What is the glass firing process?

Under a certain formula, the properties of the final material are most related to the baking process, and the foaming process is divided into several stages: preheating, sintering, foaming, foam stabilization and annealing.

1. The preheating process is mainly to remove chemically bound water, adsorbed water and free water from the batch; Due to the poor thermal conductivity of green body, direct high-temperature heating and sintering will lead to surface carbon oxidation and uneven foaming. Therefore, between room temperature and 400℃, the heating rate is generally 5 ~ 8 k/min, and the temperature is kept at 400℃ for 20 ~ 30 min.

sinter

The preheated green body is rapidly heated to the sintering temperature (650 ~ 750℃). The purpose of rapid heating is to prevent excessive decomposition of foaming agent, so that the gas phase which increases rapidly with the increase of green body temperature is wrapped in the green body.

In the sintering process, the heating rate is generally 8 ~ 10K/min. After foaming, the sintered body is heated to the foaming temperature at the rate of 10 ~ 15K/min for foaming (750 ~ 1000℃) and kept at the foaming temperature for a period of time (750 ~ 1000℃).

After the stable foaming is completed, the billet is quickly cooled to about 600℃, and the cooling speed is relatively fast, generally at 15 ~ 20k/min. Its purpose is to quickly fix the generated pore structure.

Due to the rapid cooling of the blank, annealing will produce stress. To relieve stress, keep the temperature at about 600℃ for 20 ~ 35 minutes, and then gradually cool to room temperature. Because of the low thermal conductivity of foam glass, its annealing cooling speed is much slower than that of ordinary glass, and the total annealing cooling time is generally more than 24 hours.