Home / News & Blog / Abrasive Blog / The Best Types of Abrasive Grains for Refractory Castables in High-Temperature Kilns
Author: Leif Shi | DOMILL Abrasive Technology
When it comes to high-temperature kilns—used in steel plants, ceramics, glass manufacturing, and incineration—the heart of long-lasting performance lies in the quality of the refractory castable. One key component often overlooked? The abrasive grains used as aggregates or fillers. These grains directly impact the thermal resistance, mechanical strength, and erosion resistance of the final castable.
Having worked with refractory manufacturers for over two decades, I’ve seen firsthand how choosing the right abrasive grain can extend service life, reduce maintenance downtime, and cut costs in the long run. So let’s dive into the best abrasive grain options for refractory castables, and when to use each.
Refractory castables are a mix of ceramic aggregates, binders, and additives poured into shapes or applied in place to line kilns and furnaces. Abrasive grains act as structural skeletons, and their thermal properties define how well the castable performs in:
High-temperature stability (1500–1800°C); Thermal shock resistance; Corrosion resistance; Erosion from hot gases or molten materials.
Here’s a rundown of the most commonly used—and effective—abrasive grains for high-performance castables:
Al₂O₃ content: 99.3%+
Key benefits: Ultra-high purity, corrosion resistance, high melting point (~2050°C)
Best for: Ultra-high temperature kilns, non-ferrous metallurgy, glass furnaces
Why choose WFA: Ideal where iron contamination must be minimized.
Al₂O₃ content: ~95%
Key benefits: Excellent toughness, cost-effective, stable performance
Best for: Steel industry kilns, general-purpose linings
Pro tip: High-temp calcined BFA improves thermal shock resistance.
Structure: Sintered alumina with large crystal platelets
Key benefits: Low porosity, exceptional thermal stability
Best for: High-purity, high-strength castables needing excellent creep resistance
Key benefits: Thermal conductivity, erosion resistance, resistance to slag attack
Best for: Incinerators, boilers, and areas exposed to rapid temperature swings or corrosion
Note: Reacts with certain slags at very high temperatures—consider design compatibility.
Composition: Al₂O₃ + SiO₂ (~70:30)
Key benefits: Thermal shock resistance, moderate cost
Best for: Areas needing better resistance to spalling and thermal cycling
Why choose it: Great compromise between WFA and BFA performance and price.
The grain size you choose also matters. Coarse particles (e.g., 3–5 mm) build structure; finer particles (0–1 mm) improve packing density and strength.
Angular grains (e.g., BFA, WFA) = better mechanical interlock
Rounded grains (e.g., tabular alumina) = lower water demand, better flow
At DOMILL, we customize grain size distributions based on your specific pouring or gunning process.
Need Purity? Consider Magnetic Separation & Air-Washing
Kiln applications demand low iron content. We recommend air-washed and magnetically cleaned abrasive grains to avoid unwanted reactions in the kiln lining. DOMILL offers BFA and WFA with magnetic content <0.02%.
Not all abrasive grains are created equal. When choosing the right material for your refractory castable:
High purity & temperature → White Fused Alumina
Toughness + value → Brown Fused Alumina (especially calcined)
Extreme erosion → Silicon Carbide
Thermal cycling → Fused Mullite or Tabular Alumina
And always consider particle shape, grain size, and purity level.
With 30+ years of experience and 50,000 tons annual output, DOMILL offers tailored abrasive grain solutions for refractory manufacturers worldwide. From bulk orders to custom size blends, we help you improve kiln performance, reduce wear, and extend service life.
Contact us for free samples and material consultations.
