Cutting Alloy Steel
Alloy steel is a name applied to a range of alloys with different characteristics depending on the specific alloy. The alloy steels most frequently encountered are Ni steel, Cr-Mo and Cr-Mo-V steels, and some high strength alloys containing Cr, Ni, Mo and other elements. The processes used for thermal cutting of alloy steel are oxygen cutting, plasma cutting, and laser cutting. The MMA process may also be used for gouging, grooving and cutting after welding to remove unwanted metal. Oxygen cutting is the most readily available and uses oxygen with acetylene or other appropriate fuel gas. Edges can be cut accurately but the quality of the cut depends on the alloy steel being cut. Preheat may be necessary to prevent edge cracking. Plasma cutting is used in shops with high throughput of steel, and gives good, clean, accurate, cuts. There is usually a requirement to grind back the HAZ to remove any hardened or damaged areas and some alloy steels are prone to cracking and need preheating. Laser cutting is ideal for cutting up to 4mm steel (but will cut up to 20mm) and the cut surfaces normally need no further treatment before welding. MMA gouging and grooving electrodes may be used to dress weld metal but are not suitable for accurate cutting operations. Depending on the process used the safety issues may include electrical, radiation, flames, compressed gases, hot metal, noise, and fumes.
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