Abstract: A mixture as described herein and a process for forming a coherent refractory mass on a surface of a refractory comprised of at least one silicon compound, the process including providing a mixture comprised of combustible particles including silicon particles, refractory particles of one or a plurality of substances which constitute a major portion by weight of the mixture, and particles of another substance or precursor thereof which are nonmetallic and which cause the incorporation of silica, formed by the combustion of silicon, into a crystalline lattice within the coherent refractory mass; and projecting the mixture against the surface of a refractory, simultaneously with oxygen, so that the combustible particles react in an exothermic manner with the projected oxygen and release sufficient heat to form the refractory mass under the action of heat of combustion.

Abstract: A ceramic welding process for the formation of a coherent refractory repair mass on a surface of an electrocast refractory material includes providing an electrocast refractory material having a surface to be repaired; providing a first powder mixture comprised of combustible particles, refractory particles, and at least one constituent which enhances production of a vitreous phase in the coherent refractory repair mass; and projecting the first powder mixture in a gas stream containing oxygen against the surface to be repaired so that the combustible particles react with the projected oxygen against the surface in a highly exothermic manner and release sufficient heat of combustion to form a first coherent refractory repair mass.

Abstract: A ceramic welding process for forming a coherent refractory mass on a surface of a refractory which is hot and which is comprised of at least one silicon compound includes providing a mixture composed of combustible particles including silicon particles, refractory particles which are silicon carbide particles and which constitute a major portion by weight of the mixture, and particles of one of (a) another substance selected from the group consisting of CaO, MgO, FeO, and mixtures thereof or (b) particles of a nonmetallic precursor of the another substance, which another substance causes incorporation of silica, formed by combustion of the silicon particles, into a crystalline lattice of a compound formed between the silica and the another substance within the coherent refractory mass being formed; and projecting the mixture against the surface of the refractory, simultaneously with substantially pure oxygen, so that the combustible particles react in an exothermic manner by combusting with the projected oxy

Abstract: A process for forming a coherent refractory mass on a surface of a refractory, which refractory includes at least one silicon compound, the process including providing a mixture including (1) combustible particles including silicon particles, (2) refractory particles of one or a plurality of substances which constitute a major portion by weight of the mixture, and (3) particles of another substance or precursor of the another substance which particles are nonmetallic and which another substance causes incorporation of silica, formed by combustion of the silicon particles, into a crystalline lattice of a compound formed between the silica and the another substance within the coherent refractory mass to be formed; and projecting the mixture against the surface of a refractory, simultaneously with oxygen, so that the combustible particles react in an exothermic manner with the projected oxygen and release sufficient heat to form the coherent refractory mass under action of heat of combustion and so that silica i

Abstract: A ceramic welding process, including projecting a ceramic welding powder including a mixture of refractory particles and fuel particles composed of a fuel material which is capable of being oxidized to form a refractory oxide against a surface in at least one stream of carrier gas which contains at least sufficient oxygen for substantially complete oxidation of the fuel particles, whereby sufficient heat is released for at least surface melting of the projected refractory particles and a ceramic weld mass is formed against the surface under the heat of oxidation of the fuel particles; and projecting at least one additional stream of gas selected from the group consisting of carbon dioxide, nitrogen, and a gas containing oxygen against the surface so as to form a substantially continuous gas curtain surrounding the at least one stream of carrier gas.

Abstract: A composition of matter which is a powder mixture for use in a process of forming a porous refractory mass on a surface, the composition including refractory particles, fuel particles which are capable or reacting exothermically with an oxidizing gas to forming at least one refractory oxide and which are present in a quantity effective to release, on projection together with the oxidizing gas, sufficient heat to melt at least the surfaces of the refractory particles so that the refractory particles and at least some of the at least one refractory oxide bond together; and particles of porosity-inducing material comprised of at least one of hollow and porous particles which become incorporated in the refractory mass formed on projection and which have at least one of a composition and a particle size selected so that incorporation of the porosity-inducing material in the powder mixture results in the formation of porosity within the refractory mass formed on projection.

