Microalloyed steel

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

The Microstructure and Mechanical Properties of Hot Forged Vanadium Microalloyed Steel

Abstract: In this article, the effect of hot forging parameters (deformation temperature, strain, and cooling rate) on the microstructure and mechanical properties of commercial vanadium microalloyed forging steel (30MSV6) was investigated. Final, microstructures and mechanical properties were evaluated by optical microscopy, Charpy impact, Brinell hardness, yield, and tensile strength tests. The results show that increasing the cooling rate changes the ferritic-pearlitic microstructure to the acicular ferrite-bainite. It is shown that by increasing post forging cooling rate, both yield and ultimate tensile strength increase, while the impact energy decreases significantly. The specimens with the same cooling rate differ not only in deformation temperature, and the deformation ratio is immaterial in establishing a grain size.

Numerical simulation of NbC precipitation in microalloyed steel

Abstract: This work describes with the investigation of the precipitation kinetics of NbC in microalloyed steel. Using the thermo-kinetic software MatCalc, computer simulations of NbC precipitation are carried out and compared with several independent experimental results, measured in austenite and ferrite. The selected experiments involve a variety of different dislocation densities originating from distinct thermo-mechanical treatments. Two separate populations of NbC precipitates are accounted for in the simulations, representing precipitates on grain boundaries as well as dislocations. Furthermore, three different diffusion mechanisms are taken into account, which are bulk diffusion in the undisturbed crystal, accelerated diffusion along the dislocation core and fast diffusion along grain boundaries. It is demonstrated that deformation-induced dislocation densities higher than 1013 m−2 lead to prominent diffusion along dislocation networks. Therefore, in such cases, the precipitation kinetics of NbC is dominated by the pipe diffusion mechanism, and the precipitation process is several orders of magnitude faster compared with NbC precipitation in unstrained, well-annealed microstructures.

Determination of Non-Recrystallization Temperature for Niobium Microalloyed Steel.

Abstract: In the present investigation, the non-recrystallization temperature (TNR) of niobium-microalloyed steel is determined to plan rolling schedules for obtaining the desired properties of steel. The value of TNR is based on both alloying elements and deformation parameters. In the literature, TNR equations have been developed and utilized. However, each equation has certain limitations which constrain its applicability. This study was completed using laboratory-grade low-carbon Nb-microalloyed steels designed to meet the API X-70 specification. Nb- microalloyed steel is processed by the melting and casting process, and the composition is found by optical emission spectroscopy (OES). Multiple-hit deformation tests were carried out on a Gleeble® 3500 system in the standard pocket-jaw configuration to determine TNR. Cuboidal specimens (10 (L) × 20 (W) × 20 (T) mm3) were taken for compression test (multiple-hit deformation tests) in gleeble. Microstructure evolutions were carried out by using OM (optical microscopy) and SEM (scanning electron microscopy). The value of TNR determined for 0.1 wt.% niobium bearing microalloyed steel is ~ 951 °C. Nb- microalloyed steel rolled at TNR produce partially recrystallized grain with ferrite nucleation. Hence, to verify the TNR value, a rolling process is applied with the finishing rolling temperature near TNR (~951 °C). The microstructure is also revealed in the pancake shape, which confirms TNR.