Workpiece surface hardening - by quenching in quenching fluid with addition of gasified low temperature coolant

摘要

Railway rails and parts of points and junctions are surface hardened to the specified figures by heating to the hardening temp. and quenching in a quenching medium. Just before the quenching operation, a coolant is added to the quenching medium at a rate depending on the temp. of the mixt. This reduces the high flow rate required for the quenching medium (compressed air) and reduces the noise level. A uniform fine sorbitic structure with a strength of 120-130 h bar is now achieved to a depth of 8-12 mm.