The gas metal arc (GMA) brazing process (a novel approach that combines GMA welding and brazing) was applied for joining a new-generation automotive steel (interstitial-free steel) using silicon-containing copper-based filler metal. During this joining process, an interface region of very high hardness was developed through the diffusion of the silicon present in the molten braze metal into the solid steel. The interface microstructure consisted of silicon-enriched, iron-based intermediate phase alpha (1) for lower heat input and dispersed submicroscopic Fe5Si3 particles in alpha (1) matrix for higher hear input. The calculated diffusion distance or silicon was in excellent agreement with the measured interface width, which envisaged the diffusion of silicon in iron matrix as the controlling factor for evolution of the interface region .The thermodynamic calculations exhibited the lowest Gibbs free-energy change for Fe5Si3 as compared to other compounds of Fe and Si to justify the stability of Fe5Si3 in the microstructure. Accordingly, during tensile shear tests, the failure occurred in the base metal region, i.e.. not at the harder and stronger joint interface. These results suggested a successful joining with 100% joint efficiency.
GMA brazing of galvannealed interstitial-free steel
Welding Journal, New York ; 92 , 2 ; 29s-35s
2013
7 Seiten, 15 Bilder, 3 Tabellen, 20 Quellen
Aufsatz (Zeitschrift)
Englisch
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