LASER BEAM WELDING OF METAL-SUPPORTED AUTOMOTIVE CATALYTIC CONVERTERS

摘要

We performed laser welding tests on 45μm and95μm thick Fe20Cr5Al foils of Sandvik 0C404 inorder to study the welding feasibility of thecatalytic converter monolith. In accordance withthe contact configurations occurring between thecorrugated foil and the flat foil during the coilingprocess of the honeycomb-structured monolith,several laser welding techniques are selected andtested in pulsed and continuous wave mode. Foreach technique, processing domains are explored toidentify the ranges of usable energetical and opticalparameters. Continuous-wave in keyhole mode isselected for offering better compatibility with theother manufacturing operations. Optimizedirradiationconditions in argon protectiveatmosphere for overlapped-joint welding of2? 45μm foils correspond to full penetration-depthand fusion zone widths of 120μm and 80μm.Specific clamping tools are used in order toconsolidate honeycomb structure prototypes underthe optimized-laser beam conditions. We carry outengine-bench durability tests on these laser weldedprototypes and on prototypes strengthened byconventional joining processes. The monolithshows higher performances when consolidated withlaser welding than with conventional capacitydischargewelding. These demonstrates thefeasibility of the laser welding technique. To studythe laser weld behaviour under a stress field and anenvironment representative of service conditions,isothermal oxidation in both ambient and syntheticair (TGAnalysis) and tensile and creep tests atelevated temperatures are performed on samplesincluding large fractions of laser seams. The laserweld differs significantly from the base material interms of oxidation and thermomechanicalbehaviors at high temperature. We interpret thesedifferences by the change in grain morphology andin the localization and combination of the reactiveelements, carbon and nitrogen during the fastfusion/solidification cycles.