Cast alumina parts from Blasch, from 99.7% ultra high alumina to mullite bonded and zirconia toughened grades.
The same oxide makes a crucible for superalloys, a ferrule for a waste heat boiler and a liner for a cyclone.
What changes is the purity, the bond and the structure inside the part.
Alumina ceramic, aluminum oxide (Al2O3) formed and fired into a solid part, is the right choice when a component has to resist high temperature, chemical attack or molten metal and must not conduct electricity. It reaches its limits where fast temperature swings or heavy impact dominate, and in coarse abrasive flow silicon carbide often lasts longer. Blasch casts alumina parts from about 88% to 99.8% Al2O3 and sets purity, density and porosity for the one job each part has to do.
Alumina is aluminum oxide. It is not the metal aluminum: the oxide is a ceramic, hard, chemically stable and an electrical insulator, with a melting point far above that of the metal.
An alumina ceramic part is made from alumina powder that is shaped and then fired, so the grains bond into a solid body. How pure the powder is, what holds the grains together and how much pore space remains decide how the part behaves in service.
Blasch casts these parts net shape in its own process in Albany, New York, to a linear tolerance of about 0.5%, with part weights from 1 oz to 2 tons. How the Blasch casting process works
"Alumina" covers a whole family. The grades Blasch uses differ mainly in purity and in what bonds the alumina grains.
| Grade | Al2O3 content | Typical Blasch use |
|---|---|---|
| Ultra high alumina | 99.7% to 99.8% | Backup ram behind crucibles, ferrules in high heat flux |
| Dense alumina | up to 99.6% | Hex head ferrules, cyclone and pipe liners |
| High alumina (ProCaster) | high alumina, by grade | Crucibles for superalloy, steel and nonferrous melting |
| Alumina zirconia (ProCaster 087) | 5% ZrO2 minimum | Crucibles, tundishes and launders with the most corrosive alloys |
| Mullite bonded high alumina | about 88% alumina and mullite | Flue gas tunnels and checkerwalls in reformers and sulfur furnaces |
High purity: the fewer impurities such as silica, iron oxide and alkalies, the less the alumina reacts with molten metal and slag. That is why the ALRAM backup rams behind ProCaster crucibles are 99.7% and 99.8% Al2O3.
Bond: a mullite bond keeps alumina stiff at temperature. In published tests, mullite bonded alumina kept a hot modulus of rupture of 1,700 psi, where super duty firebrick stayed under 600 psi.
Zirconia addition: a share of zirconia raises corrosion resistance in contact with aggressive melts. The Procaster-Z grade (087) carries at least 5% ZrO2 and is rated for 1,650 °C (3,000 °F) continuous and 1,760 °C (3,200 °F) intermittent.
Purity tells you what an alumina part resists, but its structure decides whether it survives the first fast heat-up.
Alumina is a good first choice in four situations.
Where alumina is not the first choice: in fast thermal cycling, dense alumina is more sensitive than silicon carbide, cordierite or fused silica. Under coarse particle impact, reaction bonded or alumina bonded silicon carbide usually wears slower. And where molten aluminum must not stick, an oxide bonded silicon carbide or aluminum titanate is the better match. Silicon carbide grades
Blasch works around the thermal shock limit through the structure of the part: particle packing, binder system and a continuous network of fine pores, 3 to 5 micron, take up stress that would crack a fully dense body. A Blasch video shows 99.7% ultra high alumina ferrules going through a thermal shock test. Watch the ultra high alumina thermal test
Each part is designed for its application from your dimensions and operating conditions.
High alumina crucibles for induction melting, as a replacement for zirconia crucibles in many alloys.
One and two piece ferrules from dense and ultra high alumina that protect the tubesheet.
Dry ultra high alumina ram, 99.7% and 99.8% Al2O3, behind crucibles from 5 lb to 1,000 lb.
Low mass alumina supports that carry ware through sintering and firing furnaces.
Dense alumina also lines hydrocyclones and cyclones, forms air heater inserts, and an ultra high alumina loop is one of the options for channel furnace linings. Alumina mullite is used for threaded sample cups for molten metal.
Plants that use these parts are mostly in molten metals and refining and chemical processing. If you are deciding between alumina and its toughened relative, see zirconia ceramics.
Many searches for alumina ceramic end at sprayed alumina coatings. Blasch does not coat. The part itself is cast from alumina, so there is no layer that can chip or wear through to the steel underneath.
Material grades and Blasch values: Blasch product information sheets for ALRAM 3030 and 4041, Procaster-Z (087) and ProCaster crucibles; Blasch company presentation; Nitrogen+Syngas, July/August 2016. General properties of alumina: W. D. Kingery, H. K. Bowen, D. R. Uhlmann, Introduction to Ceramics, 2nd ed., Wiley, 1976.
No. Alumina is aluminum oxide, a ceramic. It does not melt or corrode like the metal and does not conduct electricity.
Yes, like every ceramic it breaks rather than bends. Part design with generous radii, the right wall thickness and room for expansion keeps tensile stress low.
It depends on the grade. Blasch high alumina crucibles are used up to 3,200 °F (1,760 °C); the limit for a given part also depends on load and temperature cycling.
No. Blasch casts solid alumina parts, such as ferrules, crucibles and liners, that replace the worn part rather than covering it.
When a part sees impact, sliding wear or an especially aggressive melt and needs more toughness than alumina offers.
Send the dimensions, the temperature and the medium. A Blasch engineer recommends the grade and designs the part.
