Cu-Mn合金系フィラを用いたダクタイル鋳鉄と軟鋼の接合

抄録

  For the purpose of developing a new filler metal with lower melting point, Cu-Mn alloys containing 25, 34 and 48 mass % Mn were applied to the brazing of ductile cast iron (DCI) and mild steel. Irrespective of the Mn content in the filler metal, Fe-Mn-Cu-C alloys precipitate at DCI side and grow toward the steel side. As the bonding temperature rises, precipitated crystals develop, and the bond-strength increases. In the case of bonding temperatures from 1223 to 1323K. the bond-strength, when brazed with the Cu-25 % Mn filler metal, is considerably higher than that when brazed with the other two Cu-Mn filler metals. By using the Cu-25 % Mn filler metal, bonding temperatures can be lowered by about 80K compared with the usual temperature of copper brazing, and almost the same bond-strength as brazed with pure copper can be obtained. Based on the above results, it can be said that the Cu-25 % Mn alloy is a promising filler metal for joining cast iron and steel. However, it was found that carbide layer forms on the surface of DCI at temperatures lower than 1323K, which could lower the bond-strength.