Alumina-silicon Refractory Bricks

Fused Silica Bricks

Name: Fused Silica Bricks
Brand: XZK

Fused silica bricks are made from amorphous fused silica with an SiO2 content of 97% or 98%. Their defining property is an extremely low coefficient of thermal expansion, a fraction of that of any crystalline silica or alumina brick, which gives them thermal shock resistance better than almost...

SiO₂:≥97%

Bulk Density:≥1.86g/cm³

Cold Crushing Strength:≥40MPa

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

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Fused Silica Bricks Overview

Fused silica bricks are made from amorphous fused silica with an SiO₂ content of 97% or 98%. Their defining property is an extremely low coefficient of thermal expansion, a fraction of that of any crystalline silica or alumina brick, which gives them thermal shock resistance better than almost any other refractory and makes them the material of choice where a furnace zone cycles hard.

XZK Group supplies fused silica bricks in a pressed grade, XZK-FS98-P, and a cast grade, XZK-FS97-C, for the forehearth, throat and other thermally cycled, contamination-sensitive positions.

Why Fused Silica Behaves Differently

Ordinary silica brick is crystalline: it is fired to convert quartz into tridymite and cristobalite, and those phases have a relatively high and strongly temperature-dependent expansion. Fused silica is different. It is made by melting high-purity quartz and quenching it, so the material is amorphous glass, and amorphous silica has a thermal expansion coefficient of roughly 0.5 × 10^-6/°C, an order of magnitude lower than a crystalline brick.

The practical effect is that a fused silica brick barely changes dimension when it is heated or cooled. That is why the material survives 30 water-cooling cycles at 1100°C without spalling, and why it can be brought up to temperature quickly without the slow, carefully controlled heating curve that a silica crown requires. The same low expansion makes the brick dimensionally stable in service.

The limitation is devitrification. Held above about 1100°C for a long period, amorphous silica slowly converts to cristobalite, and the accompanying volume change can crack the brick. Fused silica bricks are therefore used in positions that run below that threshold or that tolerate the risk, and they are not a general substitute for a silica crown. With SiO₂ at 97–98% and Al₂O₃ held below 0.4%, they are also very low in contaminants, which matters in glass contact.

Key Properties

SiO₂ content of 97–98% with Al₂O₃ below 0.4%.
Very low coefficient of thermal expansion, giving exceptional resistance to thermal shock.
Thermal shock resistance of 30 water-cooling cycles at 1100°C, the highest of any brick in this range.
Can be heated and cooled rapidly, unlike crystalline silica brick, which needs a controlled heating curve.
Low bulk density of 1.86–1.90 g/cm³ and low thermal conductivity, reducing structural dead weight and heat loss.
Refractoriness under load of 1600–1650°C at 0.2 MPa and cold crushing strength of 40–45 MPa.

Technical Specifications

Technical Properties	XZK-FS98-P (Pressed)	XZK-FS97-C (Cast)
SiO₂ (%)	≥ 98	≥ 97
Al₂O₃ (%)	≤ 0.3	≤ 0.4
Bulk Density (g/cm³)	≥ 1.90	≥ 1.86
Apparent Porosity (%)	≤ 18	≤ 19
Cold Crushing Strength (MPa)	≥ 45	≥ 40
Refractoriness Under Load (0.2MPa, ℃)	≥ 1650	≥ 1600
Thermal Shock Resistance (1100℃ water-cooled, cycles)	≥ 30	≥ 30

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 two grades differ in purity and in the forming route. XZK-FS98-P is the pressed grade at 98% SiO₂, with bulk density of at least 1.90 g/cm³, cold crushing strength of 45 MPa and refractoriness under load of 1650°C. XZK-FS97-C is the cast grade at 97% SiO₂, used for large or complex shapes that cannot be pressed.

Specify the pressed grade where strength and purity are needed, and the cast grade where the geometry of the piece governs the choice. Both carry the same 30-cycle thermal shock resistance, which is usually the property that decides the application.

Because of devitrification, fused silica should be selected against the actual continuous service temperature of the position. Where a zone runs hot and continuously, a sillimanite, mullite or silica brick is usually the correct answer; where the demand is rapid cycling and low contamination, fused silica has no equal.

Industry Applications

Glass Industry: Suspended flame - blocking bricks in melting furnaces and hot - repair bricks for arch roofs.
Metallurgical Industry: Coke oven carbonization chambers and continuous casting submerged nozzles.
Other Fields: Arch roofs of ceramic kilns, high - temperature parts of hot - blast stoves, and other load - bearing structures.

Where Fused Silica Brickss Are Used in a Glass Furnace

Fused silica bricks are used where thermal cycling and glass purity matter more than load capacity, in particular:

Forehearth roof and cover blocks. The conditioning section cycles as the flow is controlled, and fused silica covers handle that cycling without spalling into the glass.
Throat and throat structures. The melt passage combines thermal cycling with high velocity, and the low-expansion brick resists the cracking that damages crystalline materials.
Doghouse and charging area, where the charging cycle imposes repeated thermal shock and the brick must tolerate it without a slow heating regime.
Crown and superstructure positions in rapidly cycled furnaces, where the low expansion is worth more than load capacity.
Glass contact applications needing low contamination, where the high silica purity and low alumina content avoid introducing colouring or refractory defects.

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

Fused silica bricks are supplied with mullite bricks, sillimanite bricks, zircon bricks and mullite insulating bricks. See the alumina-silicon bricks range, the monolithic refractories range or browse all refractory products.

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About XZK Group

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Innovation

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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.