Argon Bubbles in Slabs.

Abbel, Gert; Damen, Wout; Gendt, Geert de; Tiekink, Wouter

doi:10.2355/isijinternational.36.suppl_s219

Cited by 24 publications

(22 citation statements)

References 1 publication

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“…Most particles are captured 1-3 m below the meniscus, independent of casting speed, 162,169) which corresponds to a specific distance through the strand thickness. 163) Often, inclusions concentrate at one-eighth to one-quarter of the thickness from the top of the inside radius surface, 112,140) in addition to the surfaces, as verified by AK Steel Middletown Works (Fig. 32).…”

Section: Caster Curvaturementioning

confidence: 99%

“…153,159,162) Gas bubbles also capture inclusions as they flow in the mold. 163) Figure 29 shows a typical bubble coated with inclusion clusters. 153) A tremendous number of alumina particles can be captured by a single bubble, as shown in Fig.…”

Section: Argon Gas Injectionmentioning

confidence: 99%

“…153) Even if no gas is injected into the tundish nozzle, defects can form from bubbles originating far upstream. 163) 6.2.5. Submergence Depth Increasing submergence depth naturally shifts the flow pattern downward, which lessens fluctuation and instability of the steel/slag interface, 166) and tends to improve surface quality, as shown in Fig.…”

Section: Argon Gas Injectionmentioning

confidence: 99%

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State of the Art in Evaluation and Control of Steel Cleanliness.

2003

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This paper first reviews the current "state-of-the-art" in the evaluation of steel cleanliness, discussing over 20 different methods. The demand for cleaner steels requires lowering non-metallic oxide inclusions and also controlling their morphology, composition and size distribution. Because no single method can measure all of these aspects accurately, it is best to combine several methods together to quantify steel cleanliness in a given operation. Owing to the cost, time requirements, and sampling difficulties, steel cleanliness is widely inferred using total oxygen, nitrogen pick-up, and other indirect methods. Recent cleanliness values using these indicators are summarized for LCAK at many steel plants around the world. Secondly, this paper reviews operating practices to improve steel cleanliness at the ladle, tundish and continuous caster, emphasizing findings quantified with plant measurements. Inclusions come from many sources, including deoxidation, reoxidation, slag entrapment, refractory wear, and chemical reactions. They generate many defects such as cracks and slivers in the steel product. Steel cleanliness is controlled by attention to a wide range of important operating conditions throughout the steelmaking and casting processes. For ladle operations, FeO and MnO in the slag, ladle treatments, and inclusion modification are discussed. For tundish operations, tundish depth and capacity, casting transitions, refractory lining, tundish flux; gas stirring, and flow controls are discussed. Important transfer operations from ladle to tundish and from tundish to mold, such as argon protection, sealing issues, and SEN clogging are summarized. Caster operations reviewed include the effect of casting speed, fluid flow pattern control, surface level control, and caster curvature.

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Section: Caster Curvaturementioning

confidence: 99%

Section: Argon Gas Injectionmentioning

confidence: 99%

Section: Argon Gas Injectionmentioning

confidence: 99%

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State of the Art in Evaluation and Control of Steel Cleanliness.

2003

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“…[3][4][5] Abbel et al reported that large argon bubbles (diameter >0.5 mm) had a nonhomogeneous distribution in slab in respect width and depth based on radiographic method. 6) Miyake et al believed that the distribution of bubbles in slab depends on the steel grade, especially on the sulfur content based on study on Kakogawa Work; and the authors pointed that electromagnetic stirring in the mold (M-EMS) was effective for removing bubbles and reduce sliver defect. 7) In cold rolled IF steel, slivers and blow-holes were two main types of visual surface defects; generally, the defects were caused by argon bubbles or argon bubbles in combination with entrapped mould powder; the sliver defects had relationship with the argon bubbles containing the alumina clusters or mould slag.…”

