Tundish Metallurgy May08

Tundish Metallurgy

Tundish Metallurgy To transfer liquid steel from a teeming ladle to the continuous casting machine mould, an intermediate vessel, called a tundish, is used. Tundish is a rectangular big end up, refractory lined vessel, which may have a refractory lined lid on the top. The tundish bottom has one or more nozzle port(s) with slide gate(s) or stopper rod(s) for controlling the flow of liquid steel. Tundish is often divided into two sections namely (i) an inlet section, which generally has a pour box and where liquid steel is fed from the steel teeming ladle, and (ii) an outlet section from which liquid steel is fed into the continuous casting machine mould(s). Various flow control devices, such as dams, weirs, baffles with holes, etc., may be arranged along the length of the tundish. Longer path is preferred to prolong residence time of liquid steel to promote floatation of macro inclusions. Important tundish metallurgy elements of a tundish are shown in Fig 1. Fig 1 Important tundish metallurgy elements of a tundish The continuous casting tundish serves as a buffer and links the discontinuous process of the secondary steel making in the ladle with the continuous casting process in the mould. It acts as a reservoir during the ladle change periods and continues to supply liquid steel to the mould when incoming liquid steel is stopped, making sequential casting by a number of ladles possible. The main causes for inclusion formation and contamination of the liquid steel include reoxidation of the liquid steel by air and carried over oxidizing ladle slag, entrainment of tundish and ladle slag, and emulsification of these slags into the liquid steel. These inclusions must be floated out of the liquid steel during its flow through the tundish before being teemed...