Coltello: differenze tra le versioni

Versione delle 09:43, 6 ott 2006

Versione delle 10:17, 6 ott 2006

Riga 17:

====Materiali====

Le lame dei coltelli sono normalmente di [[acciaio]]. Tutto l'acciaio per coltell è temprato, ossia [[martensite]] costituita da una struttura cristallina molto fine con irregolarità del [[reticolo cristallino]] che indurisce il materiale. ItSi isforma formedper asrapido itraffreddamento isin [[quench|quenched]],acqua changingod itolio fromdi theacciaio portato ad alta temperatura; a queste temperature l'acciaio assume la struttura cristallina [[austenite|austeniticaustenitica]] structuree, thatper iteffetto hasdel atrapido highraffreddamento temperaturepassa toalla astruttura hardmartensitica, butmolto brittledura martensiticma structurefragile. ThePer bladeridurne isla thenfragilità, la lama viene sottoposta al processo di [[tempering|tempereddistensione]] byche heatingconsiste tonel anriscaldare intermediatenuovamente temperaturela forlama ad una temperatura inferiore a periodquella di tempra per un tempo adeguato e toraffreddandola makein itmaniera lessmeno brittleviolenta. Knife steel has fairly low nickel content, because nickel tends to keep steel in the austenitic structure, even when cold. Steels having high carbon but low chromium content ("carbon steel") are prone to rust and pitting if not kept dry and oiled.

[[Stainless steel]] knives have gained popularity in the latter half of the twentieth century. Stainless steel is steel with very high (12–18%) [[chromium]] content — stainless knife steels are high in carbon, but "carbon steel" means there is not also a lot of chromium. Stainless steel is highly resistant to [[corrosion]] (though knife steel is less so than higher nickel stainless steel) because, except in acid, one of the metals or one of the oxides is always stable Stainless steel knives usually only rust under extreme conditions. Stainless steel usually has particles of chromium (or other alloy metal) carbides. These explain its reputation for long wear (the carbides are harder than the metal) and for being harder to sharpen and not taking as good an edge as rustable, low alloy ("carbon") steel (the ceramic particles themselves cannot be sharpened easily.), although tests indicate that stainless steel knives hold an edge better than regular steels.<ref>by Razor Edge Systems, described in their book "The Razor Edge Book of Sharpening".</ref> The bulk hardness and toughness of stainless steel tend to be lower than those of low alloy steel. Stainless and semi-stainless steels include D2, S30V, 154CM, ATS-34, and 440C.