Effect of different cooling rates on thermomechanically processed high-strength rebar steel

Zaky, A.I.; El-Morsy, Abdel-Wahab; El-Bitar, Taher

doi:10.1016/j.jmatprotec.2008.04.011

Cited by 29 publications

(17 citation statements)

References 10 publications

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“…Due to intermediate cooling the narrow interface region of the tempered martensite rim and ferrite-pearlite core region transforms to bainite. [20][21][22] In all types of samples the measured tempered martensite rings are about 1.0-1.6 mm ( Table 2). Figures 2-4 show three distinctive regions where the outer region comprises tempered martensite, the transition zone has narrow bainitic structure and the core zone consists of polygonal, non-polygonal ferrite of white contrast and pearlite of dark contrast.…”

Section: Microstructure Evolutionmentioning

confidence: 95%

Microstructure, mechanical properties and corrosion performance of a few TMT rebars

Nandi

Tewary

Saha³

et al. 2016

Corrosion Engineering, Science and Technology

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The present work aims to study the evaluation of the microstructure, tensile properties, hardness, corrosion behaviour of the various grades of rebars. The microstructures of all rebar samples comprise an outer tempered martensite ring with an inner core of ferrite-pearlite in between a narrow bainitic transition zone. Maximum hardness is achieved at the periphery which gradually decreases towards the centre. Chinese grade has a similarity with the Fe 600 rebar in terms of strength and % elongation, whereas Fe 500D and Fe 500 have lower strength but higher ductility. The EDS analyses of corrosion products obtained after immersion test in 5% NaCl solution for a period of 7 days apparently indicate the occurrences of iron oxy-hydroxides and iron oxides. X-ray diffraction and FTIR studies of the corrosion products formed on all thermomechanically treated (TMT) rebar surfaces after the aforesaid immersion test primarily indicate the presence of Lepidocrocite (γ-FeOOH), Goethite (α-FeOOH), Magnetite (Fe 3 O 4 ) and Maghemite (γ-Fe 2 O 3 ). Fe 500 (12 mm) and Chinese rebars have lower corrosion resistance as compared to the other rebars in 5% NaCl solution. Nevertheless, all the TMT rebars are corrosion resistant and can be satisfactorily used for construction purposes.

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Section: Microstructure Evolutionmentioning

confidence: 95%

Microstructure, mechanical properties and corrosion performance of a few TMT rebars

Nandi

Tewary

Saha³

et al. 2016

Corrosion Engineering, Science and Technology

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“…Therefore, the value of D also serves to explain why AlN precipitates are coarser than V(C,N) and Nb(C,N), and consequently why they are not effective to inhibit recrystallisation and to strengthen the austenite during hot rolling. Austenite strengthening is known to refine grain size and consequently improve the mechanical properties 24.…”

Section: Resultsmentioning

confidence: 99%

Effects of TiN and AlN Nanoparticles in Hot Deformation of Austenite in Steels

Medina¹,

Gómez²,

Vallés

2010

steel research int.

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Recrystallisation kinetics of two low‐carbon steels, of which one with Ti and the other with Al as precipitate‐forming elements was studied by means of hot torsion tests. The mean size of TiN and AlN particles that precipitate during hot deformation was analysed by transmission electron microscopy (TEM). These results, along with the determination of the activation energy, the precipitated volume fraction and the diffusion coefficients of Ti, Al and N in austenite explain the ineffectiveness of these particles to inhibit the static recrystallisation.

