Container for molten metal, use of the container and method for determining an interface

A tundish for molten metal comprising:

• an outlet for outflow of the molten metal from the tundish, the outlet being located in a bottom portion of the tundish;
• a tapered bushing fixed in a wall of the tundish, the tapered bushing being made of refractory material and having an inner sidewall and an outer sidewall, each of the inner sidewall and outer sidewall having a conical shape and a diameter which becomes smaller toward an interior of the tundish;
• and
• a temperature measuring device arranged in the tapered bushing, the temperature measuring device comprising:
• a monolithic protective sheath projecting into the tundish interior and having a closed end arranged in the tundish interior, the protective sheath being tapered along at least part of its length such that a diameter of the protective sheath becomes smaller toward the tundish interior, the protective sheath consisting essentially of a mixture of a heat-resistant refractory metal oxide and graphite and a length of the protective sheath extending through substantially an entire thickness of the tundish wall to the closed end of the protective sheath, the closed end of the protective sheath projecting into the tundish interior at least 50 mm from the tundish wall,
• an opening extending inside the protective sheath from an end opposite the closed end,
• a temperature measuring element arranged in the opening of the protective sheath in a close fitting relationship, the temperature measuring element being substantially inseparable from the protective sheath, an end of the temperature measuring element facing away from the tundish interior having a connector, and
• a protective tube is arranged in the protective sheath and surrounding the temperature measuring element, an outer diameter of the protective tube being smaller than a diameter of the opening of the protective sheath, the protective tube being spaced apart from the protective sheath at a distance of 0.1 to 1.0 mm,
• wherein the tapered bushing is fixed in the tundish wall between the tundish wall and the protective sheath and wherein the protective sheath is fixed into the tapered bushing by a dense, powder-free refractory cement.