LASER CUTTING OF METALLIC COATED SHEET STEELS

This paper discusses the laser-beam machining of metallic coated sheet steels such as ZINCALUME, ZINCANNEAL and GALVABOND of 1 mm thickness. These materials are essentially zinc and aluminium coatings of varyin g skin thickness on steel. The experimental work explores some methods for reducing thermal damage of the coatings vis-a-vis the parent!base metal which impose severe machining restrictions by virtue of their h igh reflectivity and thermal conductivity. A 500 W continuous-wave, 10 .6 mu m CO2 CNC laser centre was used to improve the cut quality in te rms of good surface finish, reduced kerf width and dress. An analytica l model was developed to establish the finite-element characteristic o f the cutting process and it has been clarified that an efficient choi ce of the process parameters is a pre-requisite for minimum thermal da mage of the coatings. The topographical characteristics of the uncut-t hrough. kerf and surface roughness are discussed. Some visualisational experiments were also performed for further understanding of the micr o-and macro-mechanics of the cutting process. It is proven that the cu tting speed is a function of the input power and that the laser proces sing of these materials is a commercially viable option. (C) 1998 Publ ished by Elsevier Science S.A.