Abstract: A method of repairing an eroded refractory wall pierced by one or more openings using a ceramic welding technique. A member of shape substantially complementary to the desired shape of the repaired opening is placed into each opening so that the member projects from the refractory wall by an extent at least equal to the local depth of erosion. Such complementarily-shaped member is so composed that it is adapted to withstand ceramic welding temperatures. A desired refractory repair mass is built up, by ceramic welding, adherent to the eroded wall and surrounding the complementarily-shaped members(s) while leaving its end or their ends exposed, and the complementarily-shaped member(s) is or are thereafter removed from the repaired openings(s). Such complementarily-shaped member may, for example, be of refractory carbon or of steel, such as stainless steel. Such a steel member may be tubular for the circulation of coolant.

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: A process of forming a refractory mass on a surface, which process includes spraying against that surface a mixture of refractory particles and oxidisable particles which react exothermically with oxygen to generate sufficient heat to soften or melt at least the surfaces of the refractory particles and so bring about formation of said refractory mass, and causing the sprayed mixture to be heated sufficiently to cause the oxidisable particles to undergo such exothermic reaction, the granulometry of the particles which are sprayed in the mixture being such that the mean of the 80% and 20% grain sizes of the refractory particles is greater than the mean of the 80% and 20% grain sizes of the oxidisable particles and that the size range spread factor of the refractory particles is at least 1.2.

Abstract: A lance for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas is characterized in that the lance 1 comprises at least one feed passage 2,3 for conveying material to be sprayed to a lance head 4 which comprises a plurality of spray nozzles 5 for spraying such material, and in that the flow path of the material being sprayed branches or turns a corner and a cup-like recess 7,9 is located at the or each such branch or corner, open to the flow path upstream thereof, for catching particulate material conveyed along said flow path so that the material caught itself forms a barrier against abrasion at the location of such recess.A method of using such a lance to spray particulate refractory-forming combustible material, particulate refractory material and a comburent gas against a surface so that on combustion a coherent refractory mass is formed on such surface is also disclosed.

Abstract: A silica refractory structure may be added to, e.g. by way of repair, in a working environment at a temperature in excess of 600.degree. C. Such addition is made using one or more vitreous silica bricks bonded into position by projecting a mixture composed of finely divided particles of exothermically oxidizable material, e.g. Si optionally with Al and particles of silica, and burning the mixture during its projection to form a coherent refractory mass which bonds the addition together and to the original structure.

Abstract: A method of manufacturing a composite refractory article having a flow passage through which a molten metal stream may be conducted and comprising a first body of refractory material which defines a surface of that passage, the first body being bonded to a second body of refractory material. The second body is provided to define a passageway of greater cross-sectional dimensions than the flow passage. Within the passageway, the first body of refractory material is provided for defining the flow passage surface, the first body being formed in the larger passageway by causing its refractory material to cohere and bond to the second body by fusion or partial fusion in situ.

Abstract: In a process of forming a refractory mass in which having an average grain size of less than 50 .mu.m are burned while mixed with solid particles of at least one incombustible refractory material during projection of the mixture against a surface to form a coherent mass on said surface, the oxidizable material comprises silicon and aluminium, the aluminium being present in an amount not exceeding 12% by weight of the total mixture.