Papers by Author: Woo Hyun Song

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Authors: Kazuyoshi Saida, Woo Hyun Song, Kazutoshi Nishimoto
Abstract: The wetting and flowing behaviors of the filler metal during laser brazing process were analyzed by the computer simulation. Two situations of the wetting and flowing during laser brazing were modelled, i.e., the metled Au-18%Ni and Ag-10%Pd filler metals on the butt joint of Inconel 600, and the melted Cu-8%Sn filler metal on the dissimilar butt joint of type 304 stainless steel to Cu. The filler metal droplet wetted and spread on the base metals and simultaneously infiltrated into the joint gap with the lapse of time. The Au-Ni and Ag-Pd filler metal infiltrated into the 0.3mm wide joint gap at the completion of brazing even in the single beam brazing. The Au-Ni filler metal did not infiltrate into the joint gap completely at the brazing clearances of 0.1-0.2mm in the single beam brazing, however, it could be filled up in the joint gap in the tandem beam brazing. The Cu-Sn filler metal wetted on the both base metals of stainless steel and Cu and filled up the 0.3mm wide joint gap when the location of preheating beam deviated in 0.5mm to Cu substrate, however, it did not infiltrate into the joint gap completely at the deviation distance of preheating beam to Cu substrate being 1.0mm. It followed that the wetting and flowing behaviors of the filler metal during laser brazing process could be predicted by the computer simulation.
271
Authors: Kazuyoshi Saida, Woo Hyun Song, Kazutoshi Nishimoto, Makoto Shirai
Abstract: The diode laser brazing of heat-resistant alloys with precious filler metals has been conducted using tandem beam which consisted of preheating beam and main brazing beam. The 1mm thick Inconel 600 and A286 alloys were laser-brazed with the 0.5mm diameter Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals using a brazing flux. The processing parameters of laser power of tandem beam and brazing clearance were varied. Sound butt joints could be obtained by using tandem beam with laser powers of 200-400W/100-150W even at the narrow gap brazing below 0.3mm where the melted filler metal did not infiltrate completely the joint gap by only using the main brazing beam (single beam). The tensile strength of the brazed joint using Ag-Pd filler metal increased with decreasing brazing clearance and attained about 70% of the base metal strength at brazing clearance of 0.1mm, while those using Au-Ni and Ag-Cu-Pd filler metals were comparable to the base metal strength at any brazing clearance between 0.1-1.5mm. The preheating during the tandem beam brazing resulted in superior brazability at the narrow gap to wide gap brazing because of the improvement in wetting/spreading and erosion esistance of melted filler metal by depressing the extremely high peak temperature and steep temperature distribution in the base metal.
493
Authors: Kazuyoshi Saida, Woo Hyun Song, Kazutoshi Nishimoto
Abstract: The diode laser brazing of heat-resistant alloys with precious brazing filler metals has been conducted using the tandem beam consisted of preheating beam and main brazing beam. The 1mm thick plates of Inconel 600 and A286 alloys were butt-brazed with the 0.5mm diameter Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals using a brazing flux. The sound butt joints which were free from brazing defects such as porosity and lack of penetration could be obtained at the brazing clearances of 0.1-1.5mm. Fracture strength of braze joints using Au-Ni and Ag-Cu-Pd filler metals was comparable to the base metal strength at any brazing clearance between 0.1-1.5mm, whereas that using Ag-Pd filler metal increased with decreasing the brazing clearance and attained about 70% of the base metal strength at brazing clearance of 0.1mm. The computer simulations of the braze metal flowing and the base metal erosion suggested that the preheating effect during the tandem beam brazing resulted in the superior brazability at the narrow-gap as well as wide-gap brazing attributed to the improvement in the wetting, spreading, infiltrativity and the erosion resistance of melted filler metal.
4053
Authors: Kazuyoshi Saida, Woo Hyun Song, Kazutoshi Nishimoto
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