Alumina-silicon Refractory Bricks

Mullite Brick

Name: Mullite Brick
Brand: XZK

Sintered mullite bricks with 65-70% Al2O3 for glass furnace regenerator checkerwork, rider arches and forehearth covers. Low creep under load and refractoriness up to 1700C. Grades XZK-ML70-A, XZK-ML70-B and XZK-ML65-C.

Al₂O₃:≥65%

Bulk Densit:≥2.50g/cm³

Cold Crushing Strength:≥75MPa

Load-softening Temperature at 0.2MPa:T0.6≥1600℃

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Mullite Brick Overview

Mullite bricks are refractories whose crystal structure is dominated by mullite (3Al₂O₃·2SiO₂), a phase that is prized for one property above all others: it does not deform under load. In a glass furnace regenerator, where hundreds of tonnes of checkerwork press down on the bottom courses for years, that resistance to creep is what keeps the structure standing.

XZK Group manufactures sintered mullite bricks in grades XZK-ML70-A and XZK-ML70-B (machine pressed) and XZK-ML65-C (cast block), from our Xinmi plant in Henan. They are used in regenerator checkerwork, rider arches, forehearth covers and high-temperature structural positions across glass, steel and ceramic industries.

Why Mullite Bricks Resist Creep

Creep — slow plastic deformation under sustained load at high temperature — is the mechanism that ends the life of structural refractories. A brick that sags by a few millimetres per year closes joints and distorts a lining; a hanging wall that creeps eventually drops brick. Mullite's interlocking needle-like crystal structure resists this deformation far better than fireclay or high-alumina bodies:

High refractoriness under load, from 1600°C for the cast grade up to 1700°C for XZK-ML70-B.
Excellent thermal shock resistance from a low and stable coefficient of thermal expansion, allowing the brick to survive the repeated reversals of a regenerative furnace.
Good alkali vapour resistance. Mullite is a practical choice for the upper regenerator courses where flue gas carries alkali, and it performs particularly well where sand dust carry-over is high but alkali content is lower.
Chemical stability and low iron content. Grades run as low as 0.2% Fe₂O₃, minimising contamination risk in sensitive applications.
Volume stability. Low permanent linear change keeps brick dimensions predictable across a long campaign, which matters for a structure carrying accumulated load.

Technical Specifications

Technical Properties	XZK-ML70-A (Pressed)	XZK-ML70-B (Pressed)	XZK-ML65-C (Cast Large)
Al₂O₃ (%)	≥ 70	≥ 70	≥ 65
Fe₂O₃ (%)	≤ 1.2	≤ 0.2	≤ 0.8
Bulk Density (g/cm³)	≥ 2.55	≥ 2.65	≥ 2.50
Apparent Porosity (%)	≤ 18	≤ 17	≤ 17
Cold Crushing Strength (MPa)	≥ 80	≥ 80	≥ 75
Refractoriness Under Load (0.2MPa, ℃)	≥ 1620	≥ 1700	≥ 1600

Test methods follow GB/T and ISO practice; ASTM equivalents and full certificates of analysis are issued with every shipment.

Choosing Between the Three Grades

XZK-ML70-A — the general-purpose machine-pressed grade, balanced between performance and cost. Suitable for standard regenerator checkerwork and structural courses.
XZK-ML70-B — the high-performance grade with 0.2% Fe₂O₃ and refractoriness under load of 1700°C. Specify it for the most heavily loaded courses, rider arches and positions where contamination matters.
XZK-ML65-C — cast block for large or complex shapes that cannot be pressed, such as oversized checkerwork blocks and custom structural pieces.

For floors and walls that see significant sand dust carry-over, andalusite bricks and sillimanite bricks offer complementary performance in the same regenerator. Where alkali attack dominates, chrome corundum bricks are the better choice for the hot and condensation zones. Mullite insulating bricks handle the thermal insulation layer behind them.

Industry Applications

Glass Industry: Used for bricks in the upper structure of melting furnaces and feeder channel bricks.
Metallurgical Industry: Applied to the linings of hot - blast stoves and medium - temperature kilns.
Cement Industry: Used as linings in the transition/pre - heating zones of kilns.
Petrochemical Industry: Used as the protective layer of high - temperature reaction equipment.

Where Mullite Bricks Are Used in a Glass Furnace

Mullite's role in a glass tank is structural. It carries load and holds shape while other materials handle direct corrosion.

Regenerator checkerwork and chamber walls. The regenerator runs a three-zone duty cycle. Above 1100°C, checker bricks face thermal shock and alkali scour. Between 800 and 1100°C, alkali vapour reacts with sulphur oxides to form sulphate condensates that corrode brick and block flues. Below 800°C, the checkerwork must simply carry the accumulated dead weight of everything above it — and that is where mullite's low creep rate is decisive.
Rider arch and rider bricks. The rider arch supports the entire checkerwork. Mullite's resistance to creep under sustained load makes it the base material for this foundation.
Port crowns and burner port necks, where the combination of thermal cycling and structural load requires a material that will neither spall nor sag.
Forehearth and feeder channel covers. Above the melt, mullite cover blocks resist thermal shock and prevent the spalling that would contaminate glass.
Superstructure positions, particularly in furnaces where sand dust carry-over is significant but alkali levels are moderate.

Manufacturing and Quality Control

Mullite bricks are produced by high-temperature sintering from high-purity mullite and alumina raw materials, on CNC presses of 630 to 2000 tonnes. Firing runs through four 108-metre fully automatic tunnel kilns and five ultra-high-temperature shuttle kilns, giving uniform soak and predictable densification. Every batch is tested for bulk density, apparent porosity, cold crushing strength and refractoriness under load, and ships with a certificate of analysis.

XZK Group holds ISO 9001, ISO 14001, ISO 45001 and ISO 50001 certification and is recognised as a National High-Tech Enterprise. We operate the Henan Provincial Engineering Technology Research Centre for Sintered Refractories for Glass Furnaces and have contributed to industry standards including JC/T 2574-2020 (Sillimanite bricks for glass furnaces).

Related Refractory Products

Mullite bricks are supplied as part of a complete regenerator package, together with sillimanite bricks, andalusite bricks, chrome corundum bricks, low porosity fire clay bricks and mullite insulating bricks. See the mullite bricks range for zoning guidance or browse all refractory products.

Proven Global Projects

About XZK Group

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Innovation

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Facilities

Honors

Product Portfolio

Specializing in premium zircon, corundum, sintered AZS, and monolithics. With a $70M+ annual output, we deliver durable linings for global high-temp industries.

Capacity

✔ 4 automated microcomputer batching systems.

✔ 4 ultra-high-temp tunnel kilns & 5 shuttle kilns.

✔ 20+ CNC hydraulic presses (630-1500T).

✔ Digitalized workshops with 100,000T annual capacity.