Microalloyed steel

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

Improved Model for Static Recrystallization Kinetics of Hot Deformed Austenite in Low Alloy and Nb/V Microalloyed Steels

Abstract: Using torsion tests a improved model has been constructed to predict the static recrystallization kinetics of deformed austenite in low alloy and microalloyed steels. The model quantifies the influence of the most common elements (C, Si, Mn, Mo) in low alloy steels and the typical elements (V, Nb) in microalloyed steels, when they are in solution. Activation energy (Q) is the parameter sensitive to the content and nature of each alloying element, and an expression for Q is shown as a function of the percentage of each one. Nb is the element that contributes most to increasing the value of Q, and thus that which most delays recrystallization kinetics. C is seen to be the only alloying element that contributes to lowering the value of Q, and thus to accelerating recrystallization kinetics. Extrapolation of the expression of Q to pure iron in the austenitic phase gives a value of 148 637 J mol-1, which is similar to other values found in the literature for the grain boundary self-diffusion energy of pure Feγ . Static recrystallization kinetics follow Avrami's law and expressions are given for the parameter t0.5 and the exponent n.

Orowan strengthening effect on the nanoindentation hardness of the ferrite matrix in microalloyed steels

Abstract: Although it is well known that there is a significant contribution of precipitation strengthening to the strength of structural steels, it is difficult to experimentally separate the precipitation contribution from the overall strength due to the complex nature of steel microstructures. In this study, the contribution of precipitation strengthening to the matrix strength of ferrite in steel was experimentally investigated through nanoindentation tests. Nanoindentation hardness values of the ferrite matrix in precipitates-containing steels were greater than those in precipitate-free steels, which may be due to the Orowan strengthening mechanism based on the interaction between precipitates and dislocations. To better understand the precipitation strengthening contribution, interparticle spacing values of precipitates were calculated for each microalloyed steel and used for the analysis of hardness change. It was revealed that the trend of nanoindentation hardness change with variation in interparticle spacing corroborated the expectation based on classic Orowan theory.

Recrystallization–precipitation interaction during austenite hot deformation of a Nb microalloyed steel

Abstract: The role of Nb during austenite processing of High Strength Low Alloy (HSLA) steels has been the subject of considerable interest and discussion over the past decades. In this work, the precipitation state of a Nb microalloyed steel is studied extensively during the different stages of the process, i.e. after reheating, during cooling, during deformation and during recrystallization. To do so, a combination of experimental methods was applied: Transmission Electron Microscopy in combination with Energy Dispersive X-ray Spectroscopy (TEM-EDX), Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) and X-ray Diffraction (XRD). To obtain the best accuracy for these precipitation measurements, a model alloy was designed that showed extensive precipitation. From this experimental study, a correlation between the precipitate pinning and the recrystallization driving force could be made and the precipitation state during recrystallization could be linked to the recrystallization kinetics by comparison of the recrystallization driving force to the Zener pinning force. It was confirmed that recrystallization occurred during the precipitate nucleation and coarsening stage, while it was halted completely during the precipitation growth stage.