Welding electrodes are metal wires with baked on chemical coatings. The rod is used to sustain the welding arc and to provide the filler metal required for the joint to be welded. The coating protects the metal from damage, stabilizes the arc, and improves the weld. The diameter of the wire, less the coating, determines the size of the welding rod. This is expressed in fractions of an inch such as 3/32", 1/8", or 5/32." The smaller the diameter means it requires less current and it deposits a smaller amount of filler metal.
The type of base metal being welded, the welding process and machine, and other conditions determines the type of welding electrode used. For example, low carbon or "mild steel" requires a mild steel welding rod. Welding cast iron, aluminum or brass requires different welding rods and equipment.
The flux coating on the electrodes determines how it will act during the actual welding process. Some of the coating burns and the burnt flux forms smoke and acts as a shield around the welding "pool," to protect it from that air around it. Part of the flux melts and mixes with the wire and then floats the impurities to the surface. These impurities are known as "slag." A finished weld would be brittle and weak if not for the flux. When the welded joint is cooled, the slag can be removed. A chipping hammer and wire brush are used to clean and examine the weld.
The metal-arc welding electrodes may be grouped as bare electrodes, light coated electrodes, and shielded arc or heavy coated electrodes. The type used depends on the specific properties required that include: corrosion resistance, ductility, high tensile strength, the type of base metal to be welded; and the position of the weld that is flat, horizontal, vertical, or overhead.
The American Welding Society's (AWS) classification number series has been adopted by the welding industry. The electrode identification example below is for a steel arc-welding rod labeled E6010:
· "E" indicates "electrode" for electric arc welding
· The first two (or three in some cases) digits (60) indicate tensile strength in thousands of pounds per square inch
· The third (or fourth in some cases) digit (1) indicates the position of the weld. An "O" indicates that this classification is not used; "1" is for all positions; "2" is for flat and horizontal positions only; 3 is for flat position only
· The last two digits together (10) indicate the type of coating and the type of power supply required, 10 organic coating and DC current with reverse polarity.
· Therefore, a welding rod numbered E6010 indicates "E" an manual arc-welding electrode with (60) a minimum strength of 60,000 psi., that can be used (1) in all positions and (10) DC reverse polarity is required.