In steelmaking, refractory failure is rarely caused by temperature alone.

A lining is simultaneously exposed to molten steel, aggressive slag, mechanical impact, gas injection, thermal cycling, oxidation and continuous changes in process conditions. Choosing a refractory simply because it has a higher alumina or MgO content, higher strength, or higher service temperature can therefore lead to disappointing performance.

Effective refractory selection for a steel plant starts with a different question:

What is actually causing wear in this particular zone of the furnace or vessel?

The answer can be completely different at the slag line, hearth, impact zone, tuyere, snorkel or steel-contact area.

That is why modern refractory engineering is increasingly based on zone-by-zone lining design, rather than using one refractory grade throughout an entire vessel.

Why Refractory Selection Matters

Refractories represent only one part of steelmaking cost, but their performance affects much more than refractory consumption.

A properly engineered lining can contribute to:

• Longer and more predictable campaigns
• Fewer emergency repairs and shutdowns
• Lower shell temperatures and heat losses
• Reduced gunning, patching and maintenance
• Better steel-temperature retention
• Improved protection against hot spots and breakouts
• More consistent steel quality
• Higher furnace availability

For plant owners, therefore, cost per tonne of steel is usually a more useful measure than refractory price per tonne.

A more expensive refractory that reduces downtime, repairs or heat loss may ultimately cost considerably less to operate.

Refractory performance should therefore be monitored through parameters such as refractory consumption per tonne of steel, repair material per heat, refractory-related downtime, residual lining thickness, shell-temperature distribution and steel-temperature loss.

Different Areas Inside a Steel Plant

Each steelmaking vessel creates its own combination of chemical, thermal and mechanical stresses. More importantly, conditions also vary considerably within the same vessel.

Electric Arc Furnace (EAF)

An EAF is one of the most demanding refractory environments in a steel plant.

Its lining must withstand:

• Scrap charging impact
• Electric-arc radiation
• High-temperature slag
• Oxygen and carbon injection
• Foaming slag
• High bath movement
• Rapid thermal cycling
• Localized hot spots

The slag line, burner and oxygen-injector areas, hearth, delta and eccentric bottom taphole (EBT) can consequently experience very different wear rates.

Charge material also matters.

A scrap-based EAF and a DRI-based EAF should not automatically use identical refractory designs. DRI can introduce additional oxide gangue and increase slag volume. If flux addition does not adequately compensate for this, slag basicity can fall and refractory attack can increase.

For this reason, EAF refractory selection should consider the charge mix, slag chemistry, FeO level, arc exposure, oxygen practice and maintenance strategy together.

Basic Oxygen Furnace (BOF)

Inside a BOF, oxygen blowing creates an intense metal-slag-gas emulsion.

The lining experiences:

• FeO-rich oxidizing slag
• High temperatures
• Scrap impact
• Gas and dust abrasion
• Carbon oxidation
• Tapping wear
• Repeated thermal cycling

Wear is highly zoned.

The mouth and upper cone experience significant abrasion. Slag crossover regions face strong chemical attack. Trunnion zones can be difficult to protect through slag coating, while bottom and tuyere regions experience localized erosion and thermomechanical stress.

MgO-C refractories are widely used for BOF working linings, but using the same MgO-C grade everywhere misses the point of zoned refractory design.

Carbon content, magnesia quality, antioxidants, density and brick design should be adjusted according to the duty of each zone.

Steel Ladle

A steel ladle is no longer simply a vessel for moving molten steel.

Depending on the plant, it may also undergo:

• Arc reheating
• Argon stirring
• Alloy additions
• Flux additions
• Vacuum treatment
• Calcium treatment
• Long holding periods
• Repeated heating and cooling

The slag line generally experiences the most severe chemical attack, while the barrel, impact zone, bottom, well blocks and purging-plug areas face different levels of erosion and thermal-mechanical loading.

Steel cleanliness introduces another consideration.

For ultra-low-carbon and demanding clean-steel grades, carbon-bearing refractory in direct steel contact may need to be limited. A ladle may therefore use MgO-C in the aggressive slag line while using low-carbon or carbon-free alumina-magnesia systems in selected metal-contact areas.

This is a good example of why the best refractory for lining life is not always the best refractory for steel quality.

Tundish

The tundish is the final refractory-lined vessel before steel enters the mold.

