An analysis of the heat transfer during arc welding has been carried out. The study is applicable to pure metals or alloys and to low or high boiling temperature materials and includes the effects of conduction, radiation, evaporation, boiling, and variable properties. Two evaporation models were studied and the results were compared with experimental data for stainless steel. The penetration depth was also calculated for lead, a low boiling temperature material, and the results were compared with previous calculations and with experimental data.