Abstract: A killed and vacuum-degassed very-low-carbon steel containing, by weight, between 0.10 and 0.35% manganese, less than 0.006% nitrogen, less than 0.025% phosphorus, less than 0.020% sulphur, less than 0.020% silicon, at most 0.08% of at least one of the elements copper, nickel and chromium, as well as aluminum. The steel is cast in the form of a slab, the slab is hot rolled in order to obtain a hot-rolled sheet, the hot-rolled sheet is coiled, the hot-rolled sheet is cold rolled in two rolling operations separated by a continuous annealing operation. The steel contains at most 0.006% carbon by weight and 0.010% aluminum and the hot-rolled sheet is coiled at a temperature below 620° C. Preferably, the steel is killed by mixing with a slag containing adjusted amounts of aluminum and of alumina.

Abstract: A method of making a powder for covering an ingot mold for the continuous casting of steel, in particular steels with ultra-low carbon content. The powder comprises a base powder and particles of at least one metal nitride, its free carbon content being between 0 and 1% by weight, the method comprising forming a slip of raw materials for the basis powder, at least one metal nitride and water and atomizing the slip to form a mist and drying the mist to form granules having diameters lying between 20 &mgr;m and 800 &mgr;m.

Abstract: A powder for covering an ingot mold for the continuous casting of steel, in particular steels with ultra-low carbon content. The powder comprises a base powder and particles of at least one metal nitride, its free carbon content (%C.sub.free) being between 0 and 1% by weight, it being produced by atomization, and having the form of granules of between 20 and 800 .mu.m in diameter. In one application of the invention, the nitride is silicon nitride, and its weight content (%Si.sub.3 N.sub.4) is equal to: %Si.sub.3 N.sub.4 =0.5-0.28.times.%C.sub.free .+-.0.10.