The present paper concerns a new method for determining the cold-brinleness temperature T~ b in tests lbr impact toughness. Results of estimation of metal quality based on conventional characteristics and tile suggested parameter of resistance to defects are compared for ship steels 10KhSND and 12KhN3. Impact toughness is essentially an integral characteristic of a metal. The energy capacity of fracture depends on the strength and ductility simultaneously, as well as on the test conditions and the shape of the specimen, which in many cases makes estimation of metal quality ambiguous. The authors consider nontraditional approaches to determination of the embrittlement action of various stress concentrators. The aim of the work consists in establishing a relation between the universally used mechanical properties determined in impact toughness tests and toughness parameters such as K, (toughness coefficient) and De (resistance to defects).