Today, we will review the various gas types used for welding, how they work, and which type of gas works best.
In addition, an examination of gases might determine which gas is the safest, the danger 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 for those who use welding gases. Keep reading to find out all the information you need to know about welding gases.
What is the Best Gas for Welding?
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 called mixtures of three gases.
Pure Welding Gases
The pure welding gases are:
- Carbon Dioxide
Acetylene is used for oxy-fuel applications, and it is excellent for welding, brazing, and cutting steel alloys less than 1” thickness. Air carbon arc gouging or plasma arc cutting (PAC) processes are performed with industrial air.
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 and stainless, copper, and magnesium alloys. Weld pool ‘fluidity and travel speed’ increases with the addition of helium.
Hydrogen is used in metal fabrication; it provides a protective atmosphere 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 cutting of plasma, food processing, 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).
Scrap yards use propane 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.
Welding Gas Mixtures
We cannot look at welding gases without considering mixtures.
Welding gas mixtures include:
- Argon-Oxygen Mixtures
- Argon-Helium-Carbon Dioxide mixtures
- Laser gases
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, used since the 1960s for cutting and welding, offer better precision and control, better accuracy, higher cutting and welding speeds, cleaner working, and the costs of using lasers save money.
Which Type of Gas Works the Best?
When choosing a welding gas, it is probably best to seek the input of knowledgeable welding supply store staff.
After all, 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 that is probably in the air.
This process can either be automatic or semi-automatic. 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.
But Which Type of Gas Works Best?
Chris Dumford, a welding inspector and expert from Cincinnati, traveled across the country to climb a 330’ high cell tower in order to perform a visual inspection. The tower had undergone improvements to strengthen it, and Dumford needed to verify its wind load capacity.
If Dumford found distressed welds, we can assume that he or another welding expert would need to make repairs.
Remember, Dumford used rappelling gear as he worked his way up and down the structure. Any structural damage might need to be successfully repaired quickly, a situation he was prepared to tackle. Structural damage includes fatigue cracks.
Other damages could include corrosion or cracking. He would need to strengthen, repair, or retrofit. There are different strategies and determinations that must be applied for various damages, so mitigating any problem would depend on the cause of the damage.
HOW TO KNOW WHAT THE BEST GAS IS?
For our purposes, then, we will assume that a small crack was observed midway up the tower.
The crack appears to be new, and Dumford notes that there are no other cracks or signs of fatigue on the structure. He considers the condition that led to the crack and decides that its position at a weld point is the culprit.
Upon closer inspection, it appears the weld area is unclean at the point of the crack. Inspection before, during, and after welding should have included edge preparation for cleanliness.
Yet the workmanship of the welded joint doesn’t appear to Dumford to have been flagged. He makes a note to insist that visual, possibly radiographic or ultrasonic inspection, will need to be discussed with the team.
In this case, the base materials were known, and Dumford chose the filler materials. He decided to use the following gases mixture; he wanted results that would not spatter while providing good spray transfer and penetration. Therefore, he chose: a mixture of 66% argon, 24.5% Helium, and 7.5% Carbon Dioxide.
This gas mixture works with any thickness in any position. It welds well over rust and oil and produces ‘good mechanical properties and weld puddle control.’
The choice could prove to render great results for Dumford. No splatter nor spatter. Remember, he was rappelling, fixed to a line of rope that would help steady his progress up and down the tower.
He was open to the elements, and he required a mixture that would both seal the cleaned and prepped crack as well as keep spatter at bay.
How Dangerous Are Welding Gases?
Welding gases can be hazardous to your health. The gases produce fumes that can make you sick. It must be a goal for all welders to ensure that they take precautions against inhaling the fumes.
The carbon dioxide used for shielding, for example, can form carbon monoxide that can kill you. Carbon monoxide can also form in oxyacetylene welding. MIG and TIG welding makes the most ozone, and that increases when aluminum is welded.
Those fumes can damage the eyes, nose, throat, ears, and lungs. Using some nitrogen oxides can also harm the lungs because their use can build up fluid in the lungs.
It is difficult to separate the gases’ safety from the welding process because toxic chemical and metals are produced during welding.
Fume content includes the composition 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.
Dangers of Welding Gases:
- Most harmful workplace hazards
- Produce toxic fumes
The welding gases themselves are not the most harmful hazards facing the hard-working welder. Instead, it is welding fumes that are produced through the process of welding that is of greatest concern.
These hazardous fumes that are the product of welding are not gases. That is an important distinction to remember.
Manganese produces 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 speaking reported that 20% of welders showed 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. They are the product of the welding process.
Types of Gases That You Should NOT Use for Welding
An obvious gas unfit for welding is gasoline. 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.
More About Acetylene
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:
- A high flame temperature
- A high rate of flame propagation
- Adequate heat content
- A minimum chemical reaction of flame with base and filler metals
Safety Tips for Using Welding Gases
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):
- Cap – to protect the skull, head, and hair
- Apron – to cover clothing (the apron should be made of leather)
- Gauntlet gloves – these are tremendously important for hand protection
- Helmet – especially made for welding
- Sleeve Corners – for arm protection above the gloves
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:
- Hot Work Permits (required for many jobs)
- Fire extinguisher – be sure it is operational
- Clean work area – no trash that could interfere with work or ignite
- No smoking – the designated spot is away from the workplace
- No flammable substances – clear the work area
- Use indicator or sensor – combustible gas indication will detect airborne gases
- Clear floor – this includes wetting down or covering a wood floor
- Cover flammables – a fireproof tarp is essential
- Pay close attention – it will keep you safe
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.Last updated on: