Exothermically Assisted Shielded Metal Arc Welding

摘要

Exothermic flux additions to SMAW electrodes can assist in the generation of heat and increase the rate of electrode melting. The exothermic additions consisted of various combinations and concentrations of aluminum and magnesium powders in a mixture with hematite. Aluminum reactive additions were significantly more effective than magnesium-rich additions at melting the electrode, melting the weld bead and penetrating the base plate. Magnesium was less effective at supplying heat because its reaction rate was too fast with respect to the electrode melting rate. This magnesium "exothernic meltback" prevented effective transfer of the chemically generated heat to the base plate. The rate at which the exothermic reaction occurs with respect to the melting rate of the electrode determines the efficiency with which the exothermic heat is used for welding. Exothermic reactions can produce as much as 25-30% of the total heat necessary to produce a shielded metal arc weld.