Its job extends beyond transferring steel. Tundish design influences:

• Steel flow
• Residence time
• Inclusion flotation
• Temperature consistency
• Reoxidation
• Nozzle performance

A typical tundish system may contain an insulation layer, permanent lining, disposable working lining, impact pads, dams, weirs, well blocks, nozzles and shrouds.

High-alumina castables are commonly used for permanent linings, while magnesia-based materials are widely used as disposable working linings.

Because the tundish is the last refractory contact before casting, refractory purity becomes especially important.

Reducible oxides such as FeO and SiO₂ can contribute to reoxidation of aluminum-killed steel, while eroded refractory particles can become exogenous inclusions.

Tundish refractory selection therefore needs to balance lining life with steel cleanliness and flow-control requirements.

RH Degasser

The RH degasser presents a particularly aggressive combination of high-temperature steel flow, vacuum operation and thermal cycling.

Steel circulates rapidly through the up-leg snorkel, vacuum vessel and down-leg snorkel.

Published operating data for demanding RH service reports steel temperatures around 1480-1630°C, circulation rates of approximately 100-150 tonnes per minute, and thermal swings approaching 800-900°C.

The refractory must therefore resist:

• High-velocity steel erosion
• FeO-rich slag attack
• Argon-driven abrasion
• Severe thermal shock
• Vacuum cycling
• Oxygen blowing in applicable processes

Direct-bonded magnesia-chrome refractories have traditionally been used in severe RH applications because of their combination of corrosion, erosion and thermal-shock resistance.

However, environmental and disposal concerns associated with possible Cr⁶⁺ formation have increased interest in validated chrome-free systems such as spinel-periclase-zirconia refractories.

Argon Oxygen Decarburization (AOD)

AOD converters are primarily used for stainless and other high-alloy steels.

The process introduces another difficulty for refractory engineers: the slag chemistry changes significantly during the heat.

During decarburization, the refractory can face high-chromium oxidizing slag. Conditions change again during reduction and desulfurization.

At the same time, intense gas injection produces severe bath movement and localized erosion around the tuyere region.

Magnesia-doloma and doloma refractories are widely used in AOD lining systems.

However, refractory life is strongly influenced by:

• CaO/SiO₂ ratio
• Cr₂O₃ content
• MgO saturation
• Flux selection
• Gas-flow rate
• Slag fluidity
• Moisture control

A more fluid slag may improve metallurgical reactions while simultaneously increasing refractory penetration and dissolution. Process optimization and refractory optimization therefore cannot be treated as separate exercises.

Selection Criteria for Steel Plant Refractories

A refractory data sheet contains dozens of properties. Five operating factors, however, should be examined before choosing the material.

1. Temperature

Maximum service temperature is useful, but it should never be the only basis for refractory selection.

Engineers need to consider:

• Normal operating temperature
• Peak temperature
• Duration at peak temperature
• Heating rate
• Cooling rate
• Temperature gradients through the lining
• Frequency of thermal cycling

A material that survives a continuously operated furnace may fail rapidly when exposed to repeated heating and cooling at the same peak temperature.

The temperature cycle is therefore often more important than the maximum temperature itself.

2. Slag Chemistry

Slag is one of the primary causes of refractory wear.

The refractory should be chemically compatible with the slag it encounters.

Basic MgO-based refractories generally perform well against basic steelmaking slags, while alumina-magnesia and spinel systems are commonly used in selected ladle applications.

But slag chemistry changes during processing.

FeO-rich oxidizing slags, acidic gangue from DRI, high-chromium AOD slags and strongly basic refining slags can attack the same refractory differently.

Carbon provides MgO-C refractories with useful non-wetting and thermal-shock properties. In highly oxidizing conditions, however, FeO can oxidize the carbon. Once carbon is removed, the refractory structure becomes more open and easier for slag to penetrate.

Slag practice and refractory selection should therefore be engineered together.

3. Thermal Shock

Refractories expand when heated and contract when cooled.

If this temperature change occurs too quickly, stresses develop inside the material. Repeated cycles can eventually cause cracking and spalling.

Thermal-shock resistance depends on more than strength. It is influenced by:

• Thermal expansion
• Thermal conductivity
• Elastic modulus
• Fracture resistance
• Lining geometry
• Thickness
• Expansion joints
• Installation quality

This is why the strongest refractory on a laboratory data sheet is not necessarily the material that survives longest in a thermally cycled vessel.

RH snorkels, EAF deltas, ladles and frequently cycled tundishes all require particularly careful consideration of thermal shock.

4. Abrasion, Erosion and Impact

Not all refractory wear is chemical.

