A magnetic pump in a pump well in a molten metal furnace with a long, relatively thin side wall that wraps around a significant fraction of the circumference of the pump, which facilitates creation of an eddy current based flow field in the molten material with better magnetic coupling, thereby enhancing the effectiveness of the pump. Breach of the well wall will not result in spillage of metal outside the furnace, and the well can be monitored for any such breach or other change so that the pump can be lifted out of the well to protect it from contact with the molten metal in the event of such a breach, or other appropriate action can be taken.

A steel sheet according to the present invention includes a predetermined chemical composition, in which amounts of each elements by mass % in the chemical composition satisfy both of expression 0.3000{Ca/40.88+(REM/140)/2}/(S/32.07) and expression Ca0.00580.0050C, and a number density of carbonitrides including Ti which exists independently and has a long side of 5 m or more is limited to 5 pieces/mm.sup.2 or less.

Provided are a molten metal refining device and method. The molten metal refining method includes: preparing molten metal; dipping an impeller into the molten metal; supplying a liquid dephosphorization agent on top of the molten metal; and stirring the molten metal by rotating the impeller, wherein a solid dephosphorization agent in a powder state is supplied through the lower portion of the impeller in the stirring of the molten metal, thereby improving the stirring efficiency of the molten metal and efficiently controlling the phosphorus concentration in the molten metal.

Provided are a molten metal refining device and method. The molten metal refining method includes: preparing molten metal; dipping an impeller into the molten metal; supplying a liquid dephosphorization agent on top of the molten metal; and stirring the molten metal by rotating the impeller, wherein a solid dephosphorization agent in a powder state is supplied through the lower portion of the impeller in the stirring of the molten metal, thereby improving the stirring efficiency of the molten metal and efficiently controlling the phosphorus concentration in the molten metal.

A pump for transferring molten metal is provided. The pump includes a motor, a base having an impeller chamber, a shaft connected to the motor at one end, an impeller connected to the other end of the shaft and rotatable in the impeller chamber, and a riser disposed on an upper surface of the base. The base includes a shaft opening and an outlet opening in a top surface. The riser assembly has a first open end facing the base. The first open end is dimensioned to encompass the shaft opening and the outlet opening.

Disclosed are degassers, couplings, impeller shafts and impellers for use in molten metal. One such coupling transfers gas into an impeller shaft, the coupling having a smooth, tapered internal surface to align with a corresponding surface on the impeller shaft and help prevent gas leakage and to assist in preventing damage to the impeller shaft. Improved impellers for shearing and mixing gas are also disclosed, as is a degasser including one or more of these components.

An impeller for stirring a melt pool includes: an impeller body extending in the length direction; a blowing nozzle which is provided in such a way as to pass through one part at the bottom end of the impeller body; and a blade provided on the upper part of the impeller body. As a result, when the impeller is used, a stirring flow produced due to the blade and a stirring flow due to substances blown into the melt-pool via the blowing nozzle correspond to each other, and the two flows are combined such that the overall stirring force is improved. Consequently, it is possible to improve the efficiency of stirring by the impeller as compared with hitherto, and, as a result, refining efficiency in the refining step is improved as the rate of reaction between the melt-pool and additives is increased.

An impeller for stirring a melt pool includes: an impeller body extending in the length direction; a blowing nozzle which is provided in such a way as to pass through one part at the bottom end of the impeller body; and a blade provided on the upper part of the impeller body. As a result, when the impeller is used, a stirring flow produced due to the blade and a stirring flow due to substances blown into the melt-pool via the blowing nozzle correspond to each other, and the two flows are combined such that the overall stirring force is improved. Consequently, it is possible to improve the efficiency of stirring by the impeller as compared with hitherto, and, as a result, refining efficiency in the refining step is improved as the rate of reaction between the melt-pool and additives is increased.

After molten metal has been poured from a ladle 6 into a converter, metal 6b adhering to the ladle 6 is dropped into the ladle 6 on-line, and molten metal is poured from an electric furnace into the ladle 6 into which the metal 6b has been dropped. As a result, the metal 6b is melted and is recovered as a material.

Disclosed are degassers, couplings, impeller shafts and impellers for use in molten metal. One such coupling transfers gas into an impeller shaft, the coupling having a smooth, tapered internal surface to align with a corresponding surface on the impeller shaft and help prevent gas leakage and to assist in preventing damage to the impeller shaft. Improved impellers for shearing and mixing gas are also disclosed, as is a degasser including one or more of these components.