Effect of various heat and thermo-mechanical treatments on low alloyed CMnAlNb high strength steel

Abstract

Low carbon low alloyed high strength steel with the chemical composition suitably designed to support the stabilization of retained austenite was used in this work. The steel was processed by conventional annealing for a reference and several different heat and thermo-mechanical treatments were further proposed to test typical TRIP (transformation induced plasticity), DP (dual phase) steel and QP (quenching and partitioning) processing routes. All the processing methods used the same soaking temperature of 1050 °C. Processed samples were subjected to metallographic analysis, hardness measurement and tensile test to characterise resulting microstructures. While simple annealing reached tensile strength of 861 MPa with 25% of total elongation, the best combination of the highest tensile strength of 903 MPa and total elongation of 32% was obtained after processing typical for TRIP steel. QP treatment resulted in the highest tensile strength of 1289 MPa with a total elongation of 19%.