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2013 №02 (05) 2013 №02 (07)

The Paton Welding Journal 2013 #02
The Paton Welding Journal, 2013, #2, 31-36 pages  

FLUX ARC BRAZING OF ALUMINIUM TO GALVANISED STEEL

V.F. KHORUNOV and O.M. SABADASH


E.O. Paton Electric Welding Institute, NASU, Kiev, Ukraine
 
 
Abstract
The study was dedicated to investigation of the processes occurring in DC flux arc brazing of overlap joints between thin-sheet aluminium and galvanised steel. Aluminium AD1, galvanised steel 08Yu, and reactive flux of the KF-AlF3-K2SiF6-KZnF3 system were used in the experiments. It was shown that reactive flux of the K-Al-SiF system used for brazing without passage of the filler alloy through arc gap improves conditions of formation of the overlap joints (wetting, spreading and filling of capillary gaps by the aluminium-silicon filler alloy) between aluminium and galvanised steel due to rapid destruction of the oxide film and formation of layers of low-melting point metal melts in the brazing location due to reactions of the flux with the materials being brazed. It was found that in brazing under conditions of arc heating the rate of spreading of the filler alloy on galvanised steel is approximately 3 times as high as on aluminium. The non-equilibrium contact angle on galvanised steel is 28-33°, and on aluminium Е 8-10°. The data are given on structure of the brazed joints, composition of individual phases and chemical heterogeneity of the joints. According to the X-ray spectral microanalysis results, the 2-5 mm thick variable-composition Al-Fe-Si system transition layer containing small amounts of manganese (from steel) and zinc (from coating) forms at the contact boundary with steel. It was shown that the brazed joints between alloy AD1 and galvanised steel 08Yu produced by using the aluminium-silicon filler alloy have strength equal to that of the aluminium alloy. The overlap joints tolerate bending to an angle of 180°, while in multiple inflections (5-6 times) fracture occurs in aluminium. 23 Ref., 2 Tables, 5 Figures.
 
 
Keywords: aluminium, galvanised steel, arc brazing, reactive flux, spreading of filler alloy, reaction layer, brazed joints
 
 
Received:                13.11.12
Published:               28.02.13
 
 
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