Apparatus and method for continuously casting steel slabs

A method of continuously casting thin slabs of metal having a substantially greater width then thickness, comprising the steps of:

• causing molten metal to flow through a mold tube having a cross-sectional shape corresponding to the cross-sectional shape of the slab being cast, said mold tube including an inlet, an outlet, relatively wide opposite faces, relatively narrow opposite sides edges and opposite corners, and said molten metal defining a meniscus zone as it flows through the mold tube;
• dividing the surface of the mold tube into a plurality of different cooling zones, including a first cooling zone extending completely over the length and width of each side edge and over small, adjacent portion of the width of each face along the entire length of the face, and a plurality of additional cooling zones arrayed along the length of each face of the mold from the inlet to the outlet thereof, said additional cooling zones each extending completely across the width of each face of the mold between said first cooling zones at the edges, and each extending over only a portion of the length of the mold;
• predetermining a ratio of the rate of heat extraction in one zone in relation to the rate of heat extraction in another zone to obtain uniform cooling of the cast slab and thereby minimize surface cracks and other casting flaws int he cast slab;
• providing cooling means in association with each cooling zone for extracting heat at a different rate in each zone in accordance with said predetermined ratios;
• and
• selectively and controllably cooling the mold tube at said different heat extraction rates in the different zones to effect the greatest rate of heat extraction in a cooling zone extending over the relatively wide faces of the mold tube from the inlet to the meniscus zone, and the least rate of heat extraction in the first cooling zone at the relatively narrow side edges of the mold tube.