Wednesday, January 28, 2009
Shielded metal arc welding is extremely attractive for commercial work because it is fast and produces strong welds. An electric welding machine produces a specific amount of current, which passes through a cable, called an electrode lead, to a special handle that holds an electrode. An electrode is similar to a welding rod used for gas welding except that it must also conduct electricity. Electrodes are covered with flux.
An arc is struck by moving the electrode close to the metal being welded. The arc is extremely hot, enough to melt both the end of the electrode and the edges of the metal. The current passes through the electrode, melting the end of the metal where the arc from the electrode touches the metal.
A work-lead cable connects at the welding machine and is also clamped to the metal being welded, making it possible for the electric current to complete the circuit. The flux coating on the electrode produces an inert gas when an arc is struck, and the gas shields the arc and the weld from the surrounding atmosphere.
At the same time deoxidizers are produced that purify the electrode metal. This flux also form a slag, which protects the molten metal from oxidation. After the weld has cooled a bit, the slag is commonly removed with a special tool.
Arc cutting uses a powerful electric force to melt the metal. The molten metal is then oxidized with a special attachment that introduces compressed air. Special electrodes coated with insulating material that does not conduct electricity are used. This coating allows the welder to touch the metal being cut without freezing the electrode. The coating on a cutting electrode acts as a stabilizer, which concentrates on the arc and the same time intensifies the arc’s action.
- Auto darkening welding helmet is vital to protect eyes
- The current used for Arc Welding must be suitable to prevent damages
- Do not touch the material welded with bare hand
- Put on gloves and goggles
- Ensure that the work lead is attached to the base metal
- Do not attempt Arc Welding without knowledgeable supervision
- Never leave the electrode freeze on the work piece while the current flowing