Microalloyed steel

About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.

The effect of warm deforming and reversal austenization on the microstructure and mechanical properties of a microalloyed steel

Abstract: The influence of warm deforming and reversal austenization on the microstructure and mechanical properties of a microalloyed steel was elucidated. Grain refinement induced by warm deforming and reversal austenization was studied by thermal simulation experiments, and its effect on properties was assessed by thin-plate hot rolling experiments. The study suggested that austenite was refined to ~10 µm after reversal austenization, which was further refined to ~5 µm after reversal austenization and application of warm deforming. Warm deforming recrystallized the microstructure during the reheating process, when the reheating rate was less than 2 °C/s. While recrystallization was inhibited at reheating rates greater than 5 °C/s. The ultimate microstructure obtained from the refined austenite via combination of warm deforming and reversal austenization, comprised of fine-grained (4.7±3.2 µm) ferrite and pearlite with small colony size (1.3±0.6 µm). On the other hand, the fine-grained microstructure was characterized by reduced extent of coarse precipitation (9.3±3.4 nm), compared to the coarse-grained thermo-mechanical controlled processing (TMCP) plate with dispersed and fine precipitation (4.0±1.3 nm), which was responsible for lower strength (~70 MPa) of the fine-grained plate than the coarse-grained TMCP plate. However, the fine-grained plate had an excellent low temperature toughness resulting from fine grain size, coarse precipitation, and small pearlite colony size.

Improving the Abrasive Wear Resistance of a Microalloyed Steel by Plasma Nitriding

Abstract: The aim of this work was to study the micro-abrasive wear resistance of an API 5L X-70 microalloyed steel plasma nitrided under different conditions of time and temperature. Pulsed DC plasma nitriding experiments were performed under a treatment atmosphere of 10%N2 + 90%H2, at temperatures of 410, 440 and 470 °C and for nitriding times of 1, 3 and 5h. The results show that plasma nitriding performed at 440 °C and 1h led to the formation of a compound layer constituted mainly of e-Fe2-3N nitride and a diffusion zone with large needle-like nitride, offering the highest wear resistance. The amount of γ’- Fe4N phase was found to increase with the plasma nitriding time, decreasing the wear resistance of the material.

Improvement of Hot Ductility in the Nb-microalloyed Steel by High Temperature Deformation

Abstract: Loss of hot ductility at the straightening stage of the continuous casting of HSLA steel is attributed to different microalloying elements, in particular Nb. However, such elements are essential for the desired mechanical characteristics of final product. Since the chemistry cannot be altered to alleviate the problem, thermomechanical processing was studied in order to improve the hot ductility. A Nb-microalloyed steel was examined. The thermal history occurring in the continuous casting process was taken into account as well. Firstly, it was noticed that the steel has a low hot ductility after being subjected to in situ melting followed by the thermal schedule. Then, the effect of deformation applied in the vicinity of the δ→γ transformation, while the thermal schedule was being executed, was investigated. Such deformation appeared to improve the hot ductility considerably. Finally, the mechanism of such improvement in the hot ductility was discussed.