Pick the crucible family from the metal first—wetting, dissolve risk, carbon or oxygen pickup, slag attack, and vapor compatibility—then layer process type, atmosphere, purity budget, and thermal cycle. Melting point is only a first screen. Alumina covers many oxide-stable laboratory and analysis duties; graphite and silicon carbide dominate non-ferrous foundry heat transfer and shock; boron nitride earns its place where non-wetting release under vacuum or inert gas matters; zirconia extends corrosive and very-high-temperature melts; refractory-metal liners (platinum, molybdenum, tungsten, tantalum) remain industry options when ceramic families cannot meet the chemistry. No single wall material covers every metal and every process.
Why metal chemistry beats maximum temperature when you pick a crucible
The frequent miss is ranking candidates by published temperature ceiling. A wall can survive the furnace setpoint and still fail if the melt reduces the oxide, dissolves carbon, wets and sticks, or opens an impurity pathway the RFQ never named. Chemical compatibility and thermal compatibility are separate gates: thermal means the body survives the heat without mechanical failure; chemical means melt and wall do not react, dissolve, or exchange contaminating species at that heat.
Atmosphere flips answers that looked settled on paper. Graphite oxidizes in air at elevated temperature, so open-air service and vacuum or inert service are different problems. BN surface condition and non-wetting behavior degrade when air oxidation is active—treat the air boundary as qualitative and grade-specific, not a universal hard cutoff. Oxide ceramics that look stable in air can become problematic under reducing or carbon-bearing gas. Wetting, dissolve, and impurity pathways—not dew-point tube lore—decide whether the shortlist survives melt contact.
Crucible shortlist by metal family (starting matrix, not a guarantee)
Use the matrix as a starting shortlist, not a guarantee of compatibility. Every row still needs supplier data plus a melt-contact or evaporation trial when purity, sticking, or vapor chemistry is critical.
| Metal / material family | Common candidate families | Use with caution | Main selection driver |
|---|---|---|---|
| Aluminum / Mg alloys | Graphite, SiC, BN; alumina for selected lab use | Alumina if sticking/cracking; graphite in oxidizing high-temp air | Wetting, oxidation, carbon pickup, thermal shock |
| Copper / brass / bronze | Clay-graphite, SiC; alumina/zirconia for lab | BN or alumina without melt-contact testing | Thermal shock, flux, alloy chemistry |
| Nickel alloys | Alumina, zirconia, yttria, MgO paths | Graphite when carbon pickup matters | Temperature, oxygen/carbon contamination |
| Precious metals | Alumina, zirconia; Pt labware as industry option | Low-grade refractories | Purity, corrosion, assay requirement |
| Titanium / zirconium / niobium | BN, PBN, yttria, CaO/ZrO2 paths; refractory-metal liners (industry) | Graphite or alumina without reaction review | Reactivity; oxygen/carbon pickup — trial required |
| Silicon / germanium | Quartz; BN/PBN for specialty growth | Graphite/alumina without contamination review | Wetting, oxygen, carbon, crystal process |
| Rare earth metals | BN; Ta/W/Mo (industry); yttria, CaO | Alumina/silica without reaction review | Oxygen sensitivity, crucible reaction |
| Zinc / low-melting nonferrous | Graphite, SiC, clay-graphite | Materials sensitive to flux or vapor | Thermal cycling, vapor, flux attack |
| Evaporation metals | Alumina, BN, graphite; Mo/W/Ta liners (industry) | Default crucible without deposition compatibility review | Vapor compatibility and source geometry |
Al / Mg: BN for clean vacuum or inert release; SiC and clay-graphite for foundry-scale durability where trace carbon is acceptable. Cu alloys: flux and slag often dominate wall attack over direct metal–ceramic reaction. Ti / reactive metals: no oxide ceramic is universally safe—shortlist BN/PBN or yttria/CaO–ZrO2 paths, then trial. Si / Ge: quartz remains the Czochralski baseline; BN/PBN appear where non-wetting and purity budgets tighten. Evaporation: source vapor chemistry and liner geometry matter as much as bulk melt compatibility.
Cracking, sticking, contamination: do not swap materials before you diagnose
A cracked, stuck, or short-lived crucible does not automatically mean the family was wrong.
- Cracking: radiant cracks after fast cool or heat usually track thermal shock or freeze expansion against the wall, not a temperature-rating miss alone. Geometry (corners, wall thickness, fill fraction) often dominates.
- Contamination: unexpected impurities can come from tools, flux residues, furnace atmosphere, or feedstock as readily as from the crucible body. Control those paths before blaming the wall chemistry.
- Sticking: strong wetting is one cause; inadequate taper, bottom radius, overfill, or a cooling curve that bonds before shrinkage is another. Non-wetting families help many metals, but poor geometry still sticks.
- Short life in air: graphite, BN, and refractory-metal options have air-service boundaries. Confirm atmosphere before another grade change.
Inspect service records and the failed piece. Swap families only after the diagnostic question is answered.
Same metal, different crucible: melting, vacuum, evaporation, crystal growth
Process type is the second gate after metal chemistry. The same alloy can need a different wall in open-air casting, vacuum melting, thermal evaporation, or crystal growth.
- Open-air melting and casting: thermal shock, flux/slag compatibility, heat transfer, and campaign durability lead. Clay-graphite and SiC are the usual non-ferrous foundry workhorses when modest carbon pickup is inside alloy limits.
