The Role of Mn Depletion in Intra-Granular Ferrite Transformation in the Heat Affected Zone of Welded Joints with Large Heat Input in Structural Steels.

Mabuchi, Hidesato; Uemori, Ryuji; Fujioka, M.

doi:10.2355/isijinternational.36.1406

Cited by 158 publications

(115 citation statements)

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“…Also, Mabuchi et al 60) found that all the following phases Ti 2 O 3 , TiN and MnS could exist in the same inclusion for effective nucleation of acicular ferrite. In addition, Yamamoto et al 61) reported that the precipitation of MnS and TiN on the already existing Ti 2 O 3 inclusions acted as preferential nucleation sites for AF.…”

Section: Complex Oxy-sulfides and Multi-phase Inclusionsmentioning

confidence: 99%

“…During the last 10-15 years many studies 10,12,46,[60][61][62][63][64][65] have discussed the effect of a Mn-depleted zone (MDZ) near inclusions on the acicular ferrite formation. It is well known that an increased Mn content promotes the enlargment of the austenite zone in steel.…”

Section: Depletion Of Mn Content Near Inclusionsmentioning

confidence: 99%

“…10,12,46,[60][61][62][63][64][65] It should be pointed out that it is, in many cases, difficult to decide which mechanism that is most important for formation of acicular ferrite. Instead, it is believed that these mechanisms often work together to promote the intragranular nucleation on inclusions.…”

Section: Mechanisms Of Acicular Ferrite Nucleationmentioning

confidence: 99%

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On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

2009

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The effects of non-metallic inclusions in nucleating acicular ferrite in steels during cooling from a weld or cooling from an austenitic temperature are reviewed. The influence of the acicular ferrite (AF) structure on mechanical properties of steels such as strength and toughness is briefly mentioned. The different factors affecting the formation of acicular ferrite, such as the soluble content of alloying elements in steel, cooling rate from austenitizing temperature, austenite grain size and inclusion characteristics in steel, are discussed. The mechanisms of acicular ferrite formation on non-metallic inclusions, such as reduction of interfacial energy, mismatch strain between the inclusion and ferrite/austenite, thermal strains at the inclusions and changes in matrix composition near the inclusions are also discussed. Finally, the effects of inclusion characteristics, such as size, number and composition are described and their effectiveness in nucleating acicular ferrite is discussed.KEY WORDS: non-metallic inclusions, intragranular acicular ferrite formation, strength and toughness, steel. 1063

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Section: Complex Oxy-sulfides and Multi-phase Inclusionsmentioning

confidence: 99%

Section: Depletion Of Mn Content Near Inclusionsmentioning

confidence: 99%

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On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

2009

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“…[10][11][12] In the present study, the austenitizing at 1 623 K for 1.8 ks was also employed before isothermal holding for ferrite transformation. Even though the austenite grain size slightly increased from 155 to 170 mm by raising the austenitizing temperature, there was no change in the effect of MnS as intragranular ferrite nucleation site.…”

Section: Effect Of Mns On Intragranular Ferrite Transformationmentioning

confidence: 99%

Nucleation of Proeutectoid Ferrite on Complex Precipitates in Austenite

et al. 2003

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Effect of various intragranular inclusions or precipitates (MnS, VC and V(C,N)) on the microstructure and kinetics of intragranular ferrite transformation at the temperatures between 973 and 823 K was studied using various Fe-2Mn-(0.13, 0.2)C(mass%) alloys with the small addition of sulfur, vanadium, and nitrogen. In Fe-2Mn-0.13C-50ppmS and Fe-2Mn-0.2C-470ppmS alloys, MnS particles, mostly incoherent in austenite, do not act as effective nucleation sites of ferrite. V addition slightly improves the potency of MnS as ferrite nucleation site by forming MnSϩVC complex precipitates. The addition of both V and N largely enhances the intragranular nucleation of ferrite idiomorph on the MnSϩV(C,N) complex precipitate. It is considered that two factors, i.e., (1) the advantage in the balance of interphase boundary energy and (2) the increase in the fraction of V(C,N) precipitate by the addition of nitrogen, are mainly responsible for the promotion of intragranular ferrite formation on the MnSϩV(C,N) complex precipitate.KEY WORDS: phase transformation; precipitation; steel; austenite; ferrite; carbide; nitride; sulfide; inclusion; crystallography; interphase boundary. contain similar dispersion of MnS as that of Steel C. In Steel D, VC precipitates in austenite with the addition of 0.3 mass% V. V(C,N) precipitation occurs in Steel E due to the addition of both V and N. The solution temperatures of inclusion/precipitate phases in austenite were calculated by using the solubility product equation proposed by Turkdogan 9) for MnS and Thermo-Calc for VC and V(C,N). Figure 1 shows the heat treatments employed in the present study. Austenitizing was made at 1 473 K for 0.6 ks after homogenizing at 1 473 K for 43.2 ks of hot-rolled plates. The average grain sizes of austenite after this treatment were 520 mm for Steel A, 450 mm for Steel B, and nearly equal to 150 mm for all of Steels C-E. After austenitizing at 1 473 K, the precipitation treatments of VC and V(C,N) at 1 173 K for various periods were performed for Steels D and E, followed by isothermal holding in the temperature range between 973 and 823 K to promote proeutectoid ferrite transformation.Microstructures of the transformed specimens were observed by means of optical, scanning and transmission electron microscopy (SEM and TEM). Volume fractions of ferrite were determined by point counting in optical micrographs. Electron probe microanalyzer (EPMA) and TEM-EDS (energy dispersive X-ray spectroscopy) analyses were made for identifying precipitate phases which act as ferrite nucleation sites. For optical and SEM observations, specimens were etched with 5 % nital. TEM thin foil specimens, 3 mm in diameter, were prepared by mechanical thinning followed by Argon ion thinning. TEM observation was performed by using Joel JEM-200CX and Philips CM200, CM200FEG operated at 200 kV. Figure 2(a) shows the optical microstructure of the specimen water-quenched after austenitizing in Steel C containing 470 ppm of S. Because the specimens were hot-rolled, MnS particles are aligned ...

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“…Tais problemas metalúrgicos são freqüentemente associados à zona afetada pelo calor (ZAC) [6][7][8][9] de dimensões reduzidas. Assim, o estudo das transformações microestruturais e conseqüentemente o estudo do ciclo térmico destas regiões torna-se ainda muito relevante.…”

Section: Introductionunclassified