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

Abstract

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...

Análise Física E Matemática Da Turbulência Na Interface Metal/Escória Na Região Do Menisco Em Molde De Lingotamento Contínuo

“…Um modelo físico em acrílico, construído em escala = 0, 6 critério de similaridade. O mapa de velocidades foi determinado por meio da técnica PIV.…”

State of the art in the control of inclusions during steel ingot casting

“…Stokes collision [38,55,58,63,64] may also contribute to the growth of inclusions. Zhang and Pluschkell recently have combined classic homogenous nucleation theory, thermodynamic analysis, and a multiple size grouping methodology to develop a fundamental model of nucleation and growth of alumina inclusions in steel using numerical simulation.…”

“…[4] adding deoxidizer, particles nucleate or precipitate, and quickly grow. Starting from the rapid supersaturation that occurs when alloys are released and dispersed into the melt, homogeneous nucleation is very fast, occurring in 1 to 10 ms. [54] Inclusion growth is controlled by diffusion of the deoxidization elements and oxygen, [38,40,[55][56][57][58] local thermodynamics, [31,38,42,[59][60][61][62] Ostwald ripening, [40,55,58,63,64] and Brownian collisions [38,40,55,56,58] when inclusions are smaller than 1 mm.…”

Design of a Submerged Entry Nozzle for Thin Slab Molds Operating at High Casting Speeds

“…In the actual caster such conditions would eventually lead to the entrainment of flux. 24) The larger presence of green areas in SEN-3 indicates a more stable meniscus. It is also important to emphasize the different frequencies of meniscus oscillations comparing the SENs.…”

“…Some slab casting submerged nozzle designs induce strong meniscus instability and high amplitude oscillations of liquid steel in the mold. 6) Takatani et al 7) found that in a conventional slab mold the horizontal velocity under the meniscus fluctuates strongly. Using a physical model Yoshida et al 8) identified downward flows at the meniscus along the outer surface of the SEN due to the existence of differential pressure in this region.…”