Sumitomo Metal Industries, Inc.

Nippon Steel Sumitomo Metal Corporation

Nippon Steel Corporation

Masahito Hanao

Masayuki Kawamoto

Hiroshi Hayashi

Nobuhiro Okada

Atsushi Hirata

Yuichi Tsukaguchi

Manabu Adachi

Hiroaki Uchiyama

Kohei Fujimoto

Masatoshi Miyahara

Toshihiko Murakami

Masahiko Oka

Seiji Kumakura

Masaki Nagashima

Kouji Takatani

Hirohisa Kikuchi

Yoshinori Tanizawa

Masatsugu Ishibashi

Daiki Naito

Kozo Ota

A mold flux for continuous casting has a base material composition containing 25 to 60 mass % of CaO, 15 to 45 mass % of SiO, 5 to 25 mass % of F, 0.2 to 1.0 mass % of S, and 0 to 20 mass % of a total of LiO, NaO, and KO, and in the base material composition, f(1) is 0.90 to 1.90, f(2) is 0.10 to 0.40, f(3) is 0 to 0.40, and a total of CaO, SiO, F, S, LiO, NaO, and KO is 90 to 100 mass %.

Mold flux for continuous casting and continuous casting method

A primary object of the present invention is to provide a technique of avoiding occurrence of surface defects caused by an electromagnetic brake while checking internal defects with this electromagnetic brake, so that cleanliness of a cast steel can be improved compared with prior arts, and the present invention provides a method for continuously casting steel, the method comprising supplying molten steel into a funnel mold while applying an electromagnetic brake to an outlet flow discharged from an outlet port of an immersion nozzle, wherein magnetic flux density (B) of the electromagnetic brake is within a range of the following (Formula 1): 

Method for continuously casting steel

A mold flux is used in continuous casting of Ti-containing hypo-peritectic steel so as to prevent longitudinal cracks from forming on a surface of a slab. The mold flux contains CaO, SiO, an alkali metal oxide and a fluorine compound as major components. f(1), f(2) and f(3), which are calculated from the initial chemical composition, are (1.1&#x2212;0.5&#xd7;T) to (1.9&#x2212;0.5&#xd7;T), 0.05 to 0.40 and 0 to 0.40, respectively, if the Ti content of the molten steel (mass %) is T. The TiOcontent in the melting state during the casting is no more than 20 mass % and the ratio of the first peak height of perovskite to the first peak height of cuspidine in the mold flux film is no more than 1.0.

Mold flux for continuous-casting Ti-containing hypo-peritectic steel and method therefor

Provided is mold flux that can prevent longitudinal cracks from forming on a surface of a slab upon continuous-casting hypo-peritectic steel, wherein CaO, SiO, an alkali metal oxide and a fluorine compound are contained, 1.1&#x2264;(CaO)/(SiO)&#x2264;1.9, 0.10&#x2264;(CaF)/((CaO)+(SiO)+(CaF))&#x2264;0.40 and 0&#x2264;(alkali metal fluoride)/((CaO)+(SiO)+(alkali metal fluoride))&#x2264;0.10 are satisfied, a solidification temperature is no less than 1300&#xb0; C., and viscosity at 1450&#xb0; C. is no more than 0.1 Pa&#xb7;s.

Mold flux for continuous-casting steel

A primary object of the present invention is to provide a technique of avoiding occurrence of surface defects caused by an electromagnetic brake while checking internal defects with this electromagnetic brake, so that cleanliness of a cast steel can be improved compared with prior arts, and the present invention provides a method for continuously casting steel, the method comprising supplying molten steel into a mold while applying an electromagnetic brake to an outlet flow discharged from an outlet port of an immersion nozzle, wherein magnetic flux density (B) of the electromagnetic brake is within a range of the following (Formula 1): 

