Materials & Specifications

Density, hardness, flexural strength, wear loss and maximum service temperature for all four alumina grades, published in full.

These are the numbers that decide whether a quotation is for the material you actually need. We publish them here rather than hiding them in a PDF, because a 30% price difference almost always traces back to a 3% difference in alumina content.

The four grades, compared

Grade	Al₂O₃	Density	Hardness	Flexural σ	Compressive σ	Wear loss	Max temp.	Typical duty
AL-92Standard duty	92%	3.60 g/cm³	82 HRA	220 MPa	1,800 MPa	≤ 0.10 g	1,400 °C	General chute, hopper and bin lining where cost per tonne matters most.
AL-95High wear	95%	3.70 g/cm³	84 HRA	280 MPa	2,200 MPa	≤ 0.07 g	1,500 °C	The default for mining, cement and steel plants — best life-to-cost ratio.
AL-99Severe wear & corrosion	99%	3.85 g/cm³	88 HRA	320 MPa	2,600 MPa	≤ 0.05 g	1,600 °C	Fine grinding media, chemical duty and high-temperature fixtures.
AL-99.7Precision grade	99.7%	3.90 g/cm³	90 HRA	350 MPa	2,800 MPa	≤ 0.04 g	1,700 °C	Semiconductor, medical, electronic and vacuum-process components.

Typical values from routine production testing. Apparent porosity is ≤ 0.5% for AL-92 down to ≤ 0.1% for AL-99.7. Batch test reports are issued with every shipment; tell us the duty and we will confirm the grade in writing.

What each grade is for

AL-92

Porous enough to be affordable, hard enough for large low-impact surfaces: silos, bins, hoppers, non-critical transfer points.

Standard duty

AL-95

The workhorse. Handles impact-abrasion in mining, cement and steel and usually gives the lowest cost per tonne handled.

High wear

AL-99

Where hardness alone is not enough — acid and alkali contact, fine slurry, elevated temperature, low contamination requirement.

Severe wear and corrosion

AL-99.7

Semiconductor, medical, electronic and vacuum-process parts where purity and dimensional stability dominate.

Precision grade

Grade selection by duty

Operating duty	Recommended	Why
High impact, coarse particles	AL-95	Thick tiles with a studded backing; AL-99 is more brittle in shock loading.
Fine abrasive slurry	AL-99	Higher hardness limits polishing wear on pipe bores and pump internals.
Acid or alkali contact	AL-99	Porosity below 0.2% restricts chemical penetration at the grain boundary.
Continuous duty above 1,400 °C	AL-99.7	Higher purity resists creep and grain growth inside kilns and furnaces.
Large area, cost-driven	AL-92	Acceptable life where impact energy is low and the surface is not critical.
Extreme abrasion, thermal shock	SiC	Silicon carbide outlasts alumina but is less impact tolerant and costs more.
Toughness with sharp edges	ZTA	Zirconia-toughened alumina resists chipping on cutting and trimming edges.

Test methods and tolerances

Property	Method	Typical tolerance
Al₂O₃ content	XRF	± 1.0% on stated grade
Bulk density	Archimedes	± 0.02 g/cm³
Apparent porosity	Water absorption	see grade table
Hardness	HRA, 60 kg load	± 1 HRA
Flexural strength	Four-point bend	≥ 95% of nominal
Abrasion resistance	Wear-loss rig, reference coupon	see grade table
Press-formed dimensions	Vernier / gauge	± 0.5 mm (as-fired)
Ground dimensions	CMM / micrometer	± 0.005 mm achievable
Flatness and parallelism	Surface plate	0.01 mm / 100 mm

Tolerances shown are what the process can hold in routine production. If your drawing asks for something tighter, we tell you before quoting rather than after shipping.

Chemical resistance

Alumina is inert to most mineral and organic acids, to alkalis at ambient temperature, and to steam. It is attacked by hydrofluoric acid and by hot concentrated phosphoric acid, and by strong alkalis above roughly 100 °C. Where that is a risk we will recommend silicon carbide instead — or a different sealing arrangement.

Need the data sheet as a file?

Data sheets are issued against your company details so revisions can be tracked. Request them through the contact form and you will normally have them the same working day.

Tell us the duty and we will name the grade

Material, particle size, temperature, equipment type — that is usually enough for a written recommendation.

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Send us your drawing — get a quotation with a firm lead time

PDF, DWG, STEP, IGES or a photo with the critical dimensions marked. Engineering review within one working day.

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