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If you need clarity on welding processes, you just need to read this guide. The purpose of this article is to provide basic information on welding and the main welding processes: MIG MAG, MMA, and TIG.

Information on the meaning of the acronyms will be provided, an equivalent alternative acronym will be indicated, there will be the opportunity to understand the basic principle of each individual welding process and some fundamental indications will be found on the materials to be used in each individual process.

Here is an overview of the three welding processes: MIG MAG, MMA and TIG.

MIG MAG WELDING

CONTINUOUS ARC WELDING WITH GAS SHIELD (GMAW) OR WITHOUT GAS SHIELD (FLUX OR SELF SHIELDED WIRE)

• MIG Metal Inert Gas
• MAG Metal Active Gas
• GMAW Gas Metal Arc Welding

The continuous wire welding process consists of obtaining heat from the arc between the piece to be welded and the electrode wire which acts as a filler material, i.e., as a power source for the welding area.

The torch therefore serves to supply the filler metal and the shielding gas. In MIG MAG welding, the gas protects the electrode wire, the molten pool, the arc, and the workpiece.

To carry out the MIG MAG welding process you therefore need gas , whether inert, active or mixed, in a cylinder (refillable or disposable, the type of welding kit you need to adopt for your welder depends on this choice) and solid electrodes.

As mentioned, shielding gases are divided into inert and active ones.

1. Inert shielding gases : argon, helium, and argon-helium mixtures
2. Active shielding gases : carbon dioxide, mixtures of argon with oxygen or carbon dioxide.
3. Active shielding gases : carbon dioxide, mixtures of argon with oxygen or carbon dioxide.

• Argon (Ar) is suitable for almost all welding applications: good arc stability and easy ignition. Flowable material droplets
  Helium (He) is a rare and expensive inert gas: lower arc stability but greater penetration, although to ensure protection more gas must be consumed; it is used for welding large thicknesses and materials with high thermal conductivity (copper and aluminum).
  Carbon dioxide (CO2) is an active gas; it causes excessive spatter and establishes an unstable arc: it is necessary to work with a short arc with constant length, good penetration is obtained
  Active mixtures . Argon-Oxygen, Argon-Oxygen-CO2, Argon-CO2 to exploit the characteristics of individual gases.
• Helium (He) is a rare and expensive inert gas: lower arc stability but greater penetration, although to ensure protection more gas must be consumed; it is used for welding large thicknesses and materials with high thermal conductivity (copper and aluminum).
• Carbon dioxide (CO2) is an active gas; it causes excessive spatter and establishes an unstable arc: it is necessary to work with a short arc with constant length, good penetration is obtained
• Active mixtures . Argon-Oxygen, Argon-Oxygen-CO2, Argon-CO2 to exploit the characteristics of individual gases.

MMA WELDING

MMA MANUAL METAL ARC WELDING WITH COATED ELECTRODES

• MMA Manual Metal Arc
• SMAW Shielded Metal Arc Welding

The MMA welding process uses an arc as a heat source, striking between the coated electrode and the material to be welded . The heat thus generated allows the base material and the filler metal to melt, allowing the weld to be made.

An electrode is said to be coated when it has a core and a coating. The core is the current conductor that powers the arc and provides the material to fill the joint, while the coating protects the weld pool and stabilizes the arc , as well as characterizing the weld.

Acid-coated electrodes : iron oxides, manganese ferroalloys, and silicon. Good arc stability, they operate on both AC and DC. They produce a very fluid weld pool, so they cannot be used for positional welding. Their high cleaning power can cause cracking, and they also cannot withstand high drying temperatures, creating the risk of residual moisture.
Rutile-coated electrodes for use on thin layers offer excellent arc stability and a high weld pool fluidity, allowing for aesthetically pleasing welds. The easily achievable soft melting process allows for the formation of a large, viscous slag. They also do not clean well and cannot withstand drying at high temperatures. The arc stability allows for use with both alternating current (AC) and direct current (DC) in forward polarity.
Electrodes with a cellulose coating integrated with ferroalloys (magnesium and silicon). These electrodes allow for vertical welding. They produce "hot" weld pools, which generate deep-penetrating welds with little slag in the pool. The resulting weld is mechanically perfect but aesthetically unattractive. The unstable arc requires reverse-polarity direct current (DC) operation.
Electrodes with a basic coating of iron oxides, ferroalloys, and calcium and magnesium carbonates combined with calcium fluoride to produce fluorite, which facilitates fusion. They produce high-quality welds with high mechanical strength. They withstand high drying temperatures well. Fluorite, however, makes the arc very unstable, and must be kept very short; therefore, they are suitable for experienced operators. These electrodes are suitable for vertical, overhead, and other positioning welds. It is recommended to use direct current (DC) generators with reverse polarity. They are suitable for welding thick joints.

TIG WELDING

TIG TUNGSTEN INERT GAS WELDING WITH A NON-FUSIBLE TUNGSTEN ELECTRODE

• TIG Tungsten Inert Gas
• GTAW Gas Tungsten Arc Welding

The TIG welding process involves arc welding using an inert gas with a non-consumable tungsten electrode . Heat is generated between a non-consumable electrode and the material being welded. An inert gas, supplied by a welding torch, protects the weld area. The gas thus protects the molten metal and the electrode. To TIG weld, you can choose between using a rod with additional material or using the material melted by the electric arc.

Shielding gases are: argon, helium, argon-helium mixtures and argon-hydrogen mixtures.

• Argon (Ar) provides a rather stable arc with a less hot weld pool, suitable for welding thin thicknesses.
• Helium (He) offers high heat, recommended for welding materials with high thermal conductivity,
• Gas mixtures used to obtain shielding gases of intermediate characteristics.

Non-consumable electrodes for TIG welding are made of different materials.

• Pure tungsten electrodes require low current intensity and work in alternating current to have a more stable arc
• Thoriated tungsten electrodes . For working at high current intensity in direct current with forward polarity. The arc is stable. Suitable for welding steels.
• Zirconium tungsten electrodes for manual welding of aluminum, magnesium and its alloys at medium-low current intensity.
• Cerium electrodes, thanks to their high electron emission, allow good penetration and satisfactory wear resistance.

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