Refractories & Furnace Linings

Start here: ten words every newcomer needs

Overheard on the job

Real-sounding lines from the floor, translated into plain English.

• Hot spot at 32 metres went red overnight, the coating's gone, bring the kiln down before a patch turns into a reline.

  TranslationA hot area on the kiln shell is now glowing red because the protective clinker layer and brick have failed, so stop the kiln now to avoid a much bigger repair.

• Ball-in-hand says it's wet, dump it, and tell the tender to weigh the water this time.

  TranslationThe castable batch has too much water, so throw it out and measure the water precisely for the next mix.

• Key the ring tight before you pull the pogos, or it'll be spiraling by Friday.

  TranslationDrive the final locking bricks in firmly before removing the temporary props, or the loose ring will twist out of alignment as the kiln turns.

• Slag line on 7 is down to one brick but the walls are fine, so it's a zone reline, not a full tear-out.

  TranslationThe fastest-wearing band of the ladle lining is nearly gone while the rest still has life, so replace only that zone.

• Hold at 120 until the steam stops, then 25 an hour to 540, or you'll get explosive spalling.

  TranslationKeep the dry-out at 120 C until the free water is gone, then heat slowly to 540 C so steam pressure does not burst the new lining.

• Nozzleman's getting too much rebound in the cone, trim the water and keep it off the anchors.

  TranslationThe gunning operator is losing too much material bouncing off the wall; adjust the water at the nozzle and avoid trapping rebound around the anchors.

• Free open rate's slipping, check the well sand and how long those ladles sit full before the caster.

  TranslationMore ladles are failing to start flowing on their own, so check the nozzle filler sand and how long ladles are held before casting.

• Mud gun's pushing short, the taphole's getting shorter and the hearth thermocouples say the elephant foot is growing.

  TranslationLess clay is going into the taphole and it is shortening, while hearth temperatures suggest the erosion at the hearth corner is deepening.

What refractories are made of, from fireclay and silica to magnesia-carbon, spinel and fused-cast AZS.

• AZSalso fused-cast AZS, AZS 33
  Alumina-zirconia-silica fused-cast refractory, the standard glass-contact material in glass melting furnaces.
• Basic refractoryalso basic, basic lining
  Refractory based on magnesia, lime or dolomite that resists basic slags with high lime-to-silica ratios.
• Calcium aluminate cementalso CAC, high-alumina cement
  Hydraulic cement that binds most refractory castables, sold in grades of roughly 40 to 80 percent alumina.
• Dead-burned magnesiaalso DBM, sintered magnesia
  Magnesia fired so hard it barely reacts with water, the main raw material of basic refractories.
• Finesalso matrix fines, micro-fines
  Smallest particle fraction of a refractory mix, which fills the gaps between coarse grains and forms the bond.
• Fireclayalso firebrick, fireclay brick
  Alumina-silica clay refractory, the classic firebrick, graded from low duty to super duty.
• Grogalso chamotte, calcined fireclay
  Pre-fired clay or crushed brick added as aggregate to cut shrinkage and cracking in refractory bodies.
• High-alumina brickalso high-alumina, hi-alumina
  Alumina-silica brick with more than 45 percent alumina, graded in steps such as 50, 60, 70, 80 and 90 percent.
• Magalso magnesite, mag brick
  Clipped shop word for magnesia, magnesia brick or a magnesia-based mix. Shop talk
• Magnesia-carbon brickalso mag-carbon, mag-carb
  Resin-bonded brick of magnesia and graphite, the workhorse lining of BOFs, electric arc furnaces and ladle slag lines.
• Magnesia-chrome brickalso mag-chrome, direct-bonded mag-chrome
  Basic brick of magnesia and chrome ore, prized for resistance to aggressive slags in copper smelting and degassers.
• Refractoryalso refractories, refractory lining
  Non-metallic material built to keep its shape and strength at furnace temperatures while resisting slag, metal and gas.
• Silica brickalso silica, dinas brick
  Brick of over 93 percent silica with high hot strength but sharp volume changes when cooled below red heat.
• Silicon carbidealso SiC, carbide
  Hard, highly conductive refractory used where abrasion, thermal shock and heat transfer all matter.
• Spinelalso MA spinel, mag-spinel
  Magnesium aluminate mineral used in chrome-free basic bricks and slag-resistant ladle castables.

