Welding gas is an important component of MIG and TIG. While you can attempt to MIG without it, the quality of the final result is not as good. And in the case of TIG, gasless welding is not possible. When it comes to sizes, there are many different options. The most common and best welding gas bottle and cylinder sizes are the 40, 80 & 125 cubic ft ones. Below, we’ll share some of the best options available to you.
Unbeknownst to many, choosing what gas to use is not limited to selecting which one is suitable for your chosen workpiece. You also need to consider other aspects. What are the right settings for MIG and TIG, and are the cylinder sizes suitable for your workshop? Here’s everything you need to know about welding gas bottle sizes.
Best welding gas tanks & bottle sizes
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At a loss about all these? You don’t have to be. You need to keep reading to learn more and tips that can prove handy for all your projects. We will walk you through all the different aspects that are important to you. Then we will be sure to leave you knowing a lot more about the topic as you are done reading this article.
It’s important to know that there are different kinds and ways to be used. Each of the different types has its own set of functions that it is trying to achieve.
When we talk about gases in welding, most people would immediately think of the shielding one. What they don’t realize is that there are different types used. There are also ones used to clean the welds formed or protect the materials after the bond has been made.
Some metals or filler rods require preheating before welding to ensure a final quality or brazing. For this purpose, you need to use heating gas. This type is typically a mix of fuel gas with some oxygen added. When it is lit up, it gets warm enough to heat the materials. However, it cannot melt them. Read on to learn more about the individual types.
To prevent the contamination of the molten pool when doing MIG or TIG, you need to use a shielding option. Otherwise, the result will be ugly. This type of gas is important because it affects the following parts of the weld:
- the appearance,
- bead shape and penetration,
- alloy content,
- fumes produced,
- and many other things.
Shielding gases are often inert and can either be pure or made up of a single type. They can also be a mix of different types. The pure options are argon, carbon dioxide, and helium. In contrast, the mixtures used as shielding options can include different combinations of pure options. Adding oxygen, nitrogen, or hydrogen to them can be done.
Argon is the most widely used shielding option among all the pure choices. It is inert and will not cause a reaction to the metals being worked on. It is suitable for working on aluminum and other metals that are refractory or reactive for that reason. You can use this with all types of materials in TIG, while its use in MIG is limited to nonferrous materials.
Argon also causes a low heat transfer because its ionization potential and thermal conductivity are low. It creates the deep and narrow penetration it is known for. Not only that, but you also get a very stable arc that allows you to have better control over the pool that is created. Also, argon aids in the breaking down of any oxides present in the workpiece.
In contrast, helium has high ionization potential and thermal conductivity. The result is a deep but wider weld and increased heat. Unfortunately, it also makes starting the arc much more difficult. It’s especially the case if you do not use the correct settings of your MIG or TIG. This type is not commonly used in MIG and is only suitable for nonferrous metals for TIG.
Carbon dioxide is normally only used for MIG and the highly-similar flux core method because it has complex interactions with different metals. With this type, you get a balanced ratio in terms of depth and width due to its wide penetration and high heat. This increased heat is also because of its low thermal conductivity and ionization potential.
Using different shielding mixtures is a common practice. These mixtures even work better with certain metals compared to using pure gases. Found below are the different metals and recommended mixtures to be used:
- Carbon steel – argon and carbon dioxide, argon and oxygen, argon, carbon dioxide, and oxygen
- Stainless steel – argon and carbon dioxide, argon, carbon dioxide, and helium (aka tri-mix), nitrogen and hydrogen (only for austenitic stainless steel)
- Aluminum – argon and helium, tri-mix
- Light gauge steel – argon and oxygen
- Nickel – argon and helium
- Copper – argon and helium
A common issue is that craftsmen take strides to ensure a neat final result on the surface but neglect the underside. Because of this, the underside looks different and can even be contaminated because any shielding gas unprotects it.
To address all these, doing a back purge is necessary for a clean weld on both the surface and its underside. When back purging, a purging gas that acts as a shielding mechanism is used for the underside. This process is usually done on stainless steel, nickel, and titanium alloys.
