Quote:
Originally Posted by OneOfOne
Interesting, the laser could slice through 3mm steel (admittedly through a lens and with oxygen to get it all going) but it would not cut through alfoil! Steel is something like 60% reflective and gets enough heat in to get started whilst ali is more like 99% preventing the stuff from getting going. Apparently a couple more kW and it would melt and the reflectivity dropped significantly...then you could cut it.
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This is not a surprise... In case of cutting though steel the oxygen is crucial. Cutting of steel with acetilene flame works only because there is excess of oxygen supply so steel is actually burning and this is where the required heat energy is coming from, not from the flame itself.
Aluminium has much better reflectivity, but also much better thermal conductivity, so it cools down more rapidly. Also, there is always that very thin and dense layer of oxide on aluminium surface that prevents further oxidation...