Standard shapes, brickwork practice, lining layers and the people who lay them.

• Arch brickalso arch, side arch
  Tapered brick whose thickness narrows across its width, used to turn thin arches and rings.
• Brickiealso bricky, refractory mason
  Shop name for a refractory bricklayer, especially in Britain, Australia and steel plant crews. Shop talk
• Butteralso buttering
  To spread mortar onto the faces of a brick before setting it in place. Shop talk
• Checkeralso checkers, checkerwork
  Brick laid in an open lattice inside a regenerator or hot blast stove to store and return heat.
• Closeralso closure, cut brick
  Brick cut to size to fill the last gap in a course, ring or wall. Shop talk
• Expansion jointalso expansion allowance, expansion gap
  Gap deliberately left in a lining so bricks or castable can grow with heat without crushing or lifting.
• Hard brickalso dense brick, dense firebrick
  Shop name for dense firebrick, as opposed to lightweight insulating soft brick. Shop talk
• Hot facealso hot-face lining
  Surface of a refractory lining exposed to the furnace interior, as opposed to the cold face against the shell.
• Keyalso key brick, keystone
  The last brick driven into an arch or ring to lock it tight, or a shape that tapers in width for turning circles.
• Pogo stickalso pogo, pogos
  Telescoping prop used to hold bricks against the upper shell of a rotary kiln until the ring is keyed. Shop talk
• Refractory mortaralso mortar, refractory cement
  Fine refractory mix used to lay and bond firebrick, either heat-setting, air-setting or phosphate-bonded.
• Safety liningalso permanent lining, backup lining
  Refractory layer behind the working lining that holds molten metal back if the working lining fails.
• Skewbackalso skew, skew brick
  Angled brick or support course from which a sprung arch springs and pushes its thrust into the steelwork.
• Soapalso soap brick, half-width brick
  Brick of standard length and thickness but half the width, such as 9 by 2.25 by 2.5 inches.
• Splitalso half-thickness brick
  Brick of standard length and width but reduced thickness, used to adjust course heights.
• Straightalso 9-inch straight, nine-inch
  The standard rectangular firebrick, 9 by 4.5 by 2.5 inches in US sizing, used as the counting unit for brickwork.
• Tenderalso mason tender, hod carrier
  Laborer who supplies brick, mortar and castable to refractory masons and keeps the job moving. Shop talk
• Wedge brickalso wedge, end arch
  Brick whose thickness tapers along its length, used for arches and rings 9 inches or more thick.
• Working liningalso wear lining, hot lining
  Innermost refractory layer in contact with the process, designed to wear and be replaced on a schedule.

Castables, plastics and gunning mixes, and the field methods and tools used to place them.

• Anchoralso V-anchor, Y-anchor
  Metal or ceramic tie welded to the shell to hold a monolithic lining in place.
• Ball-in-hand testalso ball test, ball in hand
  Quick field check of castable water content: squeeze a ball of mix, toss it, and see whether it holds. Shop talk
• Burnout fibersalso organic fibers, polypropylene fibers
  Plastic fibers mixed into castables that melt during dry-out, leaving channels for steam to escape.
• Castablealso refractory concrete
  Dry refractory mix of aggregate, fines and binder that is mixed with water and poured or pumped like concrete.
• Curealso curing
  To hold freshly placed castable moist and at moderate temperature so its cement can fully hydrate.
• Dry vibratablealso DV, dry vibe
  Dry granular refractory compacted by vibration without water and sintered in place by heat.
• Greenalso unfired
  Describes refractory that has been formed or placed but not yet fired, dried or heated in service.
• Gunitealso guniting, gunite crew
  Shop name for gunned refractory and the dry-gun process, borrowed from the concrete trade. Shop talk
• Gunningalso gun, gunned refractory
  Spraying refractory through a hose and nozzle with compressed air to build or repair a lining.
• Hex meshalso hexmesh, hexmetal
  Hexagonal steel grid welded to a shell to hold thin erosion-resistant linings, mainly in refinery cyclones.
• Low-cement castablealso LCC, low cement
  Dense castable with 1 to 2.5 percent lime from cement, using micro-fines and dispersants for strength and low porosity.
• Monolithicalso monolithics, unshaped refractory
  Unshaped refractory supplied as a mix and installed in place to form a jointless lining.
• Nozzlemanalso nozzle operator, gunman
  Operator who handles the gunning nozzle and controls water and placement on a gunning or shotcrete crew. Shop talk
• Plastic refractoryalso plastic, ramming plastic
  Moist, workable refractory delivered ready to use and pounded into place with a pneumatic rammer.
• Ramming mixalso ram mix, ramming refractory
  Drier, granular refractory mix compacted in layers with a pneumatic rammer to build dense linings.
• Reboundalso rebound loss
  Material that bounces off the wall during gunning instead of sticking, wasted and often harmful.
• Self-flow castablealso SFC, self-leveling castable
  Castable designed to flow and level under its own weight, with no vibration needed.
• Shotcretealso wet gunning, refractory shotcrete
  Wet-mix gunning: castable pumped through a hose and set instantly by accelerator added at the nozzle.
• Stingeralso poker, vibrator
  Shop name for the immersion vibrator head pushed into fresh castable to consolidate it. Shop talk
• Tear-outalso wreck-out, wrecking
  Demolition of a worn or failed refractory lining so a new one can be installed. Shop talk

