Cutting Stainless Steel
Stainless steels frequently need to be cut to size or shape. The processes most suitable for thermal cutting of stainless steel are plasma cutting and laser cutting. Oxygen cutting using exothermic powders, powder cutting, has been used in the past but has now been largely superceded. Plasma cutting is probably the most frequently used process for cutting stainless steel. It produces clean, accurate cuts and the stainless may be welded without dressing although it is sometimes necessary to remove the HAZ for certain applications. Nitrogen, argon, hydrogen-nitrogen, and argon-hydrogen are the most suitable plasma gases. The hottest plasma is derived from argon. Cheaper nitrogen or nitrogen-hydrogen mixtures may be satisfactorily applied on stainless steel up to 38mm thick but issues can arise with nitrogen pick-up on the cut face and because of this some fabrication codes require the cut face to be machined back. For laser cutting a CO2 laser, with nitrogen as the assist gas, can be used for cutting stainless steel. The cut is usually quite narrow, about 0.5mm. Laser cutting results in very low distortion levels and an extremely narrow heat affected zone. Subsequent welding can normally take place without dressing the cut edges. The main safety issues are electrical, radiation, inert compressed gases, and fume and noise from plasma. To combat this plasma cutting may be carried out in a water bath, as well as reducing fume this can reduce distortion levels.
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