engleski

Prediction of Mechanical Properties Distribution in Quenched and Tempered Steel Specimen

The mathematical model and method of computer simulation for the prediction of mechanical properties of quenched and tempered steel was developed. Numerical modelling of hardness distribution in as-quenched steel components was performed based on chemical composition of steel as well as based on experimentally results of Jominy test. Hardness of quenched and tempered steel was expressed as function of maximal hardness of actual steel and representatives of chemical diffusivity of steel according to the time and temperature of tempering. After that, distribution of other relevant mechanical properties was found out based on predicted as-quenched and tempered hardness of steel. Experimental investigation was performed on high-hardenability steel for tools and dies. The established procedure for estimation of quenched and tempered properties of steel was applied in computer simulation of mechanical properties of quenched and tempered steel workpiece. The time of cooling at workpiece points was predicted by numerical simulation using the finite volume method. Since the critical cooling rate of martensite transformation of high-hardenability steels is less then maximal cooling rate of Jominy specimen the application of the original Jominy test in computer simulation is not suitable. Modified Jominy test was designed for hardenability prediction of high-hardenability steels. The performances of investigated, modified Jominy test have been estimated by comparison of cooling curves of modified Jominy specimen and cylindrical one cooled in different quenchants. Yield strength and fracture toughness distributions were estimated using the Hahn-Rosenfield approach. Fatigue resistance was estimated based on predicted microstructure and hardness.

Quenching; Computer simulation; High-hardenability steels

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