Corundum Series Refractory Bricks

Corundum Mullite Brick

Name: Corundum Mullite Brick
Brand: XZK

Corundum mullite bricks combine a corundum (α-Al2O3) skeleton with a mullite (3Al2O3-2SiO2) bonding matrix, giving an alumina content of 80-90% and a refractoriness under load of at least 1700°C. The two-phase structure trades a little of the purity of a straight corundum brick for markedly...

Al₂O₃:≥80%

Bulk Density:≥2.75g/cm³

Cold Crushing Strength:≥85MPa

Load-softening Temperature at 0.2MPa:T0.6≥1700℃

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Corundum Mullite Brick Overview

Corundum mullite bricks combine a corundum (α-Al₂O₃) skeleton with a mullite (3Al₂O₃·2SiO₂) bonding matrix, giving an alumina content of 80–90% and a refractoriness under load of at least 1700°C. The two-phase structure trades a little of the purity of a straight corundum brick for markedly better thermal shock and creep behaviour.

XZK Group manufactures corundum mullite bricks in grades XZK-CM80, XZK-CM85 and XZK-CM90 at our Xinmi plant in Henan. They are specified across the glass furnace superstructure — crown, breastwall, port crown, burner block, throat hanging wall and forehearth cover — in float, photovoltaic and end-fired furnaces.

What Is a Corundum Mullite Brick?

A corundum mullite brick is not a blend of two aggregates; it is a two-phase ceramic. Fused or sintered corundum grains form the load-bearing skeleton, while mullite grows between and around those grains during firing and bonds them together. Alumina content defines the grade — CM80 carries at least 80% and CM90 at least 90% — but the ratio between the phases defines the behaviour. Raising corundum increases hardness, density and refractoriness; raising the mullite fraction absorbs thermal strain, because mullite's crystal lattice accommodates expansion without cracking.

The body is pressed from graded corundum aggregate and high-purity alumina with a mullite-forming addition, on CNC presses rated 630 to 2000 tonnes. Press force sets the green density, and a controlled tunnel-kiln or shuttle-kiln schedule then completes mullitisation and sintering. Iron oxide is held between 0.15% and 0.20%, low enough that the brick neither colours the glass nor forms the low-melting phases that soften an alumina body under load.

The practical result is a brick that keeps its shape under sustained load. Creep rate at 1500°C over 5–50 h is 0.3% or lower for CM80 and CM85, and refractoriness under load is at least 1700°C in every grade. At the same time the material tolerates the cycling of port reversals and batch charging: CM85 reaches at least 15 cycles in the 1100°C water-quench test against 7 cycles for CM80.

Key Properties

Alumina content 80–90% with corundum as the load-bearing phase and mullite as the bonding matrix, graded as XZK-CM80, CM85 and CM90.
Refractoriness under load ≥ 1700°C (0.2 MPa) in all three grades, so the brick keeps its dimensions where fireclay and standard high-alumina bodies deform.
Low creep — 0.3% or less at 1500°C over 5–50 h in the CM80 and CM85 grades, which is what protects hanging walls and arch structures across a long campaign.
Thermal shock resistance of at least 7 cycles (CM80) and 15 cycles (CM85) in the 1100°C water-quench test, covering the reversal cycling of burner ports and crown positions.
Very low iron of 0.15–0.20% Fe₂O₃, limiting glass contamination and the formation of low-melting phases at the hot face.
Bulk density 2.75–3.00 g/cm³ with apparent porosity of 17–18%, producing a tight, low-permeability body against alkali vapour migration.

