Mechanical properties of dual phase structured boron steel

The aim of this study is to examine the possibilities of improving the ductility of medium-carbon high-strength low-alloy boron steel, which will be structured in two phases, by heat treatment applications of intermediate quenching and annealing in the region between critical temperatures, without sacrificing strength. The mechanical properties of boron steels with a dual-phase microstructure (ferritic-martensitic), which will be developed by heat treatments of intermediate quenching and annealing in the region between critical temperatures, were compared with hardened and tempered samples. The hardness, changes in microstructure and mechanical properties of the samples were examined before and after heat treatments. Clemex Vision Lite image analysis program was used to determine phase ratios. As a result of the study; The highest average hardness was measured in samples with rapidly cooled martensite microstructure, and the lowest average hardness was measured in samples without heat treatment. Intermediate quenching process (Q1: 870 oC, 25 minutes / Water + Q2: 760 oC, 5 minutes / Water) improved the tensile and yield strength while providing a ductility close to the unheated sample. Samples annealed between critical temperatures provided some improvement in tensile strength compared to samples without heat treatment, while increasing elongation to fracture by 58-74% compared to the sample without heat treatment. It has been determined that the dual-phase configuration allows improving ductility without sacrificing strength.