During the firing process, a series of changes occurred in the arrangement and structure of the graphite crucible and the graphite saggar, mainly plastic refractory clay. The basic process of crucible firing can be divided into the following four stages:

(1) Therefore, during the high temperature sintering process, attention should be paid to the melting state of the graphite crucible and the graphite saggar glaze layer to avoid the sintering intention due to excessive sintering.

(2) During the sintering process of the crucible, due to the thermal effect of the plastic refractory clay, the graphite and the clinker are consolidated into a whole with a certain mechanical strength.

(3) Therefore, the unevenness of the sintering temperature and the temperature control during operation have an important influence on the quality and service life of graphite crucibles and saggers.

(4) In the preheating and baking stage, the temperature should be strictly controlled, and the crucible will simply crack and explode in the chimney.

(5) In the low temperature firing stage, as the kiln temperature increases, the bound water in the crucible begins to be decomposed and purified, and the heating rate needs to be slow. If the heating speed is too fast and uneven, the pot body will simply burst and collapse.

(6) High temperature combustion stage: The temperature in this stage is 1000-1200 cc. At this time, the clay in the crucible is agglomerated by the medium temperature sintering structure, and then gradually transformed into mullite. During the high temperature sintering process, the glaze layer of the crucible is completely melted.

(7) A glass glaze film is formed and sealed on the outside of the crucible. If the sintering temperature exceeds the temperature limit of the glaze, the oxidation of the crucible is simple.

(8) In the medium temperature sintering stage, the graphite and clinker in the crucible will be connected and solidified into a whole. During the medium temperature sintering process, the glaze layer on the surface of the graphite crucible and the graphite saggar gradually melted as the temperature increased.

(9) A glass glaze film is formed to seal or cover the appearance of the crucible, thereby protecting the crucible from oxidation. During this period, the heating rate is fast, and the reduction flame is the best flame in the kiln.

Graphite saggar production technology:

After the graphite box is bored, it should be inspected according to the semi-finished product specifications and procedures. During the glazing process, the qualified product is glazed with the glaze. After the glaze is dimmed and fixed, it can be fired in the kiln. The purpose of sintering is to increase the density and mechanical strength of the crucible and improve the quality of the product.