Which refractory, where in the furnace?
Pick a vessel and click the lining zones. Each zone needs its own refractory for the attack it sees — slag, temperature, abrasion. See what works where, and why.
A ladle looks simple but is one of the harshest refractory environments: molten steel at 1600–1700 °C, active slag at the contact line, and a severe thermal cycle every time it empties and fills. No single lining works — each zone gets the refractory for the attack it sees. Click the map.
Click each zone
Slag line
1600–1700°CThe most aggressive zone of the whole ladle — active slag eats the lining right here. It needs corrosion resistance, not just refractoriness.
Alumina-magnesia spinel and fused magnesia are the standard here.
Barrel (wall)
1500–1650°CThe largest area in contact with molten steel. Here the balance of thermal resistance, dimensional stability and cost matters — an alumina-spinel castable is the common choice.
Low-cement castable based on tabular and reactive alumina.
Bottom
1500–1650°CCarries the full weight of the molten steel and takes the impact when steel is tapped from the furnace. A high-alumina or spinel castable with high compressive strength.
High-alumina castable bonded with pure calcium aluminate cement.
Nozzle & well sand
1600–1700°CThe steel discharge channel. The filler sand must stay open against molten steel so the ladle drains freely on tap — free opening depends on this sand.
Ladle well sand — chromite-based or chrome-free olivine.
Safety (permanent) lining
< 1000°CThe layer behind the working lining — if the working lining is penetrated it stops the melt reaching the steel shell and cuts heat loss. Insulation matters more than corrosion here.
Lightweight insulating brick behind the working lining.
An electric arc furnace melts steel scrap with an arc several thousand degrees hot. Its lining endures three attacks at once: direct arc radiation, hot active slag, and the mechanical impact of the scrap charge. Each zone gets the refractory for the attack it sees most.
Click each zone
Hot spots (facing electrodes)
> 1800°CThe wall facing the electrodes takes direct arc radiation. The hottest and most-consumed spot in the furnace; a high-graphite magnesia-carbon brick is needed here.
Magnesia-carbon brick with fused magnesia; graphite raises thermal conductivity.
Slag line
1600–1700°CThe contact line where hot slag continually erodes the lining. Corrosion resistance is decisive.
Magnesia-carbon or spinel with high corrosion resistance.
Lower wall & bank
1500–1650°CBelow the slag line, in contact with molten steel. A balance of thermal resistance and cost — dead-burned magnesia is common.
Dead-burned magnesite brick or ramming mass.
Tap hole (EBT)
1600–1700°CThe eccentric bottom tap hole. The filler sand must stay open against molten steel so it drains freely on tap — chrome-free to avoid contamination.
Olivine EBT sand, the chrome-free alternative to chromite sand.
Roof (delta)
1400–1700°CThe roof takes arc radiation and hot gases from above and carries the electrode ports. A high-alumina castable with good thermal-shock resistance.
Low-cement high-alumina castable for the roof delta.
The blast furnace has the tallest and longest-lived refractory lining in industry — a campaign can run 15 to 20 years. High up it is charge and gas abrasion; low down it is molten iron and slag. See each zone on the section.
Click each zone
Throat & upper stack
200–800°CSolid charge — coke, ore, flux — keeps falling on the lining and abrades it. Here abrasion, not temperature, is decisive.
Silicon-carbide and bauxite brick and castable for abrasion resistance.
Belly & bosh
900–1400°CWhere iron oxide is reduced and the charge begins to soften. Chemical attack by alkalis and CO gas is significant.
Silicon carbide for thermal conductivity and alkali resistance.
Bosh (tuyere zone)
1400–1800°CThe hottest zone; hot blast is injected through the tuyeres and coke burns. A combination of extreme heat, abrasion and chemical attack.
Nitride-bonded silicon carbide withstands the harshest conditions.
Hearth (molten pool)
1450–1550°CMolten iron and slag collect here. The life of the whole furnace campaign depends on how long this hearth lasts.
High-alumina and carbon blocks; the furnace’s most critical lining.
Unlike a ladle or blast furnace, a cement kiln is horizontal and rotating: feed enters one end and clinker leaves the other. The temperature climbs in steps along the kiln and peaks in the burning zone. See the zones along its length.
