Plasma arc spot welding of car body steels containing vaporizable ingredients

Method of one side spot welding of a metallic auto body construction having construction having superimposed metal plys with vaporizable coatings or ingredients, the construction having overlapping metal plys, comprising:

• (a) implying a plasma column on a selected spot of one side of said construction having vaporizable coatings or ingredients, said plasma column being created by passing a plasma gas at a predetermined flow rate through an electrical arc created by a predetermined electrical current path;
• (b) shielding said plasma column in an inert gas containing at least 5-30% by volume oxygen, said shielded plasma column melting at least the metal of one ply at said spot while the oxygen increases the fluidity and wetability of the melted metal and reduces its surface tension allowing any vaporization of the ingredients to quiescently escape through the molten metal;
• and
• (c) ceasing plasma arc impingement for allowing the molten metal to solidify and complete the spot weld.