Section: Introductionmentioning

confidence: 99%

Distribution and Detriment of Bubbles in Continuous Casting Interstitial Free Steel Slab

et al. 2015

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The distribution and detriment of bubbles in ultra low carbon interstitial free steel were studied by X-ray radiographic and cold-rolled experiment; a total of 24 pieces samples with size 230 mm × 65 mm × 2 mm were detection and 150 bubbles were counted; the results showed that: (1) Two bubbles bands formed in continuous casing slab; bubbles distributed asymmetrically in thickness direction of the slab; small bubbles mainly concentrated in inner art side 1/8 to 1/4 in thickness direction; large bubbles were main in center of the slab in thickness direction; (2) Hundreds of inclusions with sizes 2 μm to 10 μm accumulated in cone-shape region after bubbles. Inclusions or Fe and FeO particles often attached or mixed with the bubbles. (3) Small bubbles entered into down-flow easily and rushed out the mould, bubbles and inclusions accumulative band formed in inner art side of the slab. (4) The bubbles, inclusions around the bubbles or large Fe and FeO particles mixing with bubbles became source of the sliver defect.

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“…This class of bubbles comprises only a small fraction of all bubbles present in a typical slab of IF-steel. 7,8) Some researchers stress the importance of hydrogen in steel production. [9][10][11][12] The hydrogen is presumed to enter the steel somewhere during downstream processing increasing the internal hydrogen pressure at defects present in the steel.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Hydrogen on the Visibility of Pencil Pipe Defects.

et al. 2002

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During casting of interstitial free steel, argon bubbles are caught in the solidification front of the steel slab. During downstream processing, these bubbles develop into sub-surface defects called blowholes or pencil pipe defects. Atomic hydrogen can enter the steel in the pickling line and accumulate in the defects, causing an increase of the internal pressure. In the presented study, blowholes are charged with hydrogen both electrochemically and by exposing the blowholes to pickling acid. The pressure and composition of the gas inside the blowholes are determined by opening the blowholes under ultra high vacuum conditions. It is shown that the accumulated pressure is capable of deforming the blowholes plastically, enhancing the visibility of the defects in the sheet. Calculations of the threshold pressure for plastic deformation show to be in reasonable agreement with measured pressures inside the blowholes. Industrial pickling conditions are discussed as well. It is concluded that hydrogen does not influence the blowholes significantly for the considered industrial conditions. Most likely the blowholes become visible in sheet steel at recrystallisation annealing. The final shape of the blowholes is determined by the temper rolling process.KEY WORDS: blowhole; pencil pipe defect; interstitial free steel; hydrogen; argon; pickling; surface defects.performed at room temperature using a 0.1 M NaOH solution. The sample served as cathode and a platinum grid positioned opposite to the sample acted as anode. A constant current density of 20 mA cm Ϫ2 was used. The hydrogen charging with an acid was performed using 20 mass% hydrochloric pickling acid. The acid is taken directly from the pickling line at Corus IJmuiden (including pickling inhibitor). The temperature of the acid was kept constant at 85°C.The electrochemical method was used to show deformation resulting from accumulation of hydrogen in the blowhole. Due to the low temperature and the lower efficiency (compared with pickling), the charging process is slow and therefore easy to control. Another difference is the charging time: the electrochemical method does not dissolve the steel surface and can be pursued for periods of one day or more. Because of etching effects the maximum pickling time is limited to about 10 min.Before and directly after charging, height profiles of the samples were taken using a UBM laser profile meter. This method gives a height resolution of 60 nm. Recording a height profile over an area of 4ϫ15 mm (with a lateral resolution of 20ϫ100 mm) takes about 30 min. Directly after taking the scan, the samples are stored in liquid nitrogen preventing hydrogen permeating out of the samples.The samples are analyzed by opening the blowholes in a closed vacuum chamber. After removing a sample from the liquid nitrogen, the sample is cleaned in ethanol, dried and placed in the above-mentioned ultra-high vacuum set-up. The sample is mounted in a sample holder shown in Fig. 1. The sample is kept in its place by a spring and a screw for adjustment....

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Argon Bubbles in Slabs.

Abstract: The effect of applying an EMBR was studied.

Cited by 24 publications

References 1 publication

State of the Art in Evaluation and Control of Steel Cleanliness.

State of the Art in Evaluation and Control of Steel Cleanliness.

Distribution and Detriment of Bubbles in Continuous Casting Interstitial Free Steel Slab

The Influence of Hydrogen on the Visibility of Pencil Pipe Defects.

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