Brown fused alumina

Identity and manufacture

Elfusa’s ALOMAXRC is ceramic-coated fused alumina and ALOMAXST is silane-coated. Elfusa gives resin adhesion as the purpose. CERPASS seeded sol-gel grain has a separate production route. Elfusa abrasive grades Washington Mills coated-abrasive line card, p. 2 Washington Mills lists Mohs 9 for its brown fused alumina family. Washington Mills family page

Elfusa fuses bauxite in an electric arc furnace for its regular BT grade. Its AR refractory sheet identifies alpha alumina. Minor oxides vary by grade. Elfusa abrasive grades AR sheet

Synthesis. A grain name identifies neither a finished grinding wheel nor a coated belt. Grain chemistry, particle shape, size distribution, treatment, and the finished product's bond or backing describe different parts of an abrasive system.

Composition belongs to the named grade

The following are producer-reported analyses, not a universal BFA specification. DURALUM's sheet explicitly states that its information is not a specification and that chemistry can vary. Elfusa labels the sheet values typical.

Sources for the rows are the DURALUM producer sheet hosted by FinTec, SFAR-L coated sheet, and SFAR-F grinding sheet. The DURALUM sheet also reports 0.15% CaO. Elfusa labels its analyses XRF.

Elfusa's undated microgrit web page reports SFAR TiO₂ as 1.43%, whereas the dated coated microgrit PDF reports 1.59%. The sources do not explain this difference. The web value does not silently replace the PDF value. Elfusa microgrit page

Synthesis. An Fe₂O₃ entry does not measure free metallic iron or establish an iron-free contamination condition. Likewise, total SiO₂ and free crystalline silica are different analytical claims. Neither a typical oxide analysis nor a product-family name establishes a lot's contamination limits, phase composition, or suitability for a contamination-sensitive workpiece.

Grade variants and related aluminas

Washington Mills distinguishes white fused alumina made from Bayer-process alumina, with over 99% Al₂O₃, from brown grades. Its DURALUM CR3 page identifies a deep-pink fused alumina alloyed with chrome oxide. These are different grain identities, not a universal mechanical ranking. Fused alumina families, DURALUM CR3

Its September 2007 coated-abrasive line card separately lists conventional brown grains, low-titania grades, low-temperature-treated grades, blue-roasted grades, and CERPASS seeded sol-gel ceramic aluminum oxide. Synthesis. Ceramic coating on a fused grain and a sol-gel ceramic grain identify different material routes. A treatment color alone does not identify the chemistry or manufacturing route. Producer line card, page 2

Density, hardness, and fracture resistance

These three rows refer only to the DURALUM sheet marked updated 9-08.

Elfusa AR reports "True Specific Gravity" 3.94 g/cm³ and "Apparent Specific Density" 3.82 g/cm³, preserving the producer's labels and units. It associates apparent density and 3.32% apparent porosity with ASTM C20-00. Neither is a loose-grain bulk-density specification or a theoretical density of pure corundum. AR version 05, 07.07.2023

ISO 9136-1:2004's public scope covers a bulk-density test for bonded and coated abrasive macrogrits. That scope does not make a value measured under another cited method automatically equivalent. ISO public overview

Synthesis. Mohs scratch hardness, Knoop indentation hardness, and resistance to grain fracture measure different behavior. They do not directly specify a wheel's grade, grain retention, material-removal rate, or finish. Loose bulk density includes packing space between particles. It cannot replace particle density or theoretical crystal density in a volume calculation.

Original heat-treatment evidence

Passos and Rodrigues studied Elfusa ASFE, ASF, and AR P60 grains. Their fracture resistance index, FRI, is the percentage retained after a 10-minute ball-mill test and subsequent 70-mesh sieving, citing ANSI B74.8. Higher FRI means less fracture in that test. Their dimensionless NFRI equals FRI divided by 100, multiplied by real density divided by bulk density. 2016 study, methods and equations D and E

The study varied temperature, duration, atmosphere, and composition. Its P60 results did not establish a direct correlation between blue color and NFRI. Alumina-rutile material gained fracture resistance without turning blue. The authors also report that P220 grains sintered at 1400 °C, preventing NFRI characterization. These are experimental conditions, not a commercial treatment recipe. Study, results and conclusion

Synthesis. The study supports separating color from tested fracture behavior. It does not establish wheel life, cutting rate, or a universal preferred heat treatment.

Grain-size designations

A grit designation describes a distribution under a named system. The public publisher scopes distinguish these families.

Elfusa's SFAR-L coated microgrit sheet cites FEPA 43-2:2017. Its SFAR-F grinding microgrit sheet cites FEPA 42-2:2006. Those are the sheets' declared bases, distinct from the ISO editions above. Coated sheet, grinding sheet

Synthesis. A bare "60 grit," "240," or "mesh" omits information needed to compare products. Equal numbers across F, P, ANSI, and sieve designations do not establish equal particle-size distributions. No universal mesh-to-micrometre conversion or grit-to-roughness conversion follows from these sources.

Applications and limits

Washington Mills lists blasting, polishing, and flat lapping for DURALUM, with examples including glass, ceramics, granite, silicon, and metal. The current page's general "metal" category does not qualify every ferrous or nonferrous alloy. DURALUM product page

Its LT page specifically names heat-sensitive steels, alloys, and rubber. Those are examples for that grain family, not an all-BFA workpiece list. DURALUM LT and DURABLU LT

AR is a separate refractory raw material. Elfusa does not recommend splits over 2.00 mm for molded refractories above 1300 °C. This is a product-and-form limitation, not a universal BFA service-temperature rating. AR sheet

Synthesis. An abrasive's final behavior depends on its exact grain and treatment, size distribution, bond or coating construction, workpiece, and process conditions. The sources establish no universal pressure, speed, removal rate, attainable finish, reuse count, or customer-approved setup. Grain hardness alone cannot settle those quantities. Related context is available in Finishing process references.

Source versions and coverage

Reviewed on 29 October 2026 PDT. Undated producer pages are retrieval snapshots. The DURALUM numerical reference is a historical producer document hosted by FinTec, marked "updated 9-08," with an explicit non-specification disclaimer. Its figures are not represented as current guaranteed limits.

The Elfusa AR, SFAR-L, and SFAR-F PDFs carry the versions and dates identified above. The unresolved SFAR website/PDF discrepancy prevents a single merged composition. The Washington Mills coated line card is printed September 2007 and establishes historical product distinctions, not current availability.

The original study is E. R. Passos and J. A. Rodrigues, Cerâmica 62, 2016, pages 38 to 44, DOI 10.1590/0366-69132016623611960. Its named research samples are not assumed identical to today's commercial grades. Only public publisher scopes support the standards discussion. No paid standard text or distribution-limit tables are reproduced.

Coverage excludes lot certification, free-iron test results, a complete Knoop test procedure, quantitative cross-grade toughness comparisons, and finished-product qualification. Safety data are handling references for their identified grades and jurisdictions, not process-performance evidence.