Induction Hardening
Induction hardening is a process
used for the surface hardening of steel and other alloy components. The parts
to be heat treated is placed inside water cooled copper coil and then heated
above their transformation temperature by applying an alternating current to
the coil. The alternating current in the coil induces an alternating magnetic
field within the work piece, which if made from steel, caused the outer surface
of the part to heat to a temperature above the transformation range. Parts are
held at that temperature until the appropriate depth of hardening has been
achieved, and then quenched in oil, or another media, depending upon the steel
type and hardness desired.
The core of the component remains unaffected by the
treatment and its physical properties are those of the bar from which it was
machined or preheat treated. The hardness of the case can be HRC 37 - 58.
Carbon and alloy steels with carbon content in the range 0.40 - 0.45% are most
suitable for this process. In some cases, parts made from alloy steels such as
4320, 8620 or 9310, like steel and paper mill rolls, are first carburized to a
required case depth and slow cooled, and then induction hardened. This is to
realize the benefit of relatively high core mechanical properties, and surface
hardness greater than HRC 60, which provides excellent protection.
While Induction Hardening is most
commonly used for steel parts, other alloys such as copper alloys, which is
solution treated and tempered, may be induction hardened as well. Applications
include hardening bearing races, gears, pinion shafts, crane (and other) wheels
and treads, and threaded pipe used for oil patch drilling.
Induction Flame Hardening
Flame hardening is similar to
induction hardening, in that it is a surface hardening process. Heat is applied
to the part being hardened, using an oxy- acetylene (or similar gas) flame on
the surface of the steel being hardened and heating the surface above the upper
critical temperature before quenching the steel in a spray of water. The result
is a hard surface layer ranging from 0.050" to 0.250" deep. As with
induction hardening, the steel component must have sufficient carbon (greater than
0.35%). The composition of the steel is not changed; therefore core mechanical
properties are unaffected. Flame hardening produces results similar to
conventional hardening processes but with less hardness penetration.
Applications for flame hardening are similar to those for Induction Hardening in Faridabad,
although an advantage of flame hardening is the ability to harden flat
surfaces. Flat wear plates and knives can be selectively hardened using this
process.
