Austenite transformation and age hardening of HSLA-80 and ULCB steels

Gorni, Antonio Augusto; Mei, Paulo Roberto

doi:10.1016/j.jmatprotec.2004.04.245

Cited by 21 publications

(10 citation statements)

References 7 publications

(5 reference statements)

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“…Outros estudos [13,14] aplicaram diversas taxas de resfriamento a aços de alta resistência mecânica e baixa liga e determinaram que a temperatura de início da formação da ferrita acicular dependia da taxa de resfriamento. Igualmente foi determinado [13] que altas taxas de resfriamento levaram a menores temperaturas de início da transformação da austenita para ferrita.…”

Section: Efeitos Da Taxa De Resfriamento Na Soldagem Do Aço Api 5l-x80unclassified

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Efeitos da Taxa de Resfriamento na Soldagem do Aço API 5L-X80

et al. 2015

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Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualq'uer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado. Resumo: Uma das principais razões para o desenvolvimento do aço API 5L-X80 foi seu uso em Regiões Polares, onde se faz necessário alta tenacidade em baixas temperaturas. Neste trabalho foi estudado o efeito da taxa de resfriamento na soldagem sobre as propriedades mecânicas e metalúrgicas deste tipo de aço. Estas diversas taxas de resfriamento simulam também diversas energias de soldagem. As diferentes taxas de resfriamento foram obtidas através de cinco distintos pré-aquecimentos. A temperatura de interpasse foi igual à temperatura de pré-aquecimento de cada uma das juntas em duplo V com face de raiz, sendo as soldagens robotizadas realizadas por arco elétrico com gás de proteção e eletrodo consumível ("Metal Active Gas" -MAG), arame maciço com resistência mecânica equivalente ("matching") ao metal base e gás de proteção composto de 75% Ar e 25% CO 2 . Para análise das juntas soldadas foram utilizados microscópio de luz e microscópio eletrônico de varredura (MEV), bem como ensaios mecânicos de tração, dobramento, impacto (Charpy-V) e dureza (Vickers). Os resultados dos testes mecânicos foram satisfatórios e apresentaram correlação com as análises metalúrgicas. As juntas apresentaram alta resistência ao impacto (Charpy-V) em temperaturas de teste de até -40 °C.Palavras Chave: Soldagem; API 5L-X80; Taxas de resfriamento; Propriedades mecânicas. Cooling Rate Effects in the Welding of API 5L-X80 SteelAbstract: One of the main reasons for the development of the API 5L-X80 steel was its utilization in Polar Areas where a relatively high toughness in low temperatures is needed. The present work aimed at studying the welding cooling rate effects on the mechanical and metallurgical properties of this type of steel. These various cooling rates also simulate various heat input's. These different cooling rates were obtained through five distinct pre-heatings. The interpass temperature was the same of the pre-heating temperature presented by each one of the double V joints with root face; being the robotics weldings itself performed through gas metal arc welding (GMAW), using solid wire with matching mechanical resistance, and as a shielding gas a mixture of 75% Ar and 25% CO 2 . In order to analyze the welded joints, light microscope and scanning electron microscope (SEM) were utilized, as well as mechanical tests, such as tension, bending, impact (Charpy-V) and hardness (Vickers). The results of such mechanical tests were satisfactory and suitable correlated with the metallurgical analyses. The joint presented a high Charpy-V impact resistance in testing temperatures up to -40 °C.

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Section: Efeitos Da Taxa De Resfriamento Na Soldagem Do Aço Api 5l-x80unclassified

“…Igualmente foi determinado [13] que altas taxas de resfriamento levaram a menores temperaturas de início da transformação da austenita para ferrita. Quanto menor a temperatura de início da transformação da austenita para ferrita, mais refinada e dura será a nova fase.…”

Section: Efeitos Da Taxa De Resfriamento Na Soldagem Do Aço Api 5l-x80unclassified

Efeitos da Taxa de Resfriamento na Soldagem do Aço API 5L-X80

et al. 2015

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“…Upon further cooling, the delta-ferrite transforms to austenite, and at yet lower temperatures, austenite transforms to alpha-ferrite. While the theory of solidification of MA steels [7][8][9][10] and the kinetics of austenite to alpha-ferrite phase transformation [11][12][13][14] were extensively studied and developed, comparatively little information is available concerning the kinetics of the delta-ferrite to austenite transformation and its effect on the grain size. The reason for this is that the final alpha-ferrite grain size is largely controlled by the parent austenite grain size.…”

