Corundum Bricks
High-purity Al₂O₃ refractories engineered for glass furnace superstructures, regenerators and throats — from 62% to 99% alumina, sintered and fused.
Corundum bricks are the workhorses of the glass furnace superstructure. Built on a corundum (α-Al2O3) crystal matrix with alumina content from 62% to 99%, they hold their shape and volume at temperatures where silica and fireclay refractories begin to creep, and they stand up to the alkali vapour and batch dust that attack every melting campaign.
XZK Group has manufactured corundum-based refractories since 2002 from our Xinmi plant in Henan — the heartland of China's refractory industry. Our corundum family covers sintered corundum bricks, chrome corundum bricks with 10–30% Cr2O3, corundum mullite bricks, zirconia corundum grades and the patented Three-Resistant (3R) brick — a complete range for glass tanks, metallurgical furnaces and high-temperature process equipment.
What Are Corundum Bricks?
Corundum is the crystalline form of aluminium oxide. In refractory service it is valued for three properties that rarely appear together: a melting point above 2000°C, a Mohs hardness of 9, and near-total chemical inertness in oxidising and weakly reducing atmospheres. A corundum brick carries those properties into the furnace wall.
Unlike fused cast AZS, corundum bricks are produced by high-pressure pressing or slip casting followed by sintering at 1700–1800°C. The result is a dense, uniformly microstructured body with no glassy phase — which matters in glass melting, because a glassy phase is what exudes from a refractory and becomes a stone or cord defect in the finished glass.
Where corundum refractories earn their place in a glass tank
Corundum bricks are specified where two conditions meet: high temperature and aggressive chemistry. In a glass furnace that means the superstructure, the throat, the forehearth and the regenerator. In each location the specific grade changes with the dominant wear mechanism — and choosing the wrong variant is the most common cause of a short campaign.
Types and Grades of Corundum Bricks
Five distinct families sit under the corundum heading. They differ in alumina content, secondary phase, and therefore in which wear mechanism they are designed to defeat.
Sintered corundum
Corundum Brick
XZK-CR95 · XZK-CR99
High-purity sintered corundum with 95–99% Al2O3 and very low iron. The default choice for glass contact and high-wear areas where chemical purity matters as much as refractoriness.
Al2O3 ≥ 95–99% · Bulk density ≥ 3.15–3.20 g/cm³ · CCS ≥ 80–90 MPa
Chrome-bearing
Chrome Corundum Brick
XZK-CC10 · CC12 · CC15 · CC30
Corundum combined with 10–30% Cr2O3. Chromium oxide suppresses slag wetting and raises thermal shock resistance, making these grades the standard for regenerators and burner zones.
Cr2O3 10–30% · RUL ≥ 1700°C · Thermal shock ≥ 12 cycles (950°C air-cooled)
Mullite-bonded
Corundum Mullite Brick
XZK-CM80 · CM85 · CM90
Interlocking corundum and mullite crystals form a dense network that resists creep while tolerating thermal cycling. Preferred for suspended structures such as the L-shaped wall and throat hanging wall.
Al2O3 ≥ 80–90% · RUL ≥ 1700°C · Creep (1500°C) ≤ 0.3%
Patented · ZL201310431067.6
Three-Resistant Brick (3R)
XZK-3R
Our patented chrome-zirconia-corundum composition. The ZrO2 fraction arrests crack propagation while Cr2O3 resists alkali, delivering simultaneous spalling, erosion and thermal shock resistance in burner blocks and crown-breastwall joints.
Al2O3 ≥ 70% · Cr2O3 ≥ 10% · ZrO2 ≥ 7% · Thermal shock ≥ 10 cycles (1100°C water-cooled)
Fused · α and β
Fused Corundum Brick
White fused alumina based
Electrically fused α-alumina provides maximum density and the highest refractoriness in the range. The β-alumina variants are formulated for sodium-rich atmospheres, where they resist alkali vapour attack that degrades conventional alumina bodies.
Used in the rear superstructure and areas of a float tank subject to alkali evaporation.
Zirconia-bearing
Zirconia Corundum Brick
Cr-Zr-Corundum family
Zirconia additions raise resistance to molten glass and thermally induced cracking. These grades bridge the gap between corundum refractories and full AZS materials, and are frequently specified alongside them in the same lining.
