Improvement of Hot Ductility in Continuously Cast Strand by Ferrite Precipitation Control

Ito, Yoshiki; Kato, Toru; Yamanaka, Akihiro; Watanabe, Tadao

doi:10.2355/tetsutohagane1955.89.10_1023

Cited by 10 publications

(5 citation statements)

References 9 publications

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“…Because so much of the transverse cracking problem is associated with either the presence of the soft ferrite film at the c boundaries and/or having precipitation at the c boundaries when fully austenitic, some recent work by Sumitomo 25,26 looks very promising for entirely eliminating the problem. In this work by cooling rapidly (SCC) below the mould to below the Ae 3 and then allowing the strand to heat up to above this temperature, not only is the thin film of ferrite at the boundaries replaced by isomorphic islands of ferrite within the c grains but precipitation now takes place homogeneously in a fine form within these islands away from the boundary.…”

Section: Progress In Testing Techniquesmentioning

confidence: 99%

Hot ductility of steels and its relationship to the problem of transverse cracking in continuous casting

Mintz¹,

Crowther²

2010

International Materials Reviews

137

237

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The influence of composition and cooling rate on the hot ductility of steels has been reviewed. Models to predict hot ductility behaviour have been discussed and the parts of the trough which can be used to predict the likelihood of cracking occurring are highlighted. On tensile testing both deformation induced ferrite in sufficient quantity to improve ductility and dynamic recrystallisation occur but not when straightening during continuous casting; the strain being too low. This limits the use of the hot ductility curve in predicting cracking behaviour. The temperature range in which straightening of the continuously cast strand should be carried out is either 30uC below the Ar 3 when there is a large amount of ferrite (y40%) present before deformation or above the T d , the temperature at which dynamic recrystallisation starts to take place in a tensile test; this being when the ferrite film no longer forms and precipitates are sufficiently coarse and few in number to influence the ductility. The influence of C,Mn,N, Nb,V,B,Ti,Al and the residuals Cu and Sn on hot ductility are examined and recommendations made with regard to the amounts and cooling conditions required to give freedom from transverse and edge cracks. The hot ductility of the new transformation induced plasticity (TRIP) and twin induced plasticity (TWIP) steels has also been reviewed. P has been shown to have little influence on the hot ductility, but for Al based TRIP and TWIP steels, Al levels need to be closely controlled and high Al levels, (1?5 to 2%Al) are favoured.

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Section: Progress In Testing Techniquesmentioning

confidence: 99%

Hot ductility of steels and its relationship to the problem of transverse cracking in continuous casting

Mintz¹,

Crowther²

2010

International Materials Reviews

137

237

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“…The appearances of their original austenite grains were compared, and the results are shown in Figure 9. The original austenite grain boundary was outlined using the proeutectoid ferrite structure precipitating along the original austenite grain boundary [26]. It can be seen that the austenite grain size after the magnesium treatment was smaller than that before the magnesium treatment.…”

Section: Solidification Structure Analysismentioning

confidence: 99%

Effect of Magnesium Treatment on the Hot Ductility of Ti-Bearing Peritectic Steel

Wang

et al. 2020

Metals

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Surface cracking is a major defect in the production of continuous casting slabs of peritectic steel. The difference in crystal structure between δ phase (before peritectic transformation of steel) and γ phase (after peritectic transformation) results in volume contraction, which leads to uneven cooling of mold and thus forming slab shells with different thicknesses. Then, coupled with the concentration of local stress, surface cracking occurs on slabs. In this paper, the effect of magnesium treatment on the hot ductility of Ti-bearing peritectic steel was studied, and the characteristics of solidification structure and TiN particles were analyzed. Magnesium treatment for Ti-bearing peritectic steel could significantly improve the hot ductility of continuous casting slabs by refining the original austenite structure. After the magnesium treatment, the average grain size of the original austenite of peritectic steel decreased by about 18.7%, and the size of Mg-rich TiN particles decreased by about 41%. In addition, the minimum reduction of area at the third brittle zone after the magnesium treatment was higher than 60%, and the fracture appearance changed from intergranular fracture to ductile fracture after the treatment. The contents of Mg, Ti, O, and N in peritectic steel and the cooling conditions were adjusted reasonably to promote the formation of highly dispersed Mg-rich TiN particles with a sufficient number density and a proper size in the initial solidification stage of peritectic steel, so as to induce the high-temperature δ-ferrite nucleation. Based on the fine δ structure formed by peritectic transformation, through the use of structure heredity and the pinning effect of secondary-precipitated nano TiN particles on the austenite grain boundary, a fine and dense original austenite structure could be obtained to improve the hot ductility of peritectic steel. Industrial tests showed that through the magnesium treatment, the surface cracks of Ti-bearing peritectic steel were effectively restrained, and the corner cracks of slabs were basically eliminated.

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“…Temperature accuracy, stability and distribution were also inspected beforehand. 13) These apparatus were placed in a chamber and experiments were carried out in argon atmosphere.…”

Section: Hot Tensile Testmentioning

confidence: 99%

Prevention of Slab Surface Transverse Cracking by Microstructure Control

Kato¹,

Ito²,

Kawamoto³

et al. 2003

ISIJ International

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Improvement of Hot Ductility in Continuously Cast Strand by Ferrite Precipitation Control

Cited by 10 publications

References 9 publications

Hot ductility of steels and its relationship to the problem of transverse cracking in continuous casting

Hot ductility of steels and its relationship to the problem of transverse cracking in continuous casting

Effect of Magnesium Treatment on the Hot Ductility of Ti-Bearing Peritectic Steel

Prevention of Slab Surface Transverse Cracking by Microstructure Control

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