Today, we will review the various gas types used for welding, how they work, and which type of gas works best.
We will examine which gas is the safest, the dangers associated with welding gases, and the types of gases that should NOT be used for welding.
Finally, an investigation into welding cannot be complete without including safety tips. Keep reading to find out all the information you need to know about welding gases.
To answer this question, we must familiarize ourselves with the various welding gases.
Some are pure, and others are blends.
Most blends are mixes of two gases, while a few are a mixtures of three gases.
The pure welding gases are:
Acetylene is used for oxy-fuel welding applications, and it is excellent for welding, brazing, and cutting steel alloys less than 1” thickness. Usually used with Air carbon arc gouging or plasma arc cutting (PAC) processes.
Argon is considered the gas of choice for aluminum. It is used in casting, metal fabrication, and is often blended because it enhances the ‘arc characteristics or facilitates metal transfer in Gas Metal Arc Welding (GMAW or MIG).
Atmospheric contamination of molten weld metal during gas shielded electric arc welding is prevented when using carbon dioxide with argon as a shielding gas while welding or in a pure vapor state.
Helium is used to create an inert gas shield, and it prevents oxidation during welding of such materials as aluminum, stainless steel, copper, and magnesium alloys. Weld pool ‘fluidity and travel speed’ increases with the addition of helium.
Hydrogen is used in metal fabrication; it provides an enhancement effect or shielding effect when operating in high temperatures for stainless steel manufacturing. (H2) is mixed with argon for austenitic stainless welding. It enhances the operation of plasma welding and cutting.
Nitrogen can enhance the cutting of plasma and heat-treating. This gas can be used as a ‘purge gas’ with stainless steel tube welding. If using argon-based shielding gases, small additions of Nitrogen might be used for welding stainless by either the GMAW or MIG process.
Oxygen supports oxyfuel cutting. It can be added to shielding gases (in small quantities), and it is used as the plasma cutting gas on carbon steel (with Hafnium electrodes). It also causes oxidation(rust), so care needs to be taken as it can’t be used with copper, aluminum or magnesium.
Scrap yards use propane in Oxy-fuel processes for cutting carbon steel because the quality of the cut isn’t typically critical.
Propylene burns hot, and the cutting speed must be calculated case-by-case before you choose this (as your most) economical choice for fuel gas.
Argon, helium, carbon dioxide, and oxygen are the most popular shielding gases. Their purpose is to prevent exposure of the ‘molten weld pool’ to oxygen, nitrogen, and hydrogen that are all contained in the atmosphere.
We cannot look at welding gases without considering mixtures.
Welding gas mixtures include:
Argon-Oxygen mixtures are 1, 2, or 5% oxygen and used for welding heavy section carbon steel for heavy equipment such as heavy farm, military transport, auto assemblies, and ships.
Generally, these blends are used on carbon and stainless steel. If making out-of-position welding, higher levels of oxygen will increase puddle fluidity.
There are two argon-helium-carbon dioxide mixtures. One is made up of 90% helium, 7.5% argon, and 2.5% carbon dioxide. They are good for short-circuiting stainless steel.
The mixture minimizes carbon absorption, and it assures ‘good corrosion resistance, especially in multipass welds.’ It provides good arc stability and gives a depth of fusion.
The higher helium gives extra heat input that can overcome stainless steel’s naturally sluggish weld pool.
The combination of 66% argon, 24.5% helium, and 7.5% carbon dioxide is best for ‘spray and pulsed spray arc welding of both carbon and low-alloy steels.’ It is good for any thickness in any position.
It welds well over rust and oil and produces good mechanical properties and weld puddle control.
Laser gases are pure or pre-blended mixtures: the gases include helium, nitrogen, carbon dioxide, and sometimes carbon monoxide.
Laser gases, were used since the 1960s for cutting and welding, as they offer better precision and control, better accuracy, higher cutting and welding speeds, cleaner working, and the costs of using lasers save money. But their applications are limited.
When choosing a welding gas, it is probably best to check online and then double-check with the hopefully knowledgeable welding supply store staff.
The gas choice is very much dependent on the type of welder, the properties of the metal(s), the process--such as GMAW or MIG, and the situation under which the welding operation will occur.
To best understand the welding operation and how welding gases are used, it is important to have a basic understanding of welding itself.
Welding is the process in which an electric arc forms while using certain gases. This arc occurs between a consumable wire electrode and a component metal(s). The electrode heats the component(s) and causes them to melt, thus they join.
In addition to the wire electrode, a shielding gas feeds through the welding gun. This shields the process from contamination such as oxygen that can corrode the metals and other pollutants that are probably in the air.
This process can either be automatic or semi-automatic depending on the required job. A constant voltage, a direct current power source is usually used with GMAW. A constant current system and alternating current can also be used.
Metal transfer in GMAW consists of four primary methods: globular, short-circuiting, spray, and pulsed spray. Each transfer type is different and has its own advantages and limitations.
This is always a tough question. One needs to take in quite a few factors.
Most standard welds of both techniques will use some percentage of argon as it is inert, stable, and relatively cheap compared to other noble gases. But depending on the properties of the metals and desired results you will sometimes need to use a mix of gasses instead of pure argon.
