Stopper for continuous casting and continuous casting method

A stopper for continuous casting comprising:

• a cavity for conveying gas in a vertical direction center of the stopper;
• one or a plurality of gas discharge holes passing through from the cavity to the outside in a distal center or a side surface of a reduced-diameter region including a fitted portion to a lower nozzle;
• and
• a pressure control component in a part of the reduced-diameter region, the part being above the gas discharge hole within the cavity,
• wherein the pressure control component is made of a dense refractory having no gas permeability under a condition of pressurizing a sample of the refractory having a length of 20 mm at 8×10−2 MPa,
• wherein the pressure control component includes one or a plurality of through holes disposed within the pressure control component or between an outer periphery of the pressure control component and a body of the stopper so as to pass through from an upper end to a lower end between the pressure control component or the outer periphery of the pressure control component and the body of the stopper,
• wherein the through hole has a diameter having a size between φ0.2 mm and φ2 mm both inclusive, the size being obtained by assuming a cross section of the hole as a circular shape and converting the cross section into a circle, and
• wherein the number of through holes satisfies Equations 1 and 2:
• (−0.44×Hd2+1.88Hd−0.08)≤Ha≤{1.67×ln(Hd)+3.66} Equation 1
• Hn=Ha÷(Hd2×π÷4) Equation 2, where
• Ha is a numerical value of a total cross-sectional area of the through hole(s),
• Hn is the number of through holes,
• Hd is a numerical value of a diameter of the through hole, and
• π is a circular constant,
• with the total cross-sectional area measured in mm2 and the diameter of the through hole measured in mm.