- Vacuum and inert-gas melting: carbon pickup and clean release matter more. Reactive metals narrow toward BN, PBN, yttria, CaO-stabilized zirconia, or refractory-metal options under controlled atmosphere.
- Thermal evaporation sources: vapor chemistry at source temperature and liner geometry govern—not only melt-contact charts. Alumina, BN, graphite, and Mo/W/Ta liners (industry) all appear depending on evaporant and deposition process.
- Crystal growth: contamination budgets are orders of magnitude tighter than foundry casting. Quartz for silicon Czochralski; BN/PBN for selected germanium and compound-semiconductor growth where non-wetting and purity combine.
- Powder sintering / sample prep: interaction is with binders, volatiles, and possible liquid phases—not a full molten bath. Alumina, zirconia, and BN boats or crucibles are chosen from powder chemistry and sinter atmosphere.
Where alumina, BN/PBN, zirconia, SiC, and graphite stop being the right answer
After metal and process are named, family boundaries finish the shortlist. Graphite and Pt/Mo/W/Ta appear here as industry options for contrast—not as catalog SKUs on this site.
| Family | Best-fit strength | Main limitation | Typical RFQ question |
|---|---|---|---|
| Alumina | Lab heating, thermal analysis, oxide-stable melts | Thermal shock, sticking, selected melt reactions | Is Al2O3 compatible with this alloy and flux? |
| Zirconia | Very high temperature, corrosive / precious-metal work | Stabilization grade, cycling, cost | Which stabilized zirconia grade is required? |
| BN / PBN | Non-wetting release, vacuum/inert, reactive metals | Air oxidation boundary (qualitative), cost/geometry | Is hot-pressed BN or PBN needed? |
| SiC | Thermal shock, heat transfer, non-ferrous foundry | Oxidation / carbon / slag compatibility | Which SiC grade and atmosphere? |
| Graphite (industry) | Heat transfer, induction coupling, non-ferrous melts | Air oxidation, carbon contamination | Is carbon pickup acceptable? |
When the shortlist points to oxide-stable laboratory or analysis duty, review the alumina crucible grade catalog for melt-contact review (capacity band 3–4000 ml on the alumina path, purity and lid/geometry per drawing). For vacuum or non-wetting melts, compare boron nitride crucible options for vacuum and non-wetting melts. Corrosive high-temperature melts that outgrow alumina often need a zirconia crucible review for corrosive high-temperature melts. Non-ferrous foundry shock and heat-transfer duty points to silicon carbide crucible options for non-ferrous foundry duty. Multi-family browsing starts from the multi-material ceramic crucible hub—not as a substitute for the alumina catalog link above.
RFQ pack for a metal-specific crucible recommendation
A usable recommendation needs the full process context—not only metal name and a temperature number.
- Metal / alloy composition (major + minor / trace elements that drive contamination)
- Process type: melting, casting, evaporation, sintering, or crystal growth
- Atmosphere: air, vacuum, argon, nitrogen, hydrogen, or other reducing gas
- Operating / peak temperature and hold time (as selection ceiling vs process window—not a life promise)
- Flux, slag, salt, or oxide chemistry that may attack the wall faster than the metal
- Purity targets and elements that must be excluded
- Geometry: OD, ID, height, wall, bottom radius, taper, lid, spout; drawing or old part when available
- Reuse expectation: single-use, short campaign, or repeated cycles
- Trial need: melt-contact or evaporation compatibility sample before production quantities
- On the alumina path only: form factor, capacity in the 3–4000 ml review band, cover style, and drawing/old-part reference
With those fields filled, a supplier can confirm family, flag boundary conditions that need a liner or different grade, and say whether a trial is warranted before volume.
Frequently Asked Questions
What wall family fits aluminum melting?
Foundry-scale air melting usually lands on clay-graphite or SiC for shock and campaign life. Clean laboratory or vacuum/inert work where carbon pickup and release matter often evaluates BN. Atmosphere and purity budget decide—not a single default for every aluminum job.
What about copper, brass, or bronze?
Clay-graphite and SiC remain the production defaults for thermal cycling and typical flux/slag chemistry. Laboratory contamination control may push toward high-purity alumina or zirconia. Put flux composition on the RFQ beside the alloy list.
Can alumina contain molten metals?
Yes for selected oxide-stable alloys when temperature, cycle, and contamination from the wall are acceptable. It is a poor first pick for titanium and similar reactive metals, and strong oxide wetting can stick. Run a trial before production use.
What is used for titanium or other reactive metals?
BN and PBN are common evaluation paths for some melting and evaporation duties under vacuum or inert gas. Yttria and CaO-stabilized zirconia appear in vacuum-arc or induction containment reviews. Refractory-metal liners remain industry options. Treat every reactive-metal row as shortlist plus trial—not a guarantee matrix.
What belongs on a metal-specific crucible RFQ?
Composition, process type, atmosphere, temperature/hold, flux/slag, purity exclusions, geometry (and drawing), reuse expectation, and whether a melt-contact or evaporation trial is required. “What crucible for [metal]?” alone is not enough for a chemical-compatibility answer.
Related reading
- BN versus graphite crucible selection — non-wetting / carbon-pickup contrast outside this by-metal matrix
- Alumina crucibles in quartz glass manufacturing — single-scene use/avoid split, not the full metal matrix
- Zirconia crucibles for melting and casting stability — ZrO2 melt/cast focus beyond the short boundary table above
