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

Isasti, Nerea; García-Riesco, Pedro Manuel; Jorge-Badiola, D.; Taheri, Mitra L.; López, Beatriz; Uranga, Pello

doi:10.2355/isijinternational.isijint-2015-036

Cited by 12 publications

(9 citation statements)

References 18 publications

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“…The transformation diagrams obtained for the steel investigated were confronted with CCT/DCCT diagrams of similar steel grades available in the literature [6,7]. Figure 19 shows the CCT diagram of the steel containing 0.13 C -1.53 Mn -0.25 Si -0.01 V -0.043 Nb (in weight %) based on a combination of dilatometer tests and HAZ tests performed on the Gleeble 3800 simulator [7].…”

Section: Discussionmentioning

confidence: 99%

“…The results of extensive work related to the design and modeling of the CCT/DCCT diagrams of HSLA steels with varying contents of Nb and Mo were published by Isasti et al [6]. The experiments were carried out on the deformation dilatometer Bähr DIL805D after the annealing of the specimens at the temperatures of 1473 -1523 K, ensuring the dissolution of niobium rich MX precipitates.…”

Section: Discussionmentioning

confidence: 99%

“…The final cooling rate makes it possible to control the austenite softening processes, and phase transformations during decomposition of austenite and grain growth. The published results [4][5][6][7][8][9][10][11][12], and our experiences gained in the laboratory conditions using the hot deformation simulator Gleeble 3800 [13][14], as well as the semi-continuous hot rolling mill [15][16] prove the crucial role of the cooling parameters after hot forming. This can be deduced from the continuous cooling transformation diagrams, especially when considering the previous deformation history.…”

Section: Introductionmentioning

confidence: 99%

“…CCT diagram of the 28NbHC steel grade; black points and curves[6] superimposed with the CCT diagram presented inFig. 14 -blue curves…”

mentioning

confidence: 99%

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Continuous cooling transformation diagrams of HSLA steel for seamless tubes production

Schindler

Kawulok

Seillier

et al. 2019

J min metall B Metall

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The CCT and two DCCT diagrams were constructed for the HSLA steel containing Cr, V, Nb, and N microadditions, taking into account industrial processing parameters of this material in a seamless tubes rolling mill. The typical finish hot rolling temperature of 1173 K was used for the construction of the standard CCT diagram and the effect of previous austenite deformation at this temperature was evaluated in the DCCT diagram. Another DCCT diagram was developed after heating at 1553 K, followed by plastic deformation at 1173 K. The prior austenite grain size in the hot rolled material after heating at 1173 K was approx. 10 m, the heating of the as-cast material at 1553 K resulted in the prior austenite grain size over 200 m. The effect of the previous austenite deformation after low-temperature heating on the CCT diagram was negligible. The high-temperature heating showed a great influence on the austenite decomposition processes. The Ferrite-start temperature was significantly reduced at high cooling rates and the preferred decomposition of coarse grained austenite to acicular ferrite suppressed the bainite transformation at medium cooling rates. The developed DCCT diagrams can be used for the prediction of austenite decomposition products during the cooling of the seamless tubes from the finish rolling temperature. The CCT diagram can be utilized for the quality heat treatment of tubes.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…CCT diagram of the 28NbHC steel grade; black points and curves[6] superimposed with the CCT diagram presented inFig. 14 -blue curves…”

mentioning

confidence: 99%

See 2 more Smart Citations

Continuous cooling transformation diagrams of HSLA steel for seamless tubes production

Schindler

Kawulok

Seillier

et al. 2019

J min metall B Metall

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show abstract

“…Both the Mo and Nb additions were proved as effective in the lowering of the transformation temperatures, and a greater effectiveness was observed regarding the Mo and the Nb in the ferritic and bainitic regions, respectively. 44) Especially, the Nb is particularly effective in the retardation of the recrystallization, thereby ef cient for grain re nement. 45) Mo is also known as an alloying element for the retardation of the ferrite formation, and this is ef cient for lowering bainitic transformation temperature, and especially in terms of its assistance of the Nb for the recrystallization retardation.…”

Section: Surface Analysesmentioning

confidence: 99%

Alloying Effects of Molybdenum and Niobium on Chromium Bearing Low Alloy Steel for Water Ballast Tank

2017

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This study examines the effects of chromium (Cr), molybdenum (Mo) and niobium (Nb) alloying on the corrosion properties of low alloy steel for water ballast tank using electrochemical tests for 15 days in arti cial seawater and surface analyses. The EIS and LPR tests revealed the outstanding corrosion resistance Cr+Mo+Nb bearing steel. An SEM analysis after 15 days immersion in the arti cial seawater indicated that, among the tested specimens, the Cr+Mo+Nb bearing steel formed the smoothest rust layer with the least cracks. An EPMA analysis for the cross section of the rust layer con rmed that the Nb elements of the Cr, Cr+Nb, and Cr+Mo+Nb bearing steels were enriched at the rust layer; however, the Mo element was enriched only at the rust layer of the Cr+Mo+Nb bearing steel, and not at that of the Cr+Mo bearing steel. This nding is because the small grain size of the Cr+Mo+Nb bearing steel results in the formation of more active sites, where a dissolution and precipitation of the alloying elements occurs. For this reason, the Cr, Mo, and Nb elements are concentrated at the rust layer of the Cr+Mo+Nb bearing steel, thereby improving the corrosion resistance of low alloy steel.

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Thermodynamic prediction and experimental verification of phase transformation kinetics in 3Mn steel with Ti and V microadditions

Wojtacha,

Kozłowska,

Morawiec

et al. 2024

J Therm Anal Calorim

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In this work, the phase transformation kinetics and precipitation processes were studied using thermodynamic calculations and a dilatometric method to determine the optimal chemical composition of medium-Mn steel and its initial parameters of heat treatment. The investigated steel is intended for forgings with the microstructure composed of bainitic matrix and retained austenite (RA). An influence of Al and Si on the Ms temperature was characterized to obtain the best chemical composition in terms of RA stabilization. Theoretical continuous cooling transformation (CCT) and time–temperature transformation (TTT) diagrams were determined and compared with dilatometric results. Microstructural observations were compared with the dilatometric results. The hardenability of steel was high due to increased Mn and Mo additions. A very small fraction of cementite is expected in the microstructure due to Al and Si additions. The shortest time to start and finish the bainitic transformation was noted for the isothermal heat treatment at 420 °C. The completion of the bainitic transformation took about 25 min and is acceptable from the industrial point of view. The obtained results constitute a good basis for designing thermomechanical processing routes of bainitic steels with RA.

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

Cited by 12 publications

References 18 publications

Continuous cooling transformation diagrams of HSLA steel for seamless tubes production

Continuous cooling transformation diagrams of HSLA steel for seamless tubes production

Alloying Effects of Molybdenum and Niobium on Chromium Bearing Low Alloy Steel for Water Ballast Tank

Thermodynamic prediction and experimental verification of phase transformation kinetics in 3Mn steel with Ti and V microadditions

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