球状黒鉛鋳鉄のじん性に及ぼす熱処理の影響

抄録

  In ferritizing annealing, the ferrite grain size is refined and the toughness is increased when it is below the A₁ temperature after normalizing. On the other hand, in annealing below the A₁ temperature after quenching from the austenite range the transition temperature by precipitation of secondary graphite and refining of the ferrite grain size tends to become low, but energy absorption in the upper shelf range of the transition curve is reduced. The martensite matrix of nodular cast iron is not good in terms of toughness because the carbon content is apt to become very high. It is found, on the other hand, that the bainite matrix has good toughness and strength.