Lightweight brick, fiber and castables that keep heat in and shell temperatures down.

• AES woolalso AES fiber, biosoluble fiber
  Alkaline earth silicate wool, a body-soluble high-temperature fiber used in place of ceramic fiber.
• Blanketalso fiber blanket, ceramic blanket
  Flexible, needled mat of ceramic or biosoluble fiber sold in rolls by density and thickness.
• Ceramic fiberalso RCF, refractory ceramic fiber
  Wool-like high-temperature insulation spun from molten alumina-silica, sold as blanket, modules, board and paper.
• IFBalso insulating firebrick, insulating brick
  Insulating firebrick: light, porous brick rated by the maximum temperature it can face, such as group 23 or 26.
• Insulating castablealso lightweight castable, LWC
  Lightweight castable made with porous aggregates that trades strength for low thermal conductivity.
• Modulealso fiber module, stack-bond module
  Block of folded or stacked fiber blanket, compressed and fitted with anchor hardware for fast furnace lining.
• Soft brickalso soft firebrick, insulating brick
  Shop and kiln builder name for insulating firebrick, light enough to carve with a hand saw. Shop talk
• Thermal conductivityalso k-value, k-factor
  How readily a material conducts heat, the number used to size lining layers and predict shell temperature.

The lab numbers on a refractory data sheet and what each one says about performance.

• Abrasion resistancealso erosion resistance, C704
  How well a refractory stands up to scouring by moving solids, usually measured by the ASTM C704 test.
• Apparent porosityalso AP, open porosity
  Share of a refractory's volume made up of open pores that liquids and gases can penetrate.
• Bulk densityalso BD, density
  Mass of a refractory divided by its total volume including pores, a quick check on quality and compaction.
• CCSalso cold crushing strength, crushing strength
  Cold crushing strength: the room-temperature compressive strength of a refractory, in MPa or psi.
• Creepalso creep deformation, compressive creep
  Slow, permanent deformation of a refractory under steady load at high temperature over hours to years.
• HMORalso hot MOR, hot modulus of rupture
  Hot modulus of rupture: the bending strength of a refractory measured at high temperature.
• PCEalso pyrometric cone equivalent, cone value
  Pyrometric cone equivalent: a refractory's softening point expressed as the number of a matching standard cone.
• PLCalso permanent linear change, reheat change
  Permanent linear change: the lasting shrinkage or growth of a refractory after heating and cooling.
• Refractorinessalso refractory temperature
  Ability of a material to withstand high temperature without softening or melting.
• RULalso refractoriness under load, load test
  Refractoriness under load: the temperature at which a refractory starts to deform under a small steady load.
• Thermal shock resistancealso spalling resistance, TSR
  Ability of a refractory to survive rapid temperature changes without cracking and spalling.

How linings crack, spall, dissolve and burn through, and the warning signs crews watch for.

