鉛フリー黄銅のろう付と異材接合

抄録

Brazing between Pb–free brass and stainless steel is a very important technology for fabricating fields. Pb–free brass contains Bi and/or Si. However, the additional effect of Bi and/or Si on interfacial reaction during brazing is not clear. Bi migrated from brass base metal to molten brazing filler metal during brazing and Bi in the brazing filler metal influenced mechanical properties of the brazed joint between Pb–free brass and stainless steel, according to previous studies. And interfacial reaction mechanism during brazing is not clear. Therefore, the purpose of this study is to clarify the interfacial reaction mechanism between Pb–free brass and stainless steel by foil–type Ag–based brazing filler metal.

Base metal brass with Sn and/or Bi and commercial stainless steel were used as a base metal in this study. Foil–type Ag–based brazing filler metal, BAg–7, with relatively low liquidus temperature, 650°C was employed as a brazing filler metal. Brazing was done by commercial electric heated furnace. Brazing temperature was 680, 700, 710 and 740°C. Brazing time was 5min. After brazing, the brazed specimen was picked up from the furnace and cooled down in the air. Brazing–ability was estimated by the observation of cross–sectional microstructure at the brazed joint and the elemental distributions at the brazed joint analyzed by EPMA.

Dissolution of brass base metal was the main interfacial reaction during brazing between Pb–free brass and stainless steel. And Bi migrated from the brass base metal to molten brazing filler metal by dissolution of brass base metal.

Constitutive phases of the brass were influenced by Sn content and temperature. And then, it appeared that dissolution conditions were changed and the amount of migrated Bi was changed.