Abstract
In general, quenching is a method for giving high mechanical strength, toughness and fatigue resistance to steel. It is widely applied in various machine parts such as spindle, gear and so on. When carbon steel is carried out quenching, it is known well that quenching crack occur in the cooling process. In order to prevent quenching crack, it's necessary to erect numerical analysis technique for calculating thermal stress with a high degree of accuracy in the cooling process. Additionally, it is necessary to bring out genesis phenomenon of quenching crack in perspective of fracture mechanics, and erect the technique to evaluate genesis of quenching crack. However, estimation method using fracture mechanics for quenching crack doesn't have been yet established. In the present study, we measured fracture toughness of quenched medium carbon steel. Thermal stresses during the cooling process are analyzed using finite element method and then put genesis of quenching crack in perspective of fracture mechanics. As a result, it's conceivable that the estimation method used stress intensity factor can evaluate genesis of quenching crack.
