Kawasaki Steel Corporation

Jfe Steel Corporation

Chikashi Tada

Sumio Yamada

Toshikazu Sakuraya

Hajime Bada

Keizo Taoka

Yuji Miki

Kenichi Sorimachi

Saburo Moriwaki

Masato Kumagai

Seiji Itoyama

Hisahiro Matsunaga

Hidenari Kitaoka

Hidemitsu Negishi

Chitoshi Matsumura

Shinichi Kaneko

Takahiro Mitumune

Masafumi Maeda

Rei Yamada

Molten steel is refined in an electric furnace by using iron scrap as a main iron source, and is tapped into a separate refining vessel. Thereafter, metallic-Al containing material and CaO are added onto a bath surface of the molten steel, and an oxygen containing gas is supplied to the molten steel. Thereby, a nitrogen-removal reaction utilizing an AlN formation reaction is caused to proceed. Consequently, even in the case of molten steel having a low carbon content, a low-nitrogen steel can be refined and produced at low costs.

Removal method of nitrogen in molten steel

The slag in a molten state formed at a step of refining stainless steel is adjusted such that the slag has a basicity in the range of 1.3-4.0, and the slag is mixed with a sulfur-containing material wherein the sulfur is zero or minus in valence, thereby setting the concentration of sulfur in the slag to be not less than 0.2% by weight. The slag is so modified that Cr is substantially completely prevented from being eluted and can be effectively utilized as a roadbed material and a reclamation material for civil works. The slag is quenched at such a speed of cooling that the temperature of the slag is decreased from 1200&deg; C. to 400&deg; C. within 48 hours so that noticeable effects are attained.

Method for the treating stainless steel refining slag

Water-cooling slabs by dipping to yield steel sheets with a minimum of scabs and uneven gloss, with their larger faces upside and underside, by water injection at a flow rate of 10-150 L/m,&middot;min perpendicular or oblique to the underside of the slabs, with the position of water injection 30-500 mm away from the underside of the slabs.

Method for water-cooling hot metal slabs

A mold powder for use in continuous casting, containing specified amounts of CaO, Al.sub.2 O.sub.3, TiO.sub.2, Li.sub.2 O, BaO, MgO, F and Na.sub.2 O, and further containing at least one of BN and C as aggregate. The mold powder, when used in continuous casting of a steel rich in strong reducing metal elements such as Al, Ti, REM and so forth, remarkably suppresses generation of deterioration in the surface quality of the slab and break out of the slab which are attributable inferior lubrication.

Mold powder for continuous casting

Reduction of chromium oxide is performed by utilizing refinement or reduction container having top-blowing capability. Chromium oxide is charged in the molten iron bath in the aforementioned container. Content of slag is adjusted to maintain the following condition:

Method for producing chromium containing molten iron with low sulphur

A process of production of chromium containing molten iron generally comprises two steps. In a first step, top and bottom-blown reduction for reducing chromium is performed with charging carbon containing material and slag forming agent from the top of a converter for melting stainless scrap and for rising temperature of molten iron bath. In a second step which is performed subsequently to the first step, top and bottom-blown injection with charging chromium oxide and carbon from the top of the converter for reduction of chromium.

Process for producing chromium containing molten iron

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Tokyo, Japan

Chikashi Tada