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Glossary

 

Alloy: A metallic material consisting of a mixture of 2 or more metals or of metal with nonmetal elements. Steels or combined metals are the product of elements (C, Cr, Ni, Mn, etc…) incorporated in the iron.
 
Crushing / Grinding: To break metal into smaller particles. At a cements works, for example rocks extracted from the quarry are passed through different crushes until the material reaches a size of +-50mm. The are various types of crushes: with cones, jaws, blow bars, hammers, anvils and impellers. These works either on a vertical axis (VSI stands for vertical shaft Impactor), or on a horizontal axis (HSI stand for horizontal shaft Impactor). The grinding process in carried out in ball mills or vertical mills. This allows material to be ground to a much finer consistency, which cannot be achieved by crushers.
 
Grinding process: The series of stages which a bulk material of a certain consistency is first broken, then crushed the finally ground to reach the required fineness.
 
Heat treatments: The heat process which grant particular properties to a casting in a defined alloy. The parameters of temperature and time are extremely important and the greatest precision is required. For example, quenching increases hardness while tempering reduces internal stresses.
 
Linings: A ball mill is simply a cylindrical tube positioned horizontally on 2 supports and rotating.
It is filled, partly, by hundreds of tones of very hard steel grinding media, weighing up to several kilos each. In order to protect the steel shell of the mill, lining plates are fixed to the whole internal surface. These must clearly have excellent wear and impact resistance. The particular profile of these linings is designed to give the best energy transmission to the ball charger when the mill is rotating.
 
Pyro-processing: A term enveloping all operations within a high temperature environment (Pre heaters, kilns, coolers, etc). Therefore clinker, which will become cement after the fine grinding process, is produced from the limestone at a temperature of more than 1.470°C in a long horizontal kiln.
 
Refractory Steels: Are steel that are able to resist high and even extreme temperatures or thermal shocks which can prove to be destructive. Corrosion and abrasion complete this list of harmful wear factors. Chrome and nickel are among the elements most frequently used in heat resistant steels.
 
Vertical mill: Takes its name from the vertical axis upon which the mill rotates. As in old mills, where the 2 “millstones” would turn against each other, thus creating sufficient pressure to crush the material being fed through the mill. (In comparison to a ball mill which turns on its horizontal axis.)
 
Wear mechanisms: Abrasion, corrosion and impact are the 3 main contributory factors that cause wear. High temperature and thermal impact equally contribute to wear.

Alumina. Aluminum sesquioxide, Al2O3. (It occurs in several forms, the principal being gamma- alumina and alpha-alumina (or corundum). So called beta-alumina contains a small amount of alkali metal oxide.)

Alumina refractory. A pure-alumina refractory.

Andalusite. One of three minerals having the same composition (AI2O3.SiO2) but different crystalline forms.

Apparent porosity. The ratio of the volume of the open pores to the bulk volume of the material, expressed as a percentage. 

Basic refractory. A refractory with a high content of alkaline earth oxides (MgO, CaO).

Batch. The whole of the various constituents making up the mixture for one operation.

Bauxite. A sedimentary rock that consists principality of one or more hydrates of alumina (diaspore, gibbsite, boehmite), and that may also contain clay minerals and hydrated iron oxides.

Binder. A substance added to a non-plastic granulator material to give it workability and green or dry strength or both. (Term sometimes used synonymously with "bond").

Blending. Mixing together of different sized grains to obtain a desired texture.

Bond. A material that binds together the discrete grains of a mix. (Term sometimes used synonymously with "binder”.)

Bulk density. The mass of a material per unit of bulk volume.

Calcinations. Heat treatment that produces physical or chemical changes in certain raw materials.
Campaign. The working life of a furnace between major repairs (relines).

Castable refractory. A mixture of refractory aggregate and heat resisting hydraulic cement or other suitable binder. (These products are generally cast in situ.)

Ceramic bond. The vitreous or crystalline material formed on firing, between the coarser constituents of a ceramic body and giving cohesion and mechanical strength to the fired product.

Chamotte. Refractory clay that has been specially fired for use as a non-plastic material.

Checker brick. Brick used for checkers in regenerators.

Checkers. Bricks or shapes set in such a way that the hot gases can pass between them in a regenerator chamber.

Chemically bonded brick. A brick in which mechanical strength is imparted by chemical binding agents instead of by firing.

Chrome-magnesia refractory. A refractory made from a mixture of chrome ore and dead-burned Magnesite, the chrome ore predominating.

Chrome spinal. A spinal in which the trivalent metal is chromium, e.g. (Mg, Fe)O.Cr2O3

Cold crushing strength. The ultimate load per unit area, at room temperature, that a refractory will withstand before it is crushed.

Converter. A vessel for refining crude pig iron into steel by hot air or oxygen.

Corrosion. Wear caused by chemical attack.

Corundum. Alpha-alumina, Al2O3. (The only form of alumina stable at temperatures over 1000°C).

Course. A layer of row of bricks in a structure.

Crack. Unless modified to "surface crack", or "internal crack" a fissure extending inwards from the surface of a product.

Creep. Isothermal deformation of a stressed product as a function of time.

De-airing. The removal of entrapped air from a body by means of a partial vacuum.

