In-Situ Measurement of Fracture Strength of Solidifying Steel Shells to Predict Upper Limit of Casting Speed in Continuous Caster with Oscillating Mold.

Suzuki, Mikio; Suzuki, Makoto; Yu, Chong-Hee; Emi, Toshihiko

doi:10.2355/isijinternational.37.375

Cited by 26 publications

(17 citation statements)

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“…The fracture strength of low carbon steels and peritectic medium carbon steels is shown in Figs. 7(a) and 7(b), 29) against the average temperature of the shell determined by the solidification temperature and the interfacial temperature of the shell touching the chill block. In the figures, the fracture strength measured with the in-situ melting and solidified tensile test 32) (hereafter in-situ MST test) are compared with those of SSCT test.…”

Section: Upper Limit Of Casting Speed Of Continuous Castermentioning

confidence: 99%

“…Suzuki et al 29) predicted the upper limit of casting speed in a continuous caster with an oscillating mold by comparing the frictional force between a shell and a mold wall with the fracture strength of the solidifying shell at the initial stage of solidification in a mold. Hence, they measured in-situ the fracture strength of solidifying shell using a method similar to "Submerged Split Chill Tensile test" (hereafter SSCT test) which Ackermann et al 30) developed.…”

Section: Upper Limit Of Casting Speed Of Continuous Castermentioning

confidence: 99%

“…The fracture strength of low carbon steels and peritectic medium carbon steels is shown in Figs. 7(a) and 7(b), 29) against the average temperature of the shell determined by the solidification temperature and the interfacial temperature of the shell touching the chill block. frictional force, F f , is a sum of the shear force throughout a whole mold, given as ... (1) where w is the width, d is the thickness of a mold, z is the distance from the meniscus, f ᐉ is the frictional force per unit interfacial area, h ᐉ is the viscosity of mold powder film and DV m /Dx is the velocity gradient of the infiltrated powder film.…”

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Perspectives of Research on High-speed Conventional Slab Continuous Casting of Carbon Steels.

Suzuki

Nakada

2001

ISIJ International

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Two decades ago the casting speed of the conventional slab continuous caster was increased stepwise to a level over 2 m/min. Henceforth, the casting speed has been remained a similar level. In this review the reasons for constraining the casting speed are discussed. As a result the constraints of the high-speed casting are thought mold powder entrapment and longitudinal facial crack occurring in high-speed casting.Some measures to prevent the mold powder entrapment and the longitudinal facial crack are discussed. Resultantly the research issues we should develop are considered such as prevention of alumina built-up in a submerged entry nozzle, control of fluid flow in a mold and control of heat transfer through mold powder film interved between a solidifying shell and a mold wall. They are most important to realize the high-speed continuous casting of conventional slab.KEY WORDS: high-speed casting; conventional slab; mold powder entrapment; longitudinal facial crack; upper limit of casting speed.order to realize the ideal process, i.e., full hot direct rolling, technologies for more stability of the casting practice and the production of higher slab quality should be realized.The casting speed of the conventional slab caster with an oscillating mold has been remained a 2 m/min level because such higher-speed casting deteriorates slab quality. Therefore, we will investigate what the factors for restraining the casting speed of the conventional slab caster are. Present State of High-speed Continuous Casting of Steel Slab Trend of Casting Speed of Conventional SlabContinuous Caster We will survey the present state of high-speed casting in a conventional slab caster. The trend of the casting speed is shown in Fig. 3 10) for the conventional slab casters in Japanese steel companies. The main specifications and the casting speed are listed in Table 1 of the conventional slab casters. [11][12][13][14][15][16][17][18] The casting speed has been stepwise increased and attained approximately twice in two decades. Fifteen years ago a synchronized operation began between a continuous caster and a hot strip mill, i.e., hot direct rolling. 19) Since the hot direct rolling operation needs the productivity of the caster to be met to that of the hot strip mill, the casting speed should be increased. Heat Transfer and Lubrication Phenomena inContinuous Casting Mold at High-speed Casting The infiltration of liquid powder into a shell/mold gap is a very important process in continuous casting since it is necessary to ensure both good lubrication and uniform heat transfer between a shell and a mold. Failure to provide these conditions could result in the creation of surface defects and sticker breakouts.We will survey the heat transfer and the lubrication phenomena in a mold at a casting speed over 2 m/min of slab casters.Local heat flux in casting of low carbon Al killed steel is shown in Fig. 4 20) against the remaining time in a mold. The local heat flux during the conventional slab casting given by Suzuki et al.,21) and Grilles...

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Section: Upper Limit Of Casting Speed Of Continuous Castermentioning

confidence: 99%

Section: Upper Limit Of Casting Speed Of Continuous Castermentioning

confidence: 99%

“…The fracture strength of low carbon steels and peritectic medium carbon steels is shown in Figs. 7(a) and 7(b), 29) against the average temperature of the shell determined by the solidification temperature and the interfacial temperature of the shell touching the chill block. frictional force, F f , is a sum of the shear force throughout a whole mold, given as ... (1) where w is the width, d is the thickness of a mold, z is the distance from the meniscus, f ᐉ is the frictional force per unit interfacial area, h ᐉ is the viscosity of mold powder film and DV m /Dx is the velocity gradient of the infiltrated powder film.…”

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Perspectives of Research on High-speed Conventional Slab Continuous Casting of Carbon Steels.

