The Art of Welding. William Galvery

       courtesy of Lincoln Electric]

      The electrode is coated with a flux. Heat from the electric current causes the flux’s combustion and decomposition. This creates a gaseous shield to protect the electrode tip, the work, and the molten pool from atmospheric contamination. The flux contains materials that coat the molten steel droplets as they transfer to the weld and become slag after cooling. This slag also floats on the weld puddle’s surface and solidifies over the weld bead when cool, where it protects the molten metal and slows the cooling rate. The flux coating on some electrodes contains metal powder to provide additional heat and filler to increase the deposition rate. The electrode flux and metal filler electrode determine the chemical, electrical, mechanical, and metallurgical properties of the weld as well as the electrode handling characteristics. Only 50% of the heat power furnished by the power supply heats the weld; the rest is lost to radiation, the surrounding base metal, and the weld plume. See Figure 4-1.

Figure 4-1. The Shielded Metal Arc Welding process

When can stick welding be used?