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Microalloyed steel

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


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TL;DR: In this article, a multiphase microstructure was developed in a V-bearing medium carbon microalloyed steel using a two-step cooling and annealing (TSCA) treatment following finish forging.
Abstract: In an attempt to improve fatigue and fracture resistance, a multiphase (ferrite–bainite–martensite) microstructure was developed in a V-bearing medium carbon microalloyed steel using a two-step cooling and annealing (TSCA) treatment following finish forging. The monotonic, cyclic stress–strain and low cycle fatigue behavior of this steel are reported. These results are compared with those of ferrite–pearlite and tempered martensite microstructures obtained by air cooling (AC) and quenching and tempering (Q&T), respectively. The tensile properties of the multiphase microstructure are superior to those of the ferrite–pearlite and the Q&T microstructures. Under cyclic loading, the ferrite–pearlite microstructure showed hardening at higher total strain amplitudes (≥0.7%) and softening at lower total strain amplitudes (<0.7%). The quenched and tempered and the ferrite–bainite–martensite (TSCA) microstructures displayed cyclic softening at all total strain amplitudes employed. Despite the cyclic softening, the ferrite–bainite–martensite structure was cyclically stronger than the ferrite–pearlite and the Q&T microstructures. Bilinearity in the Coffin–Manson plots was observed in Q&T and the multiphase TSCA conditions. An analysis of fracture surface provided evidence for predominantly ductile crack growth (microvoid coalescence and growth) in the ferrite–pearlite microstructure and mixed mode (ductile and brittle) crack growth in Q&T and the multiphase TSCA microstructures.

77 citations

Journal ArticleDOI
TL;DR: In this paper, a C-Mn-Nb steel has been heavily deformed by torsion at temperatures below the determined nonrecrystallization temperature (Tnr), and specimens are cooled at a constant cooling rate of 1 °C/s.
Abstract: It is well established that the ferrite grain size of low-carbon steel can be refined by hot rolling of the austenite at temperatures below the nonrecrystallization temperature (Tnr). The strain retained in the austenite increases the number of ferrite nuclei present in the initial stages of transformation. In this work, a C-Mn-Nb steel has been heavily deformed by torsion at temperatures below the determined Tnr for this steel. After deformation, specimens are cooled at a constant cooling rate of 1 °C/s, and interrupted quenching at different temperatures is used to observe different stages of transformation. The transformation kinetics and the evolution of the ferrite grain size have been analyzed. It has been shown that the stored energy due to the accumulated deformation is able to influence the nucleation for low undercoolings by acting on the driving force for transformation; this influence becomes negligible as the temperature decreases. At the early stages of transformation, it has been observed that the preferential nucleation sites of ferrite are the austenite grain boundaries. At the later stages, when impingement becomes important, ferrite coarsening accompanies the transformation and a significant reduction in the number of the ferrite grains per unit volume is observed. As a result, a wide range of ferrite grain sizes is present in the final microstructure, which can influence the mechanical properties of the steel.

77 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the dynamic recrystallization of austenite in the Cu-bearing HSLA-100 steel and found that at high temperatures, flow stress exhibited a linear relation with temperature while at temperatures below 950°C the behavior changed to non-linear.
Abstract: Dynamic recrystallization of austenite in the Cu-bearing HSLA-100 steel was investigated by hot compression testing at a temperature range of 850–1150 °C and a strain rate of 0.001–1 s −1 . The obtained flow curves at temperatures higher than 950 °C were typical of DRX while at lower temperatures the flow curves were associated with work hardening without any indication of DRX. At high temperatures, flow stress exhibited a linear relation with temperature while at temperatures below 950 °C the behavior changed to non-linear. Hence, the temperature of 950 °C was introduced as the T nr of the alloy. All the flow curves showed a yield point elongation like phenomenon which was attributed to the interaction of solute atoms, notably carbon, and moving dislocations. The maximum elongation associated with the yield point phenomenon was observed at about 950 °C. Since the maximum yield point elongation was observed about the calculated T nr , it was concluded that carbon atoms were responsible for it. It was also concluded that the temperature at which the yield point elongation reaches the maximum value increases as strain rate rises. The stress and strain of the characteristic points of DRX flow curves were successfully correlated to the Zener–Hollomon parameter, Z , by power-law equations. The constitutive exponential equation was found more precise than the hyperbolic sine equation for modeling the dependence of flow stress on Z . The apparent activation energy for DRX was determined as 377 kJ mol −1 . The kinetics of DRX was modeled by an Avrami-type equation and the Avrami's exponent was determined around 1.1.

76 citations

Journal ArticleDOI
TL;DR: In this article, the local deformation properties of spot-welded similar and dissimilar material joints in shear tension tests were investigated for a TRIP steel and a micro-alloyed steel (HX340LAD).
Abstract: Numerical simulation of component and assembly behaviour under different loading conditions is a main tool for safety design in automobile body shell mass production. Knowledge of local material behaviour is fundamental to such simulation tests. As a contribution to the verification of simulation results, the local deformation properties of spot-welded similar and dissimilar material joints in shear tension tests were investigated in this study for a TRIP steel (HCT690T) and a micro-alloyed steel (HX340LAD). For this reason, the local strain distribution was calculated by the digital image correlation technique (DIC). On the basis of the hardness values and microstructure of the spot welds, the differences in local strain between the selected material combinations are discussed. Additionally, the retained austenite content in the TRIP steel was analysed to explain the local strain values. Results obtained in this study regarding similar material welds suggest significant lower local strain values of the TRIP steel HCT690T compared to HX340LAD. One reason could be the decrease of retained austenite in the welded area. Furthermore, it has been ascertained that the local strain in dissimilar material welds decreases for each component compared with the corresponding similar material weld.

76 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of the most common elements in low alloy steels (C, Mn, Si, Mo) and in microalloyed steels on peak strain has been studied.

76 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202328
202288
202164
202090
201986
201888