Above we have provided a handy table that details what gasses can be used for what metals and what techniques.
First let’s talk about MIG welding.
In addition to Argon one can add Helium (He) to increase penetration and fluidity of the weld pool.
Pure Argon or Argon/Helium can be used on all welding grades.
Sometimes small percentages of oxygen (O2) or carbon dioxide (CO2) are needed to increase electrical conductivity and improve the arc stability.
This in term leads to an increase in fluidity and results in a better weld deposit. Specifically for stainless steel oxygen (O2) or carbon dioxide (CO2 can be replaced with small amounts of hydrogen (H2).
The typical mixes are Pure Argon, Argon with 30% added Helium, and a 3 gas mix of Argon 30% Helium and mix of 1-2% O2/CO2/H2/N2 depending on the welded materials properties.
Pure argon is preferred when it comes to pulsed MIG welding, while short arc welding prefers Helium with mixes of other gasses.
Now let’s talk about TIG welding.
As with MIG welding Argon is the preferred inert noble gas used for welding. Helium again can be used to increase the weld penetration and fluidity if necessary or desired.
Now with TIG welding adding Nitrogen (N2) or Hydrogen (H2) can have some special enhancing effects.
Hydrogen(H2) is often used and has all the effect of Helium but amplified but it comes at a risk of porosity if doing multi weld runs on the same material.
Nitrogen(N2) carries similar properties but can only be used in nitrogen alloyed grades of welds.
Any oxidizing gasses are not used in TIG welding as that would destroy the tungsten electrode.
Welding gases can be hazardous to your health. The gases can react with metals to produce fumes that can make you sick or worse. All welders should ensure they take precautionary measures when dealing with welding gasses.
The carbon dioxide used for shielding is exposed to very high temperatures, an oxygen molecule can be stripped away in certain conditions and carbon monoxide (CO) is formed, this gas is odourless and tasteless if you are in a closed environment CO levels can build up and prove fatal. Carbon monoxide can also formed in oxyacetylene welding.
MIG and TIG welding makes the most ozone, and that increases when aluminum is welded. Ozone can damage the eyes, nose, throat, ears, and lungs.
Inhaling some nitrogen oxides (NO2 and similar) can also harm the lungs as they cause fluids to build up in the lungs.
It is difficult to filter the gases’ safety from the welding process because toxic chemical and metals are produced during welding.
Welding fume contains trace amounts of the welding rods, base materials, and the material that’s being welded. For this reason, it is imperative that all welders — and even people who work in or around welding sites — keep away from exposure.
The welding gases themselves are not the most harmful thing facing the hard-working welder. Instead, one needs to take care of the fumes created after welding.
These hazardous fumes are not inert gases you used, but a mixture of all the post weld processes that can be incredibly toxic.
If working with Manganese alloys one really needs to take care as they produce the most toxic fumes. Manganese inhalation can cause serious damage to the brain and nervous system. Manganese exposure can even lead to Parkinson’s disease. In 2001 a neurologist study reported that 20% of welders showed early signs of Parkinson’s.
The incidence of Parkinson’s is so high that lawyers continue to file cases for welders suffering from Parkinson’s and diseases related to it. Parkinsonism or Parkinsonian syndrome are now medical terms resulting from manganese poisoning.
An obvious gas unfit for welding is gasoline vapor. Sometimes ethyne is used for welding, but ethane cannot be used.
Ethyne, which is an acetylene, is used with oxygen for welding. The triple configuration of the chemical bond enables the storage of a good deal of energy that can be released as heat.
The triple bond that makes the oxy-acetylene flame the hottest of all gas flames is also responsible for two or three other properties of acetylene gas. Such properties seem to defy the law of definite proportions.
The first is that, when free gaseous acetylene is subjected to shock or ignition, some of the triple bonds break. This releases enough energy to cause all other molecules in the enclosed volume to decompose into carbon and hydrogen. This can result in an explosion.
In other words, acetylene is very flammable.
Second, the flammability range of mixtures of air and acetylene is greater than any other fuel or gas/air mixture. The acetylene/air mixture(s) can be ignited when they hold anywhere from 2.5% acetylene to 80% acetylene.
Generally, any fuel gas that is burned with oxygen must have the following:
If safety measures are ever ignored, welders face many hazards that are potentially dangerous. Hazards can include electric shock, inhalation of fumes and gases, and even fire and explosions.
In other words, if in doubt regarding safety requirements, consult an OSHA (Occupational Safety and Health Administration) manual or a local expert.
The following items should be worn on the body for basic welding needs:
(note that Arc welding requirements are stricter than basic welding):
Welding safety in the workplace includes a ‘DANGER’ sign to alert anybody who might pass by the welding area. A curtain on a rod will help protect others from accidentally ‘looking’ into the welding glare.
Other important recommendations include:
Welding requires a great deal of equipment and preparation. The equipment is meant to keep the welder and others in the workplace safe.
If at any time a portion of weld were to break on a high building or structure, it could be a rappelling firefighter or possibly a rappelling welder that fixes it.