Abstract: A process for the in-ladle treatment of liquid steels by injecting gas through the ladle bottom. The process comprises injecting at least one inert gas from locations which are distributed over the ladle bottom in such a way as to form at the surface of the liquid steel an annular swelling, the outside edge of which is close to the inside edge of the lining of the wall of the ladle. An oxidizing gas may be mixed with the inert gas for decarburization. The process is applied in particular to the treatment of carbon steels.

Abstract: Spray nozzle permitting the spraying of liquid, having a body provided with a cylindrical chamber of given diameter for the passage of a liquid into a nozzle in which the nozzle liquid outlet has a plurality of equidistantly spaced, identical holes, whose axes are inclined relative to the nozzle axis. A member positioned at the intake of the liquid into the nozzle defines a passage for the liquid outflow, and has a diameter less than the diameter of the chamber. The member has a concave face at the inlet and a constriction of the passage limits the liquid flow entering the nozzle. Fixing means permit the member to be fixed to the nozzle body.

Abstract: A device for fluidizing and distributing a powder in suspension in a carrier gas, characterized in that it comprises, between an inlet conduit fed with said powder and an outlet conduit adapted to distribute the powder once fluidized, a separating means dividing said inlet conduit into two pipes which open and converge into a chamber communicating with said outlet conduit.

Abstract: The apparatus comprises a plasma torch capable of an output speed of at least 100 m/s, a fine powder distributor, and a substrate holder which can be heated electrically and cooled by water, which is at an adjustable distance from the torch, and which is movable in two transverse directions at adjustable speeds. The method consists in starting from ceramic having a low roughness CLA and from powder having a narrow granulometric distribution over an average value of at most 10 .mu.m, and projecting the melted powder onto the substrates kept at a regulated temperature and subjected to the said transverse movements.