Rammed refractories

Abbreviations AF = amphibolite faeies BIF = banded iron formation BSF = bluesehist facies GF = granulite faeies GG = granitic gneiss or chamockite GSF = greenschist facies RAM = refractory accessory mineral thermometer Qtzt = quartzite. 

Ramming refractories are similar to plastic, but somewhat more stiff. 

Tuyere Block Bottom. One form of bottom for a converter (q.v.). The passages for the air blast are separate pre-formed tuyeres each having several holes these tuyere blocks are interspersed with solid refractory blocks, the whole bottom then being finished by ramming refractory material into any spaces. 

Pihutin lA, Frolov VF, Yurkov AL. Implementation of semidry ramming refractory lining of induction furnaces IAT-6 (in Russian). Tsvetn Met. 2(X)3 l 85-8. 

Refractory moldable materials are also termed as plastic or ramming refractory materials. These are again subdivided into two as outlined in the following sections. 

These moldable materials are usually described as plastic or ramming refractory materials. 

Refractories may be preformed, ie, shaped, or formed and installed on-site, ie, specialties. Iimovations in placement and vessel constmction has led to a greater emphasis on specialty refractory products. Castables, gunning mixes, and plastic and ramming mixes are used either for repair or for complete new constmction of what is known as monolithic linings. The tendency to use monolithics instead of constmctions using shaped products has been steadily increasing. As of the mid-1990s, monolithic installations are as common as conventional shaped product constmction. 

Plastic Refractories and Ramming Mixes. Plastic refractories are mixtures of refractory grains and plastic clays or plasticizers with water. Ramming mixes may or may not contain clay and are generally used with forms or steel work. The amount of water used in these products varies but is held to a minimum to faciUtate drying. Plastics are generally suppHed in a ready-to-use state. 

Specialty Refractories. Bulk refractory products include gunning, ramming, or plastic mixes, granular materials, and hydrauhc setting castables and mortars. These products are generally made from the same raw materials as their brick counterparts. 

Hot pressing requires a refractory die, pressure and heat sources and temperature- and pressure-indicating devices. For many applications the die containing the sample to be hot pressed is heated either by a separate furnace (for < 1000°C) or by inductive or resistance heating of the die body itself. Uniaxial pressure is applied through the ram of a hydraulic or pneumatic press. 

Heavy fuel oil feedstock is delivered into the suction of metering-type ram pumps which feed it via a steam preheater into the combustor of a refractory-lined flame reactor. The feedstock must be heated to 200°C in the preheater to ensure efficient atomisation in the combustor. A mixture of oxygen and steam is also fed to the combustor, the oxygen being preheated in a separate steam preheater to 210°C before being mixed with the reactant steam. 

Other common refractory forms include setter tile and kiln furniture, fusion-cast shapes, cast and hand-molded refractories, insulating refractories. castables and gunning mixes, plastic refractories and ramming mixes, mortars, composite refractories, and refractory coatings,... 

Refractory shapes are generally produced on a mechanical toggle press, screw press, or hydraulic press. Some special shapes are produced by air-ramming which is similar to hand molding, except that reinforced steel molds are required. Special shapes can also be formed by slip easting and hot pressing. 

A modified pressing method, ramming, is utilized in the forming of large objects (e.g. refractory blocks). In such cases, compaction by pressing would not be uniform, so that gradual compression by repeated impact is a suitable solution. 

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