Technical Specifications

Technical Properties	XZK-CM80	XZK-CM85	XZK-CM90
Al₂O₃ (%)	≥ 80	≥ 85	≥ 90
Fe₂O₃ (%)	≤ 0.15	≤ 0.20	≤ 0.20
Bulk Density (g/cm³)	≥ 2.75	≥ 2.90	≥ 3.00
Apparent Porosity (%)	≤ 18	≤ 17	≤ 17
Cold Crushing Strength (MPa)	≥ 85	≥ 90	≥ 90
Refractoriness Under Load (0.2MPa, ℃)	≥ 1700	≥ 1700	≥ 1700
Thermal Shock Resistance (1100℃ water-cooled, cycles)	≥ 7	≥ 15	-
Creep Rate (1500℃ × 5-50h, %)	≤ 0.3	≤ 0.3	-

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

Available Grades and How to Choose

The three grades differ in alumina content, density and thermal shock rating rather than in basic chemistry, so selection follows the mechanism that will wear the brick in service.

XZK-CM80 — 80% Al₂O₃, bulk density 2.75 g/cm³, porosity 18% max, cold crushing strength 85 MPa min and 7 water-quench cycles. The economical grade for general superstructure courses and large wall areas where the thermal load is steady.
XZK-CM85 — 85% Al₂O₃, bulk density 2.90 g/cm³, porosity 17% max, cold crushing strength 90 MPa min and 15 water-quench cycles. Specify it for burner ports, port crowns and any position with strong reversal cycling; it is the best thermal-shock performer of the range.
XZK-CM90 — 90% Al₂O₃, bulk density 3.00 g/cm³, porosity 17% max and cold crushing strength 90 MPa min. The most refractory and most corrosion-resistant grade, chosen for the hottest superstructure positions and where alkali load is highest.

Industry Applications

Glass and Ceramic Industry: Used for the runner covers, burner bricks of glass kilns, and the linings of ceramic kilns.
Metallurgical Industry: Applied to the hot - blast stoves of blast furnaces, and the working linings of ladles and tundish.
Petrochemical Industry: Used for the refractory linings of cracking furnaces and synthetic ammonia gasifiers.
Power and Special Industries: Applied to the combustion chambers of boilers, and the protection of high - temperature components in aerospace.

Where Corundum Mullite Bricks Are Used in a Glass Furnace

In a glass tank, corundum mullite bricks occupy the superstructure: the parts of the furnace that face high radiant heat, alkali vapour and repeated thermal cycling without direct contact with the melt.

Crown. Crown courses in end-fired and photovoltaic furnaces, and in crown positions where alkali and batch dust attack matter more than the volume behaviour of silica. The mullite matrix holds the arch profile while the corundum phase resists vapour attack.
Crown corner and breastwall junction. At the springing line, structural stress concentrates and alkali vapour migrates upward from the melt. A dense corundum mullite brick with porosity below 18% slows that path and keeps the joint closed.
Port crown and burner port neck. The port neck is cycled between flame and cold combustion air at every reversal. Thermal shock resistance rather than refractoriness alone decides how long the block survives, which is why the higher-shock CM85 grade is used here.
Throat hanging wall and L-shaped suspended wall. A suspended wall hangs from anchor points and carries its own weight in tension and compression; a brick that creeps sags, opens joints and eventually drops. The 0.3% creep rate at 1500°C is the property that keeps the wall in place.
Forehearth and feeder channel covers. Above the melt, cover blocks resist thermal shock and must not spall into the glass. The corundum mullite body is dense and non-exuding, so it protects glass quality in the conditioning section.
Target wall and gable wall. In end-fired furnaces these walls face direct flame impingement and reversal cycling, and are built from the same high-alumina family for structural stability under localised thermal load.

Manufacturing and Quality Control

Manufacturing is controlled from raw material through to finished brick. Four automatic batching lines feed 20 CNC presses ranging from 630 to 2000 tonnes, so density is set by press force rather than operator judgement, and firing runs through four 108-metre fully automatic tunnel kilns and five ultra-high-temperature shuttle kilns for a uniform soak.

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 operates the Henan Provincial Engineering Technology Research Center for Sintered Refractories for Glass Furnaces.

Related Refractory Products

Corundum mullite bricks are normally specified together with corundum bricks for maximum purity, chrome corundum bricks for regenerator and burner service, zircon mullite bricks for crown corners and Three-Resistant bricks where spalling, erosion and thermal shock act together. See the corundum series for zoning guidance or browse all refractory products.

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About XZK Group

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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.