Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification

Isasti, Nerea; Jorge-Badiola, D.; Taheri, Mitra L.; Uranga, Pello

doi:10.1007/s11661-013-1738-3

Cited by 55 publications

(44 citation statements)

References 40 publications

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“…This fact is related to the development of more non-polygonal or bainitic microstructural features as the coiling temperature decreases. This trend was previously reported both for coiling simulations as well as for continuously cooled samples [2,9]. …”

Section: Microstructural Characterizationsupporting

confidence: 86%

“…Different transformation products can be distinguished depending on the chemical composition and the coiling temperature. In this article, the Iron and Steel Institute of Japan (ISIJ) Bainite Committee notation is adopted [2,8].…”

Section: Microstructural Characterizationmentioning

confidence: 99%

“…Each one of these elements affects different mechanisms. On one hand, many studies agree that Nb is able to induce strain accumulation in the austenite prior to transformation, providing significant microstructural refinement [2]. Mo, in addition to having a solute drag effect on the static recrystallization kinetics, enhances the formation of complex non-polygonal Table 1.…”

Section: Introductionmentioning

confidence: 99%

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Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

Larzabal

Isasti

Rodríguez-Ibabe

et al. 2017

Metals

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Low carbon microalloyed steels show interesting commercial possibilities by combining different "micro"-alloying elements when high strength and low temperature toughness properties are required. Depending on the elements chosen for the chemistry design, the mechanisms controlling the strengths and toughness may differ. In this paper, a detailed characterization of the microstructural features of three different microalloyed steels, Nb, Nb-Mo and Ti-Mo, is described using mainly the electron backscattered diffraction technique (EBSD) as well as transmission electron microscopy (TEM). The contribution of different strengthening mechanisms to yield strength and impact toughness is evaluated, and its relative weight is computed for different coiling temperatures. Grain refinement is shown to be the most effective mechanism for controlling both mechanical properties. As yield strength increases, the relative contribution of precipitation strengthening increases, and this factor is especially important in the Ti-Mo microalloyed steel where different combinations of interphase and random precipitation are detected depending on the coiling temperature. In addition to average grain size values, microstructural heterogeneity is considered in order to propose a new equation for predicting ductile-brittle transition temperature (DBTT). This equation considers the wide range of microstructures analyzed as well as the increase in the transition temperature related to precipitation strengthening.

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Section: Microstructural Characterizationsupporting

confidence: 86%

Section: Microstructural Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

Larzabal

Isasti

Rodríguez-Ibabe

et al. 2017

Metals

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“…The starting point of the present study are the continuous cooling transformation (CCT) diagrams derived in previous papers by Isasti et al 2,3) and the PhD thesis by García-Riesco 4) for a series of low carbon Nb and Nb-Mo microalloyed steels tested at different prior austenite conditions. These diagrams were built with the help of the information provided by dilatometry tests (transformation start and finish temperatures), microstructural characterization, and Vickers hardness measurements.…”

Section: Modeling Of Cct Diagrams and Ferrite Grain Size Prediction Imentioning

confidence: 99%

Modeling of CCT Diagrams and Ferrite Grain Size Prediction in Low Carbon Nb–Mo Microalloyed Steels

Isasti¹,

García-Riesco²,

Jorge-Badiola³

et al. 2015

ISIJ Int.

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In this paper a multi-linear regression analysis is developed to predict continuous cooling (CCT) diagrams in low carbon Nb and Nb-Mo microalloyed steels. The inputs to the analysis include the weight percentage of alloying elements, the prior austenite grain size, the retained strain and the cooling rate. To develop the model, 11 steels with different combinations of Nb and Mo were considered. In some cases, the resulting equations have been validated with external data from the literature. Additionally, the model was also employed to predict hardness and ferrite grain size with the aim of providing a tool to link microstructural features with mechanical property predictions. Both Nb and Mo additions promote a reduction of ferrite and bainite start temperatures, where the effect is more pronounced for Nb in the bainitic region. Both microalloying elements contribute to an increase in hardness and a refinement of the microstructure.

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“…É conhecido o efeito destes elementos para promover o endurecimento por solução sólida e o refino de grão, que favorecem o aumento da resistência mecânica dos aços [3]. Outro elemento de liga importante é o molibdênio que favorece a formação de produtos de transformação displacivos com aumento da resistência mecânica e da tenacidade [4]. Desta forma e considerando a composição química e diferentes tratamentos térmicos, o objetivo deste trabalho foi avaliar a microestrutura e as propriedades mecânicas em tração de um aço microligado forjado submetido ao aquecimento a 855, 900 e 1000 °C com posterior resfriamento resfriado em água.…”

Section: Introductionunclassified

Influência Da Temperatura De Aquecimento Na Resistência Mecânica De Um Aço Microligado

Oliveira¹,

Silva²,

Loiola³

et al. 2017

Anais Do Congresso Anual Da ABM

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ResumoO processo usual para elaboração de aços utilizados na indústria de petróleo e gás é a laminação controlada, porém, não é adequado para fabricação de peças de geometria complexa, como juntas e conexões. Nestes casos, o forjamento é a melhor opção, pois permite maior diversidade de conformação. A produção de componentes por esta técnica exige tratamentos de têmpera e revenimento para obtenção das propriedades exigidas em trabalho. O objetivo deste projeto é avaliar o comportamento em tração e a microestrutura de um aço microligado submetido ao aquecimento a 855, 900 e 1000°C. Modelos termodinâmicos de Kasatkin foram utilizados para cálculo das temperaturas de transformação austenítica. Os resultados mostram que o tratamento realizado na zona de transformação intercrítica favorece a formação de uma estrutura bifásica de ferrita e martensita com maiores valores da tensão de escoamento e resistência máxima à tração. Nos tratamentos térmicos realizados em maiores temperaturas há diminuição na resistência mecânica, porém com aumento no alongamento em consequência de uma estrutura composta de bainita e ferrita acicular. Palavras-chave: Aços microligados; Forjamento; Tratamentos térmicos; Propriedades mecânicas. EFFECT OF HEATING TEMPERATURE ON THE MECHANICAL PROPERTIES OF A FORGED MICROALLOYED STEEL AbstractControlled rolling is the most usual way for fabrication of steels used in the oil and gas industry, however, this process is unsuitable to produce complex geometry tools, such as joints and connections. Forging presents as a viable option to manufacture this kind of components, allowing a wider diversity of conformation. Fabrication by forging demands the use of quenching and tempering treatments to achieve the work required properties. The objective of this project is to evaluate the strain behavior and microstructure of a microalloyed steel under heating at 855, 900 and 1000 °C. Kasatkin thermodynamic models were used to calculate the austenitic transformation temperatures. Results show that the treatment in the intercritical region promotes a bifasic microstructure of ferrite and martensite with higher values of yield strenght and ultimate stress. In higher temperatures treatments there is reduction in the mechanical properties with higher alongation due to a structure composed of bainite and acicular ferrite.

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Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification

Cited by 55 publications

References 40 publications

Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

Modeling of CCT Diagrams and Ferrite Grain Size Prediction in Low Carbon Nb–Mo Microalloyed Steels

Influência Da Temperatura De Aquecimento Na Resistência Mecânica De Um Aço Microligado

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