The right protective gas for your project
One of the most important components in welding – in addition to good equipment, of course – is the shielding gas. But why is the shielding gas so important in welding? These and all other questions about shielding gas will be answered on this page.
Here you can jump directly to the different points.
What is inert gas?
The protective gas is a gas which is used to displace the atmosphere. It protects your weld metal from oxygen and other gases from the ambient air. But shielding gases are not only used for welding.
Protective gas is used in the following applications:
- In the food industry: the next time you shop in a supermarket, look out for the label “Packed in a protective atmosphere”. Protective gases are used to ensure that food stays in its packaging for as long as possible. CO2 and nitrogen (N2) are usually used here.in electrical engineering: to prevent sparking or to extinguish sparks, an atmosphere of protective gases is also created here.in continuous casting, the noble gas argon (Ar) is used to decant the liquid metal.in hardening, protective gases ensure that oxygen from the air cannot react with the metal.of course, protective gas is also used in welding. In this article, this field of application will be dealt with comprehensively.
Why a shielding gas when welding?
These gases ensure that the surrounding atmosphere is kept away from your weld. The result of your work is decisively influenced by different compositions and mixing ratios. For the optimal welding result you must choose the right gas.
The protective gases are divided into “active protective gases” and “inactive protective gases”. The difference is whether or how strongly the selected shielding gas reacts with the weld pool. The shielding gas table shows you which gases are classified in which category and when you use which.
Mostly argon, hydrogen, nitrogen, helium and oxygen or a mixture of these gases are used. The used gases will be introduced to you in more detail. Without inert gas you will not be able to achieve a clean and break-proof weld seam!
Especially when welding high quality steels or aluminium you will have to find a suitable gas. The table under “Which shielding gas do I need” shows you which compositions have proven to be effective.
Can we do without?
The shielding gas is extremely important to keep the oxygen from the atmosphere away from your weld. Otherwise it could react with the hot metals. This could cause corrosion or burns. Of course you don’t want that. 😉
Although the inert gases are so important for the reasons mentioned above, it is also possible to do without them completely. In this case, however, your electrode welding unit* will be used. 😉 This page does not deal with electrode welding units in any further detail. (If you want to get more information about these devices, you will find different models here or here).
Which protective gas do I need?
Which shielding gas is right for you naturally depends on which metals you want to weld and which welding process you use. Here you will find a small overview of the different shielding gas welding processes:
Which shielding gas is used for MAG, which for MIG or TIG welding? The following table will help you to find out which category is the right one for you:
Welding methodsCategoryExampleWIG,plasma welding,MIGinactive gasArgonHeliumMAGactive gasMixed gas of argon and CO2Mixed gas of argon and O2
As shown in the table, active gases are used in metal active gas welding (MAG for short). In MIG welding, on the other hand, inert gases are used.
Inactive vs. active gas:inactive gas active gasThese shielding gases are very inert and hardly react with the environmentActive shielding gases actively influence your weld seam or the arc.
Note to previous tables: For TIG-welding I recommend only Argon 4.6. To weld aluminium (-alloys) helium or an argon-helium-mixture is often used. You have to answer the cost/benefit ratio of these or other gas types for yourself. I think, here the price often decides. Quite simply.
The different protective gases:
The following gases are used in protective gases:
- Argon: Argon is often used in gas shielded arc welding. The shielding gas 18, for example, consists of 82% argon. (The rest is mainly carbon dioxide). Of course the gases Argon 5.0 and Argon 4.6 (which is also used for aluminium welding) also have a high proportion of AR.Helium: Helium-argon mixtures are also popular shielding gases. With helium you can work very fast and your seams have a higher quality. (This also depends on your skills – don’t blame everything on the shielding gas 😉 )Oxygen: Oxygen stabilizes the arc during welding. This active gas is also used in MAG welding*.carbon dioxide The shielding gas 18 got its name because of the 18% carbon dioxide content. Nitrogen: Nitrogen protects the welding wire and the molten metal from the oxygen in the surrounding air.
The fact that the shielding gas is not really cheap should already be considered and taken into account before buying a shielding gas welding machine – such as the BT-GW 150 from Einhell (which can even be operated with 230Volt)*. After all, the costs for refilling, for a new gas cylinder or for exchanging it will come up regularly. Depending on where, how much and how often you weld, this cost factor even comes up relatively often.
The advantages and disadvantages of an exchange cylinder compared to a proprietary cylinder or the leased protective gas cylinder will be discussed in more detail in this article.
Carbonated beverages as a cheap alternative?
I have often heard about the “trick” of simply buying a carbon dioxide bottle from a pub in the neighbourhood.carbon dioxide is carbon dioxide.in fact you can weld with beverage carbon dioxide. But that does not lead to a clean result! I’d advise against it. You can do it this way. But then it’s just… (you know 😉 )
The reason for this is, shielding gas for welding is cleaned and stocked.
Carbon dioxide, which is mixed in soda or beer anyway, is not dried. Why should it?