In a mold for continuously casting a round billet with a curved type continuous casting apparatus, assuming that D(m) is an inner diameter at a lower mold edge and R(m) is a curvature radius of an outer curvature side at the lower mold edge, when a rate of change Tp (%/m) in mold inner diameter per unit length along a casting direction is expressed by Formula 1, and when a rate of change Rp (%/m) in curvature radius of an outer curvature side per unit length along the casting direction is expressed by Formula 2, the rate of change Tp in mold inner diameter and the rate of change Rp in curvature radius satisfy a relationship expressed by Formula 3;=(1/)&#xd7;()&#xd7;100(%/)&#x2003;&#x2003;Formula 1=(1/)&#xd7;()&#xd7;100(%/)&#x2003;&#x2003;Formula 2where D in Formula 1 is a mold inner diameter at a distance x away from an upper mold edge and R in Formula 2 is a curvature radius of the outer curvature side at the distance x,=(/2)&#xd7;()&#x2003;&#x2003;Formula 3 Uniform and good contact is obtained between the billet and a mold inner peripheral surface over a whole circumference, so that the casting-defect-free high-quality round billet can stably be produced.

Continuous casting mold and continuous casting method of round billet

In a mold for casting a billet with a curved type continuous casting apparatus, D(m) is an inner diameter at a lower mold edge and R(m) is a curvature radius of an outer curvature side at the lower mold edge. When a rate of change Tp (%/m) in mold inner diameter per unit length along a casting direction is Tp=(1/D)&#xd7;(dD/dx)&#xd7;100 (%/m), and when a rate of change Rp (%/m) in curvature radius of an outer curvature side per unit length along the casting direction is Rp=(1/R)&#xd7;(dR/dx)&#xd7;100 (%/m), the rate of change Tp in mold inner diameter and the rate of change Rp in curvature radius satisfy a relationship expressed Rp=(Tp/2)&#xd7;(D/R), where D is a mold inner diameter at a distance x away from an upper mold edge and R in Formula 2 is a curvature radius of the outer curvature side at the distance x.

A method for continuously casting a billet with a small cross section in which a curved type or vertical type continuous casting machine is used while oscillating the mold upward and downward is characterized in that the casting machine is provided with a mechanism for withdrawing speed oscillation. The mechanism has structural play in the directions of driving and reverse driving in such a manner that the amount of a play-incurred displacement from the neutral position of the structural play in the direction of billet driving or reverse driving is &#xb1;2 to &#xb1;30 mm in the direction of driving on the pinch roll circumferential length equivalent basis. The mechanism produces a returning force toward the neutral position and operational parameters such as the billet length, the specific amount of secondary cooling water, the casting speed as well as the oscillation amplitude and frequency are optimized.

Method of continuous casting of small cross section billet

Continuously casting a billet with a small cross section by pouring molten steel into a mold using a cylindrical immersion nozzle is characterized by measuring the molten steel level in the mold using an eddy current sensor. The level is controlled based on the thus-measured value, motion of steel in the mold is adjusted by electromagnetic stirring, a cooling zone during the final period of solidification is disposed within a certain region ranging from the meniscus to the specific site, and casting speed is adjusted so that the region in which the solid phase ratio at the billet center is 0.3-0.99 may be included in the cooling zone during the final period of solidification. The secondary cooling water amount and the billet surface temperature at the entrance to the cooling zone the density of cooling water in the cooling zone during the final period of solidification are optimized.

Method for continuously casting billet with small cross section

A method of continuous casting of a steel employs a mold power having a viscosity of 0.5-1.5 poise at 1,300&deg; C. and a solidification temperature of 1,190-1,270&deg; C., in which the mass ratio of CaO to SiO is 1.2-1.9, and casting is carried out under the following conditions: casting speed is 2.5-10 m/minute; mold oscillation stroke is 4-15 mm; and specific cooling intensity in secondary cooling of a slab is 1.0-5.0 liter/kg-steel.

Method for continuous casting of steel

A mold powder for continuous steel casting, contains CaO, SiO.sub.2 and fluoride as the main components. The ratio by weight of CaO', represented by the following equation, to SiO.sub.2 is 0.9-2.8 and the CaF.sub.2 content is about 5-60 wt. %. The powder contains Na.sub.2 O in an amount of 0-25 wt. % and C in an amount of 0-10 wt. %.

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Kashima, Japan

Masahito Hanao