The first appearance of cracks appearing net result is how, this is due to the life of the crucible is too long, too obsolete.
The second casting material melting slower, for this reason life is approaching the limit of the crucible,
Third glazed off, causing the general reason is because the cooled crucible placed directly inside the hot crucible furnace heating cause, there may be due to heating caused when the temperature too quickly.
Fourth bottom protruding upward and crack, causing the main reason for this is that when the bottom of the crucible sticky coke or slag, such as the crucible placed on the hard ground, causing the crucible bottom protruding upward and cracks.
Fifth crucible bottom cracking, causing the reason for this is due to the expansion of the resulting slag.
Sixth Pan-green appearance of the crucible and begin to soften, resulting in the crucible of this reason is due to long hours of work over 1460 ℃.