JM28 Insulation Brick

JM28 Insulation Brick, made of high-quality raw materials, is a top-tier thermal insulation solution designed to offer exceptional performance in high-temperature environments. Known for its outstanding thermal insulation properties, JM28 is ideal for use in furnaces, kilns, boilers, and other high-temperature industrial applications. With its excellent insulating qualities, low thermal conductivity, and robust physical properties, JM28 Insulation Brick provides significant benefits to industries aiming to improve energy efficiency, reduce operational costs, and increase the lifespan of high-temperature equipment.

The 2026 international market reference price for export-grade JM28 insulation bricks typically ranges from:

USD 1.80 – USD 4.50 per piece (standard dimensions)
USD 650 – USD 1,150 per metric ton (FOB China, bulk orders)

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Insulation Brick

JM28 Mullite Insulation Brick — 1540°C Service Temperature

High-alumina mullite formulation for demanding high-temperature environments. Steel, glass, petrochemical. Factory-direct from Zhengzhou China. ISO 9001:2015 certified.

1540°CMax Service Temp

≥64%Al₂O₃ Content

0.85–0.95Bulk Density g/cm³

0.32–0.40Thermal Conductivity W/m·K

72 hrsStandard Dispatch

What Is JM28 Insulation Brick?

JM28 is a high-purity mullite insulation brick rated to a maximum service temperature of 1540°C (2800°F). The designation follows ASTM C155 classification: "28" represents 2800°F, the classification temperature in the American system. In Chinese GB/T standards, the same product is sometimes referenced as JM28 or LG-28.

Compared to JM26, JM28 contains a higher proportion of synthetic mullite and reactive alumina in its formulation, raising the Al₂O₃ content from ≥58% to ≥64%. This shift increases resistance to high-temperature creep, improves refractoriness under load, and extends the useful service ceiling by approximately 110°C — at a modest increase in bulk density and thermal conductivity.

JM28 is the highest-volume grade we supply to steel and glass sector customers. Its operating range — continuous service up to approximately 1450–1480°C — covers the majority of reheat furnace, glass lehr, and industrial boiler lining applications that require a lightweight insulating brick rather than a dense refractory.

JM28 Technical Specifications

All values tested per GB/T 3995 and aligned with ASTM C155. Third-party SGS / TUV testing available on any production batch.

Property	Test Condition / Standard	JM28 Value
Classification Temperature	ASTM C155 / GB/T 3995	1540°C (2800°F)
Bulk Density	GB/T 2997	0.85 – 0.95 g/cm³
Al₂O₃ Content	XRF analysis	≥ 64%
SiO₂ Content	XRF analysis	≤ 30%
Fe₂O₃ Content	XRF analysis	≤ 0.7%
Cold Crushing Strength	GB/T 5072	≥ 2.5 MPa
Modulus of Rupture	GB/T 3041	≥ 1.6 MPa
Thermal Conductivity @ 400°C	GB/T 5990	0.32 W/m·K
Thermal Conductivity @ 600°C	GB/T 5990	0.34 W/m·K
Thermal Conductivity @ 800°C	GB/T 5990	0.36 W/m·K
Permanent Linear Change	1510°C × 8h	≤ ±0.5%
Porosity	GB/T 2997	52 – 60%
Thermal Expansion @ 1000°C	—	~ 0.8%
Refractoriness Under Load T₀.₆	GB/T 5989	≥ 1480°C
Standard Dimensions	—	230×114×65mm; custom available
Color	—	White

Standard: 230×114×65mm. Arch, wedge, circle, and non-standard profiles available. Mold tooling: 3–5 working days.

JM Series Comparison: Where JM28 Fits

Grade	Max Temp	Al₂O₃ (%)	Bulk Density (g/cm³)	CCS (MPa)	Typical Use
JM23	1260°C	≥46	0.55–0.65	≥1.5	Backup insulation, low-temperature furnaces
JM26	1430°C	≥58	0.78–0.85	≥2.0	Ceramic kilns, heat treatment furnaces
JM28 ← You are here	1540°C	≥64	0.85–0.95	≥2.5	Steel reheat, glass manufacturing, petrochemical
JM30	1650°C	≥73	1.00–1.10	≥3.5	EAF roof, ultra-high temperature direct contact

JM28 vs JM26 — when does the upgrade justify itself? If your continuous operating temperature exceeds 1350°C, or if your application involves repeated thermal cycling through the 1300–1450°C range, JM28's higher Al₂O₃ content and improved creep resistance will extend service life meaningfully. For temperatures consistently below 1300°C, JM26 is the more economical choice.

Performance Characteristics

High-Temperature Stability

Al₂O₃ ≥64% suppresses viscous flow at operating temperature. Refractoriness under load (T₀.₆) ≥1480°C — the brick maintains structural integrity under compressive load well into its rated range.

Thermal Shock Resistance

The open-pore mullite microstructure accommodates thermal expansion differentials across rapid heating and cooling cycles without progressive cracking — a critical property in batch-process kilns.

