Abstract
In order to clarify such brazing conditions for making sound joints of Al-alloys to stainless steel as to wet the Al-Si brazing filler on the stainless steel before rapid isothermal solidification of the filler, the solidification time is estimated by the numerical analysis and is also measured experimentally. The numerical analysis is conducted for the brazing process of the A1050 pure aluminum base metal and BA4045 aluminum-silicon brazing filler. The analysis contains both the initial dissolution of the base metal by the molten brazing filler and the follow-ing isothermal solidification behavior. The movement of the solid-liquid interface is calculated and the total solidification time is estimated. The brazing experiment between the same combination of metals shows the total solidification time is much less than the numerically esti-mated time. The element analysis by EPMA indicates that the zinc in the flux plays the dominant role in the brazing process. According to the results, the time to solidify the brazing filler layer is 30×10-3H2 s, where H is the initial brazing filler layer width in μm. To obtain the brazed joint between the Al alloys and stainless steel, the initial brazing filler layer of at least 30 μm and the holding time of at least 30 s at the braz-ing temperature are considered to be suitable for the brazing.
