The effects of primary thermo-mechanical processing routes and intercritical annealing on the mechanical properties of st37 low carbon steel

摘要

The effect of thermo-mechanical processing routes on the microstructure and mechanical properties of st37 low carbon steel was studied. Several dual phase (DP) ferritic-martensitic steels were produced by intercritical annealing of the martensitic, cold-rolled martensitic, and bimodal-sized ferritic microstructures. The latter microstructure was produced by subcritical tempering of cold-rolled DP steel to develop an aggregate of ultrafine and large ferrite grains. The DP steel obtained by intercritical annealing of cold-rolled martensite was shown to exhibit better strength-ductility balance compared with that obtained by intercritical annealing of the as-quenched martensite due to much finer microstructure and enhancement of work-hardening behavior in the former. The bimodal-sized ferritic structure showed high yield stress, yield-point elongation, and less pronounced work-hardening regime. The DP steel obtained by intercritical annealing of bimodal-sized ferritic structure exhibited inferior strength-ductility tradeoff compared with that obtained by intercritical annealing of cold-rolled martensite due to the coarser microstructure in the former. Conclusively, it is possible to enhance the mechanical properties of st37 low carbon steel by simple processing routes.