The refractory material which uses high-speed air flow as the carrier of refractory material for spray construction is called spray refractory, which includes gunning material for repairing damaged lining and spraying coating for constructing new lining. Now people call this kind of construction method as the formless construction method, which has become one of the development directions of the amorphous refractory in the future.

Spraying refractory materials, whether repairing furnace lining by spraying or constructing new lining by spraying, can be classified into two categories: cold material spraying method and molten material spraying method according to the state of spraying materials received by the working face to be sprayed. There are five kinds of cold material injection methods: slurry injection method; dry spray method; semi wet spray method (or damp spray method); mixed spray method; wet spray method. The molten material spraying method is divided into flame spraying method, plasma spraying method and slag splashing method.

The cold material spray material is mainly composed of various granular and powder refractory materials. The binder content is generally low, and it often contains appropriate flux to promote sintering. A small amount of water is added during construction mixing.

The materials of particles and fine powder raw materials used for injection shall be selected according to the highest possible operating temperature in the furnace, temperature fluctuation range, slag properties and requirements for the properties of furnace lining. When the spraying material is used to coat on the furnace lining, the material should be equivalent to the original lining, and the chemical properties, fire resistance, high temperature strength and deformation, linear expansion, etc. of the two should be similar. The limit particle size of granular materials should be selected according to the structure of the jet machine, the thickness of gunning layer and the spraying method (such as wet or dry method). Improper selection of particle size has a great influence on the adhesion and rebound loss of spray. Springback loss refers to the part of the material that is ejected but not attached to the substrate when it is ejected onto the substrate. Generally speaking, too coarse particles and too much or too few coarse particles of wet sprayed materials are unfavorable to the density of spray layer. Moreover, coarse particles and more coarse particles often lead to large rebound loss.

Wet jet construction has been widely used to construct or repair the lining of blast furnace runner, torpedo tank, steel drum, tundish, rotary kiln and garbage incinerator.

The flame spraying material is composed of metal powder, corundum, magnesia and other refractory raw materials. Metal is not only fuel, but also molten binder. Sometimes a small amount of flux is added or only added to facilitate rapid sintering.