Click each zone
Preheating zone
800–1100°CFresh feed enters and warms up. Temperature is moderate but there is feed abrasion and alkali attack.
Fireclay and insulating brick; this zone does not justify high alumina.
Transition zone
1100–1400°CTemperature rises and clinker starts to form. Both thermal stress and abrasion are high.
Magnesia-spinel brick, the chrome-free successor to old magnesia-chrome.
Burning zone
1400–1700°CThe hottest zone; clinker forms at peak temperature. Clinker-melt attack and the thermal cycle of rotation make this the harshest spot.
Magnesia-spinel brick, the world standard for the burning zone.
A glass furnace differs fundamentally from a ladle or steel furnace: molten glass is in contact with the lining continuously for years, and any particle the lining releases shows up as a defect — a stone or cord — in the clear product. Corrosion here is very slow but relentless, which is why special refractories are required. See the key zones.
Click each zone
Glass-contact bottom & wall
1400–1600°CIn direct, permanent contact with molten glass. AZS (alumina-zirconia-silica) blocks are the standard; zirconia dissolves the least in glass.
Zirconia and AZS blocks; zirconia barely dissolves in glass.
Superstructure (above the melt)
1500–1600°CAbove the glass surface, exposed to volatile alkali vapours and high heat. Silica or alumina-zirconia resistant to alkali evaporation.
Alumina-zirconia, resistant to alkali-vapour corrosion.
Crown (arched roof)
1550–1650°CThe arched roof endures the high temperature of the combustion space and radiates heat back onto the glass surface. Silica, or alumina-zirconia in modern furnaces.
Silica or alumina-zirconia crown brick.
Regenerator (heat recovery)
800–1450°CA brick checkerwork that stores the heat of the exhaust gases and returns it to the incoming air — the heart of the furnace’s energy efficiency. Magnesia or fireclay depending on each layer’s temperature.
Magnesia checkers in the hot layers, fireclay in the cooler ones.
Copper smelting poses a problem steelmaking does not. The slag here is not limey but fayalitic: a fluid iron silicate rich in FeO. Worse than the slag is the sulphide matte itself, which wets the refractory and creeps into the smallest pore. The conclusion is plain: low, closed porosity is a necessity here, not a bonus.
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Flash smelting furnace
1200–1300°CCopper concentrate is burned with oxygen, yielding two phases: copper-rich matte and fayalitic slag. Simultaneous oxide and sulphide attack.
Magnesia-chrome brick; chrome spinel is stable against FeO.
Converter
1200–1350°CAir is blown through to burn off iron and sulphur and produce blister copper. Rotating the converter creates a severe thermal cycle — the most aggressive zone of the whole route.
Chrome-magnesite; better thermal-shock resistance than pure magnesia.
Anode furnace
1100–1250°CFinal fire refining and anode casting. The temperature is lower but the long contact with molten copper continues.
Magnesite brick or high-alumina castable.
Launders & runners
1100–1300°CThe transfer path for matte and molten copper between units. Flow abrasion plus thermal shock at every start and stop.
Silicon-carbide bearing castable; the melt does not stick to SiC.
A lime kiln, rotary or shaft, calcines limestone and drives off its CO2. The main attack here is not temperature — it is alkaline lime dust, which reacts with the silica and alumina of the lining to form low-melting phases. That is why lime refractory selection differs from cement, even though the two processes look alike.
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Preheating zone
400–900°CLimestone enters and warms up. Abrasion by coarse stone is the issue, not temperature.
Abrasion-resistant fireclay brick; high alumina is wasted money here.
Calcining zone
900–1200°CCalcium carbonate breaks down and releases CO2. Freshly formed lime dust is at its most reactive and attacks the lining.
High-alumina, low-silica brick for lime resistance.
Burning zone
1200–1450°CThe hottest zone, where quicklime forms. Lime combines with the silica of the lining to form a low-melting phase — so the lining must be low in silica and high in alumina or magnesia.
Magnesia or low-silica high-alumina; silica is the enemy here.
The cupola is the oldest and still the most widely used iron-melting furnace: scrap, coke and limestone are charged from the top and air is blown through the tuyeres. Its lining is small next to a blast furnace but sees the same three attacks — charge abrasion, hot slag and the heat of the melting zone.
