Pinhole and Inclusion Defects Formed at the Subsurface in Ultra Low Carbon Steel

Yasunaka, Hiroyuki; Yamanaka, Ryoichi; Inoue, Takeshi; Saito, Tadashi

doi:10.2355/tetsutohagane1955.81.5_529

Cited by 27 publications

(11 citation statements)

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“…At present, it can only be said with certainty that internal defects are caused by bubbles and inclusions entrapped on the shell. 7) In order to clarify the mechanism of internal defects caused by bubbles and inclusions, the authors carried out a fundamental examination of the entrapment of inclusions and bubbles on the solidified shell of molten steel during continuous casting using water model experiments and a numerical fluid flow simulation. Particular attention was given to the unbalanced time-dependent flow in the mold and attachment of inclusions to bubbles.…”

Section: Introductionmentioning

confidence: 99%

Internal Defects of Continuous Casting Slabs Caused by Asymmetric Unbalanced Steel Flow in Mold

Miki¹,

Takeuchi²

2003

ISIJ International

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Section: Introductionmentioning

confidence: 99%

Internal Defects of Continuous Casting Slabs Caused by Asymmetric Unbalanced Steel Flow in Mold

Miki¹,

Takeuchi²

2003

ISIJ International

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“…In the current model, to simplify the calculation, the overflow was set to occur only during the negative strip time (NST) [32,33]. During the positive strip time (PST), the meniscus was continuously solidified by the copper wall.…”

Section: Numerical Simulationmentioning

confidence: 99%

Hook evolution and inclusion entrapment during initial solidification process of continuous casting slab

Ping

Zhu

et al. 2018

Metall. Res. Technol.

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A two-dimensional numerical model was established to describe the mechanism of hook formation and evolution during the initial solidification process of continuous casting slab. Melting, coarsening, growing, and burying stages were observed to follow hook formation at the meniscus. The coordinates at which the hook was finally buried into the shell were determined for different casting speeds and pouring temperatures. The final hook depth was predicted to be approximately 1.8-2.9 mm, which was confirmed by metallographic experiments. A physical model was established based on the calculated shell shape, and the process by which the inclusions were entrapped by the hook structure was investigated. The results indicated that the floating inclusions were most likely entrapped under the nascent hook, and the inclusions gathering near the meniscus were easily captured by the upper part of the nascent hook when overflow of the molten steel occurred. The hooklike structure increased the area of the shell inner face, which resulted in swirling flow of the molten steel near the shell and increased the probability of the inclusions being captured.

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“…(1) ................ (1) where K is the surface tension gradient in the solidification direction x. Let's assume that the surface tension gradient K exists only in the narrow region near the interface, so called boundary layer, and is constant over the surface area of particle.…”

Section: Marangoni Force On the Bubble In The Continuousmentioning

confidence: 99%

“…These entrapped bubbles become the major cause of defects such as blisters and slivers which appear in the rolled products. 1) In order to elucidate the mechanism by which particles or bubbles are captured by the solidification front, a number of studies have been reported previously. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] When a particle or bubble touches the solid/liquid interface of steel it may be either entrapped or pushed away.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Surface Tension Gradient Effect on the Behavior of Gas Bubbles at the Solid/Liquid Interface of Steel

et al. 2012

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The mechanism which governs the behavior of bubbles in the vicinity of the solidification front where both the concentration and temperature gradients exist was investigated and the effect of the solutal and thermal marangoni forces to the entrapment of bubble were compared and discussed.When a bubble approaches the solid/liquid interface, it first encounters the thermal boundary layer, which is much thicker than the concentration boundary layer, and experiences the thermal marangoni force. This force, which occurs due to the temperature gradient in the thermal boundary layer, pushes the bubble away from the solidification front if the sulfur concentration is lower than the critical value which was found to be around 47-60 ppm, but pulls it toward the solidification front if the sulfur concentration is higher than the critical value. Only if the bubble passes through the thermal boundary layer successfully, it then arrives at the concentration boundary layer where a strong solutal marangoni force comes into action on the bubble to pull it to the solid/liquid interface.The above analysis predicts that the bubble-induced surface defect of a cast be strongly affected by the sulfur concentration and there exists a critical sulfur concentration above which the surface defect becomes increasing. The above prediction was validated by the CFD (Computational Fluid Dynamics) simulation and the trial at the commercial casting plant, and they were in good agreement with each other.

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Pinhole and Inclusion Defects Formed at the Subsurface in Ultra Low Carbon Steel

Cited by 27 publications

References 0 publications

Internal Defects of Continuous Casting Slabs Caused by Asymmetric Unbalanced Steel Flow in Mold

Internal Defects of Continuous Casting Slabs Caused by Asymmetric Unbalanced Steel Flow in Mold

Hook evolution and inclusion entrapment during initial solidification process of continuous casting slab

Numerical Analysis of Surface Tension Gradient Effect on the Behavior of Gas Bubbles at the Solid/Liquid Interface of Steel

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