TIG Welding Gas
The use of tig welding gas has always been confusing among the beginner welders. Especially when it gets compared to MIG welding gas, the usual question is, are gases used for MIG welding the same with TIG welding? So if you want to know more about gas for tig welding and have the same bothering question in mind, this is the time to discuss this topic to clear up the case.
First, it is important to understand that MIG and TIG welding both use gases either for shielding and for melting the electrodes. Also, both can use a single gas or a combination of gas depending on the kinds of metal the welders weld including the thickness of the metal. However, MIG welding can have limited capacity when it comes to fusing thin metals. The thinnest metal the MIG can weld is up to .8mm only and using the thinnest wire electrode. TIG, on the other hand, can weld up to .6 mm and unlike with MIG welding, it doesn’t warp up or burn through thin metals.
As we know, TIG means Tungsten Inert Gas so from its name we can derive that the gases that TIG welders use are inert gases. Inert gases are also called the “noble gases” based on our periodic table. These are the kinds of “inactive” gases that do not react with any element or substance that surrounds them. Being used in welding, the inert gas can serve two purposes: to serve as a shield and to melt the electrode faster.
Ideal Gas for
There are six kinds of gases used in welding and these are the argon, helium, oxygen, carbon dioxide, nitrogen, and hydrogen. However, only two of these react very well with TIG welding and these are the argon and helium. Pure argon (AR) is considered as the best tig welding gas because it can act as a shielding gas by protecting the weld pool from nitrogen absorption and oxidation. So even you weld hard to soft metals like stainless steel, mild steel, copper, or aluminum that commonly oxidizes, the arc that argon produces remains unaltered.
Helium gas, on the other hand, is lighter and possesses high thermal conductivity which means it passes heat or can transfer heat faster in which argon is not very good at. But compared to argon which is heavier, you need more of it in order to use it as a shielding gas. Helium is also not quick to ionize so you need to put up a higher amperage to start the arc using pure helium. Also, using pure helium can cause spatter. So to make helium an ideal tig welding gas it should be combined with argon.
When welding softer metals like aluminum, the usual ratio mixture is 25% helium and 75% argon. This is to increase the travel speed of heat since alternating current (AC) will be used. Argon can also be used purely on aluminum when using AC because argon as gas for tig welding can produce a more stable arc, can give out more improved cleaning action and has a quick arc starting quality. The reason why helium is added is for the purpose of increasing penetration and making the weld pool more fluid thus increasing bond on the metal.
Why Some Gas Are Not Suitable
Going back to the use of other gases specifically with TIG welding, you may wonder why the other four gases (O2, CO2, nitrogen and hydrogen) are not appropriate for use as the best gas for tig welding while they work well with MIG welding. These gases are actually described as semi-inert gases.
In MIG welding, using these gases in controlled quantities will produce better weld results. But when used on thin metals and non-ferrous metals on TIG welding, the heat these gases can produce can cause chemical reactions by oxidation both to the metal and to the tungsten electrode.
Here are the factors why the semi-inert gases would not work very well with TIG welding:
Oxygen is not suitable as a tig welding gas because it can cause oxidation on non-ferrous metals which can result in a scarred weld that will require a large amount of finishing work.
Carbon dioxide also contains oxygen. When the work metal or the filler material gets oxidized, the weld on thin or non-ferrous metals can become brittle and uneven.
Nitrogen can erode the tungsten electrode which can cause tungsten inclusion. Too much nitrogen will also result in the outcome of austenite. This is the formation of carbonized iron which can reduce weld strength by making the weld vulnerable to corrosion and cracking.
Hydrogen if used 5% can be mixed with argon in TIG welding because it has the capacity to increase the heat input while it can also protect the metal against oxidation. However, more than a 5% mixture may also result in brittle weld making it sensitive to cracking.
So the way these gases can react with softer and thinner metals even when used in TIG welding, we suggest you better stick with argon and helium for now.
Why Consider Argon
Some expert welders recommend using pure argon for tig welding because it can ensure a superior weld as it can cover and stabilize the flow of electrical current in the arc thus keeping the metal from getting oxidized. In tig welding, this is what they call high-purity welding. But to summarize the advantage of using argon as the best gas for tig welding, the following are what you should digest.
Argon can produce clean and pure weld on TIG welding. Argon can create a protective gas shield around the weld puddle and can continuously displace the air around the arc while focusing the heat on a certain zone and preventing the formation of oxides.
Argon can blend well with other gases though can work efficiently with Helium. When argon is used purely as a tig welding gas, the result is a strong ignition, the arc is more stabilized, the width of the weld will be good enough but the penetration can be slow to medium.
Using 50% argon and 50% helium, the ignition can be weak but the arc remains stabilized. The weld width has a better size and the penetration and speed of the weld pool become faster.
Combining 25% helium and 75% argon, this produces good ignition, the arc is more stabilized, the arc can produce good weld width and the penetration of melted tungsten is quicker.
Argon can reduce annealing colors on stainless steel. This is the discoloration on metal surfaces due to the application of heat thus it also reduces the cleaning time to eliminate this discoloration.
Argon is cheaper than other gas alternatives and considered a noble gas. Noble gases are the most stable of all gases as they do not change their state and have low reaction rates.
It can blend well with other gases when used in MIG welding. The typical gas used in MIG welding is CO2 which provides deep weld penetration and best for fusing thick metal. However, it cannot produce a stable arc alone and when mixed with other gases, spatters are likely to come up. But by combining argon, the arc becomes more stable, the puddle is more controlled and with less spatter compared to pure CO2 use.
Hopefully, with this introduction about the tig welding gas, we have cleared up some questions that some people frequently asked. TIG welding is known as the most complex of all the welding types which include MIG, stick and flux-cored welding. So to become good with it, you must also understand how the two most usable forms of gas like argon and helium should work with the TIG welding process.
Understanding the gas for tig welding including their mixtures can help you understand how these gases can be useful in fusing non-ferrous metals like aluminum, bronze, alloy, copper and even gold. And though it has its weakness in welding thicker metals which MIG is a better option, TIG is more preferred by professional welders in sealing gaps, welding joints and in sealing off joints on all angles regardless of metal types as long as it has thinner gauges.
For now, you can stick to the use of argon and helium as the best gases for TIG welding. Or if you want to experiment with other gases, you can do it slowly but there has to be the use of argon for better shielding. Going back to the question if you can use the same gas both for MIG and TIG welding, the answer can be found above. And for those who are asking what gases for mig welding should work, we will tackle this on our other blog as well.