Method of controlling hardening with laser beam and laser beam hardening device

Abstract

A workpiece is irradiated by a laser beam scanned in an oscillating track as the workpiece is advanced along a feed path in a hardening process. Sinusoidal variations in scan velocity are offset by decreasing the laser beam power level at phases in the scanning cycles corresponding to high and low scan displacement peaks, where the scan velocity is least. The beam power is increased near the scanning center line where the scan velocity is highest. The beam energy applied per unit of area is thus equalized over the scanning cycle. The workpiece temperature can be sampled at regular phases by a non-contact temperature sensor in the optical path, and used to control beam power versus phase in a subsequent scanning cycle. Alternatively or in addition, a sinusoidal beam power pattern can be stored and used to offset scan velocity variations as a function of phase.