Gas Welding Machine

Born out of the womb of war and dire necessity, the modern gas welding machine is a highly effective means of fusing two pieces of metal together. Using an electrical arc to create intense heat at the welding point, which both melts the metal being welded and the continuously-fed wire electrode of the welding gun (which serves as filler metal), gas welding machines of the MIG (metal inert gas) or MAG (metal active gas) types can be used easily and effectively with only a little practice. Their relatives, TIG (tungsten inert gas) welders, use a permanent electrode, a separate filler metal wire, and are even more effective at producing excellent-quality welds, but require a manual user with long practice.

The arc welding process has a few peculiarities of its own, however, which necessitate other design feature in a gas welding machine. At the blistering temperatures produced by a gas welding machine’s electrode, the molten metal can oxidize or rust in a moment if it is exposed to the open air. Oxygen therefore needs to be excluded from the welding site during the brief time it takes for the molten metal to cool and harden, lest the weld be contaminated and weakened.

This is achieved by blowing a steady stream of gas out of the nozzle of the welding gun. This gas gives the various types of welder their names, and keeps oxygen away from the welding pool of molten metal by displacing the air immediately around the welding point. For this reason, it is known as the “shielding gas.” However, the gas in a gas welding machine does more than simply protect the weld – different welding effects can also be achieved by using different gases.
 
The various uses of Shielding Gas

Some uses of shielding gas are determined by purely common sense factors. For example, more shielding gas is needed (the rate of its flow must be increased) if the weld is being made quickly. The reason for this is that less time is spent over any one point of the weld, so a thicker cloud of shielding gas must be created so that it will not disperse too quickly in the wake of the welding gun as it moves onwards. Slow welds, on the other hand, can make do with a lighter flow of shielding gas.

Different gases are used for different types of metal, and may also be varied depending on the depth of the weld desired. A ‘deep’ weld is one that penetrates a good distance into the metal and creates a very strong bond between the two pieces, while a ‘shallow’ weld bonds the pieces only in their surface layers.

Steel and stainless steel are each welded with a different shielding gas when possible. Argon produces a shallow weld on ordinary steel, so if a deep weld is desired, carbon dioxide (CO2) is needed as part of the shielding gas. Pure CO2 causes oxidation, so it is usually mixed with argon, with the mixture providing a deep weld without the risk of oxidation and the brittleness it causes. Stainless steel, on the other hand, needs oxygen for best weld quality and depth. The oxygen can be no more than 1/20 of the mixture, however, or it will cause oxidation.

Nonferrous metals such as aluminum, magnesium, and copper are usually welded with argon or a mixture of argon and helium. These shielding gases produce far better results with nonferrous metals than CO2 does. Hydrogen and nitrogen are often added to the shielding gas when welding copper. However, hydrogen is damaging to magnesium, so should not be used in the gas for this metal.

Like an alchemist of old, the modern welder can work best with different metals and produce different depths and qualities of weld – as well as different welding speeds, in some cases – by choosing the correct shielding gases to add to the welding process. A gas welding machine is a highly effective tool for bonding two pieces of metal, and to the layman, it may seem the electric arc alone is enough to get the job done. However, the shielding gas used is just as crucial – an unseen but essential element in the welding job’s success.