• Alkali attackalso alkali bursting, alkali spalling
  Damage from potassium and sodium compounds that react with alumina-silica refractories and swell them apart.
• Breakoutalso burn-through, run-out
  Escape of molten metal or slag through a failed lining and shell, the most dangerous refractory failure. Shop talk
• Carbon monoxide disintegrationalso CO disintegration, carbon deposition
  Breakdown of refractory as carbon deposits from CO gas grow inside its pores around iron oxide spots.
• Elephant footalso elephant's foot, elephant foot erosion
  Blast furnace hearth wear profile where the wall-to-floor corner erodes into the shape of an elephant's foot. Shop talk
• Explosive spallingalso steam spalling, explosive failure
  Violent failure of a castable during first heat-up when trapped steam pressure blows the lining apart.
• Hot spotalso hotspot, shell hot spot
  Area of a vessel or kiln shell running hotter than normal because the lining behind it is thin or gone. Shop talk
• Hydrationalso slaking, dusting
  Reaction of magnesia or lime in a refractory with water or humidity, causing swelling, cracking and dusting.
• Ovalityalso shell ovality, relative ovality
  Out-of-round flexing of a rotary kiln shell under its tires, which crushes and loosens the brick lining.
• Red spotalso red shell, glowing shell
  Shell area glowing visibly red from lining loss, the signal to take a kiln or vessel out of service. Shop talk
• Skullalso skulling, metal skull
  Layer of solidified metal and slag left stuck to a ladle, converter or furnace lining after emptying. Shop talk
• Slag attackalso slag corrosion, slag erosion
  Chemical dissolution and penetration of a refractory by molten slag, the main wear mode in metal processing.
• Slag linealso slagline, slag zone
  Band of a ladle or furnace lining where the slag layer floats on the metal, usually the fastest-wearing zone.
• Spallingalso spall, peeling
  Cracking off of pieces or layers from the hot face of a refractory lining.
• Spiralingalso brick spiraling, twisting
  Twisting of brick rings out of radial alignment inside a rotary kiln when the lining works loose. Shop talk

Dry-out, campaigns, relines and the plant vocabulary of steel, cement and glass furnaces.

• Campaignalso lining life, campaign life
  Working life of a furnace or lining between relines, counted in heats, tonnes, days or years.
• Coatingalso kiln coating, clinker coating
  Layer of clinker that sticks to the burning zone brick in a cement kiln and shields it from heat and wear.
• Crownalso roof, furnace crown
  Arched refractory roof of a glass furnace or other large furnace, often built of silica brick.
• Doghousealso dog house, batch charging pocket
  Small extension on a glass melting furnace where the batch is charged into the tank. Shop talk
• Dry-outalso bake-out, heat-up schedule
  Controlled first heat-up of a new monolithic lining to drive off water without cracking or spalling.
• Fettlingalso fettle, bank repair
  Quick repair of a furnace hearth and banks between heats by throwing or gunning in dolomite or magnesia. Shop talk
• Free openalso free opening, self-opening
  Ladle that starts teeming the moment the slide gate opens, with no oxygen lancing needed. Shop talk
• Mudalso taphole clay, mortar
  Shop word for the clay used to plug a blast furnace taphole, and bricklayers' word for mortar. Shop talk
• Relinealso rebrick, relining
  Replacement of a worn refractory lining, in full or in zones, at the end of a campaign.
• Ringalso kiln ring, buildup
  Circular buildup of material inside a rotary kiln that dams the flow, or one circular course of lining brick.
• Salamanderalso bear
  Pool or mass of iron left in a blast furnace hearth below the taphole, tapped or dug out at a reline. Shop talk
• Slag splashingalso slag splash, splashing
  BOF practice of blowing nitrogen onto retained slag to plaster the converter lining with a protective coat.
• Slide gatealso sliding gate, slide gate valve
  Valve of sliding refractory plates under a ladle or tundish that controls the flow of molten steel.
• Snowmanalso cooler snowman, clinker buildup
  Cement plant name for the mound of sticky clinker that builds up at the inlet of the clinker cooler. Shop talk
• Tapholealso tap hole, iron notch
  Opening through a furnace wall or bottom through which molten metal and slag are drained.

Frequently asked questions

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