Why Nickel Is Chosen for Crucible Service
Nickel melts at 1455 degrees Celsius and resists attack by alkalis and by many corrosive media, which is why nickel crucibles are a standard choice for melting ferroalloys, slag, clay and refractory materials. The metal keeps its shape and its crucible form through repeated heating cycles, so it suits the routine flux and fusion work found in a laboratory that handles mineral and metallurgical samples.
The service limit is the part that is most often misunderstood. A nickel crucible is not used at its melting point; it is used well below it, because the metal oxidises rapidly once the temperature climbs.
Key Properties at a Glance
| Property | Value or behaviour |
|---|---|
| Melting point of nickel | 1455 degrees Celsius |
| Alkali resistance | Strong; resists attack by alkaline fluxes |
| Corrosion resistance | Good against many corrosive media at moderate temperature |
| Typical melts | Ferroalloys, slag, clay, refractory materials |
| Recommended maximum working temperature | 700 degrees Celsius |
| Use for precipitate ignition or burning | Not suitable |
The 700 Degree Working Limit Explained
The melting temperature of a nickel crucible should not exceed 700 degrees Celsius. The reason is not a loss of mechanical strength but oxidation: nickel reacts readily with oxygen at elevated temperature, and the oxide layer that forms damages both the crucible wall and the melt it contains. Working continuously at the upper end of the range shortens service life even when no visible distortion appears.
Practical furnace schedules should therefore be written with the 700 degree ceiling in mind, allowing a margin for overshoot and for local hot spots inside the furnace chamber. A crucible that is run close to the ceiling on every cycle should be inspected more frequently than one used at moderate temperature.
Where Nickel Crucibles Perform Well
Fusion of ferroalloys, where alkaline flux attack would consume a less resistant vessel.
Melting of slag and refractory samples ahead of chemical analysis.
Clay and mineral fusion work in which alkali resistance matters more than high temperature capability.
Routine laboratory cycles in which the charge is held well below 700 degrees Celsius.
Where They Must Not Be Used
Precipitate burning or ignition. Nickel crucibles cannot be used for precipitate burning, because the operation demands conditions the metal does not tolerate.
Long holds close to or above 700 degrees Celsius, where oxidation becomes the limiting factor rather than melting.
Service in which the crucible is expected to survive repeated severe thermal shock together with oxidising conditions.
Handling and Care Practices
Preheat gradually so the crucible is not exposed to an abrupt temperature step.
Keep the working temperature inside the 700 degree limit and record the actual furnace set point for each batch.
Clean the crucible after each melt so residual flux does not continue to attack the wall between runs.
Retire the crucible when the wall thins, the surface pits or the base deforms, rather than waiting for a failure during a melt.
Frequently Asked Questions
Q: What is the melting point of nickel?
Nickel melts at 1455 degrees Celsius.
Q: Why are nickel crucibles used in the laboratory?
Nickel has strong resistance to alkalis and to corrosion, so the crucibles are commonly used to melt ferroalloys, slag, clay and refractory materials.
Q: What is the maximum working temperature of a nickel crucible?
The melting temperature of a nickel crucible should not exceed 700 degrees Celsius, because nickel oxidises easily at high temperature.
Q: Can a nickel crucible be used for precipitate burning?
No. A nickel crucible cannot be used for precipitate burning.
Q: Why does oxidation matter more than strength at high temperature?
Oxidation attacks the crucible wall and contaminates the melt, so the practical limit is set by oxidation behaviour rather than by mechanical softening.
Q: How can service life be extended?
Preheat gradually, keep the set point below the 700 degree limit, clean residual flux after each melt and withdraw the crucible as soon as the wall thins or pits.