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Charge & preheat zone
300–900°CSolid charge is dropped from the top and fills the shaft. Mechanical impact and abrasion of the charge dominate.
Impact-resistant fireclay brick; the low-cost part of the furnace.
Melting zone
1450–1600°CJust above the tuyeres; coke burns and the charge melts. The hottest zone, with active slag and droplets of molten iron.
Silicon-carbide bearing castable or brick; slag does not stick to SiC.
Tuyere (blast) zone
1500–1700°CBlast air enters and the coke oxidises fiercely. Local temperature climbs above even the melting zone.
Silicon carbide or high-alumina castable around the tuyeres.
Well & tap runner
1400–1500°CMolten iron collects and drains through the runner. Permanent contact with the melt plus flow abrasion.
Ramming or castable well lining; renewed each campaign.
A coke oven heats coal in the absence of air to make coke. Unlike the lime kiln, silica brick is the right choice here: at working temperature silica is stable and barely expands, holding the tall thin walls straight. The golden rule of this furnace is one sentence — never let it cool. Silica changes phase and expands sharply around 600 °C, and one full cool-down can destroy an entire battery.
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Coking chamber wall
1100–1350°CThe thin wall separating the coal from the heating flue and conducting heat across. It must be thin, conductive and stable over a 30-year campaign at once.
Silica brick; stable and virtually creep-free at working temperature.
Heating flue
1200–1400°CGas burns in these flues and passes its heat to the chamber wall. Hotter than the chamber itself, with an oxidising atmosphere.
Silica, or high-alumina fireclay in the hotter sections.
Roof & charging ports
900–1200°CThe chamber roof and the charging holes. Abrasion when coal is charged, and thermal shock every time the doors open and close.
Fireclay and castable; the doors are lined with insulating mass.
Sole & floor
1000–1300°CThe chamber floor the coal charge rests on and across which hot coke is pushed out. Constant mechanical abrasion on discharge.
Abrasion-resistant fireclay; pushing the coke wears the sole.
A reheating furnace, pusher or walking-beam, brings billets and blooms to about 1200 °C before rolling. Unlike a ladle or an arc furnace there is no slag and no melt here — the biggest hidden cost is heat loss. The lining design turns on insulation, and the critical zone is where the billet slides.
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Preheating zone
600–900°CCold billets enter and take heat from the exhaust gases. The temperature is low; the lining's real job is holding heat in.
Lightweight insulating brick and fibre; every degree lost is fuel.
Heating zone
900–1200°CBurners bring the billet to rolling temperature. Oxidising atmosphere and the scale that falls off the steel.
High-alumina castable with an insulating backup.
Soaking zone
1150–1250°CThe billet temperature evens out across its section. The hottest zone, and where molten scale can stick to the lining.
High alumina, resistant to molten scale and FeO.
Skid system (rails)
1000–1250°CWater-cooled pipes the billet slides along. Their refractory covering is critical: if it is poor, energy is wasted and a cold skid mark is left on the billet that becomes a defect in rolling.
Insulating castable over the skid pipe; reduces the cold spot.
The tunnel kiln is the standard furnace for tiles, sanitaryware and face brick: loaded cars pass slowly through a long tunnel and follow a fixed temperature curve. The refractory problem here is neither slag nor melt — it is temperature uniformity and energy use, plus the kiln furniture that goes into the fire together with the ware.
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Preheating zone
200–900°CDried ware enters and residual water and organics are driven off. Heating must be gentle or the body cracks.
Lightweight insulating brick; controlling the ramp matters more than refractoriness.
Firing zone
1100–1300°CPeak temperature; sintering and vitrification of the body happen here. Temperature uniformity across the tunnel section directly sets product quality.
Silicon carbide; high thermal conductivity evens the temperature.
Cooling zone
900–200°CThe fired ware cools gradually. Fast cooling, especially through the quartz inversion, cracks the body.
Lightweight insulation; the control here is the cooling rate, not the temperature.
Kiln furniture (cars & setters)
1100–1300°CThe plates, posts and setters the ware sits on, entering the fire with every load. They see thousands of thermal cycles — thermal-shock resistance matters more here than refractoriness.
Silicon carbide or cordierite-mullite; light and shock-resistant.
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