EBSD Analysis of Relationship Between Microstructural Features and Toughness of a Medium-Carbon Quenching and Partitioning Bainitic Steel

Li, Qiang‐Guo; Huang, Xuefei; Huang, Weigang

doi:10.1007/s11665-017-3052-5

Cited by 27 publications

(15 citation statements)

References 37 publications

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“…A Figura 22 mostra uma comparação dos resultados de tenacidade ao impacto destes estudos [21,23] com os discutidos no presente trabalho. É possível notar que o aço fundido pode propiciar resultados equivalentes aos destes estudos [21,23], mesmo considerando que os aços laminados por terem sido submetidos a processos de conformação mecânica, reúnem características microestruturais mais adequadas para uma boa tenacidade (Figura 23), tais como uma estrutura mais refinada e maior incidência de contornos de alto ângulo [4,37,52,[81][82][83][84].…”

Section: Implicações Práticas Dos Resultadosunclassified

Avaliação de Juntas Soldadas de um Aço Fundido de Alta Resistência para a Indústria Offshore

et al. 2018

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Resumo Os torpedos de ancoragem são estruturas tubulares de aço carbono soldadas, e que tem sua ligação com as linhas de ancoragem que impedem o movimento das plataformas através de olhais de carregamento que são soldados nos tubos de construção. Como estes olhais apresentam geometria complexa, é importante a utilização de peças fundidas para a fabricação destes componentes, de forma a possibilitar o atendimento da demanda do mercado. Como a literatura técnica sobre este tipo de união soldada é ainda limitada, o presente trabalho estuda o comportamento de juntas soldadas de um aço fundido de alta resistência para utilização em olhais de torpedos de ancoragem de plataformas offshore. Para tanto, foram produzidas juntas soldadas com chanfro em K utilizando um aço de classificação ASTM A 148 Gr. 105-85 com resistência mecânica da ordem de 700 MPa, pelo processo eletrodo revestido, na posição plana, com preaquecimento de 200 °C e energia de soldagem média de 1,5 kJ/mm. Após a soldagem, foi realizado tratamento térmico pós-soldagem (TTPS) consistindo de aquecimento a 620 °C por 1 hora com resfriamento ao ar. As propriedades foram avaliadas por ensaios de tração, dureza, impacto Charpy-V e metalográficos por microscopia óptica e eletrônica de varredura com utilização da técnica de EBSD (eléctron backscatering difraction), tanto na condição de como soldado quanto após TTPS. Os resultados revelaram que, embora as propriedades mecânicas obtidas na junta soldada atendam os requisitos para a aplicação em todas as condições de análise, recomenda-se a execução do TTPS para alívio das tensões residuais e promover um revenimento da martensita de alta dureza do último passe de soldagem. Adicionalmente, verificou-se ser possível obter propriedades similares as de juntas soldadas de aços laminados usualmente utilizados em componentes de ancoragem.

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Section: Implicações Práticas Dos Resultadosunclassified

Avaliação de Juntas Soldadas de um Aço Fundido de Alta Resistência para a Indústria Offshore

et al. 2018

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“…This kind of film retained austenite exhibits high stability due to subjected to high compressive stress caused by the surrounding martensite or bainite ferritic laths. The highly stable film retained austenite can contribute to the inhibition of the crack initiation in the microstructure, thus effectively improve the TRIP effect under the uniform deformation [12,37]. However, it is found that although the volume fraction of retained austenite of the sample with isothermal transformation at 220 • C for 7 h is slightly lower than that of the sample with isothermal transformation at 220 • C for 3 h and tempered at 250 • C, the uniform strain and strain hardening exponent are higher.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…As seen from Figure 7, the proportion of boundary misorientation angles greater than 15 • is about 74% in samples for all three heat treatment processes, which shows no significant difference. The boundary misorientations angles greater than 15 • are considered high angle boundaries, which should involve austenite grain boundaries, packet boundaries, and block boundaries in the lath-like microstructure, such as martensite and bainite [37,[45][46][47]. These high angle boundaries in the microstructure can act as a barrier of crack propagation, leading to more energy consumption during the fracture process.…”

