Predictions of Mechanical Properties of Quenched and Tempered Steel

Mechanical properties of quenched steel directly depend on the degree of quenched steel hardening. Fracture toughness and fatigue limit depend on microstructural constituents, and distribution of the usual intermetallic particles and non-metallic inclusions. Fatigue resistance of quenched and tempered steel is achieved by eliminating coarse alloy carbides present in steel. Properties of matrix may also have an important influence on fracture and fatigue proper behaviour. Most high-strength materials are fracture and fatigue limited. Fatigue strength is directly proportional to the difficulty of dislocation cross slip. Grain size has its greatest effect on fatigue life in the low-stress, high-cycle regime. In this paper, fatigue crack initiation threshold of quenched and tempered steel is predicted. The method of computer simulation of mechanical properties was applied for a workpiece of complex form made of quenched and tempered steel. Distribution of as-quenched hardness within workpiece of complex form was predicted by computer simulation of steel quenching using the finite volume method. Microstructure composition and hardness of tempered steel were predicted based on as-quenched hardness. Fatigue crack initiation threshold of quenched and tempered steel were predicted based on microstructure composition and hardness. It was found that the proposed method can be successfully applied in calculating fatigue crack initiation threshold of quenched and tempered steel.