What metal materials are not suitable for using a muffle furnace?

Metal materials that are not suitable for muffle furnaces mainly include the following categories:

High melting point metals:
Tungsten: Its melting point is about 3410 ℃, which is much higher than the highest temperature range of most muffle furnaces, making it unsuitable for dissolution in muffle furnaces.
Platinum: Its melting point is about 1770 ℃, which is also higher than the temperature range of most conventional muffle furnaces. Placing it in a muffle furnace can easily cause damage to the furnace, and the metal is also difficult to dissolve.
Iridium: Its melting point is about 2466 ℃, and as a rare metal, its melting point also exceeds the highest temperature range of most muffle furnaces.
Niobium: Although it is a commonly used alloying element, its dissolution point temperature is also higher than the temperature range of a muffle furnace.
Rhenium: Its melting point is about 3180 ℃, which is also higher than the highest temperature range of most muffle furnaces.

Metals that cause damage to muffle furnaces:
Due to the high melting point of the above-mentioned metals, placing them in a muffle furnace not only makes them difficult to dissolve, but also easily leads to damage to the furnace.
Special treated metals:
Rare metals and expensive metals, such as iridium, are commonly used in high-precision applications and therefore require more specialized equipment and methods for processing, rather than ordinary muffle furnaces.

Other precautions:
The use of muffle furnaces is also subject to some other restrictions, such as prohibiting the injection of various liquids and easily soluble metals into the furnace. At the same time, the maximum temperature of the muffle furnace shall not exceed the rated temperature to avoid burning out the electric heating elements.

In summary, metal materials that are not suitable for use in muffle furnaces mainly include high melting point metals (such as tungsten, platinum, iridium, niobium, rhenium, etc.), metals that are harmful to muffle furnaces, and metals that require special treatment. When using a muffle furnace, it is necessary to pay attention to these restrictions to ensure the safety and effectiveness of the equipment.