MIG or Metal Inert Gas welding is a special type of welding used for non-ferrous metals. It is also known as Gas Metal Arc Welding or GMAW. It is similar to the other arc welding processes where a consumable electrode is used to melt and join the metals. The arc is formed in the gap between the metal and the electrode. But it is different from the other welding processes as it uses a shielding gas while performing the welding. This is done to keep the welded joint free from the atmospheric contaminants. It first started in the 19th century and since then it has gone through a number of development processes.
Basic Principles of Metal Inert Gas (MIG) welding
The equipment required to perform the GMAW include
- Welding electrode which should be fed continuously with the feed unit.
- Welding Gun
- Welding Power Supply
- Inert gas (Shielding gas) supply
Principles and techniques to perform MIG welding
- The arc will be generated by the common arc welding process.
- The electrode in the form of a wire will be fed continuously with the feed unit.
- Along with the electrode feeding, the inert gas will be flown continuously from the welding gun.
- Feed mechanism can be semi-automatic or automatic.
- With constant voltage supply, DC or AC, both supplies can be used.
- At the time of welding, the wire is fed by pressing the trigger or the control switch. This switch also triggers the inert gas flow and starts the power supply. Thus an electric arc is struck.
- The welding tip generally manufactured by the chemically treated or bare copper is attached with the welding electrode. The copper tip is connected to the power source and supplies power to the electrodes.
- The gas nozzle will supply the shielding gas uniformly. It will cover the welding area. And the whole process will be free from oxidation. It should be checked that the flow of the gas is consistent or not. Insufficient flow of the gas will not protect the welding area properly.
- For high heat operations, a cooling water jet is very significant. Some machines have the provision of supplying water in the welding gun itself.
- Before welding, a welder needs to check his welding electrode holder. Semi-automatic water-cooled, fully automatic water-cooled and manual air-cooled electrode holders are available.
Advantages of MIG welding
- Superb quality welded is produced within very less time.
- Flux is not used in MIG process. So slag entrapment is there. High-quality weld is produced without any contamination.
- The arc shields provide protection to the arc. So very less power is lost in the environment from the alloy. The weld spatter produced is also very less.
- Different types of materials can be welded in MIG. It is a very versatile form of welding.
- Semi and fully automatic processes are there. So it is very effective and easier to use.
- The weld pool is easily visible. So it is very easy for the welder to perform the welding.
- Very less post-welding cleaning required whether in normal arc welding it requires a lot of cleaning and treatment.
- MIG welding provides higher rates of production. In MIG there is no need to change the electrode. There is no slug removing process needed. So welders can enjoy a faster and cleaner welding process. The productivity increases a great deal.
- Actually, MIG welding is very easy to perform. Even a technician with basic welding idea can perform MIG. But TIG welding is much tougher than the MIG.
- While performing the MIG welding, both or at least one hand remains free as the electrode is continuously fed by the feeding mechanism. So a faster welding with great quality is observed.
- The deposition rate is higher in MIG welding.
- The process is ultra-low hydrogen process.
Disadvantages of MIG welding
- The MIG use is limited to horizontal welding technique. It cannot be used in vertical or overhead positions.
- The equipment setup is complex. Also, the equipment is not portable. So complex and costly setup is involved in MIG process.
- The setup of the machines can be highly expensive at the beginning.
- Welding in outdoor conditions is very tough. In outdoor conditions shielding gas cannot be used properly as the outdoor conditions are not stable. The process can be used in draught free conditions.
- Additional electrical components are there so extra maintenance cost may be needed.
- Skilled manpower is needed to set up the welding plant.
- Some radiation effects are there. And it is severe than the normal welding conditions.
- Not efficient enough for the products where the high duty cycle is needed.
- Surface preparation is a great issue for the MIG welding. For doing MIG welding the surface should be free from dust and dirt. So before performing the welding some treating of the metal surface is needed. It there is rust then it should be removed too.
- Thicker metal welding is tougher in MIG. If the material is too thick then MIG does not work well.
- MIG sometimes provides incomplete fusion welding defect.
Applications of Gas Metal Arc Welding Technique
- The automobile industry has a huge use of MIG welding.
- Heavy constructions like bridges and building materials are welded using this process.
- Pipe welding can be done efficiently with MIG. There are different types of welding apparatus to weld the pipelines using MIG.
- MIG welding, if incorporated with robotics can be used in amazing automotive repairs. Heavy, medium to light all types of automotive vehicles can be repaired with ease. The welding is strong even if the thickness is limited to 0.5 mm. Before MIG, it was very difficult to weld automotive repairing parts.
- Worn-out railways tracks are easily repaired with MIG.
- Rebuilding is an important property of MIG that is used frequently. It is a form of repairing that can be used easily.
MIG welding is great for welding complex shapes and sizes. It is very versatile welding with great potential. As the process is easier to use it does not require any skilled technician to operate the machine.
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