Dimensional Precision: ±1mm

CNC hydraulic press forming at 200–400t. At 1540°C operating temperatures, joint quality is directly related to lining integrity. ±1mm tolerance eliminates the bypass gaps that initiate hot spots.

Low Fe₂O₃ ≤0.7%

Low iron content reduces the formation of low-melting-point glass phases that cause premature structural softening. Important in applications with oxidizing atmospheres where iron acts as a flux.

Applications

JM28 is the standard specification for furnace linings requiring continuous service between 1350°C and 1500°C.

🏗️ Steel & Metallurgy

Reheat furnace crown and sidewalls, soaking pit insulation, ladle backup lining, continuous casting tundish insulation. JM28 handles thermal cycling in batch reheating without liner cracking.

🔲 Glass Manufacturing

Annealing lehr insulation, decorating kiln lining, glass tempering furnace walls. Clean atmosphere and temperature range align precisely with JM28's performance envelope.

⛽ Petrochemical

Primary reforming furnace backup insulation, hydrogen production furnace walls, cracking furnace crown lining. JM28 withstands reducing atmospheres in backup positions.

⚡ Power & Energy

Industrial boiler furnace walls and roof insulation. Waste incineration furnace hot zone backup. The certified documentation package (ISO / SGS) satisfies EPC contractor requirements.

🏺 Advanced Ceramics

High-temperature sintering furnace linings for technical ceramics, ferrite, and specialty oxide firing. JM28 does not contaminate the process atmosphere with iron or alkali oxide.

🔩 Heat Treatment

High-temperature hardening furnaces, vacuum furnace insulation (outer shell), atmosphere-controlled carburizing and nitriding furnaces operating above 1350°C.

Why Source from Highland Refractory

The numbers below are from our documented quality and logistics records — not marketing estimates.

Capability	What It Means for Your Order
CNC press: ±1mm dimensional tolerance	Joints fit. No rework on site, no thermal bypass in service.
±0.5kg computer batching accuracy	Al₂O₃ content consistent batch-to-batch — no performance surprise at furnace startup.
77m tunnel kiln, 72-hour firing cycle	Uniform microstructure. No cold spots or under-fired zones in your bricks.
Export damage rate ≤0.8%	Industry average is 5–8%. Fumigated cases + honeycomb protection + steel strapping.
72-hour dispatch for standard stock	JM28 standard size is held in inventory. No waiting on a production run.
SGS/TUV testing on your batch	Independent verification on the bricks you actually receive, not a pre-cert sample.
ISO 9001:2015 / CE / SGS certified	Full certification documentation package accepted by global industrial procurement systems.

🔽

Need Lower Temperature? → JM26 Insulation Brick (1430°C)

More economical option for applications operating consistently below 1350°C.

📋

Compare All JM Grades: JM23 / JM26 / JM28 / JM30

Full side-by-side specification table and grade selection guide.

🏭

Our Manufacturing Facility

Production equipment, QC process, certifications, and export capabilities in detail.

Frequently Asked Questions

What is the actual maximum service temperature of JM28 insulation brick?

JM28 is classified to 1540°C (2800°F) per ASTM C155 and GB/T 3995. This is the classification temperature — the temperature at which the brick maintains acceptable dimensional stability under a standard test load. For continuous service, a working margin of 60–80°C below the classification temperature is recommended, placing the practical continuous operating limit at approximately 1460–1480°C.

What is the difference between JM28 and K28 insulation brick?

JM28 (Chinese GB/T designation) and K28 (ASTM C155 equivalent) are the same product classification — a mullite insulation brick rated to 1540°C (2800°F). When sourcing from Chinese manufacturers, these designations are interchangeable. Some suppliers also use the designation IFB-28 (Insulating Firebrick 28) in export documentation.

Can JM28 brick handle reducing atmospheres?

JM28 performs reliably in reducing atmospheres when used as a backup insulation layer behind a dense refractory hot-face. As a direct hot-face material in strongly reducing environments — particularly those involving CO, H₂, or significant carbon deposition — performance depends on the specific atmosphere composition and temperature. Contact our engineering team with your atmosphere specification for a detailed assessment.

How does JM28 compare to JM26 in energy savings?

JM28 has slightly higher thermal conductivity than JM26 (0.32 vs 0.27 W/m·K at 400°C) due to its higher density and Al₂O₃ content. For pure insulation performance, JM26 is marginally better — but only at temperatures below its 1430°C rating. In applications above 1400°C where JM28 is required, there is no valid comparison: JM26 would not survive continuous service at those temperatures.

Do you supply JM28 in custom dimensions and shapes?

Yes. Standard dimension is 230×114×65mm. Arch bricks, wedge bricks, circle bricks, and fully custom non-standard shapes are available. New mold tooling is completed in 3–5 working days. First-article samples are provided before full production begins for non-standard shapes. Minimum order for custom shapes is typically 500 pieces.