Abstract: A method of producing a composite metal material such as clad bloom by continuous casting comprises the steps of supplying molten metals of different compositions by using two immersion nozzles into the strand pool at different positions and forming a static magnetic field zone on the boundary between the two types of metals to prevent mixing of the metals of different composition. The method enables production of a composite material exhibiting a sharp boundary between the two types of metals used and enables the thickness of the respective metal layers to be easily controlled by adjusting the location of application of the static magnetic field or the withdrawal speed of the strand of cast metal.

Abstract: Production of boron-containing steel slabs free from surface defects by continuous casting, particularly prevention of the slab surface crackings by cooling the slab with a specific cooling rate through the temperature range from the melting point to 900.degree. C. so as to prevent boron-containing compounds such as BN from precipitating along the austenite grain boundary. Great advantage over the conventional art is that boron-containing molten steels which could not be continuously cast can be successfully continuously cast into slabs free from surface defects.