Highland manufactures insulating fire brick (IFB) in four ASTM C155 grades: K23 (bulk density 0.60 g/cm³, working temp 1100°C), K26 (0.80 g/cm³, 1350°C), K28 (0.90 g/cm³, 1450°C), and K30 (1.00 g/cm³, 1550°C). Al₂O₃ content 38–75% across grades.
Thermal conductivity 0.22–0.42 W/m·K at 600°C. Fe₂O₃ <1.0% — suitable for reducing atmosphere service in petrochemical and hydrogen furnaces. Dimensional tolerance ±0.5mm after six-side grinding.
ISO 9001:2015 certified with batch density and conductivity test reports. Standard grades ship within 30–40 working days. Submit your furnace type and operating temperature for grade recommendation.
| Property | Unit | K23 Grade | K26 Grade | K28 Grade | K30 Grade |
| Classification Temp | °C | 1260 | 1430 | 1540 | 1650 |
| Working Temp | °C | 1100 | 1350 | 1450 | 1550 |
| Bulk Density | g/cm³ | 0.60 | 0.80 | 0.90 | 1.00 |
| Cold Crushing Strength | MPa | 1.2 | 2.0 | 2.5 | 3.0 |
| Thermal Cond. (600°C) | W/m.k | 0.22 | 0.28 | 0.35 | 0.42 |
| Linear Shrinkage (24h) | % | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 |
| Al2O3 Content | % | 38 - 42 | 50 - 55 | 65 - 70 | 72 - 75 |
| Fe2O3 Content | % | < 1.0 | < 0.8 | < 0.7 | < 0.6 |
Highland Refractory is a leading global manufacturer and supplier of high-performance Insulating Fire Bricks (IFB). Our products are engineered for maximum energy efficiency, precise thermal control, and long-term durability in the most demanding industrial environments.
Whether you are designing a petrochemical cracker, a high-temperature ceramic kiln, or a glass furnace, our ASTM-grade IFBs provide the thermal shielding you need to minimize heat loss and maximize profitability.
Insulating Fire Brick, also known as Lightweight Refractory Brick or Soft Brick, is a type of refractory material specifically designed for its insulating properties. Unlike dense firebricks (hard bricks), which are intended for structural strength and resistance to mechanical wear, IFBs are characterized by high porosity, low bulk density, and exceptional thermal resistance.
At Highland Refractory, we utilize a specialized "burn-out" manufacturing process. We mix high-purity refractory clays with organic fillers (such as sawdust or polymer beads). During the high-temperature firing process, these organic materials burn away, leaving behind a uniform network of microscopic air pockets. These trapped air pockets act as a powerful barrier against heat transfer, resulting in one of the lowest thermal conductivity values in the refractory industry.
The industry standard for IFB is the ASTM C155 classification. These grades are categorized by their maximum classification temperature. Choosing the correct grade is critical for preventing linear shrinkage and ensuring the longevity of the furnace lining.
The K23 brick is the industry workhorse. It offers the lowest density and the highest insulation value in the K-series.
Primary Application: Backup insulation behind dense refractories or hot-face linings in low-velocity environments.
Key Advantage: Maximum fuel savings due to ultra-low thermal conductivity.
K26 bricks provide a balance between mechanical strength and thermal resistance.
Primary Application: Hot-face linings for ceramic shuttle kilns, heat treatment furnaces, and forging furnaces.
Key Advantage: Higher alumina content allows for use in more aggressive heat environments without warping.
Designed for high-temperature stability, K28 bricks are used in environments where K26 bricks would suffer from excessive shrinkage.
Primary Application: Petrochemical heaters, ammonia reformers, and carbon bake furnaces.
These are premium, high-alumina specialty bricks designed for ultra-high-temperature scenarios.
Primary Application: Hydrogen furnaces, glass tank crowns, and advanced laboratory kilns.
Why do procurement managers and engineers trust Highland Refractory? It comes down to our commitment to material purity and manufacturing precision.
Iron Oxide ($Fe_2O_3$) is the enemy of refractory stability. In reducing atmospheres (where CO or Hydrogen is present), iron acts as a catalyst for carbon deposition, causing bricks to disintegrate. Highland IFBs feature ultra-low iron content (typically <0.8%), making them ideal for petrochemical cracking and hydrogen furnaces.
Heat leaks most often occur at the joints. Every Highland brick undergoes automated six-side grinding after firing. Our dimensional tolerance of +/- 0.5mm ensures that your masonry joints are as thin as possible, creating a virtually airtight seal that further reduces energy loss.