Specify where glass contact and thermal cycling occur together.
Technical Specifications
All values are typical for the grade and are verified batch by batch in our in-house laboratory. Because a glass furnace lining is bought as a system rather than a single brick, we list the full grade set so you can match material to zone without mixing suppliers.
Sintered corundum bricks
| Property | XZK-CR95 | XZK-CR99 |
|---|---|---|
| Al2O3 (%) | ≥ 95 | ≥ 99 |
| Fe2O3 (%) | ≤ 0.3 | ≤ 0.3 |
| Bulk density (g/cm³) | ≥ 3.15 | ≥ 3.20 |
| Apparent porosity (%) | ≤ 18 | ≤ 17 |
| Cold crushing strength (MPa) | ≥ 90 | ≥ 80 |
Chrome corundum bricks
| Property | XZK-CC10 | XZK-CC12 | XZK-CC15 | XZK-CC30 |
|---|---|---|---|---|
| Al2O3 (%) | ≥ 83.0 | ≥ 80.0 | ≥ 78.0 | ≥ 62.0 |
| Cr2O3 (%) | ≥ 10.0 | ≥ 12.0 | ≥ 14.5 | ≥ 30.0 |
| Fe2O3 (%) | ≤ 0.3 | ≤ 0.3 | ≤ 0.3 | ≤ 0.3 |
| Bulk density (g/cm³) | ≥ 3.25 | ≥ 3.25 | ≥ 3.25 | ≥ 3.40 |
| Apparent porosity (%) | ≤ 17 | ≤ 17 | ≤ 17 | ≤ 17 |
| Cold crushing strength (MPa) | ≥ 100 | ≥ 100 | ≥ 100 | ≥ 100 |
| Refractoriness under load (0.2 MPa, °C) | ≥ 1700 | ≥ 1700 | ≥ 1700 | ≥ 1700 |
| Thermal shock, 950°C air-cooled (cycles) | ≥ 12 | ≥ 12 | ≥ 12 | — |
Corundum mullite bricks
| Property | 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 (0.2 MPa, °C) | ≥ 1700 | ≥ 1700 | ≥ 1700 |
| Thermal shock, 1100°C water-cooled (cycles) | ≥ 7 | ≥ 15 | — |
| Creep rate (1500°C × 5–50 h, %) | ≤ 0.3 | ≤ 0.3 | — |
Three-Resistant brick (patented)
| Property | XZK-3R |
|---|---|
| Al2O3 (%) | ≥ 70 |
| Cr2O3 (%) | ≥ 10 |
| ZrO2 (%) | ≥ 7 |
| Fe2O3 (%) | ≤ 0.3 |
| Bulk density (g/cm³) | ≥ 3.3 |
| Apparent porosity (%) | ≤ 17 |
| Cold crushing strength (MPa) | ≥ 100 |
| Refractoriness under load (0.2 MPa, °C) | ≥ 1700 |
| Thermal shock, 1100°C water-cooled (cycles) | ≥ 10 |
Test methods follow GB/T and ISO practice; ASTM equivalents and full certificates of analysis are issued with every shipment.
Where Corundum Bricks Are Used in a Glass Furnace
A float, container or fibre glass tank exposes different zones to completely different loads. Corundum refractories appear in six of them — each for a specific reason.
Superstructure — breastwalls, port crowns and tuck stones
The superstructure sees radiant heat from the melt plus a continuous upward flow of alkali vapour. Silica bricks spall; fireclay bricks creep. Corundum mullite and dense corundum grades hold their volume instead, which is why they are used in the front section where batch dust carry-over concentrates.
Typical grades: XZK-CM80 / CM85 / CM90, XZK-CR95
Burner blocks and port necks
A gas burner block faces the most violent conditions in the furnace: localised temperatures that spike during combustion, high-velocity flame turbulence, and thermal shock on every reversal. Chrome corundum and the 3R brick are specified here because chromium oxide and zirconia together blunt both flame scour and crack growth.
Typical grades: XZK-3R, XZK-CC15 / CC30, XZK-CM90
Regenerator — checkerwork and chamber walls
The regenerator runs a three-zone duty cycle. Above 1100°C, checker bricks absorb thermal shock and the scouring of high-velocity alkali vapour. Between 800 and 1100°C, volatile alkali 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 without creeping.
