mig welding

ASeminar Report

on MIG Welding

byShubhamkar BarmanAngshuman Barman

Vishal SharmaNewton Das

Manish ChandaIge Riram

MIG WeldingA GMAW PROCESS

1. Welding and its types

Welding is a process of joining similar metals by the application of heat with or without the application of pressure and addition of filer material. It is broadly classified into plastic and fusion welding.

Plastic Welding: The type of welding in which the pieces of metals to be joined are heated to a plastic state and then forged together by external pressure is called plastic welding.

Fusion Welding: In

fusion welding, the material at the joint is heated to a molten state and allowed to solidify.

2. MIG Welding and GMAW Process

MIG welding is a gas shielded metal arc welding process using the heat of an electric arc between a continuously fed, consumable electrode wire and the material to be welded. Metal is transferred through a protected arc column of inert gas to the work.

A wire of copper coated mild steel is fed continuously from a reel through a gun with a melting rate up to 5m/min.

Current through the wire ranges from 100 to 400 A depending upon the diameter of the wire.

CO2 is principally used apart from argon or argon-helium mixture as shielding gas.

The welding machine is a dc constant voltage machine.

2.1 Development of GMAW and MIG Welding

1800s

• Sir Humphry Davis discovered the electric arc and metal electrodes invented by N.G. Slavianoff and C. L. Coffin in the late 1800’s.

1920• Early predecessor of GMAW was invented by P. O. Nobel of General

Electric with no shielding gas.

1948• GMAW was further developed by Betelle Institute.• Smaller diameter electrodes were developed.• Started the use of argon for shielding.

1953• Use of carbon dioxide as a welding atmosphere was developed.

2.2 Advantages and disadvantages of MIG welding.

Advantages Disadvantages

1. No flux required. 1. The arc is less stable.

2. Fast welding and deposition rates. 2. Generates more spatter.

3. Increased corrosion resistance. 3. Limited to short –circuit mode of metal transfer.

4. Easily automated welding. 4. Relatively high heat and light generation.

5. Suitable for all metals including aluminum and stainless steel.

5. Equipment is quite complex.

6. Least expensive and highly economic. 6. Not suitable for base metal contamination.

2.3 Tools and equipment used in MIG welding.

1. Power source: MIG welding uses a dc

constant voltage transformer. 2. Wire feeder: A wire feeder is required to feed the electrode wire continuously and smoothly to the welding gun.

3. Conduit and hoses: Conduit facilitates feeding of

wire to the torch and hoses supply the shielding gas.

4.

Welding gun: it transfers the welding current to the

wire and provides the gas for shielding the arc and weld

pool.

5. Gas cylinders: They are used to store

shielding gases like CO2, argon, etc.

6. Safety equipment: They all the tools

for safety and precaution purpose like

helmet, goggles, apron, gloves and boots .

2.4 Welding defectsCracks: Cracking occurs when the arc is struck but the spot is not welded properly.

Distortion: This happens due to uneven shrinkage of metal due to heating.

Gas inclusion: Gas inclusions is a wide variety of defects that includes porosity, blow holes, and pipes.

4. Undercut: This happen when the weld reduces the cross-sectional thickness of base metal.

5. Lack of fusion: Lack of fusion is the poor adhesion of the weld bead to the base metal.

6. Inclusions:  Inclusions occur when there is slag, dirt, flux or other impurities in the weld.

2.5 Application of MIG welding

1. The most common application of MIG welding is automotive repair.

2. Special welding equipment can be used to weld pipes.

3. It can even be used to reinforce the surface of a worn out railroad track.

4. Because of its high economy and utility it is widely used in various industries.