Section: Heat Treatment Processmentioning

confidence: 99%

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Effect of Isothermal Transformation Times below Ms and Tempering on Strength and Toughness of Low-Temperature Bainite in 0.53 C Bainitic Steel

Liu

Naseem

et al. 2020

Materials

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This study aims to investigate the microstructures, strength, and impact toughness of low-temperature bainite obtained by isothermal transformation at temperature below Ms (Martensite Starting temperature) for different times and tempering process in 0.53 C wt% bainitic steel. By using the optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), electron back scatter diffraction (EBSD), and mechanical property test, it was found that the microstructures after heat treatment consist of small amounts of martensite, fine bainite, and film retained austenite. After tempered at 250 °C for 2 h, the volume fraction of retained austenite (10.9%) in the sample treated by isothermal transformation at 220 °C for three hours is almost the same as that of the sample without tempering. In addition, the retained austenite fraction decreases with the increase of holding times and is reduced to 6.8% after holding for 15 h. The ultimate tensile strength (1827 MPa), yield strength (1496 MPa), total elongations (16.1%), and impact toughness (up to 58 J/cm2) were obtained by isothermal transformation at 220 °C for three hours and tempered at 250 °C. Whereas, the impact toughness of sample without tempering is 28 J/cm2. After holding for 15 h, the impact toughness raises to 56 J/cm2, while the ductility and strength decreases. These results indicate that the tempering process is helpful to improve the impact toughness of low-temperature bainite.

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“…As a significant part of railway, rail steel often requires excellent mechanical properties and better fatigue performance. [1][2][3][4] Our previous works [5][6][7][8] indicated that the quenching and partitioning (Q&P) bainitic steel with bainite/martensite/retained austenite multiphase microstructure has better combination of strength and toughness than that of the bainitic steel with fully bainite microstructure. This multiphase microstructure can be considered to be an attractive and promising candidate microstructure for rail steel.…”

Section: Introductionmentioning

confidence: 99%

Fatigue crack propagation behavior of multiphase microstructure in a quenched and partitioned medium‐carbon bainitic steel

Zhang

Luo

2022

Fatigue Fract Eng Mat Struct

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A medium‐carbon steel was treated by the bainitic isothermal transformation plus quenching and partitioning (B‐QP) process to obtain bainite/martensite/retained austenite multiphase microstructure, and its fatigue crack propagation (FCP) behavior was evaluated in contrast with BAT (bainite austempering) sample with fully bainite microstructure. Results show that B‐QP sample exhibits a lower FCP rate and higher fatigue threshold ΔKth (12.6 MPa·m1/2). Moreover, the FCP path of B‐QP sample displays a strongly tortuosity and more crack branching due to more filmy retained austenite (7.2%) and higher percentage of high angle misoriented boundaries (68%). The larger crack tortuosity and the secondary cracks as result of crack branching are primarily responsible for the lower FCP rate of B‐QP sample. In addition, the FCP rate curve of B‐QP sample shows a pronounced small plateauing at the near‐threshold zone, which can be ascribed to the mechanical twinning that occurred in the filmy retained austenite.

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EBSD Analysis of Relationship Between Microstructural Features and Toughness of a Medium-Carbon Quenching and Partitioning Bainitic Steel

Cited by 27 publications

References 37 publications

Avaliação de Juntas Soldadas de um Aço Fundido de Alta Resistência para a Indústria Offshore

Avaliação de Juntas Soldadas de um Aço Fundido de Alta Resistência para a Indústria Offshore

Effect of Isothermal Transformation Times below Ms and Tempering on Strength and Toughness of Low-Temperature Bainite in 0.53 C Bainitic Steel

Fatigue crack propagation behavior of multiphase microstructure in a quenched and partitioned medium‐carbon bainitic steel

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