Patent ID: 8469243

Claim:
A molten metal discharge nozzle formed with an inner bore for allowing passage of molten metal and designed to be installed to a bottom of a molten metal vessel so as to discharge molten metal from the molten metal vessel through the inner bore, wherein a cross-sectional shape of a wall surface of the inner bore, taken along an axis of the inner bore, comprises a part or an entirety of a curved line expressed by the following formula (1): log(r(z))=(1/n)×log((Hc+L)/(Hc+z))+log(r(L)) (1), where: 6≧n≧1.5; L is a length of the nozzle; Hc is a calculative hydrostatic head; and r(z) is a radius of the inner bore at a position located a distance z downward from an upper end of the nozzle, the calculative hydrostatic head Hc being expressed by the following formula (2): Hc=((r(L)/r(0)) n ×L)/(1−(r(L)/r(0)) n ) (2), where: 6≧n≧1.5; r(0) is a radius of the inner bore at the upper end of the nozzle; and r(L) is a radius of the inner bore at a lower end of the nozzle, and wherein, in a graph where the distance z is plotted with respect to a horizontal axis (X-axis) thereof, and a pressure of molten metal at a center of the inner bore in horizontal cross-section at a position located the distance z is plotted with respect to a vertical axis (Y-axis) thereof, an approximation formula of a line on the graph is established without simultaneously including two or more coefficients having opposite signs, and wherein, on an assumption that the line is derived from an approximation formula based on a linear regression, an absolute value of a correlation coefficient of the line is 0.95 or more.