Stabilization in Strength of Hot-rolled Sheet Steel Strengthened by Nanometer-sized Carbides

Funakawa, Yoshimasa; Seto, Kazuhiro

doi:10.2355/tetsutohagane.93.49

Cited by 29 publications

(19 citation statements)

References 11 publications

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“…The average carbide size after 48 h holding is about 10 nm, smaller than that in the Ti-added steel (18 nm) for the same holding period. These results demonstrate that a simultaneous addition of Ti and Mo suppress the coarsening of alloy carbides, corresponding well with the fact reported by Funakawa et al 18) Funakawa et al 18) has reported that in a Ti,Mo-added steel the atomic ratio of Ti and Mo in (Ti,Mo)C particles is approximately 1:1 in the beginning of interphase precipitation, but the concentration of Ti became larger during coarsening of (Ti,Mo)C precipitates. In this situation, coarsening of precipitates would be controlled mainly by diffusion of Ti atoms.…”

Section: Transmission Electron Microscopy (Tem)supporting

confidence: 91%

“…54 (2014), No. 1 been found that the atomic ratio of Ti and Mo in the (Ti,Mo)C particles is about 7:3, corresponding with the results of Funakawa et al 18) Note also that thermodynamic calculation using Thermo-Calc has confirmed that solubility of Ti atoms in ferrite matrix is 23 mass ppm in the Ti-added steel and 0.52 mass ppm in the Ti,Mo-added steel, which leads to a slow coarsening of (Ti,Mo)C precipitates in the Ti,Mo-added steel. This discussion could explain the reason why the carbide size is smaller in the Ti,Mo-added steel than in the Ti-added steel in the present case as well.…”

Section: Figsupporting

confidence: 87%

“…These precipitates are NaCl-type FCC structured alloy carbides. In the Ti-added steel the carbides are TiC with an atomic ratio of Ti and C of approximately 1:1, while in the Ti,Mo-added steel the carbides are (Ti,Mo)C, 17,18,25,26) where some of Ti atoms in TiC carbides are replaced by Mo atoms. The spacing of such particle sheets was approximately 25 nm and 20 nm in the Ti-added and Ti,Mo-added steels, respectively, i.e.…”

Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

“…It has been reported that ferritic steels with nano-sized alloy carbides produced by interphase precipitation show both very high strength and good formability, and some kinds of alloy steels have already been in commercial use. [13][14][15][16] Many studies have been reported on mechanical properties of interphase precipitated steels so far, [17][18][19][20][21][22][23] but effects of nano-sized alloy carbides by interphase precipitation on strength and ductility of materials are not yet clear. In the present study, ferrite single phase steels with nano-sized alloy carbides were prepared using Ti,Mo-added low carbon steels, and tensile behavior of the samples were systematically investigated.…”

Section: Introductionmentioning

confidence: 99%

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Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation

et al. 2014

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Tensile behavior and structure-property relationship of ferritic steels with nano-sized carbide dispersion were invesigated using Ti-added steel and Ti,Mo-added low carbon steels. By austenitizing followed by isothermal heat treatment at 700°C, polygonal ferrites containing very fine carbides of TiC and (Ti,Mo)C were obtained in the Ti-added and the Ti,Mo-added steels, respectively. The size of such carbides was finer in the Ti,Mo-added steel than in the Ti-added steel at the same isothermal holding. The results of tensile tests for these samples showed that the strength is higher as the carbide size is smaller. The structure-based strength calculation led to a good agreement with the experiments, when it was assumed that the Ashby-Orowan mechanism is dominant for precipitation strengthening of nano-sized alloy carbides. It was also suggested that a relatively large tensile ductility is related to enhanced recovery during the tensile deformation, accompanied with promotion of secondary slips or cross slips in a finer scale due to the nano-sized particles.

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Section: Transmission Electron Microscopy (Tem)supporting

confidence: 91%

Section: Figsupporting

confidence: 87%

Section: Transmission Electron Microscopy (Tem)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation

et al. 2014

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“…[3][4][5][6][7][8][9][10][11][12][13] A newly developed steel of this kind consists of a ferrite matrix strengthened by a large amount of finely dispersed precipitates. [5][6][7][8] Funakawa and his coworkers 14) investigated the precipitation behaviour of these kinds of steels containing Ti, Nb and Mo, and reported the occurrence of the interphase precipitation. They also reported the mechanical properties of the steels developed.…”

Section: Introductionmentioning

confidence: 99%

Influence of Ti and Nb on the Strength–Ductility–Hole Expansion Ratio Balance of Hot-rolled Low-carbon High-strength Steel Sheets

et al. 2012

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To satisfy the demand for high-strength steel sheets with excellent strength-ductility-hole expansion ratio balance, high-strength steels consisting of a ferrite or bainitic ferrite matrix strengthened by a large amount of finely dispersed precipitates have been developed.In this study, the influence of the precipitation-forming elements Ti and Nb on the strength-ductilityhole expansion ratio balance of these steels has been investigated. The strength-ductility-hole expansion ratio balance of steel with Ti added was superior to that with Nb added. The reason for the superiority of steel with added Ti was discussed from various viewpoints such as microstructure, texture, the condition of the pierced surface, sulphide formation, the nucleation and propagation behaviour of cracks during hole expansion, etc. We concluded that the inferior strength-ductility-hole expansion ratio balance of the steel with added Nb was mainly caused by the formation of large textural colonies and a detrimental influence of MnS. From these inferences, we proposed a combined addition of Ti and Nb, and succeeded in improving the strength-ductility-hole expansion ratio balance of the advanced high-strength steel.KEY WORDS: high-strength steel; hole expansion ratio; precipitation hardening; ductility-hole expansion ratio balance.

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Interphase Precipitation in Cold‐Rolled Dual‐Phase Steel Strip: Design and Challenges

Lu,

Hsu,

Chen

et al. 2024

steel research int.

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In microalloyed steels, interphase precipitation involves the formation of precipitates at the ferrite/austenite interface during their transformation. The study on interphase precipitation has been ongoing since the 1970s and remains highly relevant today. While this metallurgical approach has been applied in various products of advanced steels, its application to cold‐rolled steels is still absent. This study presents a development of cold‐rolled dual‐phase (DP) steels strengthened by interphase‐precipitated carbides. A CALPHAD‐based approach is established to facilitate austenite to ferrite transformation coupled with interphase precipitation during simulated annealing for cold‐rolled DP steels. Further experimental investigations on the effects of V and Mo optimize the alloy composition, and the corresponding nano/microstructures are validated by transmission electron microscopy (TEM) and atom probe tomography. Besides, this work further addresses the impacts of interfacial segregation and microsegregation bands on the capability of interphase precipitation in the studied steels. In summary, this work charts a new pathway for the development of cold‐rolled DP steels strengthened by interphase‐precipitated carbides, advancing the realm of high‐strength steels.

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Stabilization in Strength of Hot-rolled Sheet Steel Strengthened by Nanometer-sized Carbides

Cited by 29 publications

References 11 publications

Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation

Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation

Influence of Ti and Nb on the Strength–Ductility–Hole Expansion Ratio Balance of Hot-rolled Low-carbon High-strength Steel Sheets

Interphase Precipitation in Cold‐Rolled Dual‐Phase Steel Strip: Design and Challenges

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