However, this moisture is not an advantage for you when welding.
Another disadvantage of “pure” carbonic acid is the large penetration. This is desirable in shipbuilding, for example, but many (hobby) do-it-yourselfers have to pay particular attention to the curing. Especially in the automotive sector, very thin sheets of car bodywork are often welded.
In this case, a large burn-in, which is favoured or caused by the CO2 content, is only harmful. In addition, your arc will be much more unsteady.
So here is the recommendation once again: Better use a “decent” protective gas such as protective gas 18* instead of carbon dioxide from the pub next door.
What does shielding gas cost and where can I get it?
Probably the most important question – after clarifying which protective gas is the right one for you – is the price.
However, this question cannot be answered easily. In order to make the most favourable choice for you, it must be clarified which protective gas you need. It is also important to know what type of protective gas cylinder you prefer and how much of it you need.
The first question is whether you prefer to own a proprietary bottle and take care of everything yourself or whether a swap bottle is ideal for you. If you only need supplies for a short period of time, it may also be worthwhile to simply borrow the protective gas cylinder.
Advantages & disadvantages of different gas cylinders:
Each of the suggested options has advantages and disadvantages for you. Here they are briefly summarized:
AdvantagesDisadvantagesHire a gas cylinderQuick & easyAvailable in every major DIY storeCylinders are TÜV-certifiedNo waiting times for fillingMonthly rental feesInexpensive to ownThe gas cylinder is yoursLong waiting times for refilling possibleYou have to take care of the TÜV yourselfExchange bottleQuick & easyAvailable in every major DIY storeCylinders are TÜV-certifiedNo waiting times for filling
How large should my protective gas cylinder be?
An important cost factor is of course how much shielding gas you need. Of course this point is also reflected in your running costs. The most important question for you is: “How much shielding gas do I need?”
How much shielding gas do I need?
Most shielding gases are offered in 5, 10, 20 or 50 liter cylinders. Which size you choose depends on where and how much you need to weld. Especially in workshops the larger cylinders predominate. But also the small 5-litre inert gas cylinders have their applications.
Here are the different advantages and disadvantages of the different bottle sizes:
Volume:AdvantagesDisadvantages5 Litres:Cheaper than larger cylinders,Easier to transport,You are more mobile,You can change the place of use more quickly.for larger repairs usually much too little,If you have to practice, this volume is also hardly sufficient,For welding work outdoors the 5 litres are also quickly too little.10 Litres:Contains more shielding gas than the small 5-litre cylinders,You are therefore still relatively mobile.heavier than the 5-litre cylinders,Contains of course less gas than a 20-litre cylinder.20 Litre Especially suitable for workshops,Lasts much longer than a 10 litre gas cylinder,Less mobile than smaller sizes50 Litre Especially suitable for workshops with a fixed location,Lasts much longer than smaller gas cylinders.calculated on the litre cheaperNevertheless bigger and & more unwieldy than the smaller cylinders.
As you can see, the most important features are the size and weight of the bottles. The smaller the gas cylinder is, the lower is its weight. This makes you much more mobile than with the larger gas cylinders. But the price per litre is also higher.
The larger inert gas cylinders, on the other hand, are considerably cheaper in relation to the litre, even if the acquisition costs are not negligible. They also have a considerably higher weight. This makes them ideal for workshops with a limited range of applications. A further advantage is of course that such a gas cylinder lasts much longer than the smaller versions. Have you ever run out of your protective gas at the weekend?
To name some current prices, the following costs protective gas at Amazon:
Protective Gas 18Argon 4,650 Liters:289.00 EURView at Amazon289.00 EURView at Amazon20 Liters:224.99 EURView at Amazon224.99 EURView at Amazon10 Liters:159.99 EURView at Amazon159.99 EURView at Amazon5 Liters:149.99 EURView at Amazon138.99 EURView at Amazon
How do I adjust the pressure reducer for the shielding gas?
Of course it is important to know how long your protective gas cylinder will last. Again, various factors play a role. For example, if you work in a wind-protected welding cabin you will need less gas than in the staircase of the building shell or outdoors.
In order to be able to better estimate how long your shielding gas will last or how large your shielding gas cylinder must be, you must also know where you are mainly welding. The pressure you set is not really responsible for the yield of the shielding gas during welding. Much more important is the flow rate. If your pressure reducer only has one pressure gauge for the cylinder pressure, you should buy a new pressure reducing valve. This makes it much easier to set the right amount of gas.
You can use the following formula as a reference value for the correct setting on the pressure reducer:
Reference value : Wire thickness in mm x 10 = ltr./min
You don’t want to do your own math? No problem. At our site you will find an online calculator that helps you to find out the right amount of gas. It even considers whether you are welding aluminium!
Experience has shown that this value is already a very good indication of the correct amount of gas around your weld. If you have to work in a draught or are exposed to wind, this value should be corrected slightly upwards. But you will find that out quickly with a small test seam. With this setting you are already very close to the optimal result.