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Cutting

In the case of oxyfuel, plasma and laser cutting, thermal energy is used to anneal materials up to ignition, melting or evaporation temperatures.

Oxyfuel cutting and laser cutting with oxygen use the exothermic energy of the oxygen reaction in the process. Flame and laser beam anneal materials only until ignition temperature is reached. The oxygen jet burns the material and blows out melt and slag.

The cutting speed depends on the purity of the oxygen and the shape of the cutting gas jet. High purity oxygen, optimised nozzle design and suitable gas supply means high productivity.

In plasma cutting and laser cutting with nitrogen, the material is annealed up to melting temperatures and the cutting gas blows out the melt. The nature of cutting gases needs to be adapted to application for best performance.

Lasers can also be used to evaporate materials such as wood or plastics. Evaporation of metallic material is used for example in laser drilling or piercing of the starting hole. Gases suppress ignition of flammable materials and support material removal during drilling and piercing.

Welding

As a joining method, welding has been around for centuries. Today, roughly 100 welding methods are used in different sectors of the industry. The use of industrial gases (whether as individual gases or gas mixtures) to optimise welding processes dates back to the 40s and 50s. Since then, the gas based welding processes have emerged to be the predominant group of welding methods.

Important gas-shielded welding methods are MIG, MAG, TIG and plasma. MAG welding is the preferred method for normal unalloyed steels although it can also be used on stainless steels and other materials.

The 80s and 90s saw many welding innovations. These included laser, tandem, and laser-hybrid welding.

An in-depth understanding of the ‘internal properties’ of gas components and their interactions in specialised mixtures is essential for successful use of gases in specific welding applications. The welding arc itself, a highly efficient but complex tool,consists largely of different amounts of ionised gas and metal vapour. This means the physical properties of the gas have a direct and immediate impact on the arc. In addition, the gases also contact the hot metal, a highly reactive area, in which the chemical and metallurgical effects of the gases also play an important role.