How long can graphite crucible be used at high temperature for a long time? Why can graphite crucible work stably at high temperature for a long time? It depends on the physical properties of graphite.
Graphite has the following physical characteristics: high temperature resistance, high melting point of graphite, 3850 degrees in vacuum, sublimation temperature of 2200 degrees under low pressure. Different from ordinary materials, graphite crucible not only does not soften when the temperature rises, but also increases its strength. At 2500 ℃, the tensile strength of graphite is doubled. Due to its special thermal shock resistance, the thermal expansion of graphite is anisotropic, so the macroscopic expansion coefficient is not large, and the volume change of graphite is not large under the condition of sudden temperature change. In addition, its good thermal conductivity makes graphite have good thermal shock resistance.
Combining the above two points, graphite parts should be able to work stably at high temperature for a long time. We know that everything has its service life. Graphite crucible is also a kind of crucible with a certain life. In its life, we must pay attention to the use method. Next, we will tell you how to improve the service life of graphite crucible. First of all, the graphite crucible can be heated directly, and it can not be cooled immediately after heating. Take it down with crucible tongs, and do not put it on the cold metal table top, so as to prevent it from cracking due to rapid cooling. Secondly, because the bottom of the crucible is very small, the crucible needs to be placed on the graphite pad or clay triangle when heated.