MIG Welding Machine

Introduction:

MIG Welding machine is defined as metal inert gas welding. It is also one of the types of arc welding machine. In this process no pressure is applied for welding. In this process of welding wherein coalescence is produced by heat the work piece with an electric arc establish between a  continues feed of metal electrode (copper coated) and the work piece. No flux is used as used in submerged arc welding (SAW Welding) but a shielding gas (Ar, He, Co₂₎ is used. It is also known as gas metal arc welding (GMAW).

Principle of Operation

Before welding set the current, wire feed speed and electrical connections. Now arc is struck by one of the two methods.

1^st method current and shielding gas flow is switched on and electrode is scratched against the job as usual practice.

For striking the arc by 2^nd method-electrode is made to touch the job is restricted and moved forward to carry out welding but before striking the arc shielding gas, water and current is switched on during the welding. Torch should be 10 – 12 mm. Away from the work pieces and arc length is kept between 1.5 to 4.0 mm. Arc are basically two types.

I.            Self adjusted arc

II.          Self controlled arc

In self adjusted arc, with decreases in arc length (from L₂ to L₁) voltage decreases and current increases from l₂ to l₁ melting the electrode at faster rate resulting into making the arc length normal for self adjusting arc, welding source with flat characteristics is required for self-controlled arc, when arc length decreases, arc voltage also decreases with reduces speed of electric motor and hence the feed rate of electrode this brings arc length to a set value for self-controlled arc, a welding source with dropping characteristics is preferred.

Equipment Required for MIG Welding Machine

I.             Welding power source with cables;

II.           Welding gun filler wire on a coiled spool;

III.         Shielding gas cylinder, pressure regulator and flow meter;

IV.          Control switch.

Different Types of Material can be welded by MIG Welding Machine

I.            Carbon and low alloy steel

II.          Heat resistant alloys

III.        Copper and its alloys

IV.         High strength low alloy steel (HSLA)

V.           Stainless Steel

VI.         Magnesium alloys

VII.       Aluminum and its alloys

Advantage of MIG Welding Machine

I.            Less number of spatters as compared with MMA welding;

II.           MIG is very faster process as compared with TIG Welding Machine;

III.         Deep penetration can be achieved through this process;

IV.          No use of flux during welding process;

V.            Process can be easily mechanized;

VI.          MIG produces a high quality, weld bead with minimum defeats;

VII.        Large metal deposition rate are achieved by MIG welding process.

Limitations of MIG Welding Machine

I.            Welding equipment is more costly and complex as compared to ARC Welding Machine;

II.          Trained operator is required to perform the operation;

III.         Process is not economically for job shop production;

IV.         All types of material cannot be welded.

Application

I.             For welding of Al, Cu, Mg, Ni and their alloys;

II.           For welding of aircraft, pressure vessels and shipbuilding industry;

III.         For manufacturing of refrigerator parts etc;

IV.          Rail road industries;

V.            Transport Industries.