Abstract: A process for forming a porous refractory mass on a surface is characterized in that an oxidizing gas is projected against that surface together with a powder mixture which comprises: refractory particles; particles of fuel which reacts exothermically with the oxidizing gas to form refractory oxide and release sufficient heat to melt at least the surfaces of the refractory particles so that they bond together to form the refractory mass; and particles of material whose composition and/or size is selected so that the incorporation of such material in the projected mixture results in the formation of porosity within the refractory mass formed. The porosity-inducing material may be such as to burn to evolve gaseous combustion products, it may decompose to gaseous decomposition products, or it may itself be porous or hollow.

Abstract: A process of forming a coherent refractory mass on a surface comprises projecting against that surface, together with oxygen, a mixture of refractory particles and fuel which reacts in an exothermic manner with the projected oxygen to release sufficient heat to melt at least the surfaces of the refractory particles and thus form the refractory mass. The projected mixture contains, as fuel, finely divided particles of at least one element which is oxidizable to form a refractory oxide and it also contains carbonaceous particles which are of such a size or composition that carbon particles become occluded in the formed refractory mass. The mixture may contain, as said fuel, finely divided particles having a mean grain size of less than 50 .mu.m of silicon, aluminum and/or magnesium. The carbonaceous particles may comprise a carbonaceous core which is covered by a mantle inhibiting oxidation of the core.

Abstract: An apparatus for forming a refractory mass on a surface of a substrate by spraying against the surface a mixture of particles including oxidizable particles and refractory particles in a carrier gas, which carrier gas may contain oxygen but is not substantially all oxygen, and combusting the oxidizable particles to generate sufficient heat to soften or melt at least the surfaces of the refractory particles and form the refractory mass, which apparatus includes means for mixing the mixture of particles with a stream of the carrier gas; a lance having an outlet; a feed line for conveying the carrier gas and entrained mixture of particles to the lance outlet for spraying and having defined therein at least one orifice located downstream of the mixing means and at least 1 m from the lance outlet; and means for introducing oxygen gas into the carrier gas and entrained mixture of particles connected to the at least one orifice defined in the feed line.

Abstract: In processes of forming a refractory mass on a surface, a mixture of refractory particles and oxidizable particles which react exothermically with oxygen to generate sufficient heat to soften or melt at least the surfaces of the refractory particles are sprayed against that surface to bring about formation of said refractory mass. To promote the reliable and consistent formation of a durable refractory mass, the granulometry of the particles which are sprayed in the mixture is such that the 80% and 20% grain sizes of the refractory particles (that is, the screen mesh sizes G.sub.80 and G.sub.20 through which respectively 80% and 20% by weight of the particles will pass) have a mean greater than the mean of the 80% and 20% grain sizes of the oxidizable particles and the size range spread factor f(G) of the refractory particles is at least 1.

Abstract: When forming a refractory mass on a surface a mixture of oxidizable particles and refractory particles in a comburent carrier gas is sprayed against that surface from an outlet of a lance. Thus on combustion of the oxidizable particles, sufficient heat is generated to soften or melt at least the surfaces of the refractory particles to bring about the formation of the refractory mass. The mixture of particles is itself mixed with a carrier gas stream, for example, by using venturi, and is fed along a line towards a lance outlet. Oxygen is introduced into such feed line at at least one location along the feed line and is mixed with the carrier gas/particle mixture during its flow towards the lance outlet before reaching that outlet, and preferably at least 1 meter from the outlet of the lance.

Abstract: A process of forming a coherent refractory mass on a surface comprises projecting against that surface, together with oxygen, a mixture of refractory particles and fuel which reacts in an exothermic manner with the projected oxygen to release sufficient heat to melt at least the surfaces of the refractory particles and thus form the refractory mass. The projected mixture contains, as fuel, finely divided particles of at least one element which is oxidizable to form a refractory oxide and it also contains carbonaceous particles which are of such a size or composition that carbon particles become occluded in the formed refractory mass. The mixture may contain, as said fuel, finely divided particles having a mean grain size of less than 50 .mu.m of silicon, aluminium and/or magnesium. The carbonaceous particles may comprise a carbonaceous core which is covered by a mantle inhibiting oxidation of the core.