Our proprietary fiber-reinforced slurry matrix allows our bricks to withstand rapid temperature fluctuations. This is essential for batch kilns and furnaces that undergo frequent startup and shutdown cycles.
In blast furnace stoves and annealing furnaces, IFBs are used as secondary insulation. By reducing the temperature of the outer steel casing, they prevent shell deformation and improve the safety of the working environment.
Petrochemical heaters require materials that can withstand aggressive chemical vapors. Our K26 and K28 grades are the preferred choice for lining ethylene crackers and primary reformers, where they provide long-term stability under high pressure.
The ceramics industry relies on IFB to reduce the "Thermal Mass" of kilns. Using lightweight K23/K26 bricks for kiln cars and walls allows for significantly faster firing cycles, directly increasing production capacity and lowering the cost per unit of ceramic ware.
Highland IFBs are used in carbon bake furnaces and aluminum melting furnaces as backup insulation, providing a stable thermal gradient that protects the dense refractory bricks from premature failure.
A common mistake is choosing "strength over insulation." While dense firebricks are necessary for areas with molten slag or heavy mechanical impact, using them where IFB should be used leads to massive energy waste.
Weight: IFBs are 60% to 75% lighter than dense bricks. This reduces the structural load on the furnace steelwork, allowing for lighter and cheaper furnace designs.
Heat Storage: Dense bricks act as "heat sinks," soaking up massive amounts of energy. IFBs have low heat storage, meaning the heat stays inside the furnace where it is needed.
Thermal Conductivity: IFBs offer a 300% to 500% improvement in insulation value compared to dense firebricks.
To achieve the best results with Highland IFB, proper installation is mandatory.
One of the greatest features of IFB is its ease of workability. You can use standard woodworking handsaws, drill bits, and routers to create custom fits.
Pro Tip: Always wear a P2/N95 respirator mask and safety goggles when cutting, as the process generates fine ceramic dust.
Insulated Fire Bricks must be laid with a compatible Insulating Refractory Mortar. We recommend an air-setting mortar that matches the temperature grade of the brick (e.g., using K26 Mortar for K26 Bricks). This ensures that the expansion and contraction rates are identical, preventing cracks at the joints.
Refractory walls expand as they heat up. We recommend leaving expansion gaps every 1.5 to 2 meters, filled with Ceramic Fiber Blanket or expansion strips, to absorb this movement.
Understanding why bricks fail can help you prevent costly downtime:
Thermal Spalling: Caused by heating the furnace too fast. The moisture trapped in the pores turns to steam and cracks the brick. Solution: Follow a strict "Bake-out" schedule.
CO Disintegration: Caused by high iron content in the brick reacting with CO gas. Solution: Use Highland’s Low-Iron ($Fe_2O_3 < 1.0\%$) series.
Mechanical Abrasion: Soft bricks are not meant for areas with falling logs or heavy metal impacts. Solution: Use a "Hard Face" of dense bricks in impact zones.
We recognize that IFBs are high-value, fragile items. Our packaging is designed for international sea and air freight:
Palletizing: Bricks are stacked on reinforced wooden pallets with cardboard corner protectors.
Protection: Each layer is separated by cardboard, and the entire pallet is heavy-duty shrink-wrapped.
Capacity: We can ship LCL (Less than Container Load) for small repairs or FCL (Full Container Load) for major furnace builds.
Q1: What is the difference between K23 and K26 — when should I use each?
Q2: Can insulating fire brick (IFB) contact flame directly?
Yes. Grades K26, K28, and K30 are designed for direct flame and heating element exposure. K23 is for backup only. Note: Because IFBs are soft (CCS 1.2–3.0 MPa), do not use them in zones with heavy mechanical impact or abrasion. Use a "hard face" of dense fire bricks in impact zones with IFB behind them.
Q3: What Al₂O₃ and Fe₂O₃ content is required for reformers and hydrogen furnaces?
Specify Al₂O₃ ≥65% (K28/K30) and Fe₂O₃ <0.7%. In reducing atmospheres containing CO or H₂, higher iron content catalyzes carbon deposition, causing the bricks to disintegrate. Low-iron K28/K30 bricks prevent this chemical failure.
Q4: When should I choose IFB over ceramic fiber blanket?
Q5: What is the MOQ, and can I mix K23, K26, and K28 in one shipment?
Aluminum content 75%-80% Refractory 1770℃ or above
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High alumina fine powder is a powder material with alumina (Al2O3) as the main component.
