Sumitomo Metal Industries, Inc.

Yuichi Tsukaguchi

Hiroshi Hayashi

Atsushi Hirata

Masahito Hanao

Masayuki Kawamoto

Manabu Adachi

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.

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Kashima, Japan

Yuichi Tsukaguchi