TO BLUE

Bluing (the action of bluing) is initially the result of a heat treatment (tempering). After being hardened, many parts made of Steel become too hard and too brittle to be functional. It is then necessary to carry out a heat treatment (tempering) to let down the material. Once hardened, the components are heated with the softest and most even flame possible. The component thus heated will change color as its temperature increases (straw yellow, yellow, brown, purplish, dark blue, light blue). Dark blue corresponds to the ideal temperature for the part (spring, screw, etc.) to reach optimal hardness and elasticity. The color is thus an indicator of successful tempering rather than a purely decorative element. Nowadays, the profile turning steels used to manufacture screws in particular make it possible to do without heat treatments. When they are blue, it is then often through a PVD or CVD purely decorative from then on.

Useful link:

– Steels

– Heat treatments