Mechanical damage occurs throughout a steel plant:

• Scrap impacts EAF and BOF linings.
• High-velocity steel erodes RH snorkels.
• Gas injection attacks AOD tuyere zones.
• Argon stirring increases wear around ladle purging systems.
• Tapping streams attack ladle and tundish impact zones.
• Mechanical cleaning can damage otherwise healthy refractory.

The solution is not necessarily to install the most expensive refractory everywhere.

Often, better economics come from local reinforcement: stronger refractory grades, thicker lining, precast blocks or sacrificial impact components only where mechanical duty is highest.

5. Steel Grade and Cleanliness

The refractory is part of the metallurgical system.

It can introduce or interact with carbon, oxygen, magnesium, alumina, silica and other constituents.

For critical grades, engineers should ask:

• Is the steel ultra-low-carbon?
• Is it aluminum-killed or silicon-killed?
• Is calcium treatment used?
• Can refractory contact cause carbon pickup?
• Could the lining contribute to reoxidation?
• Could refractory reactions generate inclusions?
• Is nozzle clogging a concern?
• Is long vacuum treatment required?

This becomes particularly important in ladles and tundishes, where refractory chemistry can influence the final steel entering the caster.

Common Refractory Failure Mechanisms

Understanding why the previous lining failed is often more valuable than immediately selecting a higher-grade replacement.

Chemical dissolution

If slag is undersaturated in a component such as MgO, it may dissolve that component directly from the refractory.

The solution can involve both refractory chemistry and slag control.

Slag or metal penetration

Molten material can enter pores, cracks and open joints. Internal reactions may then weaken grain bonds or form low-melting phases, eventually causing peeling and structural failure.

Low apparent porosity helps, but pore structure, wettability, grain chemistry and joint quality are equally important.

Carbon oxidation

In MgO-C refractories, carbon can react with oxygen, FeO, CO₂, steam or other oxidizing species.

Loss of carbon increases porosity and allows slag to penetrate more easily.

Thermal spalling

Rapid or uneven temperature changes generate internal stresses.

Typical symptoms include surface flaking, cracking and pieces separating parallel to the hot face.

Mechanical erosion

Fast-moving steel, slag, gas or solid material physically removes refractory.

Typical locations include AOD tuyeres, RH snorkels, EAF injection areas, ladle impact zones and tundish impact pads.

Structural cracking and joint opening

Even the correct refractory can fail because of poor geometry, shell deformation, incorrect expansion allowance, poor brick fit or badly designed transitions.

Once a joint opens, slag or steel penetration can accelerate failure very quickly.

Hydration and dry-out damage

Doloma and CaO-containing refractories are particularly moisture-sensitive.

Castables also require carefully controlled curing and dry-out. Heating retained water too rapidly can generate internal steam pressure and, in severe cases, explosive spalling.

The refractory specification therefore does not end with chemistry. Storage, installation, curing and dry-out are part of refractory engineering.

Recommended Refractory for Each Application

The following should be treated as a technical starting point. Final selection must be based on actual operating and slag data.

Application	Typical Refractory System	Critical Zones	Key Selection Factors
EAF	MgO-C sidewall/slag-zone bricks; magnesia-based hearth mixes; high-alumina or alumina-spinel roof/delta systems; dedicated EBT materials	Slag line, injectors, hot spots, hearth, delta, EBT	Scrap/DRI ratio, FeO, slag basicity, arc exposure, cooling system
BOF	Zoned MgO-C lining; premium fused-magnesia/oxidation-resistant grades in severe zones; basic repair systems	Slag crossover, trunnions, bottom, tuyeres, taphole, mouth	FeO, oxygen practice, slag splashing, scrap impact, blowing configuration
Ladle	MgO-C slag line; Al₂O₃-MgO-C, Al₂O₃-MgO and alumina-spinel systems in metal-contact and bottom zones	Slag line, impact zone, purging plugs, well blocks, bottom	Slag chemistry, argon stirring, vacuum treatment, hold time, steel cleanliness
Tundish	High-alumina permanent lining; magnesia-based disposable working lining; engineered impact and flow-control components	Impact zone, slag line, outlets, well blocks	Sequence length, steel grade, preheat, inclusion control, clogging
RH Degasser	Traditional magnesia-chrome systems or validated chrome-free alternatives; engineered gunning, ramming and precast components	Snorkels, lower vessel, oxygen-blow region	Circulation velocity, FeO, vacuum cycling, thermal shock, environmental requirements
AOD	Zoned magnesia-doloma/doloma lining with premium reinforcement around severe zones	Tuyeres, slag line, trunnions, mouth	Stainless grade, slag sequence, Cr₂O₃, basicity, gas flow, flux practice

One principle applies across every vessel:

Do not over-specify the entire lining because one zone is failing.

