New low carbon Q&amp;P steels containing film-like intercritical ferrite

Santofimia, M.J.; Minh, Tuan Nguyen; Zhao, L.; Petrov, Roumen; Sabirov, I.; Sietsma, Jilt

doi:10.1016/j.msea.2010.06.083

Cited by 167 publications

(81 citation statements)

References 18 publications

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“…In the ideal Q&P assuming the constrained carbon equilibrium (CCE), 8,9,15,16) the carbon enrichment is simply caused by the diffusion of carbon atoms from martensite to untransformed austenite until the chemical potential of carbon in both phases becomes identical. However, in most cases of Q&P of low-alloy TRIP steels, phase transformation from untransformed austenite to ferrite or bainite would take place during the partitioning treatment, 11,18) and the carbon enrichment is caused by the ejection from the transformed phase and it stops when the carbon concentration in austenite reaches T0 composition. 5,19) This means a CCE breakdown.…”

Section: Carbon Enrichment Into Retained Austenite During Partitioninmentioning

confidence: 99%

“…One of them is the kinetics of the carbide precipitation during partitioning treatment. In the conventional Q&P treatment for low-alloy TRIP steels, fairly large amount of silicon (>1.0%) must be added to suppress cementite precipitation so as not to deteriorate the stability of retained austenite, 11,12) while the Q&P-treated martensitic stainless steels produced in the previous study contained less silicon content (0.26%). Thus, the authors concluded that silicon is not necessarily required for forming retained austenite by Q&P in the case of martensitic stainless steel.…”

Section: Introductionmentioning

confidence: 96%

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Role of Silicon in Quenching and Partitioning Treatment of Low-carbon Martensitic Stainless Steel

et al. 2012

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Quenching and partitioning (Q&P) treatment was applied to 12%Cr low-carbon martensitic stainless steels containing different amount of silicon, and then the effect of silicon content on the formation of retained austenite was discussed in terms of the behaviors of phase transformation and carbide precipitation during the partitioning treatment. It was suggested that the nearly ideal constrained carbon equilibrium (CCE) condition was realized in the specimens used in this study because a large amount of chromium suppressed bainitic transformation during the partitioning treatment, although cementite was partly observed at the retained austenite/martensite interface. The cementite precipitation was greatly retarded with increasing silicon content, resulting in an increase in the amount of retained austenite and an enhancement of the thermal stability of austenite. Tensile testing for the Q&P-treated specimens revealed that the increment of silicon content leads to a marked improvement of strength-ductility balance of the 12%Cr steels through the increase of retained austenite.

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Section: Carbon Enrichment Into Retained Austenite During Partitioninmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Role of Silicon in Quenching and Partitioning Treatment of Low-carbon Martensitic Stainless Steel

et al. 2012

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“…Secondly, the partitioning step of the Q&P process is often conducted at temperatures which enable bainite formation in retained austenite [6,[16][17][18]. The formation of bainite could explain, to some extent, carbon enrichment in austenite, as in carbide-free bainitic steels [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Effects of Q&P Processing Conditions on Austenite Carbon Enrichment Studied by In Situ High-Energy X-ray Diffraction Experiments

Allain

Géandier

Hell³

et al. 2017

Metals

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Abstract:We report the first ultra-fast time-resolved quantitative information on the quenching and partitioning process of conventional high-strength steel by an in situ high-energy X-ray diffraction (HEXRD) experiment. The time and temperature evolutions of phase fractions, their carbon content, and internal stresses were determined and discussed for different process parameters. It is shown that the austenite-to-martensite transformation below the martensite start temperature Ms is followed by a stage of fast carbon enrichment in austenite during isothermal holding at both 400 and 450 • C. The analysis proposed supports the concurrent bainite transformation and carbon diffusion from martensite to austenite as the main mechanisms of this enrichment. Furthermore, we give evidence that high hydrostatic tensile stresses in austenite are produced during the final quenching, and must be taken into account for the estimation of the carbon content in austenite. Finally, a large amount of carbon is shown to be trapped in the microstructure.

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“…1). [1][2][3] Advanced alloy design and non-conventional annealing process allow to reach tensile strengths above 1 000 MPa as well as good formability and ductility. The design of such steels is also achieved by limited additions of gammastabilizers (C, Mn, Ni, Cu) in "modern steels", whereas they significantly differ from 2nd generation of AHSS, which are fully austenitic thanks to very high amount of Mn.…”

Section: Introductionmentioning

confidence: 99%

Microstructure – Properties Relationships in Carbide-free Bainitic Steels

et al. 2011

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We elaborated two carbide-free bainitic steels with different microstructures through specific alloy design and austempering process. Microstructural characterizations were performed by means of EBSD analysis and in-situ high energy synchrotron diffraction in order to evaluate the phase fractions and the carbon content in the retained austenite, as well as the microtextures. These microstructural features were correlated to the tensile properties. Both steels exhibited an excellent compromise between high strength (above 1 250 MPa), good ductility (uniform elongation up to 14%) and high fracture strain (reduction of area up to 46%). The volume fraction of MA blocks (blocks of retained austenite partially transformed into fresh martensite during the final cooling at room temperature) was a key relevant parameter that strongly influenced the work-hardening at the expense of the damaging processes at high strain.

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New low carbon Q&P steels containing film-like intercritical ferrite

Cited by 167 publications

References 18 publications

Role of Silicon in Quenching and Partitioning Treatment of Low-carbon Martensitic Stainless Steel

Role of Silicon in Quenching and Partitioning Treatment of Low-carbon Martensitic Stainless Steel

Effects of Q&P Processing Conditions on Austenite Carbon Enrichment Studied by In Situ High-Energy X-ray Diffraction Experiments

Microstructure – Properties Relationships in Carbide-free Bainitic Steels

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