Argon / Carbon Dioxide Mix
Overview
The argon-carbon dioxide mixtures are mainly used on carbon and low alloy steels and limited application on stainless steels. The argon additions to CO2 decrease the spatter levels usually experienced with pure CO2 mixtures. Small CO2 additions to argon produce the same spray arc characteristics as small 02 additions. The difference lies mostly in the higher spray arc transition currents of argon – CO2 mixtures. In GMAW welding with CO2 additions, a slightly higher current level must be reached in order to establish and maintain stable spray transfer of metal across the arc. Oxygen additions reduce the spray transfer transition current. Above approximately 20% CO2 spray transfer becomes unstable and random short circuiting and globular transfer occurs.
Gas Blends
Argon with 3-10% CO2
These mixtures are used for spray arc and short circuiting transfer on a variety of carbon steel thicknesses. Because the mixtures can successfully utilize both arc modes, this gas has gained much popularity as a versatile mixture. A 5% mixture is very commonly used for pulsed GMAW of heavy section low alloy steels being welding out-of-position. The welds are generally less oxidizing than those with98 Ar-2% 02. Improved penetration is achieved with less porosity when using CO2 additions as opposed to 02additions. In the case of bead wetting, it requires about twice as much CO2 to achieve the same wetting action as identical amounts of 02. From 5 to 10% CO2 the arc column becomes very stiff and defined. The strong arc forces that develop give these mixtures more tolerance to mill scale and a very controllable puddle.
Argon with 11-20% CO2
This mixture range has been used for various narrow gap, out-of-position sheet metal and high speed GMAW applications. Most applications are on carbon and low alloy steels. By mixing theCO2 within this range, maximum productivity on thin gauge materials can be achieved. This is done by minimizing burn through potential while at the same time maximizing deposition rates and travel speeds. The lower CO2 percentages also improve deposition efficiency by lowering spatter loss.
Argon with 21-25% CO2
This range is universally known as the gas used for GMAW with short circuiting transfer on mild steel. It was originally formulated to maximize the short circuit frequency on .030 and .035-in. diameter solid wires but through the years has become the defacto- standard for most diameter solid wire welding and commonly used with flux cored wires. This mixture also operates well in high current applications on heavy materials and can achieve good arc stability, puddle control and bead appearance as well as high productivity.
Argon with 50% CO2
This mixture is used where high heat input and deep penetration are needed. Recommended material thicknesses are above 1/8 in. and welds can be made out-of-position. This mixture is very popular for pipe welding using the short circuiting transfer. Good wetting and bead shape without excessive puddle fluidity are the main advantages for the pipe welding application. Welding on thin gauge materials has more tendency to burn through which can limit the overall versatility of this gas. When welding at high current levels, the metal transfer is more like welding in pure CO2 than previous mixtures but some reduction in spatter loss can be realized due to the argon addition
Argon with 75% CO2
A 75% CO2 mixture is sometimes used on heavy wall pipe and is the optimum in good side-wall fusion and deep penetration. The argon constituent aids in arc stabilization and reduced spatter.
DOT Information For mixtures
| Mixture | Shipping Name | UN Number | Hazard Class | Hazard Information |
|---|---|---|---|---|
| Argon with Carbon Dioxide, All Mixture Percentages | Compressed gas, n.o.s. (Carbon Dioxide, Argon) | UN1956 | 2.2 | Non-Flammable Gas |