How to strictly control the heating rate of graphite crucible?

How to strictly control the heating rate of graphite crucible? 

1. In the heating process of the graphite crucible, when the temperature is lower than 400 degrees, we also need to slow down the heating rate of the graphite crucible, slowly heating; 

2. When the temperature exceeds 600 degrees, we can accelerate the heating speed of the graphite crucible, so that the graphite crucible can quickly reach the processing temperature.

3. When preheating the graphite crucible, the heating speed of the graphite crucible should be as slow as possible to avoid the sudden heating damage to the graphite crucible.