Key points of rework processing high alloy die steel

For high- and medium-alloy die steels that are unqualified for quenching and tempering, normal spheroidizing annealing steps need to be added before rework and quenching to eliminate the formation of structural transformation during quenching and heating, and cause tensile stress and cracking on the surface.

During the secondary quenching and heating, the steel parts are heated rapidly, and the structure changes on the surface, the volume is reduced, the interior is still in a low temperature state, and the volume is in a state of expansion stress. , May induce cracks.

The heating speed of the salt bath furnace is fast. When the salt bath furnace is reworked, there are more cracks on the surface, and it is difficult to analyze the causes after the cracks.

Using air resistance furnace for heating rework will also cause this problem, but the tendency of cracking is smaller, but due to oxidative decarburization and surface tensile stress, cracks are often distributed on the surface of the workpiece after heat treatment, and the crack depth is <0.2mm .