For general-purpose ACM air classifying mills, hardened alloy steel / high manganese steel is the baseline standard liner material. For food, pharmaceutical and corrosion-sensitive batches, 304 or 316 stainless steel becomes the standard contact liner. High-chromium cast iron is also widely adopted as an upgraded standard wear liner for abrasive mineral processing. These metal liners are pre-machined into smooth or grooved/serrated plates and bolted into the grinding chamber wall, to deflect particles back toward the hammer path and protect the main mill housing from erosion.
Standard metal liners
- Hardened tool steel / high manganese steel (Hadfield steel)
This is the default liner for most general industrial ACM models. It delivers good impact toughness at moderate cost and suits soft to medium-hard materials such as calcium carbonate, talc, starch and non-abrasive chemicals. The liner surface can be smooth or multi-deflector grooved; grooved liners increase particle rebound and improve comminution efficiency, while smooth liners reduce over-fining. The limitation is gradual wear when processing high-abrasion feeds, which introduces iron contamination into powder products. - High-chromium cast iron
It is the heavy-duty standard for continuous mineral production. With high hardness and excellent abrasion resistance, it extends service life significantly compared with manganese steel. It is commonly selected for kaolin, limestone and moderately abrasive fillers. It still releases trace iron wear debris, so it cannot be used where metal contamination is strictly forbidden. - 304 / 316 stainless steel
This is the standard liner for GMP food, pharmaceutical and cosmetic powder lines. Stainless steel provides corrosion resistance and easy cleaning, meets sanitary requirements and avoids rust contamination. Its wear resistance is lower than high-chrome cast iron, so it fits low-to-medium abrasion raw materials only. Surface polishing is available for clean-in-place operations.
Optional upgraded liner materials
These are not standard factory default options but are widely specified for special requirements.
- Tungsten carbide coated liners: Metal substrate with WC hard facing. Great for highly abrasive minerals, balancing impact resistance and wear life, though iron contamination risk remains.
- Alumina / zirconia ceramic liners: Fully metal-free lining tiles. Used for battery materials, high-purity quartz and white minerals where iron must be eliminated. Ceramic liners have outstanding wear resistance, yet they are brittle, expensive and sensitive to heavy impact shocks.
- Polyurethane liners: Rare in high-speed ACM grinding zones; occasionally used for low-impact auxiliary ducts to reduce wear and noise, not the primary grinding chamber liner.
Liner geometry matching material selection
Material choice works together with liner profile. Grooved/serrated liners create stronger particle rebound for fine grinding; smooth liners reduce attrition and excess fines. The same base liner material can be manufactured in either profile to tune particle breakage behaviour.
Selection summary
The factory standard liner for general ACM mills is hardened manganese steel. High-chromium cast iron is the standard wear upgrade for abrasive minerals, while 304/316 stainless steel is the sanitary standard for food and pharma. Ceramic or carbide coatings are premium non-standard alternatives for ultra-pure or heavily abrasive powder production.
The default standard liner material of an ACM grinding chamber is hardened manganese alloy steel. High-chromium cast iron and stainless steel are common standard alternatives for mineral and sanitary applications respectively. Specialized requirements for zero iron contamination or extreme abrasion demand non-standard ceramic or tungsten carbide liners, which add capital cost while eliminating metal pollution and extending service intervals.
