Abstract: A method of repairing an oxide-based refractory body by projecting a powder mixture against a hot surface of the body and in the presence of oxygen to provide a refractory repair mass includes providing a powder mixture composed of particles of at least one refractory oxide; fuel particles which react in an exothermic manner with the oxygen to form a refractory oxide and which are particles composed of at least one element selected from the group consisting of magnesium, aluminum, silicon, and mixtures thereof; and particles of silicon carbide present in an amount which is effective to provide a reduced porosity of the refractory repair mass and which does not exceed 10% by weight based on the weight of the powder mixture; and projecting the powder mixture against a hot surface of the oxide-based refractory body and in the presence of oxygen. Preferably, the powder mixture contains at least 1%, most preferably from 1 to 5%, by weight of the particles of silicon carbide.

Abstract: In ceramic welding processes, oxidizing gas and a mixture of refractory and fuel powders are projected against a surface and the fuel is burnt to generate sufficient heat that the refractory powder becomes at least partially melted or softened and a cohesive refractory weld mass is progressively built up against that surface. In order to reduce any tendency for the weld mass to include a low-grade refractory phase and thus promote the refractoriness of that weld mass, the fuel powder is present in a proportion of not more than 15% by weight of the total mixture and includes at least two metals selected from aluminum, magnesium, chromium and zirconium, in that at least the major part by weight of the refractory powder consists of one or more of magnesia, alumina and chromic oxide, and in that the molar proportions of silica and calcium oxide present in the refractory powder (if any) satisfy the following expression:molar concentration of SiO.sub.2 in %.ltoreq.0.2+molar concentration of CaO in %.

Abstract: The invention concerns a ceramic welding process in which a mixture of refractory and fuel particles is projected from an outlet at an end of a lance in a gas stream against a target surface where the fuel particles combust in a reaction zone to produce heat to soften or melt the projected refractory particles and thereby form a coherent refractory weld mass. A method of monitoring the distance between the lance outlet and the reaction zone is disclosed in which the reaction zone and at least part of the gap between that reaction zone and the lance outlet is monitored by a camera and an electronic signal is produced indicative of the distance ("the working distance") between the lance outlet and the reaction zone.

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: In ceramic welding processes, oxidising gas and a mixture of refractory and fuel powders are projected against a surface and the fuel is burnt to generate sufficient heat that the refractory powder becomes at least partially melted or softened and a cohesive refractory mass is progressively built up against that surface. In order to reduce any tendency for the weld mass to include a low-grade refractory phase and thus promote the refractoriness of that weld mass, the fuel powder is present in a proportion of not more than 15% by weight of the total mixture and includes at least two metals selected from aluminium, magnesium, chromium and zirconium, and in that at least the major part by weight of the refractory powder consists of one or more of magnesia, alumina and chromic oxide, and in that the molar proportions of silica and calcium oxide present in the refractory powder (if any) satisfy the following expression: molar concentration of SiO.sub.2 in % .ltoreq.0.

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.