PROPERTIES OF THE SIMULATED COARSE-GRAINED MICROSTRUCTURE OF QUENCHED AND TEMPERED HIGH-STRENGTH STEEL

Quenched and tempered high-strength steels have a favorable strength-to-weight ratio. These steels are usually welded with the use of standard procedures. Due to the heat input during welding, steels undergo changes in the heat-affected zone and as a result an unfavorable microstructure and mechanical properties can occur. The coarse-grained heat-affected-zone microstructure was studied with the use of simulated thermal cycles. They were applied to the experimental quenched and tempered steel. The steel samples were heated to a peak temperature of 1350 degrees C and then cooled with different rates. A microstructure examination, dilatometry analysis and hardness measurements of the steel samples were performed. The transformation start and finish temperatures were determined using the dilatation vs. temperature data analysis. The investigation was performed to determine the appropriate cooling time t(8/5) interval for further investigation of the experimental steel.