Plasma Cutting AluminiumProbably the most frequently used method for cutting aluminium and its alloys in industry today is plasma cutting. The features of the process are a high energy density heat source to give melting and ejection of molten material in the high velocity plasma jet. This enables the process to overcome the refractory oxide surface layer and give good, clean, accurate cuts. Plasma gases may be argon/hydrogen mixtures with hydrogen contents up to 35%, compressed air, or nitrogen. Water-cooled electrodes with tantalum tips are often used because of the high heat generated. Secondary gases may be CO2, N2, or compressed air. Plasma cutting is able to cut aluminium up to 25mm thick and maybe more. Cutting speeds are dependent on material thickness but for 4mm plate can be about 15m/min. and for 20mm plate about 2m/min. The process produces a heat affected zone that must be ground back, or cracking of the subsequent weld, especially in crack sensitive alloys, may occur. The main safety issues are electrical, radiation, heat, noise and fume. Cutting may be carried out with the aluminium plate positioned under water to reduce fume, noise, and radiation.
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