Carbon dioxide and nitrogen are often used for purging purposes. Still, other inert options like helium and argon can also be used.
In instances where you need to ensure your finished product must be flaw-free, a shielding gas may not be enough to avoid contamination. As the metal cools, it can still be stained or damaged by any contaminants present in the atmosphere. Using a blanketing gas like nitrogen will protect your workpiece from these contaminants.
Shielding ones are the ones used most often. Still, it is also important to familiarize yourself with the other types you can use for your projects.
Bottle, Tank & Cylinder Sizes
A welding gas is typically not flammable, but it still poses health risks. That is why you need to choose the right cylinder size for your workshop. Not only that, but it will also provide convenience for you because you don’t have to keep getting a new one when you run out.
High-pressure welding tanks use cylinders of uniform sizes. They’re namely oxygen, helium, nitrogen, hydrogen, and carbon dioxide. A high-pressure cylinder typically has volumes ranging from 20 to 300 cubic feet. They’re also called welding bottles or tanks. Welding gas bottle sizes are indicated either by their volume or represented by letters, such as:
- R = 20 standard cubic foot or SCF
- V = 40 SCF
- Q = 80 SCF
- D = 125 SCF
- S = 150 SCF
- K = 200 SCF
- T = 300 SCF
Note that the welding bottle sizes above apply for those encased in steel cylinders. There are also aluminum cylinders available, but they have much more limited sizes.
Low-pressure options have more varied sizes. If the argon tank size is indicated with a Q, you know it’s 80 SCF.
When it comes to doing this type of work, argon is arguably considered the most important gas. Different types use different amounts of argon and other gases, so you need to know which tanks to use for your project.
The problem lies in that many of the tanks come in different sizes, depending on the manufacturer. It’s the case except for high-pressure bottles. Manufacturers purposely do this to identify which tanks are theirs easily.
Despite this, they also make tanks in sizes that can be considered common to different manufacturers. For example, argon has the following common bottle & tank sizes that are represented either by a letter or number. These range from 21 to 335 cubic feet:
- R or 20 = 21 cubic feet
- RR or 40 = 44 cubic feet
- Q1 or 60 = 65 cubic feet
- Q or 80 = 83 cubic feet
- S or 125 = 125 cubic feet
- S or 150 = 155 cubic feet
- K or 250 = 251 cubic feet
- T or 330 = 335 cubic feet
Note that the S-sized tanks have two types available. That is why you need to check the actual volume when purchasing this type of tank. And in most cases, the smallest-sized tank allows you to work continuously for an average of 1 hour to 1 hour and a half.
Settings for MIG and TIG
Aside from choosing which option to use and the right bottle size you need, you also need to determine the right settings for MIG and TIG.
Using gases is not as simple as letting them flow freely as you work. You need to make sure that just the right amount is being released because this will also affect the quality of the metal bond. Both MIG and TIG have uniform settings regardless of the type of shielding gas.
When it comes to MIG, the flow rate typically ranges from 25 to 30 cubic foot hours (CFH). Its matching pressure should be between 3 to 7 psi. Most craftsmen consider 20 CFH as an ideal flow rate since setting it higher increases spattering and make the weld porous. Note that bigger nozzle diameters and drafty conditions will require higher gas flows.
On the other hand, the flow rate of TIG is typically lower than that of MIG and ranges from 15 to 25 CFH on average. However, it can also go up to 50 CFH if you use larger cup sizes. If your flow rate is between 35 to 50 CFH, the pressure should be between 20 to 30 psi to match it. But if you have a lower flow rate, you also need to lower the psi.
MIG and TIG require the flow rate and pressure to be directly proportional. The higher the flow rate, the higher the required pressure. They only differ in the actual numbers.
When working, these different types are extremely helpful. Using them is not as straightforward as some think. Whether it’s your first time using it when welding, or you have already tried it but have yet to get satisfactory results, these tips are sure to help you out.
- Use a lens if you want the flow of shielding gas to be evenly distributed and lessen defects caused by contamination.
- If you want a laminar flow, opt for a converging nozzle with the longest length and largest diameter suitable for your project.
