活性金属ろうによるアルミナと球状黒鉛鋳鉄の接合

抄録

  The effects of brazing temperature, reaction layer and thermal cycle on the shear strength of Al₂O₃-spheroidal graphite cast iron (FCD400) and low expansion cast iron joints were studied using active filler metal. The variation of microstructures of reaction products formed at the interface between Al₂O₃ and the active filler metal was investigated by scanning electron microscopy. Auger electron microscopy and X-ray diffraction. Shear strength of about 180 MPa was obtained at the Al₂O₃-FCD400 joints brazed at 1123K for 15 min, and brazing temperatures in the range of 1075-1173K did not affect shear strength. Al₂O₃-low expansion cast iron joint showed shear strength equivalent to the Al₂O₃-FCD400 joints brazed at the same temperature. There was little change in the shear strength of Al₂O₃-FCD400 and low expansion cast iron joints after thermal cycle 5 times between room temperature and 773K by air cooling, whereas shear strength decreased significantly or failure occurred in the alumina parallel to the interface after the same thermal cycle by water cooling. TiO oxide was formed in the interface between active filler metal and Al₂O₃ and this reaction layer is attributed to higher shear strength of Al₂O₃-FCD400 and low expansion cast iron joints.