If 10% of a vessel controls the campaign, strengthening that 10% may deliver a better return than increasing refractory quality across the remaining 90%.

How Lanexis Engineers Customized Lining Systems

A refractory problem is not always solved by replacing one brick with a better brick.

The failure may originate from slag chemistry, excessive shell heat loss, poor zoning, installation, thermal cycling, lining geometry or maintenance practice.

Lanexis therefore approaches lining design as a furnace-specific engineering problem.

1. Understand the operating conditions

The engineering review begins with actual plant data:

• Furnace or vessel drawings
• Existing lining profile
• Temperature records
• Slag analysis at different process stages
• Scrap, DRI and hot-metal ratios
• Steel grades
• Oxygen and gas practice
• Treatment and holding times
• Shell thermography
• Cooling arrangement
• Repair consumption
• Previous campaign history

2. Map the failure zone by zone

Instead of treating “refractory wear” as one problem, each critical area is examined for its dominant mechanism:

corrosion, oxidation, penetration, thermal spalling, abrasion, impact, structural movement or installation-related failure.

This creates a wear map for the vessel.

3. Engineer the complete lining

The working refractory is only one layer of the system.

Lanexis evaluates the working lining, permanent lining, backup insulation, local lining thickness, brick or monolithic construction, precast components, joints and transition details together.

Premium materials can then be concentrated in the zones where they produce measurable operational value.

4. Optimize the thermal profile

Heat moving through the refractory is also money leaving the process.

Lanexis uses thermal modelling to evaluate shell temperature, heat flux, stored heat and lining temperatures before changing insulation thickness or refractory configuration.

For example, in one Lanexis ladle model, replacing a 13 mm ceramic-fiber backup with a 10 mm microporous LadlePro layer, while maintaining the same 295 mm overall lining thickness, predicted:

• Shell temperature reduction from 281°C to 246°C
• Heat-flux reduction from 6,063 W/m² to 4,656 W/m²
• Increase in stored heat from 1,107 MJ/m² to 1,231 MJ/m²

These are project-specific engineering results and should not be interpreted as guaranteed values for every ladle.

Lanexis project data also includes a 170-ton EAF where a 10 mm UltraTherm microporous backup system behind the MgO-C lining was associated with approximately 50% lower shell heat loss and 15-20% improvement in refractory life.

In another EAF installation, a 5 mm microporous layer combined with 13 mm fiber board was associated with approximately 60-70% lower heat loss and 25-50% improvement in refractory life.

Actual performance depends on furnace design, operating conditions, baseline lining and measurement methodology.

5. Engineer installation, not just material supply

A high-performance refractory installed incorrectly is still a poorly performing lining.

The engineering process therefore extends to:

• Installation drawings
• Brick and shape selection
• Expansion allowances
• Anchoring
• Shell preparation
• Mixing and water control
• Curing
• Dry-out schedules
• Installation quality checks

6. Measure what happens after commissioning

The lining should continue generating engineering information after installation.

Campaign performance can be reviewed through:

• Shell thermography
• Residual lining thickness
• Repair consumption
• Steel-temperature loss
• Hot-spot development
• Campaign life
• Refractory-related downtime
• Refractory cost per tonne of steel

This data then becomes the basis for the next lining optimization.

Build the Refractory Lining Around the Process

There is no universal refractory lining for an EAF, BOF, ladle, tundish, RH degasser or AOD converter.

Two furnaces producing the same steel can require different lining systems because their charge mix, slag chemistry, operating cycle, cooling design, maintenance practice and failure history are different.

The objective of refractory selection should therefore not be:

“Which refractory has the best specification?”

It should be:

“Which lining system gives this plant the safest and most economical performance under its actual operating conditions?”

That shift from product selection to lining engineering is where meaningful improvements in refractory life, energy efficiency and plant availability begin.

Need to Review a High-Wear Zone or Existing Lining?

Lanexis engineers refractory and insulation systems around actual furnace conditions, slag practice, steel grades, production targets and failure history.

Share your existing lining profile, operating conditions, slag data and wear pattern with our technical team for a zone-by-zone refractory lining review.