- To get the best results, you should do a pre-flow and post-flow.
- Don’t ignore any leaks. Not only will it contaminate your work, but you also end up wasting gas and money because of it.
- Back purging is the best way to prevent sugaring or oxidation on the underside of your workpiece.
- For aluminum work, lessen the gas if you are welding on A/C.
- When working on sheet metal, opt for an option with a higher argon content for less spatter.
- Use a tri-mix option consisting of 90% helium, 8% argon, and 2% carbon dioxide when MIG welding 304 and 316L stainless steel.
- Test if your flow is appropriate by placing your hand around 3 inches from the nozzle tip and allowing the gas to flow. If you feel the gas at this distance, it means you have an adequate flow that will prevent a porous weld.
- Refer to manufacturer recommendations in terms of which option to use with equipment and workpiece. Your choice should also match your wire.
- Ensure that the shielding gas flowing out sufficiently protects the molten pool to reduce spatter.
More is not necessarily better. For both MIG and TIG, you need to use the right amount for your projects. If you use more than necessary, it will be easier for your workpiece to be contaminated.
Did this article better help you understand what you came here to learn? We love receiving input from our users and often include some of their feedback in the articles. Suppose you are interested in continuing to read. In that case, we have a couple of interesting articles on plasma cutters. There is also one of the best engine-driven welders, too. Or perhaps your interest includes learning how to use a plasma cutter, which we can also help you learn.
Here at Atlantic Aspiration, we’re on a mission to transform the built world and help create more transparency. It’s the reason we create educational resources for those wishing to become better builders and creators. Suppose you have an article in mind or might be interested in providing a related article on something you are passionate about. We invite you to reach out to our team.
Suppose you don’t have time to read the entire section. Read this section that will allow you to get a lot of the same information. The above section does provide a more in-depth review of all your various options. You may want to take a closer look at that if you haven’t already.
Should you weld without shielding gas? What happens if you choose to do so?
If you don’t use the adequate amount and type, you will find your result porous and weak. You must understand the use of this material for your work. Flux-clad or flux-core arc welding can be used without shield gas, but it is otherwise imperative that you use it. You don’t want to contaminate your weld pool while working on it. You will want this gas to do its job and protect the work you are doing!
Are all gases inert? Which ones are?
The two options that are considered to be inert are helium and argon. Two gases are SEM-inert and those include carbon dioxide and nitrogen.
Can you use any type of gas?
The type you are using will depend on the welding outcome you are trying to achieve. Only some types are used. These include:
- compressed air
- carbon dioxide
- and argon.
If you are interested in learning more, we recommend you read the article on oxy-acetylene settings when using a cutting torch.
How can I make sure that I don’t end up spending significant amounts of money on gas alone? And what is the most common type used?
The easiest way to keep your cost down when you are welding is by using a mixture of argon and carbon dioxide. It will ensure that you get good results and ensure that you aren’t spending massive amounts of money on your projects. If you are doing a lot of welding, you can save a lot of money going with this combination! Because of its price tag, the argon and carbon monoxide mixture is also the most common option that craftsmen choose!
What is a shielding gas?
A shielding gas helps maintain the quality of your welding. It does so by preventing it from getting contaminated by absorbing waste products like hydrogen and oxygen. These can be found anywhere in the atmosphere.
Argon and carbon dioxide are the gases most commonly used to ensure the final product does not become contaminated.
Best options for MIG – which one should I go with?
For metal arc, your best bet is argon. It can be used no matter the grade you are going for! It can be mixed with other types depending on the result that you are trying to achieve.
Welding bottles or tanks are measured in two ways – either through cubic feet hour or liters per minute. You’ll find that most welding gas experts will use a range of 15-35 CFH, which is approximately 7- 16.5LPM.
If we’re talking about high-pressure cylinders, welding tanks will come in a range of 5-6 sizes for your convenience. The smallest sizes in high-pressure bottles are 20cf, 40cf, and 60cf. The mid-range cylinders are 80cf. The high-volume cylinders are 125, 150, or 250cf. Each size has its name. For instance, 20cf is indicated by ‘R’ while 250cf is indicated by ‘K.’