itself. On the other hand, buttering with Ni–Fe alloys, less sensitive to hot-cracking, results in crack-free weld-repairs.

The effect of process parameters on penetration in gas metal arc welding processes

In this study, the effects of various welding parameters on welding penetration in Erdemir 6842 steel having 2.5 mm thickness welded by robotic gas metal arc welding were investigated. The welding current, arc voltage and welding speed were chosen as variable parameters. The depths of penetration were measured for each specimen after the welding operations and the effects of these parameters on penetration were researched. The welding currents were chosen as 95, 105, 115 A, arc voltages were chosen as 22, 24, and 26 V and the welding speeds were chosen as 40, 60 and 80 cm/min for all experiments. As a result of this study, it was obvious that increasing welding current increased the depth of penetration. In addition, arc voltage is another parameter in incrimination of penetration. However, its effect is not as much as current’s. The highest penetration was observed in 60 cm/min welding current.

Mathematical modelling of circumferential GTA welding of pipes with single V groove

Summary This paper describes a three-dimensional model for circumferential GTA welding of pipes with a single V groove. It consists of a heat conduction model and a molten pool balance model. In the heat conduction model, the transient temperature distribution on the pipe is numerically analysed to estimate the molten pool size by the finite difference method. In the molten pool balance model, the theoretical configuration of the molten pool is calculated using the molten pool size derived from the heat conduction model with regard for the balance of gravity, the surface tension and the arc pressure. These models are used to examine the effects of various welding parameters, such as welding positions and joint geometries, as well as the effect of the arc pressure on the welding process. The results suggest that the proposed numerical model is suitable for estimation of welding process parameters during groove welding of pipes.

Theoretical investigation of penetration characteristics in gas metal-arc welding using finite element method

In the modeling of the gas metal-arc (GMA) welding process, heat inputs to the workpiece by the arc and the metal transfers have been considered separately. The heat energy delivered due to the metal transfer has been approximated in the form of a cylindrical volumetric heat source, whose dimensions of the radius and the height are dependent on the molten metal droplet characteristics. The pinch instability theory (PIT) and the static force balance theory (SFBT) of drop detachment have independently been used to obtain the expressions for various characteristics of the drop,i.e., the drop radius, the drop velocity, and the drop frequency at various welding parameters. The occurrence or the nonoccurrence of finger penetration, routinely found in the GMA welding at high welding currents, has been satisfactorily explained by the cylindrical heat source model. The effect of various welding parameters,e.g., the welding current, the wire radiusetc., on the weld bead penetration characteristics has been investigated. In this modeling effort, the heat conduction equation has been solved in three dimensions.