Characteristics of Nd:YAG laser welded high carbon steels

Abstract

A quantitative study of the relationship between the laser process parameters and the mechanical properties of welded high carbon steels was performed utilizing a Lumonics Nd:YAG pulsed laser, operating at 1.06μm, and a robotically manipulated fiber optic beam delivery system. A gage plate (0.88 mm thick) was butt welded with a constant power of 200 W and a He shielding gas was used at a pressure of 5 × 104 Pa. The welding performance of the Nd:YAG laser was strongly affected by the translation velocity, pulse length and pulse repetition frequency (PRF). The effects of varying these process parameters were quantified by measuring the sample's hardness profile, weld width, weld penetration, and tensile strength. Furthermore, micrographic examinations were conducted at the welded joints. It was shown that by increasing the pulse length and pulse repetition frequency a deeper weld penetration and a wider bead width were achieved; moreover, the weld region became tougher. Hardness profiles transverse across the weldment and as a function of weld depth were greatly reduced with increasing PRF. The quality of the laser weld was dominated by the rapid quenching rate which resulted in the weld structure being completely modified near the heat affected zone.