Precipitation of Nb in Ferrite After Austenite Conditioning. Part II: Strengthening Contribution in High-Strength Low-Alloy (HSLA) Steels

Altuna, M. A.; Iza-Mendia, A.; Gutiérrez, Isabel

doi:10.1007/s11661-012-1270-x

Cited by 52 publications

(25 citation statements)

References 29 publications

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“…6, it can be concluded that no significant strengthening contribution from dislocations is expected. Concerning precipitation, Herman et al [40] deduced that in ferrite-pearlite microstructures, the Nb remaining in solution after hot rolling (Nb free ) contributed to the yield stress with a factor of 2220 MPa per weight percent; this has been recently corroborated by the authors [39], who obtained:…”

Section: Sequencementioning

confidence: 78%

“…In this steel, the maximum contribution from N in solution can reach 39 MPa. In hot rolled C-Mn steels, N free depends, in general, on the coiling temperature, but it has been deduced that the concentration of N in solution in the matrix is quite low for microalloyed steels, even when coiled at temperatures around 600 1C [39]. The pearlite volume fraction is lower than 25%; consequently its effect on the yield stress can be ignored.…”

Section: Sequencementioning

confidence: 99%

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Generalization of the existing relations between microstructure and yield stress from ferrite–pearlite to high strength steels

Iza-Mendia

Gutiérrez

2013

Materials Science and Engineering: A

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101

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Section: Sequencementioning

confidence: 78%

Section: Sequencementioning

confidence: 99%

Generalization of the existing relations between microstructure and yield stress from ferrite–pearlite to high strength steels

Iza-Mendia

Gutiérrez

2013

Materials Science and Engineering: A

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101

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“…All specimens were heated at 900 ºC for 30 minutes and cooled in water. Then, they were tempered at 600 ºC for 50 minutes, in order to obtain the maximum contribution by the fine precipitation of carbides in ferrite and to increase the hardenability and the tensile properties 14 .The cooling was done in air. After quenching and tempering, the cubic samples were prepared according to conventional metallographic methods.…”

Section: Methodsmentioning

confidence: 99%

Influence of Niobium and Molybdenum on Mechanical Strength and Wear Resistance of Microalloyed Steels

et al. 2017

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The HSLA (High-Strength Low Alloy) steels are used in the production of pipes, flanges and connectors to build ducts for ore, oil and gas transport. The conventional processes are the rolling or forging. In the transport of ore and heavy oil, the abrasive particles impair the surfaces and reduce the pipelines lifetime. Therefore, besides the mechanical properties as API 5L, it is important to verify the wear resistance of these steels. In this context, two microalloyed steels were forged in the form of square bars. Thereafter, specimens of these bars were annealed at 930 ºC, quenched at 900 ºC and tempered at 600 ºC. Tensile and wear tests were performed. The results show that molybdenum and niobium present similar effects on phase transformation of steels, promoting a desired acicular ferrite/bainite microstructure and fulfill the mechanical strength of API 5L-X70 standard. The molybdenum has dominating effect in the hardenability when in solid solution, however, after tempering, thermodynamic simulation by FactSage software indicates that niobium probably promotes secondary hardening.

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“…The precipitation strengthening contribution in themomechanically processed samples (S1-650 to S3-650) depends on the sequence and more specifically on the Nb in solution before transformation to ferrite. The precipitates formed in ferrite are extremely fine (<3 nm) and produce a precipitation strengthening propor tional to the free Nb in austenite before phase transformation (Herman et al, 1992) that according to Altuna et al, (2012) can be expressed by the following equation:…”

Section: Nb-rich Precipitates Of Different Sizesmentioning

confidence: 99%

Effect of microstructure on the impact toughness of high strength steels

Gutiérrez¹

2014

REVMETAL

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ABSTRACT:One of the major challenges in the development of new steel grades is to get increasingly high strength combined with a low ductile brittle transition temperature and a high upper shelf energy. This requires the appropriate microstructural design. Toughness in steels is controlled by different microstructural constituents. Some of them, like inclusions, are intrinsic while others happening at different microstructural scales relate to processing conditions. A series of empirical equations express the transition temperature as a sum of contributions from substitutional solutes, free nitrogen, carbides, pearlite, grain size and eventually precipitation strengthening. Aimed at developing a methodology that could be applied to high strength steels, microstructures with a selected degree of complexity were produced at laboratory in a Nb-microalloyed steel. As a result a model has been developed that consistently predicts the Charpy curves for ferrite-pearlite, bainitic and quenched and tempered microstructures using as input data microstructural parameters. This model becomes a good tool for microstructural design. RESUMEN: Efecto de la microestructura en la tenacidad al impacto en aceros de elevada resistencia mecánica.El desarrollo de nuevos grados de acero se tropieza con frecuencia con la necesidad de incrementar la resistencia mecánica al mismo tiempo que se reduce la temperatura de transición dúctil-frágil y se eleva la energía del palier dúctil. Hacer frente a este reto requiere un diseño microestructural. La tenacidad en aceros está controlada por diferentes constituyentes microestructurales. Algunos de ellos, como las inclusiones son intrínsecos, pero otros que se manifiestan a diferentes escalas microestructurales dependen de las condiciones de proceso. Existen algunas ecuaciones empíricas que permiten calcular para ferrita-perlita en aceros de bajo carbono la temperatura de transición como suma de contribuciones de elementos en solución sólida, nitrógeno libre, carburos, fracción de perlita, tamaño de grano y, eventualmente precipitación. Con el objeto de desarrollar una formulación aplicable en aceros de alta resistencia mecánica, se han producido en laboratorio microestructuras con un grado de complejidad controlado. Como resultado de este estudio, se ha desarrollado un modelo que reproduce, partiendo de datos microestructurales, las curvas Charpy de un acero microaleado con microestructuras de ferrita-perlita, bainita y de temple y revenido. Este modelo es una herramienta útil para el diseño microestructural.

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Precipitation of Nb in Ferrite After Austenite Conditioning. Part II: Strengthening Contribution in High-Strength Low-Alloy (HSLA) Steels

Cited by 52 publications

References 29 publications

Generalization of the existing relations between microstructure and yield stress from ferrite–pearlite to high strength steels

Generalization of the existing relations between microstructure and yield stress from ferrite–pearlite to high strength steels

Influence of Niobium and Molybdenum on Mechanical Strength and Wear Resistance of Microalloyed Steels

Effect of microstructure on the impact toughness of high strength steels

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