Nippon Steel Corporation

Mitsuo Uchimura

Shigenori Tanaka

Akinobu Murasato

Takashi Sawai

Yasuharu Sakuma

Yasushi Nakamura

Masahiro Doki

Junji Nakashima

Michihisa Itou

Toyoichiro Higashi

Jun Fukuda

Hiroshi Ohba

A billet produced by continuous casting having little central segregation, in particular a billet of high carbon steel produced by continuous casting, and a manufacturing method therefor are provided. In the continuous casting billet, the size of the dendritic equiaxed crystal in a billet central portion is reduced to be not more than 6 mm. For this purpose, electromagnetic stirring is performed so that the inclining angle of the primary dendrite within 10 mm of a billet surface layer is increased to be not less than 10&#xb0;. Furthermore, the mechanical soft reduction is performed during continuous casting so that the diameter of the center porosity in the billet central portion is reduced to be not more than 4 mm. Thereby, in particular in the manufacturing of the continuous casting billet having a carbon content of not less than 0.6% by mass and a billet size of not more than 160 mm can be provided a billet in which breaking troubles in wire drawing after rolling to a rod are reduced by reducing the central segregation in the billet.

Billet by continuous casting and manufacturing method for the same

The present invention provides a steel for steel sheets excellent in workability and showing significantly decreased formation of surface defects, and a method of deoxidizing molten steel for the steel for steel sheets which prevents nozzle clogging during continuous-casting the molten steel. That is, the steel for steel sheets excellent in workability, comprises, based on weight, 0.0001 to 0.0030% of C, up to 0.03% of Si, 0.05 to 0.30% of Mn, up to 0.015% of P, 0.001 to 0.015% of S, up to 0.008% of Al, 0.02 to 0.08% of Ti, 0.0005 to 0.0020% of Ca, 0.0005 to 0.01% of N, optionally containing at least one of 0.001 to 0.02 wt % of Nb and 0.0001 to 0.0010 wt % of B, and the balance of Fe and unavoidable impurities. Moreover, the deoxidation method of the steel for steel sheets comprises properly adjusting addition amounts of Ca and Al as deoxidizing agents for the steel having the chemical composition mentioned above so that the chemical composition of the nonmetallic inclusions is controlled to prevent clogging of the casting nozzle.

Steel for steel excellent in workability and method of deoxidizing same

A low-carbon ferrochrome alloy containing a decreased amount of nitrogen can be made by this method. This method is conducted in a hydrogen stream and does not necessitate use of vacuum technique. A product of high purity can be obtained relatively simply and economically.

Method for decreasing the amount of carbon and nitrogen contained in the

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Kimitsu, Japan

Mitsuo Uchimura