Carbon Dioxide Welding: Basics and History

In the mid-20th century, thanks to the work of Soviet scientists K. V. Lyubavsky and N. M. Novozhilov, carbon dioxide welding technology was developed. Since then, carbon dioxide welding has found widespread use worldwide due to its efficiency and reliability.

Carbon dioxide welding – what is it?

The basic idea behind CO2 welding is to use CO2 as a protective atmosphere, shielding the welding zone from the harmful effects of the surrounding air. During welding, when the arc temperature reaches high levels, carbon dioxide decomposes into carbon monoxide and oxygen, creating a protective atmosphere of three components: CO2, CO, and O2.

In the arc zone, where temperatures are highest, carbon dioxide is almost completely decomposed, while at the periphery, closer to the weld pool, carbon dioxide predominates. This gas mixture effectively protects the metal from oxidation both as the electrode wire drops enter the weld pool and on its surface.

The oxidation process of metal elements in the weld zone depends on their chemical reactivity to oxygen. Silicon oxidizes first, followed by manganese, due to their high affinity for oxygen compared to iron and carbon. Adding excess silicon and manganese to the welding wire helps neutralize the oxidizing effect of carbon dioxide while maintaining its protective properties.

What to look for when choosing welding wire

The quality of steel welding in carbon dioxide depends on the silicon and manganese content of the welding wire. Ideal weld metal properties are achieved when the Mn/Si ratio is between 1.5 and 2. Oxides formed during welding do not dissolve in the metal, but form a low-melting compound that floats to the surface of the weld pool as slag.

What to look for when choosing a welding wire: the composition of the wire and its application in the work.

Welding technique

CO2 welding allows for welding in various positions, including vertical and overhead. Optimal welding parameters, such as current type and polarity, wire diameter, current strength, arc voltage, and gas flow rate, are selected based on the characteristics of the material being welded and the weld position.

Carbon Dioxide Welding Technique - Flow Chart

General structure of welding equipment and operating principle

Using carbon dioxide as a shielding medium requires specialized materials and equipment. Carbon dioxide, stored in pressurized cylinders, transforms from a liquid phase directly to a gaseous state when heated, bypassing the liquid phase. Gas supply systems are equipped with dryers and heaters to ensure consistent gas quality, and welding wires are selected based on the grade of steel being welded to achieve the best results.

The general diagram of the equipment looks like this:

Scheme of welding equipment in carbon dioxide: 1 - holder, 2 - feed mechanism, 3 - power button, 4 - protective shield, 5 - 0.6 MPa pressure gauge, 6 - adapter nipple for installing a pressure gauge, 7 - oxygen reducer with a high-pressure gauge, 8 - gas dryer, 9 - gas heater, 10 - carbon dioxide cylinder, 11 - welding rectifier (or generator), 12 - control panel