This early (circa 1885) process employed two carbon rods fastened in a holder so that their ends converged. An arc was drawn between the converging ends and caused to impinge on the work by means of a powerful electromagnet. This was also known as the "electric blowpipe" method of welding. It required so much skill that it was impractical for general use.


    A condition existing in an electric circuit when there is no voltage present. 


    A term sometimes used to describe a resistance welding procedure, which uses refrigerated electrodes for welding aluminum. The process involves welding with electrodes chilled to -17°C (0o F), which improves the operating life of the electrode. See REFRIGERATED WELDING. 

  • ZINC

    (Chemical symbol: Zn). A lustrous, bluish-white metallic element alloyed with copper to form brass, and is also used in solders. Zinc is used in protective coatings on galvanized iron and other metals. Atomic number, 30; atomic weight, 65.37; melting point, 419.4oC (786.9 oF). Specific gravity ranges from 7.0 to 7.2.

    Pure zinc is ductile; in commercial form, zinc is brittle at room temperature, but becomes ductile when slightly heated. At a temperature of 200°C (392°F), it can be powdered. At temperatures between 100 and 150°C (212 and 302°F) this metal becomes malleable and can be rolled into sheets or drawn into wire. Zinc is capable of a high surface polish; it oxidizes slowly in air. When molten zinc solidifies, it expands somewhat, so that when it is used in die casting, sharp, well defined castings can be produced. Zinc is readily attacked by mineral acids, and dissolves when boiled with caustic soda or potash solution. 


    A grayish powder given off during the welding of brass, bronze or galvanized material. These fumes produce nausea. See WELDING FUMES. 


    A material compounded or formed by the reaction of zinc or zinc oxide with alkaline solutions. 


    (Chemical symbol: Zr). A lustrous, steel-gray, somewhat brittle metal with a high melting point. It is used as an alloying agent in iron and aluminum, and is also used in nuclear reactors. Atomic number, 40; atomic weight, 91; melting point, 2350°C (4262°F); specific gravity, 6.25.

    Zirconium is very hard and is sometimes used in hardfacing material because of its resistance to corrosion. When steel is alloyed with small amounts of zirconium, fine grain size is produced, and no aluminum additions to steel are required.