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Properties of Refractory Castables

Tina Stendal Svendsen

Product Manager

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Refractory materials are subjected to following stress factors:• Thermal - by high temperatures and thermal shock• Mechanical - by pressure, impact, friction and airborne particles • Chemical - by gases, liquids, build-up, slag and melts

The properties of castables and their ability to withstand stresses are determined by:• Raw materials • Particle size distribution• Chemical reaction between raw materials at various temperatures

The properties of refractory castables can be analysed by a range of international test procedures

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Bending strength; Modulus of rupture (EN 1402-6)

Cold modulus of ruptureProvides information on material structure (QC)

Hot modulus of ruptureCharacterize the thermodynamic behaviour of the castable

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Cold Crushing Strength (EN 1402-6)

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Thermal Shock Resistance (EN 993-11)

Air quenching of 950°C hot specimens

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Abrasion resistance (ASTM C 704)

Temperature: 1000°C

Abrasion media: SiC grains

Testing angle: 45° and 90°

Results:

≤ 5cm3 loss: excellent

5cm3 to 10cm3: very good

10cm3 to 20cm3: good

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Alkali resistance (CEN/TS 15418)

Test media K2CO3 or K2SO4

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Hot-melt slag and build-up

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Slag resistance: Static test (CEN/TS 15418)

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Hot melt slag resistance (dynamic test)

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Open porosity (EN 933-1)

Test pieces are saturated in water under vacuum

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The influence of porosity on castable properties

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Other tests

• Particle size distribution

• Thermal expansion / creep

• Chemical and structural analyses; SEM and XRD

• Thermal conductivity

• Refractoriness / refractoriness under load

• CO-resistance

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Assessment of material data

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Temperature

Thermal property

Application

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Summary• Castables are subjected to thermal, mechanical and chemical

stresses• Wide range of international test standards to measure properties• Some tests are targeted for quality control • Other tests simulate operation conditions (temperature, chemicals)• Test of corrosive slags can both static and dynamic• Test slags at relevant temperatures• There is a close relationship between porosity and the physical and

chemical properties of castables• When comparing datasheets: Be aware of test-temperature and of to

which temperature has the test specimens been prefired prior to test