Typical grades: XZK-CC10 / CC12 (hot zone and condensation zone), XZK-CM85 (structural courses)
Throat and throat hanging wall
The throat is the narrowest passage in the tank and carries the highest glass velocity. It combines intense thermal shock with severe mechanical abrasion. Corundum mullite's low creep rate keeps a hanging wall dimensionally stable over a multi-year campaign.
Typical grades: XZK-CM90, XZK-CR99
Forehearth channel and roof
In the forehearth, glass quality is everything. Any exudation from the refractory becomes a blister or cord in the finished product. Dense corundum and corundum mullite bodies contain no glassy phase to exude, and they resist the thermal cycling of gob forming.
Typical grades: XZK-CR99, XZK-CM85, XZK-CM80
Tank bottom sub-layers and paving
Corundum grades appear in the bottom structure as levelling and support courses, working with zircon and AZS material to seal against the upward drilling that heavy-metal contaminants cause in the paving layer.
Typical grades: XZK-CR95, XZK-CM90 — specified together with zircon bricks and sintered AZS
On Site — Corundum and Chrome Corundum at Work
Corundum grades go where temperature and erosion are both extreme — the throat, the ports and the suspended wall at the working end.
Failure Mechanisms and How Corundum Grades Defeat Them
Refractory life is decided by whichever mechanism reaches the brick first. Naming the mechanism correctly is the difference between a six-year campaign and a six-month repair.
How to Select the Right Corundum Brick
Four questions resolve almost every corundum specification. Work through them in order.
| If the duty is… | Dominant risk | Specify | Grade |
|---|---|---|---|
| Superstructure, front section, batch dust carry-over | Dust erosion + volume instability | Corundum mullite, high alumina | XZK-CM85 / CM90 |
| Superstructure, rear section, alkali evaporation | Alkali vapour penetration | Dense corundum / fused alumina base | XZK-CR99 / fused α-β |
| Burner block, port neck, reversal zone | Thermal shock + flame scour | Chrome corundum, 3R | XZK-3R / XZK-CC15 / CC30 |
| Regenerator hot and condensation zones | Sulphate attack + alkali scour | Chrome corundum | XZK-CC10 / CC12 |
| Regenerator structural courses, rider arch support | Creep under accumulated load | Corundum mullite, low creep | XZK-CM80 / CM85 |
| Throat, throat hanging wall | Thermal shock + abrasion | Corundum mullite, dense corundum | XZK-CM90 / XZK-CR99 |
| Forehearth channel and roof | Exudation → glass defect | High-purity corundum, no glassy phase | XZK-CR99 / XZK-CM85 |
| Glass contact, highest purity required | Chemical contamination | 99% sintered alumina | XZK-CR99 |
Three practical rules from our application engineers:
- Do not over-specify the whole tank. Chrome corundum in every zone raises cost without extending life; the wear mechanisms simply differ by zone. Match grade to mechanism.
- Match expansion, not just chemistry. Neighbouring bricks with very different thermal expansion will open joints at temperature. Our engineers supply a full lining layout, not a product list.
- Tell us the furnace, not just the brick. Two 500 t/d float tanks can need different grades in the same zone if batch composition or pull rate differs. Full operating data produces the right specification.
Manufacturing and Quality Control
Corundum refractories are unforgiving of process variation. Porosity that varies between batches becomes uneven wear in service, and uneven wear is what ends a campaign early.
Four automatic batching lines feed 20 CNC presses ranging from 630 to 2000 tonnes, so brick density is controlled by press force rather than operator judgement. Firing runs through four 108-metre fully automatic tunnel kilns and five ultra-high-temperature shuttle kilns, giving the uniform soak that corundum bodies need to complete their densification.
Quality control covers the full chain: incoming raw material assay, in-process density and dimensional checks, and finished-brick testing for bulk density, apparent porosity, cold crushing strength and refractoriness under load. Every shipment leaves with a certificate of analysis.
XZK Group holds ISO 9001, ISO 14001, ISO 45001 and ISO 50001 certification, is recognised as a National High-Tech Enterprise, and operates the Henan Provincial Engineering Technology Research Centre for Sintered Refractories for Glass Furnaces. We have contributed to standards including JC/T 2574-2020 (Sillimanite bricks for glass furnaces) and T/CSTM 00853-2024 (Chrome-zirconia-corundum bricks for glass furnace regenerators).
