An Investigation on the Production of Dual-Phase Steel from AISI4140 and Its Impact Strength at Different Martensite Volume Fractions

摘要

In this study, production of dual-phase steel from AISI 4140 steel having 0.44 percent C, 0.35 percent Si, 0.71 percent Mn, 1.13 percent Cr, 0.17 percent Mo and its impact strength at different martensite volume fractions (MVF) are determined. Dual-phase steel production is accomplished by intercritically annealing at intercritical temperatures (alpha + gamma region, between 740 deg C and 795 deg C) and then by water quenching. By doing so, change in the MVF with intercritical annealing temperature (ICAT) of AISI 4140 steel is controlled. 743 deg C and 748 deg C are decided as ICAT for producing dual-phase steel impact test specimens with different MVF. For comparison, impact tests are also carried out on as-received, quenched, quenched-tempered and normalized specimens. Results show that dual-phase steel having min MVF manifests considerable higher impact energy than all the specimens except for that of the samples quenched-tempered. As a result, dual-phase microstructure produced from AISI 4140 increased the toughness significantly.