Molten Pool Geometry of Solid Iron by Plasma Heating

The presence of certain impurities in the base metal has been known to affect the molten pool geometry of an arc weld. Some views concerning dominant factors governing the weld pool geometry have been proposed, but those have not been unified as yet. So, in order to clarify the formation mechanism of molten pool, the effects of the various factors on the molten pool geometry of binary Fe-O and Fe-S test specimens were examined by use of a plasma heating equipment with a gas shielded chamber.The depth of the molten pool increased and the width decreased with the increase of the oxygen or sulfur content in the base metal.The shape changes of metal wire markers in solidified pool indicated that the outward flow occurred at the surface of the molten pool for the case using the base metal of low oxygen content and the inward flow did for the high oxygen content. The relation between the temperature coefficient of surface tension and the oxygen content could explain these flow behaviors.The width of the arc frame was kept constant in the region of the oxygen content below 0.08 mass% or the sulfur content below 0.07 mass%.Conclusively, it could be deduced that the surface tension driven flow was a dominant factor in determining the molten pool geometry.