Dead burned. Made as inert and stable as possible by appropriate heat treatment.

Dense brick. A brick with a true porosity lower than 45%

Dolomite. The double carbonate of calcium and magnesium, CaCO3.MgCO3 (This mineral is the principal constituent of dolomite rocks which are also referred to as dolomites. The term is some- times incorrectly used to denote Doloma.)

Erosion. Surface wear caused by the mechanical action of a fluid either containing or not containing solid materials.

Expansion joint. An open vertical or horizontal joint that allows expansion on heating.

Fireclay. A clay which is resistant to high temperatures, and contains mainly kaolinitic clay minerals, free silica and only a small proportion of other impurities.

Furnace. A chamber in which combustion and/or reaction takes place at elevated temperatures.

Grading. The grain-size distribution of a mix.

Graphite. An allotropic hexagonal form of carbon.

Green strength. Mechanical strength of a ceramic product in the green state.

Jamb. The vertical brickwork of a furnace door or any other opening.

Joint. Space in brickwork between bricks or refractory pieces, generally filled with mortar.

Ladle. A refractory-lined metal vessel used to hold and transport molten product (metal).

Magnesia. Magnesium oxide, MgO.

Magnesite. Strictly, the mineral magnesium carbonate, MgCO3. (At times incorrectly used to denote magnesia).

Magnesia-chrome refractory. A refractory made from a mixture of dead-burned Magnesite and chrome ore, the magnesia predominating.

Magnesia refractory. A refractory consisting essentially of magnesia.

Matrix (Ground mass). The medium in which grains or crystals are embedded.

Modulus of rupture. The nominal transverse breaking stress of a material.

Monolithic. Joint less. (A term applied to linings that are rammed or cast or slung or gunned in situ).

Particle size analysis (Grain-size analysis). The process, or the result, of a separation of a mixture of particles into classified size to determine their proportions.

Pericles. Crystalline magnesium oxide, MgO.

Permanent linear change PLC on reheating. The percentage permanent linear contraction (after contraction) or linear expansion (after-expansion), measured after cooling, that takes place when a refractory material is heated for a specified period at a specified temperature.

Permeability. The property of a porous material that is measured by the flow of a gas or other fluid through the material under specified conditions of testing.

Pore. Small void in the texture of a product. (A pore may be closed or interconnected with other pores.)

Pyrometric cone equivalent (PCE). The number of the standard cone that bends at the temperature at which the test cone bends (or the numbers of the standard cones that bend immediately before or after that temperature) under the standardized conditions of the refractoriness test.

Ramming material. A granular refractory composition. (Ramming materials are generally put into place by ramming, after the addition of a suitable liquid.)

Refractoriness under load (RUL). The behavior of a refractory material subjected to the combined effects of load, temperature, and time.

Refractory. An essentially non-metallic material or product that is difficult to break down by heat, chemical attack, or abrasion.

Screen. A wire mesh or perforated plate used for the industrial classification of crushed or ground material by size.

Sea-water magnesia. Magnesia (MgO), obtained from sea water.

Shaft kiln. A vertical kiln charged at the top and discharged at the bottom.

Shrinkage. Dimensional decrease of a refractory during manufacture or service.

Sintering. The bonding of powdered materials by solid-state reactions at a temperature lower than that required for the formation of a liquid phase. (In industrial practice, the sintering temperature is sometimes lowered by the inducement of a small amount of vitreous phase by means of suitable additions.)

Slag. Non-metallic material formed during the treatment or purification of a metal, or substance resulting from the attack on a refractory product by materials in contact with it.

Spalling. The cracking or fracture of a refractory product caused by differential expansion due to thermal shock, the effect of a steep temperature gradient, or a crystalline inversion. Mechanical. The spalling of a refractory unit caused by stresses resulting from impact or pressure. Structural.  The spalling of a refractory unit caused by stresses resulting from differential changes in the structure of the unit. Thermal. The spalling of a refractory unit caused by stresses resulting from non-uniform changes of the unit produced by a difference in temperature.

Spalling Test (Thermal shock test). A test in which refractory test pieces are subjected to periods of alternate heating and cooling under standardized conditions.

Spinal. A cubic crystalline material having the general formula R”O.R’’’2O3, where R” and R’’’ are divalent and trivalent metals respectively. (The term is also used more specifically for magnesium aluminates MgO.Al2O3.)

Strain. The change in dimension per unit dimension of a material as a result of an applied stress.
Strength. The ability to resist stress. Tensile (compressive) strength. The limiting tensile compressive) stress per unit cross-section at a given temperature that a refractory material can withstand without rupture, determined under specific conditions and on specially prepared test pieces.

Thermal expansion. The property of a material that is shown by an increase in temperature. (The effect is reversible.)

Thermal shock test. See "Spalling test".

Thermal shock. A sudden change in temperature liable to cause spalling.

Transfer Ladle. A refractory-lined container for the transfer of liquid metal from the transport ladle to the mixer or steel-making vessel.

Transition zone. The zone in a kiln between the calcining and the clinkering zones.

Transport Ladle (e.g. Kling, Demag, Torpedo). A refractory lined container for the transport of liquid metal from the blast furnace to the steel plant.