Material Machining Views: 7

Notes and safety requirements for machining magnesium alloys (AZ31, AZ91, WE43 etc.): Characteristics: 1) Light - only 2/3 the density of aluminum; the lightest structural metal; 2) Soft - low hardness, low cutting force, easy to machine; 3) FLAMMABLE - magnesium chips and powder ignite very easily (ignition point about 500C) and burn extremely hot (3000C+); water makes it worse (magnesium reacts with water producing hydrogen - explosive); 4) Good thermal conductivity - heat dissipates, tool stays cool; 5) Oxidizes easily - surface treatment needed after machining. Which tool: 1) Cobalt HSS or standard HSS - both fine; magnesium is soft, no special demands; 2) Carbide - more wear-resistant for high volume; 3) Single- or multi-flute both fine; single-flute removes chips well. Parameters: 1) speed - high, 2000-5000rpm; magnesium is soft, high-speed cutting is fine; 2) feed - large, 0.15-0.3mm/rev for efficiency; 3) depth - can be large; low cutting force. Safety requirements (MOST IMPORTANT): 1) Fire prevention - a) magnesium chips and powder ignite very easily - fire precautions mandatory; b) never dry-cut - always use cutting fluid (water- or oil-based) to cool and prevent chip ignition; c) remove chips promptly; never let them pile up in the machine; d) keep flammables away from the machine; e) keep Class D extinguishers (metal-fire: dry powder, dry sand, graphite powder); NEVER use water, foam or CO2 on a magnesium fire (explosion or fueling); 2) Dust explosion prevention - a) magnesium dust explodes at certain concentrations - dust extraction required; b) never dry-grind magnesium (massive dangerous dust); c) ventilate to lower dust concentration; 3) Burn prevention - a) magnesium burns extremely hot - keep away; b) small fires: dry sand or Class D extinguisher, never water; c) wear gloves - chips can burn; 4) Oxidation prevention - a) oxidizes fast after machining - surface treatment promptly (anodizing, plating, painting); b) oil or dry storage; 5) Cutting fluid - a) water-based fluid: magnesium reacts with water producing hydrogen; keep the fluid alkaline (pH 8.5-9.5) to suppress the reaction; b) check concentration and pH regularly; c) oil-based fluid is safer but watch fire; 6) Operating rules - a) do not leave the machine; b) on smoke or fire, stop immediately and use dry sand or Class D; c) never blow magnesium chips with compressed air (dust cloud - explosion risk); use a vacuum or brush; d) store chips in lidded metal containers, away from heat, dispose regularly. Magnesium is easy to machine (soft, low force, long tool life), but safety comes first - especially fire and explosion. With the right precautions, magnesium chamfering is simple. Our countersinks all machine magnesium - ask us.