Effect of Double Quenching–Tempering on Microstructure and Mechanical Properties of HSLA-100

In the present study, the effect of the double quenching–tempering heat treatment on the mechanical properties of the HSLA-100 steel has been investigated. In this regard, the steel studied was first subjected to two consecutive austenitization treatments at 940°C and 870°C for 45 and 30 minutes, respectively, and quenching, followed by tempering in the temperature range of 510°C to 700°C for 60 min, and finally all the samples were cooled in air. Also, to compare the results with the conventional heat treatment cycle of this steel, some samples were subjected to single quenching–tempering. Furthermore, the variations of mechanical properties of HSLA-100 steel and the resultant microstructures were investigated in terms of different tempering conditions. Accordingly, it was found that the double quenching–tempering treatment could create a substantial difference in the total elongation percentage (+24%) of the samples by making minor changes in the strength parameters.