The main gases and gas mixtures used for arc welding are:
- Argon li>
- Carbon Dioxide li>
- Argon-Carbon Dioxide (82% Ar +18% CO2, commercial name MIX-1)
- Argon-Oxygen-Carbon Dioxide (81% Ar +18% CO2 +1% O2, known as MIX-2)
- Argon, Carbon Dioxide, Helium (Ar + CO2 + He)
- Argon-Oxygen (Ar + O2)
- Argon-Helium (Ar + He)
- Argon-Carbon Dioxide-Nitrogen (Ar + CO2 + N2)
Suitable for welding non-ferrous metals: aluminum, copper, magnesium alloys; chemically active metals: zirconium and titanium. Argon provides excellent weldability, the depth of penetration and weld all of the above metals.
Argon-Carbon Dioxide (82% Ar + 18% CO2, commercial name MIX-1)
This mixture is the most versatile and popular formula. Thousands of welders throughout Ukraine recommends this mixture. Used mainly for welding carbon and low alloy steels, as well as, in rare cases, are of limited use for welding stainless steel. Carbon dioxide is added to the high content of argon at last to reduce the effect of the metal spray.
Argon-Oxygen-Carbon Dioxide (81% Ar + 18% CO2 + 1% O2, known as MIX-2)
Gas mixtures containing these three components are universal due to their ability to work using the short-, inkjet, globular, pulsed, high-density metal transfer modes. The advantage of these compounds is the ability to weld carbon and low alloy steel of any thickness, using any suitable means of transport. Of the minuses is worth noting the need for more thorough cleaning metal before welding.
Carbon dioxide-helium-argon (CO2 + He + Ar)
Additions of helium and argon, carbon dioxide increases the heat transfer, which improves the penetration, the fluidity of the metal and the weld profile. These mixtures have been developed for arc and pulse arc welding processes, which are used for carbon and low alloy steels. They can be used for any thickness of metal, and they provide better weldability of the metal than with traditional two-component mixtures of welding (even in the presence of rust, oil, and scale).
Argon-oxygen (Ar + O2)
The addition of small amounts of oxygen (1-2%) in argon significantly stabilizes the welding arc, increases the rate of drop transfer of filler metal, reduces inkjet transfer and influence on the shape of the weld.
Argon-helium (Ar + He)
Helium is often mixed with argon to obtain additional benefits from the use of the two gases. Argon provides arc stability and cleaning of the weld, while the helium promotes deeper penetration of the metal across the width of penetration.
The gas mixture of helium-argon are used mainly for welding non-ferrous metals: aluminum, copper, nickel and magnesium alloys, and reactive metals. The addition of helium to argon increases the heat transfer. The thinner the metal, the higher should be the percentage of helium, the low percentage (less than 20%) would have a negative effect on the welding arc. Increase the percentage of helium in turn increases the voltage, spatter, weld width and depth of penetration, but it reduces the porosity of the weld when welding aluminum. In order to obtain a stable deposition of the molten metal content in the gas mixture of argon and helium should be at least 20%.
Carbon dioxide-nitrogen-argon (CO2 + N2 + Ar)
These mixtures are produced with a fairly accurate values of the content of all these components. It is necessary for their use in welding a wide range of stainless steels. These mixes are suitable for all types of welding seam we catch. At the same time can be used practically all methods of metal transfer (such as a squirrel, pulse, and the most common, inkjet).
Under certain contents of CO2, such mixtures can be used for welding of austenitic stainless steel, especially in cases where it is important to control the carbon content in welding. The addition of nitrogen improves the performance of the arc by increasing its stability, the depth of penetration and prevents irregularities in the welded parts.
These compounds also help to maintain the necessary level of nitrogen content in weld metal, especially in materials such as steel melted duplex process for which the control at a chemical level is critical to ensure the integrity of the microstructure of the metal and increase resistance to corrosion.
Important economic effect of welding mixtures is:
- Saving time and materials to prepare metal surfaces for welding. li>
- Less gas used compared to CO2 li>
- Increase in the rate of welding. li>
- Savings welding electrode (less spatter during welding). li>
- No need for post weld cleaning. li>