Abstract: A nozzle orifice of a nozzle (1) includes a tapered segment (16) extending from an elliptical discharge orifice (15) and having a taper angle ? of 30 to 80°, and a large-diameter segment (18) continuing with the tapered segment. The ratio of the inner diameter of large-diameter segment (18) relative to the minor diameter of the discharge orifice (15) is not less than 3 and less than 7. Also, the discharge how from the nozzle spreads in a single direction (width direction) within a plane perpendicular to the central axis of the nozzle and the erosion thickness angle is 1.5 to 3° in the direction (thickness direction), perpendicular to the width direction. Such a descaling nozzle enables that scale is removed efficiently at low pressure and/or low flow rate while restraining the cooling of a steel plate.

Abstract: A nozzle orifice of a nozzle 1 comprises a tapered segment 16 extending from an elliptical discharge orifice 15 and having a taper angle ? of 30 to 80°, and a large-diameter segment 18 continuing with the tapered segment, and scale on a steel plate is removed by discharging water from the nozzle at a distance between discharge orifice 15 and the steel plate of not more than 600 mm, a pressure of 5 to 30 MPa, and a discharge flow rate of 40 to 200 l/minute. The ratio of the inner diameter of large-diameter segment 18 relative to the minor diameter of the discharge orifice 15 is not less than 3 and less than 7. Also, the discharge flow from the nozzle spreads in a single direction (width direction) within a plane perpendicular to the central axis of the nozzle and the erosion thickness angle is 1.5 to 30 in the direction (thickness direction) perpendicular to the width direction.

Abstract: A method of controlling a furnace pressure for preventing air from intruding to a heating furnace, a method of stable operation during low combustion load of heat regenerating burners and a method of measuring concentration of an atmospheric gas in a heating furnace are proposed.

Abstract: A ladle after teeming for a continuous casting and a subsequent slag discharge is mounted on a ladle truck and then moved by the ladle truck to a tapping station. The ladle on the ladle truck is then stationed over a predetermined stand-by time and is then immediately moved to a tapping position to receive a molten steel from a converter. The ladle is quickly heated during the stand-by time, by a regenerative-type burner system carried by a ladle lid which is attached to the ladle to cover the top opening of the ladle. This allows the tapping temperature of the molten steel to be set to a low level, offering advantages such as a remarkable reduction in the consumption of carbonaceous materials as the temperature controller, as well as extended life of ladle refractories through suppression of thermal attack. At the same time, consumption of fuel gas for heating the ladle by the burner system is reduced to contribute to saving of energy.

Abstract: A method of controlling a furnace pressure for preventing air from intruding to a heating furnace, a method of stable operation during low combustion load of heat regenerating burners and a method of measuring concentration of an atmospheric gas in a heating furnace are proposed. When the heat recovered with burners each attached with a heat regeneration body is used for heating the combustion air of burners at a combustion state, the suction ratio of the exhaust gas from the burners to the heat regeneration body is adjusted to control the furnace pressure in accordance with a combustion load on an entire heating furnace. The furnace pressure is controlled by adjusting the flow rate of dilution air in accordance with the temperature of the exhaust gas in the exhaust stack on the inlet side of a recuperator in the heating furnace and the combustion load on the heating furnace.

Abstract: A method of adjusting coating weight of a coating material with high accuracy within a wide range of operation, by setting and using a relational formula for determining a coating weight W of the coating material separately in accordance with relative relation between a nozzle-strip distance D and a nozzle slit clearance B. The adjustment of the coating weight of molten metal (coating material) is performed by controlling a nozzle pressure P and a strip speed V, and also by controlling D by equation (1) in the range of D/B.ltoreq.C (developing range) and at least one of D and B by equation (2) in the range of D/B>C (fully developed range). (.rho..sub.M =molten metal density, .mu.=molten metal viscosity, P.sub.A =pressure at nozzle outlet, .eta.=nozzle efficiency, K=ratio of specific heat of gas, and h.sub.1 and h.sub.2 =constants)W=h.sub.1 .times..rho..sub.M .times.{(K-1)/(2.times..eta..times.K.times.P.sub.A)}.sup.1/2 .times.D.sup.1/2 .times.[.mu..times.V/{(P/P.sub.A).sup.(K-1)/K -1}].sup.1/2(1)W=h.sub.2 .