オーステンパ球状黒鉛鋳鉄の水による脆化と抑制方法

抄録

  It is revealed that both the ultimate tensile strength and elongation are decreased remarkably by wetting austempered spheroidal graphite cast iron (ADI) with water at room temperature. The embrittlement behavior of ADI is investigated in detail and then the controlling methods of the embrittlement are proposed. Under the condition of wetting with water compared with the values under the dry condition (in the air), the ultimate tensile strength of ADI is decreased in the range from 65 to 80 % and also the elongation is decreased to about 10%. The white brittle fracture surface which is the starting point of failure is observed near the outer surface of the specimen. This is in contrast with the dimple pattern is usually formed in ADI tested in the air. The embrittlement behavior of ADI is depressed by the formation of ferrite layer on iron surface, because ferrite is not embrittled by water. The coating with paint for the purpose of avoiding direct contact with water is also efficient in depressing the embrittlement behavior. This is suggested that the drastic reduction of strength and ductility for ADI may be caused by hydrogen embrittlement.