Properties of Cu-P Brazing Filler Metal After Hot-Dip Tinning

The CuPSn brazing filler metal was prepared on the basis of Cu93P brazing filler metal by hot-dip tinning. The interface morphology of tin coating was observed by scanning electron microscope. The tensile strength, microhardness, melting temperature and wettability of the brazing filler metal were investigated by universal mechanical testing machine, micro-hardness tester, differential thermal analyzer, resistance furnace and stereomicroscope. The results indicate that the liquid tin reacts with the brazing filler metal to form Cu6Sn5 intermetallic compound during hot-dip tinning, which means that the brazing filler metal and tin coating form good metallurgical bonding. The tensile strength and microhardness of brazing filler metal decrease with the increase of hotdipping temperature and time. The decrease of tensile strength is due to the formation of Cu6Sn5 brittle compound and pores at the interface, and the decrease of microhardness is due to the stress-relieving annealing effect of hot-dip. Hot-dip tinning can reduce the melting temperature and improve the wettability of the brazing filler metal. The wetting area of brazing filler metal increases by about 43.15% compared with that of the matrix when 5.20wt% tin is hot dipped in it, and the Cu88.16P6.64Sn5.20 brazing filler metal possesses a good wettability. Copyright © 2021, Northwest Institute for Nonferrous Metal Research. Published by Science Press. All rights reserved.