Heat Treating
After the workpiece is done being formed, it is normalized. The blade is carefully and evenly heated and then cooled slowly. The point of normalizing is to remove the stresses which may have built up within the body of the blade while it was being forged. During the forging process the blade might be heated and cooled differentially creating stress, some parts might be hammered more than others, some areas hammered enough to work harden. If these stresses are left in the blade they could affect the finishing and when it came time to heat treat the blade, the hardening and tempering might not be as even. Potentially enough stress could be added that the blade would be weak in spots, weak enough that it could fail under enough stress.
As one of the last processes in fabricating a sword is quenching and tempering it. Quenching hardens the metal so it holds an edge longer but this also makes it very brittle. To restore some ductility and durability the sword is tempered. With swords, due to their length, the challenge is greater as in a typical quenching it is possible to bend or warp the blade if it is not introduced to the quenchant smoothly and evenly.
Swords could also be differentially hardened so that some parts, like the cutting edge, are harder than the body.
Read more about this topic: Sword Making, Process
Other articles related to "heat treating, heat":
... flex and strength vary dramatically with heat treating ... called differential tempering but this is actually an entirely different form of heat treatment ... Second, the differentiated heat treatment and the materials with which the steel comes into contact creates different coloration in the steel, resulting in the Hamon 刃紋 (frequently ...
... Precipitation hardening, also called age hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium ... Note that two different heat treatments involving precipitates can alter the strength of a material solution heat treating and precipitation heat treating ... Precipitation heat treating involves the addition of impurity particles to increase a material's strength ...
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