Thin slab casting with liquid core reduction

Yamanaka, Akihiro; Kumakura, Susumu; Okamura, Kazuo; Kanazawa, Takashi; Murakami, T.; Oka, M.; Takeuchi, Ippei; Watanabe, Tadao

doi:10.1179/030192399677301

Cited by 27 publications

(35 citation statements)

References 3 publications

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“…The critical strains mainly depend upon the steel composition and the strain rate at the solidifying front. 1,4,6,25) With the increase of carbon content and the decrease of the content ratio of Mn to S, the critical strain decreases, and with the decreasing of the strain rate at solidifying front, the critical strain increases. In this study, the critical strains were chosen from the results provided by Hiebler et al 25) who summarized the experimental data from many researchers and gave the relationship between the critical strains and the steel compositions, which is shown in Fig.…”

Section: Effect Of Strain Status On Internal Cracksmentioning

confidence: 99%

Prediction and Analysis on Formation of Internal Cracks in Continuously Cast Slabs by Mathematical Models.

2001

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The formation of internal cracks in continuously cast slabs is mainly attributed to the strain status and microsegregation near the solidifying front of the slabs. Based on this understanding, the effects of the strain status at solidifying front and the chemical composition of liquid steel on the internal cracks were studied using a strain analysis model and a microsegregation model developed in the present study. The tensile strains at the solidifying front caused by bulging, unbending, and misalignment of supporting rolls in a fourpoint-unbending bow caster were calculated. The roll gap in the caster was measured for the calculation of the strains caused by the misalignment of the supporting rolls. The calculated strain status near the solidifying front was used to predict the internal cracks. Critical strains based on some experimental data were adopted as the crack criteria. Sulfur prints of the slab transverse sections were used to verify the model predictions. The enrichment of chemical compositions in the interdendritic liquid and its effect on the freezing temperature of the liquid were studied with the microsegregation model, in which the transition of ferritic/austenitic solidification and the precipitation of MnS were taken into account. S and P were revealed to strongly accumulate at the columnar grain boundaries, and the segregation of P increases significantly when C content increases from 0.1 % to 0.2 %. With the accumulation of P and S in the interdendritic liquid, the freezing temperature of the liquid decreases obviously, thus the internal crack tendency is greatly increased.KEY WORDS: continuously cast slab; internal cracks; strain analysis; microsegregation; mathematical models.lidifying front and the steel composition on the formation of internal cracks were studied using an empirical equation based strain analysis model and a microsegregation model developed in the present study. The tensile strains at the solidifying front caused by bulging, straightening, and misalignment of supporting rolls in a four-point-unbending bow caster were calculated. The roll gap was measured for the calculation of the strains caused by the misalignment of supporting rolls. The calculated tensile strains were used to predict the formation of the internal cracks. The sulfur prints of the slab transverse sections were used to verify the model predictions. On the other hand, the accumulation of impurity elements, mainly S and P, in the interdendritic liquid and its effect on the freezing temperature of the liquid were studied using a microsegregation model, in which the transition of ferritic/austenitic solidification and the precipitation of MnS were taken into account. Mathematical Models Strain Analysis ModelThe strain analysis model for the continuously cast slab is based on a heat transfer model, which was developed to calculate the variations of surface temperature and solidified shell thickness of the slab in the casting direction. According to the characteristics of heat transfer and solidification of the...

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Section: Effect Of Strain Status On Internal Cracksmentioning

confidence: 99%

Prediction and Analysis on Formation of Internal Cracks in Continuously Cast Slabs by Mathematical Models.

2001

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“…It is reported that the cracks, originated from interdendritic liquid film, is mainly affected by the maximum principal stress. 5,16) Cracks can originate from the region where S C exceeds 1 and the possibility of solidification cracking increases with increasing value of S C . In this study, the corresponding solid fraction for LIT abd ZDT were used to be 0.9 and 0.99, which is proposed by Clyen et al 14) and Won et al, 27) respectively.…”

Section: Crack Susceptibility Coefficientmentioning

confidence: 99%

“…[3][4][5][6][14][15][16][17][18] Previous reports on the cracking condition in continuous casting of steels are listed in Table 1. Clyne et al 14) proposed the crack susceptibility coefficient to estimate the cracking ten-dency during continuous casting of steels.…”

Section: Introductionmentioning

confidence: 99%

“…Many researchers 3,5,15) estimated the possibility of cracking in comparison with the maximum principal stress and transverse stress along the wide and narrow face. And, some investigators 4,16) have used a strain based fracture criterion in the mushy zone, assuming that the material fractures if the total mechanical strain exceeds 0.2% 4) and 1.6%. 16) However, the comparison of the absolute stress and strain values is not enough to investigate the possibility of cracking during continuous casting, because the stress in the solidifying shell changes as a function of temperature and the mushy zone solidifies in almost stress free state, even though the strain occurs in the mushy zone.…”

Section: Introductionmentioning

confidence: 99%

“…And, some investigators 4,16) have used a strain based fracture criterion in the mushy zone, assuming that the material fractures if the total mechanical strain exceeds 0.2% 4) and 1.6%. 16) However, the comparison of the absolute stress and strain values is not enough to investigate the possibility of cracking during continuous casting, because the stress in the solidifying shell changes as a function of temperature and the mushy zone solidifies in almost stress free state, even though the strain occurs in the mushy zone. Kelly et al 6) and Kim et al 17,18) proposed that the solidification cracking occurs in the mushy zone, when the maximum principal stress exceeds the yield stress at that temperature.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Solidification Cracking Using the Specific Crack Susceptibility.

