Cracking resistance in low- and medium-strength steels

Effect of the structure and size of real austenitic grain on cracking resistance of low strength casting steels and wrought tempering steels of medium strength is considered. New approach and technique based on it are used for determination of fracture toughness. It is shown that the fracture toughness sharply decreases in consequence of non-uniform structure with ferrite areas during incomplete hardness penetration of medium strength tempering steels. Increase of the fracture toughness of low strength tempering steels is observed at decrease of the real austenitric grain size. The proposed calculation formula permits to analize the structural sensitivity of the fracture toughness of structional metal materials