Industries We Serve
Glass
Float, container, fibre and specialty glass tanks. Superstructures, regenerators, throats, forehearths and burner blocks — supplied as a zoned lining system rather than individual products.
Iron and steel
Ladles, tundishes, blast furnace linings and converter roofs, where corundum's abrasion resistance and refractoriness extend campaign life in high-throughput operations.
Non-ferrous metals
Aluminium and copper smelting equipment, where corundum bricks resist both metal penetration and the aggressive fluxes used in refining.
Ceramics, petrochemical and power
Kiln furniture and high-temperature zones in ceramic production; refractory linings for petrochemical reactors, gasifiers and power plant equipment.
Frequently Asked Questions
What is the difference between corundum brick and high alumina brick?
Alumina content and crystal structure. High alumina bricks carry 55–80% Al2O3 with a mullite-corundum mix; corundum bricks run from 80% to 99% Al2O3 with corundum as the dominant crystal phase. The higher corundum fraction raises refractoriness, cold crushing strength and abrasion resistance, which is why corundum grades are specified in high-wear and glass-contact zones.
Corundum brick or AZS — which should I use in the superstructure?
It depends on the zone. Fused cast AZS performs well in glass contact and high-corrosion areas but tends to exude glassy phase at high temperature in the superstructure, which can cause glass defects. Ceramically bonded corundum grades have no glassy phase, so they are increasingly preferred in superstructure positions — particularly where batch dust erosion or alkali evaporation dominates.
Which corundum grade is best for a glass furnace regenerator?
Chrome corundum, typically XZK-CC10 to CC15. The Cr2O3 fraction resists both alkali vapour in the hot zone above 1100°C and the sulphate condensates that form in the 800–1100°C range. For structural courses that carry heavy load, use a low-creep corundum mullite grade such as XZK-CM85.
Can you produce corundum bricks in custom shapes?
Yes. We press to drawing for standard shapes and use slip casting or vibration casting for complex geometries. Blocks of one tonne and above can be produced by vibration casting, with lengths beyond two metres and heights up to 400 mm. Complex burner blocks, throat blocks and channel shapes are routine for us — send a drawing and we will confirm feasibility.
What is your minimum order quantity and lead time?
MOQ depends on the grade and shape. Standard corundum and chrome corundum shapes have no practical minimum beyond a full pallet; custom shapes depend on tooling. Typical lead time is 25–40 days for standard grades, and we hold emergency stock of common repair shapes for short-notice shutdowns. Contact us with your list and we will confirm both.
Do you supply samples for testing?
Yes. We provide free samples of standard grades for dimension and quality assessment, along with the certificate of analysis for the production batch. For critical applications we can also supply post-mortem analysis of a failed brick to identify the wear mechanism and specify a better grade.
How do I get a quotation?
Send us the grade, quantity, shape drawing if custom, and the furnace zone. Our engineers review the application before quoting, so the price you receive already accounts for the right specification rather than the cheapest one. Quotations are returned within 24 hours on business days.
Why Buy Corundum Bricks from XZK Group
We are a sintered refractory specialist, not a trading company. Corundum, mullite, zircon, AZS, magnesia and insulating bricks are all produced in our own plant, which means one point of responsibility for a complete glass furnace lining — and one engineering team to hold accountable if a zone underperforms.
Our application engineers have supplied refractories to glass manufacturers across Asia, Europe, Africa and the Middle East, including float lines, container plants and fibre glass producers. That field experience is what turns a grade list into a working lining design: we read the furnace, the batch and the pull rate, then specify the zones.
Get your corundum brick specification reviewed — free
Send us your furnace data or a brick list. Our engineers will confirm the right grade for each zone, flag any mismatch, and return a quotation within 24 hours.
Related refractory products
Corundum bricks work as part of a complete glass furnace lining. Depending on the zone, they are specified alongside mullite bricks, zircon bricks, sintered AZS bricks, fused cast AZS blocks, sillimanite bricks and corundum mullite bricks. Browse the full corundum series or all refractory products for zoning guidance.
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