Zirconia Series Refractory Bricks

Zircon Mullite Brick

Name: Zircon Mullite Brick
Brand: XZK

Zircon mullite bricks carry zirconia inside a mullite-corundum matrix, so one body provides the corrosion resistance of zircon and the structural stability of mullite. Zirconia content runs from 6% to 30% and alumina from 48% to 65%, giving a grade ladder that can be matched to the severity of a...

ZrO₂:≥6%

Al₂O₃:≥48%

Bulk density:≥2.8g/cm³

Cold crushing strength:≥80MPa

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Zircon Mullite Brick Overview

XZK Group produces zircon mullite bricks in four grades — XZK-ZM6, XZK-ZM12, XZK-ZM20 and XZK-ZM30 — at our Xinmi plant in Henan, with iron oxide held at 0.2% or below in every grade. In a glass furnace they are used at the crown, the crown corner, the doghouse, burner blocks and the forehearth.

What Is a Zircon Mullite Brick?

Zircon mullite is a composite refractory. Zirconia, introduced as zircon or zirconia, is distributed through a mullite-alumina matrix during firing. The zirconia does two jobs at once: it is chemically resistant to alkali vapour and glass melt, and its phase transformation absorbs strain energy, which blunts a crack as it tries to propagate through the brick. The mullite matrix supplies the creep resistance and volume stability that a high-zirconia body alone would not have.

The bricks are pressed on CNC presses of 630 to 2000 tonnes and fired in fully automatic tunnel kilns, where the soak schedule controls the reaction between the zirconia and the alumina. Bulk density rises with zirconia content — from 2.8 g/cm³ at ZM6 to 3.3 g/cm³ at ZM30 — because zirconia is the denser phase. Low iron and a tightly controlled firing profile keep the mullite crystals interlocked and the apparent porosity at 17% or below.

Refractoriness under load is at least 1680°C and cold crushing strength at least 80 MPa in all four grades. That combination matters at the crown and the crown-breastwall junction, where a brick must carry structural load while resisting alkali vapour migrating upward from the melt. At the hot face the zirconia fraction determines how fast the vapour finds a reaction path; below it, the mullite matrix determines whether the course stays in place.

Key Properties

Zirconia from 6% to 30% and alumina from 48% to 65% across XZK-ZM6, ZM12, ZM20 and ZM30, allowing the chemistry to be matched to the position.
Refractoriness under load ≥ 1680°C (0.2 MPa) in every grade, so the brick stays dimensionally stable at the crown and crown corner.
Cold crushing strength ≥ 80 MPa, giving the load-bearing capacity needed for arch and junction courses that carry structural stress.
Low iron of 0.2% Fe₂O₃ maximum in all grades, limiting glass contamination and the formation of low-melting phases at the hot face.
Bulk density from 2.8 to 3.3 g/cm³ with apparent porosity at 17% or below, tightening the body against alkali vapour penetration as zirconia content rises.
Combined corrosion and thermal shock resistance from a zirconia phase dispersed through a mullite matrix, rather than a single-phase body that performs on one mechanism only.

Technical Specifications

Technical Properties	XZK-ZM6	XZK-ZM12	XZK-ZM20	XZK-ZM30
ZrO₂ (%)	≥ 6.0	≥ 12.0	≥ 20.0	≥ 30.0
Al₂O₃ (%)	≥ 65.0	≥ 60.0	≥ 58.0	≥ 48.0
Fe₂O₃ (%)	≤ 0.2	≤ 0.2	≤ 0.2	≤ 0.2
Bulk Density (g/cm³)	≥ 2.8	≥ 2.9	≥ 3.1	≥ 3.3
Apparent Porosity (%)	≤ 17	≤ 17	≤ 17	≤ 17
Cold Crushing Strength (MPa)	≥ 80	≥ 80	≥ 80	≥ 80
Refractoriness Under Load (0.2MPa, ℃)	≥ 1680	≥ 1680	≥ 1680	≥ 1680

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 four grades form a continuous ladder in zirconia content, density and corrosion resistance; the alumina content falls as zirconia rises, so the choice is a deliberate trade between chemical resistance and structural stiffness.

XZK-ZM6 — ZrO₂ ≥ 6.0%, Al₂O₃ ≥ 65.0%, bulk density ≥ 2.8 g/cm³. The structural grade, chosen where load and thermal cycling dominate and alkali attack is moderate.
XZK-ZM12 — ZrO₂ ≥ 12.0%, Al₂O₃ ≥ 60.0%, bulk density ≥ 2.9 g/cm³. A balanced grade for crown courses and larger wall areas exposed to moderate alkali vapour.
XZK-ZM20 — ZrO₂ ≥ 20.0%, Al₂O₃ ≥ 58.0%, bulk density ≥ 3.1 g/cm³. Used where vapour attack is stronger, such as crown corners and port surroundings, without going to the most expensive grade.
XZK-ZM30 — ZrO₂ ≥ 30.0%, Al₂O₃ ≥ 48.0%, bulk density ≥ 3.3 g/cm³. The most corrosion-resistant grade, specified for the hottest and most vapour-loaded superstructure positions, where the cost of a short campaign outweighs the cost of the brick.

Industry Applications

Glass Industry: Applied to parts directly exposed to flames like the breast walls and port arches of melting furnaces (temperatures above 1600 °C).
Metallurgical Industry: Used to manufacture key components such as aluminum - zirconium - carbon slide plates and continuous casting nozzles (temperatures between 1700 - 1800 °C).
Other Fields: Utilized as lining materials for ceramic and chemical kilns, or as aggregates for refractory castables.

Where Zircon Mullite Bricks Are Used in a Glass Furnace

Zircon mullite bricks serve the positions where alkali vapour, thermal cycling and structural load act together, in both the melting end and the combustion and distribution sections.

Crown and crown courses. In float, photovoltaic and end-fired furnaces the crown must resist alkali vapour from the melt while holding the arch profile. The zirconia fraction slows vapour attack and the mullite matrix keeps the course from creeping out of line.
Crown corner and crown-breastwall junction. Structural stress concentrates at the springing line and alkali vapour migrates upward into it. A dense zircon mullite brick with 17% porosity resists both, and is often placed alongside dense zircon bricks which block the same vapour path.
Doghouse and charging end. The charging area is cycled by batch entry and sees batch dust abrasion together with alkali. Thermal shock tolerance decides the brick life here rather than refractoriness alone.
Gas burner blocks and port necks. Localised flame temperature and reversal cycling make this the most thermally aggressive point in the superstructure. The higher-zirconia grades are positioned at the flame face.
L-shaped suspended wall and throat wall. The suspended wall mixes zircon mullite with fused cast AZS and silica bricks for structural stability, while the throat wall above the highest-velocity melt flow uses zircon mullite for creep and alkali resistance.
Forehearth and feeder channel covers. Cover blocks above the melt must resist thermal shock without spalling glass contamination into the channel.

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

Zircon mullite bricks are supplied as part of a superstructure package with corundum mullite bricks, zircon bricks, sintered AZS bricks, lightweight silica bricks for arch insulation and Three-Resistant bricks at burner blocks. See the zirconia series for zoning guidance or browse all refractory products.

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About XZK Group

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Facilities

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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.