Section: Tihe Zhou Hatem S Zurob Elachmi Essadiqi and Benoit Voyzmentioning

confidence: 99%

Kinetics of Delta-Ferrite to Austenite Phase Transformation in a Two-Phase Fe-Al-C Alloy

Zhou

Zurob

Essadiqi³

et al. 2011

Metall Mater Trans A

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The kinetics of delta-ferrite to austenite phase transformation was investigated using a quenching dilatometer in a Fe-Al-C alloy. The results showed that the austenite phase nucleated along the delta grain boundaries. The transformed austenite morphology changed from cellular to Widmansta¨tten pattern when the holding temperature decreased from 1398 K to 1123 K (1125°C to 850°C). Full partitioning of the substitutional alloying elements was observed and the spacing of the austenite plates was controlled by the diffusing distance of the substitutional elements. Interestingly, growth of the austenite front was controlled by the long-range diffusion of carbon from the center of the delta grains to the growing front. Deformation of the delta phase enhanced the nucleation of austenite at existing grain boundaries and newly formed subgrain boundaries.

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“…[7][8][9][10] When the phase transformation behavior of steels during continuous cooling is studied, the CCT curve for the formation of detailed phase products needs to be worked out by measuring the starting temperatures of phase transformations. Although numerous dilatometric studies have been conducted and a great number of CCT curves have been drawn, [11][12][13][14][15][16][17][18][19][20][21][22][23] systematic work on the quantitative relationship of phase transformation starting temperatures, composition and processing are still lacking, especially for the starting temperature for austenite to ferrite transformation (A r3 ) in high strength low alloy steels (HSLA), which is an important factor in determining the phase transformation kinetics during cooling after hot rolling.…”

Section: Introductionmentioning

confidence: 99%

The Onset Temperatures of γ to α-Phase Transformation in Hot Deformed and Non-deformed Nb Micro-alloyed Steels

Yuan¹,

Liu²,

Jiao

et al. 2006

ISIJ Int.

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In the present paper, continuous cooling transformation behaviors in Nb micro-alloyed steels were systematically investigated by the thermal dilatation method, during which the effects of Nb contents and hot deformation of austenite on phase transformation behaviors, especially the transformation start temperatures, were studied in detail. The tests were carried out with the samples having been reheatedϩhot deformed or reheatedϩnon-deformed prior to the dilation measurements. It was found that the A r3 temperatures measured from the dilatometric curves changed with increasing Nb content in parabolic ways under both hot deformed and non-deformed conditions. It is believed that dissolved Nb in austenite may have had the Nb solute drag effect that could delay austenite to ferrite transformation. On the other hand, Nb precipitates in austenite could retard the growth of austenite grains and act as potential nucleation sites, both of which could enhance the transformation kinetics. Also, the interaction of strain, precipitation and temperature was estimated by using the Sellars model, which predicted that the strain induced precipitation had occurred in hot deformed Nb steels before phase transformation started, and in non-deformed steels with Nb content greater than 0.023 mass%, precipitation was also likely to have occurred under slow cooling rate before phase transformation started, which could have played an important role in determining A r3 . These factors worked together to make A r3 changing with Nb content in the parabolic way. Based on the experimental results, a mathematical model for the A r3 calculation for Nb and C-Mn steels were developed, which exhibited a good accuracy in predicting the A r3 of the steels with and without hot deformation.KEY WORDS: Nb microalloyed steels; A r3 temperature; CCT curve; hot deformation; solute drag effect.

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Austenite transformation and age hardening of HSLA-80 and ULCB steels

Cited by 21 publications

References 7 publications

Efeitos da Taxa de Resfriamento na Soldagem do Aço API 5L-X80

Efeitos da Taxa de Resfriamento na Soldagem do Aço API 5L-X80

Kinetics of Delta-Ferrite to Austenite Phase Transformation in a Two-Phase Fe-Al-C Alloy

The Onset Temperatures of γ to α-Phase Transformation in Hot Deformed and Non-deformed Nb Micro-alloyed Steels

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