et al. 2000

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Using a 2-dimensional finite element, the effects of carbon content, slab width, narrow face taper and casting speed on solidification cracking during continuous casting of slabs were analyzed. The possibility of solidification cracking during continuous casting of slabs was predicted using the "Specific Crack Susceptibility", S S C . The new proposed parameter, S S C , can represent the averaged possibility of solidification cracking of the strand during continuous casting in the mold. The surface crack formed near corner region of strand at the initial stage of solidification, and the internal crack was found in the internal regions of wide center, corner and off-corner at the middle and final stage of solidification. The carbon range sensitive to solidication cracking is between 0.1 wt% C and 0.14 wt% C steels. At the slab widths of 1 900 mm and 2 150 mm, the possibility of solidification cracking increased in the regions of wide center, corner and offcorner in comparison with the slab width of 1 600 mm. With increasing narrow face taper, the possibility of solidification cracking decreased along the region of wide face due to the mechanical compression imposed by the narrow face taper. With increasing casting speed, the possibility of solidification cracking increased in the regions of wide center, corner and off-corner, because the shell thickness is largely decreased due to decrease of dwelling time of strand within the mold. These predictions at various casting conditions were in good agreement with the experimental observations in industry.KEY WORDS: specific crack susceptibility; solidification cracking; carbon content; slab width; narrow face taper; casting speed.dency during continuous casting of steels. They divided the mushy zone into the mass/liquid feeding zone (0.4Ͻf s Ͻ0.9) and the cracking zone (0.9Ͻf s Ͻ0.99). Cracks formed in the mass/liquid feeding zone are refilled with the surrounding liquid, whereas cracks formed in the cracking zone can not be refilled with the liquid, because the dendrite arms are close enough to resist feeding of the surrounding liquid. They proposed the critical solid fraction to resist feeding of 0.9. However, the crack susceptibility coefficient can be increased with increasing carbon content, because the mushy zone increases with increasing carbon content. Many researchers 3,5,15) estimated the possibility of cracking in comparison with the maximum principal stress and transverse stress along the wide and narrow face. And, some investigators 4,16) have used a strain based fracture criterion in the mushy zone, assuming that the material fractures if the total mechanical strain exceeds 0.2% 4) and 1.6%. 16) However, the comparison of the absolute stress and strain values is not enough to investigate the possibility of cracking during continuous casting, because the stress in the solidifying shell changes as a function of temperature and the mushy zone solidifies in almost stress free state, even though the strain occurs in the mushy zone. Kelly et al. 6) and Kim et ...

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Modeling of Hot Ductility During Solidification of Steel Grades in Continuous Casting – Part I

et al. 2010

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Hot cracking during solidification in continuous casting is one of the quality problems due to the development of local stresses and strains in the CC strand which exceeds the material strength. Strains result from alternating motion of the steel shell due to thermal and mechanical contraction expension and ferrostatic pressure, primarily in the transition region between the geometrical strong edge and the more flexible wide side of a slab. [1] The formation of hot cracks is often related to the reduced ductility of steel in the mushy zone, caused by thin liquid layers between dendrites resulting from microsegregation. Those liquid layers between dendrite arms exist up to a high fraction of solid, just until complete solidification; [2] applied strain in the mushy zone in the solid fraction range between 0.9 and 0.99 can initiate brittle cracks. The temperature at which the solid brittle fraction is 0.9 is known as liquid impenetrable temperature (LIT) while the temperature at a solid fraction of 0.99 is the zero ductility temperature (ZDT). The region between both temperatures will be referred to as brittle temperature range. Reported critical strains are varying from 0.2 to 3.8% [3][4][5][6] for different carbon contents and strain rates, while the strains analyzed in any location of the caster are 0.3% at the most. [7] In the past it was common practice to describe the high temperature properties of steels according to tensile strength vs. temperature or reduction-of-cross-section-area (RoA) vs. temperature determined by hot tensile tests following theThe present paper gives an overview of the simultaneous research work carried out by RWTH Aachen University and ThyssenKrupp Steel Europe AG. With a combination of sophisticated simulation tools and experimental techniques it is possible to predict the relations between temperature distribution in the mould, solidification velocity, chemical steel composition and, furthermore, the mechanical properties of the steel shell. Simulation results as well as experimentally observed microstructure parameters are used as input data for hot tearing criteria. A critical choice of existing hot tearing criteria based on different approaches, like critical strain and critical strain rate, are applied and developed. The new ''damage model'' is going to replace a basic approach to determine hot cracking susceptibility in a mechanical FEM strand model for continuous slab casting of ThyssenKrupp Steel Europe AG. Critical strains for hot cracking in continuous casting were investigated by in situ tensile tests for four steel grades with carbon contents in the range of 0.036 and 0.76 wt%. Additionally to modeling, fractography of laboratory and industrial samples was carried out by SEM and EPMA and the results are discussed.94

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Thin slab casting with liquid core reduction

Abstract: the temperature, l is the thermal conductivity, DH SL is the latent heat of solidification, f L is the liquid fraction, d is

Cited by 27 publications

References 3 publications

Prediction and Analysis on Formation of Internal Cracks in Continuously Cast Slabs by Mathematical Models.

Prediction and Analysis on Formation of Internal Cracks in Continuously Cast Slabs by Mathematical Models.

Analysis of Solidification Cracking Using the Specific Crack Susceptibility.

Modeling of Hot Ductility During Solidification of Steel Grades in Continuous Casting – Part I

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