Formation of pearlitic banded structures in ferritic‐pearlitic steels

Grossterlinden, R.; Kawalla, Rudolf; Lotter, Ulrich; Pircher, H.

doi:10.1002/srin.199200529

Cited by 60 publications

(30 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…If those are taken as reference compositions, and the new alloy compositions are normalised to them, the transformation temperature was obtained employing the numerical model for an austenitisation temperature of 1 373 K, an austenitisation time of 3 600 s and a microchemical wavelength of 75 mm. Figure 6 shows the results of those calculations, indicating that Mn is the major component influencing banding followed by C. This is in agreement with previous experimental work, [4][5][6] however Al and Si play also a role in the transformation behaviour. …”

supporting

confidence: 90%

“…Grange 3) observed that austenitisation at temperatures over 1 590 K prevents ferrite/pearlite band formation in Fe-C-Mn-Si steels. More recently, Thompson and Howell 4) related austenite grain size to band prevention, whereas Großterlinden et al 5) spotted Mn segregation as the determining factor in banding. There is therefore extensive literature reporting the competing factors leading to banding and its prevention, 6) however the concepts are formulated such that quantitative rules are hard to distil.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ferrite/Pearlite Band Prevention in Dual Phase and TRIP Steels: Model Development

Rivera-Dı́az-del-Castillo

Zwaag

2005

ISIJ Int.

View full text Add to dashboard Cite

A model for predicting the conditions for ferrite/pearlite band prevention in dual phase and TRIP steels has been developed. The competition between processing parameters such as the austenitisation time and temperature, the transformation temperature and microchemical segregation wavelength is explored. The effects of alloy composition in the tendency to form ferrite/pearlite bands are quantified. A simple formula combining processing parameters and compositions for describing band formation is presented. The calculations show that the most prominent factor for preventing banding is the control of the microchemical wavelength. In addition to C and Mn, Al and Si concentrations have shown to play a smaller but significant role in band formation behaviour.KEY WORDS: segregation; banding; ferrite; pearlite; microstructural homogeneity; kinetics; phase transformations; diffusion; nucleation; solidification. Model for Ferrite/Pearlite Band PreventionThe computer model combines the effects of solute segregation due to solidification, the diffusion of the segregated components during homogenisation and the nucleation of ferrite in regions possessing different concentration values during controlled cooling after hot rolling. The diffusion is assumed to occur in the austenitic field g, and the transformation either in the three phase region gϩaϩq or in the two phase region gϩq (where a stands for ferrite and for q stands for cementite), as shown schematically in Fig. 2. Solidification and Solute SegregationThe first phenomenon leading to ferrite/pearlite banding that takes place in alloy production is solidification. At this stage, the primary and secondary dendrite arms advance towards fresh liquid regions. This causes an inhomogeneous solute distribution in the dendrite, where its centre contains the low carbon content that characterises the liquid→d-ferrite reaction at the alloy concentration. The dendrite edges impinge with each other in the last stages of solidification, requiring that such interfaces be characterised by the high carbon concentration of the eutectic point. Therefore, the liquid →d-ferrite composition and eutectic reaction composition provide the extreme composition values to be homogenised in the high temperature austenitisation treatment. These were obtained for a variety of steels from a thermochemical database.9) The procedure employed for each studied alloy grade was to reduce the temperature from the liquid field to the eutectic temperature. The d-ferrite composition and the composition of the last liquid in equilibrium were assumed to be the initial segregation values present, which will approach the average alloy concentration as homogenisation proceeds.8) Reduced segregation values obtained from non-equilibrium solidification processes may be incorporated in the model through assuming an increased austenitisation time value. However, the equilibrium composition values that are assumed capture very well the expected compositional variations across the dendrites as a function of alloy composi...

show abstract

supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Ferrite/Pearlite Band Prevention in Dual Phase and TRIP Steels: Model Development

Rivera-Dı́az-del-Castillo

Zwaag

2005

ISIJ Int.

View full text Add to dashboard Cite

show abstract

“…9,10) Hot rolled bands remains inalterable after cold rolled and continuous annealing of dual phase steels, since during the intercritical heat treatment austenite formation takes place only in the carbon-rich regions featuring pearlite, while the low-carbon regions remain ferritic. 11) When rapid cooling, martensite will then form in the regions previously occupied by pearlite. The banded appearance of the microstructure affects mainly the ductility and the impact energy of the steel, while other mechanical properties are not significantly altered.…”

Section: -7)mentioning

confidence: 99%

“…Several investigations have shown manganese to be the alloying element most responsible for the development of microstructural banding in low alloy steels. [10][11][12] Moreover, austenitising temperature, austenite grain size, and cooling rate influence the severity of microstructural banding. 17) Thompson and Howell 18) investigated banding in 0.15 mass%C, 1.40 mass%Mn steel and concluded that increasing the cooling rate from the austenitic condition reduces the intensity of banding because it reduces the Ar 3 temperature differences of the segregated bands.…”

Section: -7)mentioning

confidence: 99%

Evolution of Microstructural Banding during the Manufacturing Process of Dual Phase Steels

Caballero¹,

García-Junceda²,

Capdevila³

et al. 2006

Mater. Trans.

View full text Add to dashboard Cite

The segregation of manganese during solidification from casting is responsible for banding problems of dual phase steels. Microstructural banding lasts during all the manufacture process, producing the deterioration of the material, so the final ductility and impact toughness of the sheets are decreased due to the high level of anisotropy. To avoid or reduce the problem of microstructural banding, it is proposed to modify the hot rolling parameters so the formation of ferrite-pearlite microstructures is avoided and thus the presence of banding. The study of the microstructural evolution during the whole manufacturing process reveals that the increase of the cooling rate during the hot rolling leads to a significant decrease of martensite banding in the microstructure of dual phase steels for sheets used in the automotive industry.

show abstract

“…1). A lot of publications (Bastien, 1957;Grossterlinden et al, 1992;Thompson and Howell, 1992) have been dedicated to the mechanisms of its formation. Only a few works have been published on quantitative characterization of microstructural banding through image analysis, although a lot of companies probably developed their own specific methods.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Banded Structures in Dual-Phase Steels

Krebs¹,

Hazotte²,

Germain³

et al. 2011

Image Anal Stereol

View full text Add to dashboard Cite

Dual-Phase (DP) steels are composed of martensite islands dispersed in a ductile ferrite matrix, which provides a good balance between strength and ductility. Current processing conditions (continuous casting followed by hot and cold rolling) generate 'banded structures' i.e., irregular, parallel and alternating bands of ferrite and martensite, which are detrimental to mechanical properties and especially for in-use properties. We present an original and simple method to quantify the intensity and wavelength of these bands. This method, based on the analysis of covariance function of binary images, is firstly tested on model images. It is compared with ASTM E-1268 standard and appears to be more robust. Then it is applied on real DP steel microstructures and proves to be sufficiently sensitive to discriminate samples resulting from different thermo-mechanical routes.

show abstract

Formation of pearlitic banded structures in ferritic‐pearlitic steels

Cited by 60 publications

References 4 publications

Ferrite/Pearlite Band Prevention in Dual Phase and TRIP Steels: Model Development

Ferrite/Pearlite Band Prevention in Dual Phase and TRIP Steels: Model Development

Evolution of Microstructural Banding during the Manufacturing Process of Dual Phase Steels

Quantitative Analysis of Banded Structures in Dual-Phase Steels

Contact Info

Product

Resources

About