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“…Como o aço ABNT 4340 tem elevada temperabilidade, o processo de nucleação da ferrita pró-eutetoide ou bainita nos contornos de grãos austeníticos não é efetivo, dificultando a revelação do contorno de grão austenítico prévio. Apesar do aço ABNT 1045 também apresentar significativa temperabilidade, o processo de nucleação de pequena fração de perlita fina e de bainita nos contornos de grãos austeníticos prévios, favoreceu a delimitação desses contornos na amostra deste aço [8,9].…”

Section: Têmpera Superficialunclassified

“…Entretanto, estudos específicos sobre a extensão da formação de martensita em função da profundidade de têmpera revelam que, a uma certa profundidade, a martensita deixa de estar presente e, em função da taxa de resfriamento mais baixa, ocorre a formação de pequena fração de ferrita primária e bainita nos contornos de grão austenítico prévio. A revelação desta microestrutura, portanto, aparenta ser uma potencial técnica para revelação do grão austenítico original [8,9] …”

Section: Introductionunclassified

Avaliação De Diferentes Técnicas De Contraste Para Revelar O Contorno De Grão Austenítico Prévio Em Aços

Moreirar¹,

Faria²,

Fortes³

et al. 2018

ABM Proceedings

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ResumoA caracterização do tamanho de grão austenítico prévio dos aços é importante, pois a partir desta investigação é possível estimar parâmetros metalúrgicos que repercutirão na qualidade final do produto. Desenvolver métodos para a revelação do contorno de grão prévio se faz necessário, porém, muitas pesquisas apontam para a complexidade destes métodos. Este trabalho se propõe a avaliar diferentes técnicas de contraste para revelar o contorno de grão austenítico prévio dos aços ABNT 1045 e ABNT 4340. Foram utilizadas três técnicas para revelar o contorno de grão austenítico prévio, sendo: ataque químico, ataque térmico e têmpera superficial. Destacam-se o ataque térmico e a têmpera superficial como métodos inovadores. O ataque químico foi realizado em três condições, variando-se a composição de ácido clorídrico adicionado ao reativo a base de ácido pícrico. O ataque térmico foi realizado em duas condições, em atmosfera inerte e em atmosfera oxidante/inerte. A técnica de têmpera superficial consistiu em austenitizar e promover um tratamento térmico de têmpera com restrições na taxa de resfriamento, promovendo um efeito de transformação bainitica nos contornos de grãos austeníticos prévios. Pôde-se concluir que a técnica mais eficiente para os aços estudados foi o ataque químico a base de ácido pícrico. As técnicas de ataque térmico e têmpera superficial se mostraram eficientes para o aço ABNT 1045, apresentando potencial de melhoria metodológica para outros tipos de aços. Palavras-chave: Contorno de grão austenítico prévio; Ataque químico; Ataque térmico; Têmpera superficial. EVALUATION OF DIFFERENT CONSTRAST TECHNIQUES TO REVEAL THE PRIOR AUSTENITE GRAIN BOUNDARY AbstractThe characterization of prior austenite grain boundary of steels are important, because with this parameter knowledge, is possible to estimate metallurgical parameters that could have influence on steel product quality. The development of practical methods aiming to reveal the prior austenite grain boundaries is necessary, but many research papers highlights the complexity of these kind of methods. In this context, this work proposes to evaluate different contrast techniques to reveal the prior austenite grain in ABNT 1045 and ABNT 4340 steels. Techniques as chemical etching, heat etching and surface quenching etching were applied. The heat and surface quenching methods are innovative. The chemical etching was tested in three conditions (HCl content was changed), the heat etching was evaluated in two conditions (inert and oxidizing environment), the surface quenching etching were applied with restrictive conditions in cooling rate, aiming to obtain bainite in prior austenite grain boundaries. It was possible to conclude that the most efficient method is the chemical etching with picric acid and HCl for both studied steel. The heat and surface etching were efficient only for ABNT 1045 steel.

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Effect of different cooling rates on thermomechanically processed high-strength rebar steel

Cited by 29 publications

References 10 publications

Microstructure, mechanical properties and corrosion performance of a few TMT rebars

Microstructure, mechanical properties and corrosion performance of a few TMT rebars

Effects of TiN and AlN Nanoparticles in Hot Deformation of Austenite in Steels

Avaliação De Diferentes Técnicas De Contraste Para Revelar O Contorno De Grão Austenítico Prévio Em Aços

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