Effects of Microalloying Elements on Mechanical Properties of Reinforcing Bars

Hashimoto, Shunichi; Nakamura, Morifumi

doi:10.2355/isijinternational.46.1510

Cited by 18 publications

(18 citation statements)

References 4 publications

(3 reference statements)

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“…[24] A 2 pct nital solution was used to show the transformed microstructures, and a saturated aqueous picric acid solution was used to reveal the prior-austenite grain boundaries (PAGBs). [25,26] The EBSD mappings were carried out via a FEI Sirion electron microscope with an HKL Nordlys F+ detector. EBSD mapping with a step size of 0.2 lm and accelerating voltage of 20 kV was performed on the RD-ND plane of each specimen.…”

Section: Methodsmentioning

confidence: 99%

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

Zhao

Palmiere

2017

Metall and Mat Trans A

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Although there has been much research regarding the effect of austenite deformation on accelerated cooled microstructures in microalloyed steels, there is still a lack of accurate data on boundary densities and effective grain sizes. Previous results observed from optical micrographs are not accurate enough, because, for displacive transformation products, a substantial part of the boundaries have disorientation angles below 15 deg. Therefore, in this research, a niobium microalloyed steel was used and electron backscattering diffraction mappings were performed on all of the transformed microstructures to obtain accurate results on boundary densities and grain refinement. It was found that with strain rising from 0 to 0.5, a transition from bainitic ferrite to acicular ferrite occurs and the effective grain size reduces from 5.7 to 3.1 lm. When further increasing strain from 0.5 to 0.7, dynamic recrystallization was triggered and postdynamic softening occurred during the accelerated cooling, leading to an inhomogeneous and coarse transformed microstructure. In the entire strain range, the density changes of boundaries with different disorientation angles are distinct, due to different boundary formation mechanisms. Finally, the controversial influence of austenite deformation on effective grain size of low-temperature transformation products was argued to be related to the differences in transformation conditions and final microstructures.

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Section: Methodsmentioning

confidence: 99%

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

Zhao

Palmiere

2017

Metall and Mat Trans A

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“…Influencia de la temperatura de precalentamiento sobre el límite de fluencia, la resistencia a la tracción y el alargamiento, para barras sin adición de microaleantes, con adición de niobio y con adición de niobio y vanadio [10]. 0NB: metal base; 5MB: con 0,05% Nb; 5NV: con 0,05% Nb y 0,05% V.…”

Section: Barras Microaleadasunclassified

Barras De Refuerzo De Hormigón: Mecanismos De Endurecimiento Y Performance en Uso

Madias¹,

Wright²,

Wolkowicz³

2017

Anais Do Seminário De Laminação E Conformação

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ResumoSe analizan las distintas alternativas para la producción de barras de refuerzo de hormigón: endurecimiento por solución sólida ("dureza natural"); endurecimiento por temple y autorevenido en línea (Tempcore, Thermex, etc.) y endurecimiento por precipitación (microaleación con niobio, vanadio o titanio) y su influencia sobre la performance de las barras, en lo que hace a la resistencia a la corrosión, al fuego y a los sismos.. Palavras-chave: Vergalhão; Tempcore; Aço microligado; Seismo. REINFORCING STEEL BAR: HARDENING MECHANISMS AND PERFORMANCE IN APPLICATION AbstractThe alternatives for the production of concrete reinforcing bars are analyzed: solid solution hardening ("natural hardness"); quench hardening and self-tempering (Tempcore, Thermex, etc.) and grain refining / precipitation hardening (microalloying with niobium, vanadium, or titanium) and their influence on the performance of the rebar, regarding corrosion resistance, fire and earthquakes.

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“…With a higher precipitation potential from the high N steel, an even larger precipitation strengthening contribution is observed. Hashimoto et al [9] studied the influence of Nb addition on the properties of a rebar steel with composition of 0.25C-1.2Mn-0.5Si. It is reported that the reheating temperature is a critical factor because it determines the degree of Nb dissolution, hence the precipitation potential in the following process.…”

Section: Reinforcing Bars (Rebars)mentioning

confidence: 99%

“…Meanwhile, within the limited research studies [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], it has been reported that Nb additions provide benefits in reducing cost, due to the elimination of any following heat treatment, and improvement in mechanical properties of medium and high carbon steels. Using 0.02 wt% Nb, a successful product Niobras-200 rail steel was developed which provides great performance in heavy haul iron ore service [4].…”

Section: Microalloyed Steelsmentioning

confidence: 99%

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Thermomechanical Processing of Structural Steels with Dilute Niobium Additions

Cui

Patel²,

Palmiere

2016

HSLA Steels 2015, Microalloying 2015 &Amp; Offshore Engineering Steels 2015

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-i - AbstractIn this thesis, the influence of various dilute Nb additions (0.005-0.02 wt%) on austenite microstructure evolution along thermomechanical processing, in terms of austenite recrystallisation and grain growth, were investigated using steels with three carbon content levels.At the homogenisation temperature of 1250°C, all dilute Nb additions were dissolved in low carbon steels whereas the Nb dissolution limits for 0.4 wt% and 0.6 wt% C steels were 0.012 wt% and 0.08 wt%, respectively. Dilute Nb additions did not show significant influence on homogenised austenite grain size. The dramatic increase in C contents was more influential, which decreased the homogenised austenite grain size.The influence of dilute Nb additions and C contents on dynamic recrystallisation behaviour was studied by rough rolling at high deformation temperature with low strain rate. The dilute Nb additions were found to increase the critical strain of dynamic recrystallisation whereas C contents showed no influence on the dynamic recrystallisation behaviour.The austenite recrystallisation behaviour after finish rolling and after the holding period between finishing passes were studied by means of interrupted plane strain compression (PSC) tests and double hit PSC tests. It was found that with low Nb supersaturation, recrystallisation happened prior to Nb precipitation. Solute Nb in austenite delayed the onset of austenite recrystallisation through solute drag effect.With high Nb supersaturation, Nb precipitation occurred before the onset of recrystallisation which completely retarded austenite recrystallisation.The austenite grain growth during the holding period between finish rolling passes was studied by the evolution of prior-austenite grain size before and after the 20s holding period at the highest finish rolling temperature (1050°C). There was no Nb precipitation found and the difference in austenite grain growth behaviour was Abstract -iiattributed to the solute drag effect from both Nb and C in solution. It was found that Nb in solution suppressed austenite grain growth. However, the effectiveness of solute Nb in suppressing austenite grain growth was affected by the C content. Acknowledgement

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Effects of Microalloying Elements on Mechanical Properties of Reinforcing Bars

Cited by 18 publications

References 4 publications

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

Barras De Refuerzo De Hormigón: Mecanismos De Endurecimiento Y Performance en Uso

Thermomechanical Processing of Structural Steels with Dilute Niobium Additions

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