The solution of a traveling distributed heat source on a semi-infinite plate provides information about both the size and the shape of arc weld pools. The results indicate that both welding process variables (current, arc length and travel speed) and material parameters (thermal diffusivity) have significant effects on weld shape. The theoretical predictions are compared with experimental results on carbon steels, stainless steel, titanium and aluminum with good agreement. 25 references, 23 figures, 1 table.

Temperature fields produced by traveling distributed heat sources

The evolution of temperature and velocity fields during laser spot welding of 304 stainless steel was studied using a transient, heat transfer and fluid flow model based on the solution of the equations of conservation of mass, momentum and energy in the weld pool. The weld pool geometry, weld thermal cycles and various solidification parameters were calculated. The fusion zone geometry, calculated from the transient heat transfer and fluid flow model, was in good agreement with the corresponding experimentally measured values for various welding conditions. Dimensional analysis was used to understand the importance of heat transfer by conduction and convection and the roles of various driving forces for convection in the weld pool. During solidification, the mushy zone grew at a rapid rate and the maximum size of the mushy zone was reached when the pure liquid region vanished. The solidification rate of the mushy zone/liquid interface was shown to increase while the temperature gradient in the liquid zone at this interface decreased as solidification of the weld pool progressed. The heating and cooling rates, temperature gradient and the solidification rate at the mushy zone/liquid interface for laser spot welding were much higher than those for the moving and spot gas tungsten arc welding.

https://iopscience.iop.org/article/10.1088/0022-3727/36/12/306/pdf

Heat transfer and fluid flow during laser spot welding of 304 stainless steel

The main emphasis of this review is on thermal modelling and prediction of laser welding in metals. However as similar techniques are employed to model conventional welding processes such as arc, resistance and friction, as well as related processes such as alloying, cladding and surface hardening, part of this review is given over to the modelling of these processes where appropriate. The time frame of the review is up to the year 2002.

Thermal modelling of laser welding and related processes: a literature review

The evolution of temperature and velocity fields during gas tungsten arc spot welding of AISI 1005 steel was studied using a transient numerical model. The calculated geometry of the weld fusion zone and heat affected zone and the weld thermal cycles were in good agreement with the corresponding experimental results. Dimensional analysis was used to understand the importance of heat transfer by conduction and convection at various stages of the evolution of the weld pool and the role of various driving forces for convection in the liquid pool. The calculated cooling rates are found to be almost independent of position between the 1073 and 773 K (800 and 500 °C) temperature range, but vary significantly at the onset of solidification at different portions of the weld pool. During solidification, the mushy zone grew significantly with time until the pure liquid region vanished. The solidification rate of the mushy zone/solid interface was shown to increase while the temperature gradient in the mushy zone at...

Modeling of heat transfer and fluid flow during gas tungsten arc spot welding of low carbon steel

https://web.mst.edu/~tsai/Published%20papers/Wang-IJHMT-2001-73.pdf

Impingement of filler droplets and weld pool dynamics during gas metal arc welding process

A mathematical model was developed to account for convection and temperature distributions in stationary arc weld pools driven by buoyancy, electromagnetic and surface tension forces. It is shown that the electromagnetic and surface tension forces dominate the flow behavior. In some cases, these forces produce double circulation loops, which are indirectly confirmed by experimental measurements of segregation in the weld pool. It is also shown that the surface tension driven flows are very effective in dissipating the incident energy flux on the pool surface which, in turn, reduces the vaporization from the weld pool.

Convection in arc weld pools

A mathematical formulation has been developed to describe the transient growth and collapse of axisymmetric weldpools in spot welding operations. In the statement of the problem allowance is made for both conductive and convective heat transfer. In describing convection, the driving forces included buoyancy, electromagnetic forces, and surface tension forces. In most cases it was found that convection played a major role in affecting the weldpool shape, and that this convection was often dominated by surface tension forces. The model also allowed us to represent the transient collapse of weldpools upon the cessation of the heat and current supply. It was found that the melt velocity was reduced as the weldpool shrank. Most of the solidification took place from a circulating weldpool. By calculating both the growth rate and the relevant temperature gradients, it was possible to estimate the dendrite arm spacing which was found to be of the order of tens of microns.

G. M. Oreper

Papers

Convection in arc weld pools

The Role of Transient Convection in the Melting and Solidification in Arc Weldpools