Suzuki

Nakada

2001

ISIJ International

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“…[7][8][9][10][11] This restricts operation with higher casting speed, because breakouts are more likely to occur due to the thinner shell thickness 12) and higher frictional force 8) during high speed casting. Consumption is readily measured by counting the mass of mold powder added per unit time (kg/s).…”

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Measurement and Prediction of Lubrication, Powder Consumption, and Oscillation Mark Profiles in Ultra-low Carbon Steel Slabs

et al. 2006

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The flow of melted mold powder into the interfacial gap between the strand and the mold wall is important for productivity and quality in continuous cast slabs. Some of the mold slag (flux) consumption provides true lubrication, while much of the rest is trapped in the oscillation marks on the slab surface. This work presents measurements of powder consumption from extensive careful plant trials on ultra-low carbon steels, and a new, simple, semi-empirical model to predict slag consumption. The model predicts "lubrication consumption" by deducting the slag carried in the oscillation marks from the measured total. The oscillation mark shape is estimated from a theoretical analysis of equilibrium meniscus shape, which is based on metallographic analysis of many hook and oscillation mark shapes. The model demonstrates that the fraction consumed in the oscillation marks decreases with increasing casting speed, because the oscillation mark depth depends more on casting speed than on mold oscillation conditions. The model is validated by successful prediction of known trends of oscillation mark depth and mold powder consumption with changing various operation parameters. The model provides new insight into mold lubrication phenomena, which is important for extending casting operation to higher speeds and new lubrication regimes.KEY WORDS: continuous casting; mold powder; slag; flux; lubrication; oscillation marks; mold oscillation; stroke; frequency; modification ratio; negative strip time; positive strip time; casting speed; meniscus; models; plant experiments.ISIJ International, Vol. 46 (2006), No. 11, pp. 1635No. 11, pp. -1644 slag as shown in Fig. 1(a). The solid slag layers are glassy, crystalline, or mixtures of both 14) depending on the slag composition and local cooling rate history. [15][16][17] Several previous models of heat transfer and lubrication assume that the gap has a uniform thickness. [18][19][20] However, the real strand surface contains periodic transverse depressions called oscillation marks (OM) in Fig. 1(b). The volume of these depressions generally consumes a significant amount of slag, which greatly affects lubrication and leads to nonuniform heat transfer in the mold. 21) Thus, quantifying the oscillation mark shape is a necessary prerequisite for the prediction of lubrication and heat transfer in the mold.In this study, mold powder consumption was measured during casting trials conducted at POSCO Gwangyang Works for several different oscillation conditions and casting speeds. The measured consumptions were divided into two components: 1) the slag entrapped in the oscillation marks and 2) the remaining flux, which provides lubrication to prevent sticking, as shown in Fig. 1(b). This "lubrication consumption" is a more realistic concept to represent lubrication than total mold powder consumption.17) The oscillation mark shape is calculated by combining measured OM depths with a realistic profile based on fundamentals. 22) Correlations are found for OM depth, corresponding OM consumption, l...

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“…Pierer et al [8] compared stress-based [59] strainbased [60] strain-rate-based, [61] and the Clyne and Davies model [62] with experimental data from SSCT tests. He found that, even though each criterion approaches the problem from a different perspective, the predictions of cracking susceptibility are nearly the same.…”

Section: A Hot Tearingmentioning

confidence: 99%

Measuring Mechanical Behavior of Steel During Solidification: Modeling the SSCC Test

Rowan

Thomas

Pierer

et al. 2011

Metall Mater Trans B

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The submerged split chill contraction (SSCC) test can measure forces in a solidifying steel shell under controlled conditions that match those of commercial casting processes. A computational model of this test is developed and applied to increase understanding of the thermal-mechanical behavior during the initial solidification of steel. Determining the stress profile is difficult because of the complicated geometry of the experimental apparatus and the nonuniform temperature and strength across the shell. The two-dimensional axisymmetric elastic-viscoplastic finite-element model of the SSCC test features different mechanical properties and constitutive equations for delta-ferrite and austenite that are functions of both the temperature and the strain rate. The model successfully matches measurements of (1) temperature history, (2) shell thickness, (3) solidification force, and (4) failure location. In addition, the model reveals the stress and strain profiles through the shell and explains what the experiment is actually measuring. In addition to the strength of the shell, the measured force is governed by the strength of the junction between the upper and lower test pieces and depends on friction at the shellcylinder interface. The SSCC test and the validated model together are a powerful analysis tool for mechanical behavior, hot tear crack formation, and other phenomena in solidification processes such as continuous casting.

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In-Situ Measurement of Fracture Strength of Solidifying Steel Shells to Predict Upper Limit of Casting Speed in Continuous Caster with Oscillating Mold.

Cited by 26 publications

References 0 publications

Perspectives of Research on High-speed Conventional Slab Continuous Casting of Carbon Steels.

Perspectives of Research on High-speed Conventional Slab Continuous Casting of Carbon Steels.

Measurement and Prediction of Lubrication, Powder Consumption, and Oscillation Mark Profiles in Ultra-low Carbon Steel Slabs

Measuring Mechanical Behavior of Steel During Solidification: Modeling the SSCC Test

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