Mold with convex sidewalls for continuous casting machines

A mold for a continuous metal casting machine comprising:

• a. a plurality of substantially vertical mold walls defining an open ended mold cavity;
• b. said plurality of mold walls comprises a pair of vertical planar sidewalls spaced apart in mutually facing parallel arrangement and a pair of end walls narrower than said sidewalls, with said end walls spaced apart in mutually facing parallel arrangement between the sidewalls, said end walls each define a vertical surface which is continuously convex from one of said sidewalls to the other of said sidewalls and with a crest extending between the open ends of the mold, and the adjacent engaging surfaces of said sidewalls and end walls defining four acute included angular corners extending vertically between the upper and lower ends of the open ended mold cavity for casting therein a continuous strand having at least a shell of solidified metal with a pair of oppositely facing flat planar surfaces and a pair of oppositely facing surfaces each defining a continuous concave arch;
• and
• c. at least one of said convex end walls is movable between the flat and planar sidewalls and toward and away from the other of the convex end walls.