Microstructure and toughness of the CGHAZ of an offshore platform steel

Zhou, Yuke; Jia, Ting; Zhang, Xiangjun; Liu, Zhenyu; Misra, R.D.K.

doi:10.1016/j.jmatprotec.2014.12.017

Cited by 58 publications

(27 citation statements)

References 20 publications

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“…Because the martensite structure of M-A constituents cause them to have a greater hardness than the matrix, stress concentration will be induced at the interface produced under loading [ 21 ]. Consequently, the M-A constituents are debonded from the matrix, as is shown in Figure 8 ; this finding is consistent with the reports of many previous studies [ 14 , 22 ]. The debonding creates microvoids or cracks with dimensions similar to those of the M-A constituents because the interfaces have been weakened by carbon segregation [ 23 ].…”

Section: Discussionsupporting

confidence: 92%

Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel

Zhao

Shan

2018

Materials

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The subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact toughness or peak welding temperature; the invariant subzone heated between the critical transformation start temperature (Ac1) and 770 °C exhibited unchanged high impact toughness. Furthermore, an extremely low impact toughness was found in the embrittlement subzone, heated between 770 and 830 °C, and the reduction subzone heated between 830 °C and the critical transformation finish temperature (Ac3) exhibited toughness below that of the original metal. The size of the blocky martensite-austenite (M-A) constituents was found to have a remarkable level of influence on the impact toughness when heated below 830 °C. Additionally, it was found that, once the constituent size exceeds a critical value of 3.0 µm at a peak temperature of 770 °C, the IC HAZ becomes brittle regardless of lath or twinned martensite constitution in the M-A constituent. Essentially, embrittlement was observed to occur when the resolved length of initial cracks (in the direction of the overall fracture) formed as a result of the debonding of M-A constituents exceeding the critical Griffith size. Furthermore, when the heating temperature exceeded 830 °C, the M-A constituents formed a slender shape, and the impact toughness increased as the area fraction of the slender M-A constituents decreased.

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Section: Discussionsupporting

confidence: 92%

Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel

Zhao

Shan

2018

Materials

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“…21. Generally, the tensile strength is reduced with increasing heat input due to internal imperfections (porosity) and microstructure and might due to larger grains providing lower strength [62]. Weld No.…”

Section: Mechanical Test Resultsmentioning

confidence: 99%

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

Bunaziv

Dørum

Nielsen

et al. 2020

Int J Adv Manuf Technol

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High-power lasers are very effective in welding of plates thicker than 10 mm due to the keyhole mode. High-power intensity generates a vapor-filled cavity which provides substantial penetration depth. Due to the narrow and deep weld geometry, there is susceptibility to high hardness and weld defects. Imperfections occur due to keyhole instability. A 16-kW disk laser was used for single-pass welding of 12-to 15-mm thick plates in a butt joint configuration. Root humping was the main imperfection and persisted within a wide range of process parameters. Added arc source to the laser beam process may cause increased root humping and sagging due to accelerated melt flow. Humping was mitigated by balancing certain arc and other process parameters. It was also found that lower welding speeds (< 1.2 m/min) combined with lower laser beam power (< 13 kW) can be more positive for suppression of humping. Machined edges provided more consistent root quality and integrity compared with plasma cut welded specimens. Higher heat input (> 0.80 kJ/mm) welds provided hardness level below 325 HV. The welded joints had good Charpy toughness at − 50°C (> 50 J) and high tensile strength.

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“…A análise macrográfica realizada (Figura 13) permite verificar o efeito da soldagem multipasse e a inexistência de defeitos de soldagem, confirmando que o procedimento de soldagem executado foi adequado para evitar a ocorrência de trinca a frio. Neste aspecto, é importante ressaltar que o material em estudo (Tabela 2) apresenta elevada temperabilidade e, consequentemente, alta propensão para formação de martensita na ZTA, notadamente na região de grãos grosseiros, considerada a região crítica da ZTA [37][38][39][40][41][42][43], o que foi observado no presente trabalho (Figura 14).…”

Section: Propriedades Da Junta Soldadaunclassified

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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Microstructure and toughness of the CGHAZ of an offshore platform steel

Cited by 58 publications

References 20 publications

Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel

Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel

Laser-arc hybrid welding of 12- and 15-mm thick structural steel

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

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