• Basically, an electric arc is used to heat base metals and a consumable filler rod.
• This is the most common form of welding and is used in about half of all applications.
• A power supply is used to create a high potential between an electrode (guided by the welder) and a metal work piece. When moved close enough electrodes break down the air and start to flow. The local current of the flow is so high that it heats metals up to 30000C or 54000F.
• Material is added during this welding process.This material can come from a consumable electrode, or from a rod of material that is fed separately.
• The electrodes/rods are often coated. This coating serves a number of functions,
- it protects the welder from contact
- it deoxidizes and provides a gas shield
• Problems that arise in this form of welding is contamination of the metal with elements in the atmosphere (O, H, N, etc.). There can also be problems with surfaces that are not clean. Solutions to this include,
Gas shields - an inert gas is blown into the weld zone to drive away other atmospheric gases.
Flux - a material that is added to clean the surface, this may also give off a gas to drive away unwanted gases.
• Common types of processes include,
SMAW (Shielded Metal Arc Welding)/Stick Welding - A consumable electrode with a coating that will act as a flux to clean the metal, and to create a gas shield.
MIG (Metal Inert Gas) - A consumable electrode in a gas shield. In addition to simple materials, this can handle aluminum, magnesium, titanium, stainless steel, copper, etc. This torch is normally water or air cooled.
TIG (Tungsten Inert Gas) - A nonconsumable tungsten electrode is used with a filler rods and a gas shield. This can handle aluminum, titanium, stainless steel, copper, etc. This torch is normally water or air cooled.
SAW (Submerged Arc Welding) - A normal wire is used as a consumable electrode, and the flux is applied generously around the weld. The weld occurs within the flux, and is protected from the air.
