Design of Advanced Bainitic Steels by Optimisation of TTT Diagrams and T0 Curves
Francisca García Caballero,Maria Jesus Santofimia,Carlos Capdevila,Carlos Garcia-Mateo,Carlos García de Andrés +4 more
TLDR
In this paper, a set of seven carbide free bainitic steels with a 3 wt% carbon content were proposed for manufacturing and the micro-structural and mechanical characterisation of the steels was investigated.Abstract:
Cementite is responsible of the limited application of conventional bainitic steels, however it has been proof that cementite precipitation during bainite formation can be suppressed by the judicious use of silicon in medium carbon steels In this work, thermodynamic and kinetic models were used to design steels with an optimum bainitic microstructure consisting of a mixture of bainitic ferrite, carbon-enriched retained austenite and some martensite Using these models, a set of seven carbide free bainitic steels with a 03 wt% carbon content were proposed for manufacturing The work presented here is concerned with the microstructural and mechanical characterisation of the steels manufactured Except for the steel with the highest content of alloying elements, all the grades present the same microstructure composed of carbide-free upper bainite and retained austenite after hot rolling and a two-steps cooling Theirs tensile strengths range from 1600 to 1950 MPa while keeping a uniform elongation equal to 4% and a total elongation over 10% Regarding toughness at room temperature, they match quenched and tempered martensitic steelsread more
Citations
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Microstructural development during the quenching and partitioning process in a newly designed low-carbon steel
Maria Jesus Santofimia,Lie Zhao,Roumen Petrov,Roumen Petrov,C. Kwakernaak,W.G. Sloof,Jilt Sietsma +6 more
TL;DR: In this article, a detailed characterization of the microstructural development of a new quenching and partitioning (Q&P) steel was presented, which showed that stabilization of austenite can be achieved at significantly shorter time scales via the Q&P route than is possible via a bainitic isothermal holding.
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Tensile behaviour of a nanocrystalline bainitic steel containing 3 wt% silicon
Carlos Garcia-Mateo,Francisca García Caballero,Thomas Sourmail,Matthias Kuntz,J. Cornide,Véronique Smanio,Roberto Elvira +6 more
TL;DR: In this paper, the effect of up to ∼3 ¼Si-wt.% in a steel grade adapted to low temperature bainitizing has been investigated in the context of nanostructured bainitic steels.
Journal ArticleDOI
New low carbon Q&P steels containing film-like intercritical ferrite
Maria Jesus Santofimia,T. Nguyen-Minh,Lie Zhao,Roumen Petrov,Roumen Petrov,Ilchat Sabirov,Jilt Sietsma +6 more
TL;DR: In this paper, the application of the Quenching and Partitioning (Q&P) process to two low-carbon steels has led to the development of a new kind of steel microstructure formed by laths of martensite separated by films of intercritical ferrite and retained austenite.
Journal ArticleDOI
Theoretical design and advanced microstructure in super high strength steels
Francisca García Caballero,Maria Jesus Santofimia,Carlos Garcia-Mateo,Jesús Chao,C. Garcioa De Andres +4 more
TL;DR: In this article, a theoretical design procedure based on phase transformation theory alone has been successfully applied to design steels with a microstructure consisting of a mixture of bainitic ferrite and retained austenite.
Journal ArticleDOI
New Experimental Evidence on the Incomplete Transformation Phenomenon in Steel.
F. G. Caballero,Carlos Garcia-Mateo,Maria Jesus Santofimia,Michael K Miller,C. García de Andrés +4 more
TL;DR: In this paper, the carbon distribution in austenite during isothermal bainite formation and the incomplete reaction phenomenon was analyzed by means of X-ray diffraction and atom-probe tomography in high-silicon, manganese-alloyed steels.
References
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The kinetics of grain boundary nucleated reactions
TL;DR: In this paper, the authors derived rate laws for transformations in which the new phase nucleates on grain boundary surface, grain edges, or grain corners, and in which a new phase grows with constant radial velocity.
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The mechanism of bainite formation in steels
TL;DR: In this article, microstructural evidence, together with a thermodynamic analysis, of the bainite reaction in steels are presented in support of a growth mechanism involving the propagation of displacive sub-units.
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Bainite in silicon steels: new composition–property approach Part 1
TL;DR: In this article, a quantitative relationship between the composition and some important mechanical properties of silicon containing steels, which can be transformed isothermally to an aggregate of bainitic ferrite and carbon enriched retained austenite only, has been developed.
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Acceleration of Low-temperature Bainite
TL;DR: In this article, the authors report methods for accelerating the rate of reaction without compromising strength, and show that bainitic ferrite plates produced by transformation at low temperatures can be as thin as 20 nm with a hardness in excess of 650 HV.
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A rationalisation of shear transformations in steels
TL;DR: In this paper, the authors provided experimental evidence in support of the theory that Widmanstatten ferrite formation involves the co-operative growth of mutually-accommodating plates.