アルミニウム含有フェライト型球状黒鉛鋳鉄の時効現象

抄録

  Only a few study on the aging phenomenon in cast iron, such as the studies on age-hardening in nickel-aluminum-containing ferritic spheroidal graphite and ferritic malleable cast iron, are reported. To clarify the aging phenomenon in aluminum-containing ferritic spheroidal graphite cast iron, the cast iron was prepared by adding 0∼3% of aluminum and 2% of calcium cyanamide before graphite spheroidizing treatment with magnesium. The specimens were annealed at 950°C for 2hrs., slowly cooled to 720°C, held at this temperature for 2hrs. and water-quenched before aging treatment at 550°C, 600°C and 650°C.
  The hardness of ferritic matrix increased by aluminum addition and became harder by the aging treatment. The precipitates were suggested to be AlN and Si₃N₄ by microscopic examination and nitride analysis. The size of precipitates in the over-aged specimen was about 0.5μ. The tensile strength increased about 4kg/mm² after the aging at 550°C for 500min in iron containing 3.23%Al.