Analysis of the annealing process in glass bottle production

The core objective of the heating stage is to gradually adapt the glass bottle to the rising temperature and smoothly reach the stable annealing temperature. The heating rates of glass bottles with different characteristics vary significantly. Ordinary glass bottles, due to their relatively simple structure, can have their heating rate set at 20℃/min-30℃/min. For glass bottles with thick walls and special shapes, such as those with complex patterns or irregular structures, the heating rate must be reduced. This is because the different parts of this type of glass bottle expand to varying degrees when heated. Heating too quickly can easily lead to uneven force distribution within the internal structure, creating new stress risks.

The function of the heat preservation stage is to make the temperature of all parts of the glass bottle tend to be uniform and eliminate internal stress to the greatest extent. When determining the insulation parameters, the glass transition temperature should be taken as the reference. The insulation temperature is usually 20℃ to 30℃ lower than it. This temperature range can not only ensure the effective release of stress but also will not affect the structural stability of the glass bottle. The heat preservation time is closely related to the thickness of the glass bottle. Each millimeter of wall thickness requires 1 to 2 minutes of heat preservation. For instance, when manufacturing large-capacity glass bottles with a wall thickness of 8 millimeters, the holding time should be controlled within 8 to 16 minutes. Meanwhile, professional equipment should be used to monitor the temperature distribution inside the annealing furnace to ensure there are no local temperature differences.

The slow cooling stage is an important transition between heat preservation and rapid cooling, aiming to prevent the glass bottle from generating new stress due to a sudden drop in temperature. At this stage, the cooling rate must be strictly controlled at 5℃ to 10℃ per minute. If the cooling speed is too fast, the temperature difference between the inside and outside of the glass bottle will increase sharply, and internal stress will accumulate instantly. If it is too slow, it will increase the production time cost. In actual operation, technicians will ensure that all parts of the glass bottles cool down simultaneously by precisely adjusting the ventilation system and the circulation speed of the cooling medium inside the annealing furnace, thereby reducing the risk of deformation.

The rapid cooling stage is the final step of the annealing process, with the main purpose of enhancing production efficiency and shortening the production cycle. When the temperature of the glass bottle drops to a lower annealing temperature, its internal structure has become relatively stable, and the cooling rate can be appropriately accelerated to room temperature. However, rapid cooling is not an unlimited increase in speed; it needs to be adjusted in accordance with the actual situation of the glass bottle. For small-sized glass bottles with thin walls and simple shapes, a faster cooling rate can be adopted. However, for glass bottles with thick walls and complex structures, if the cooling rate is too fast, they may still break, and this needs to be carefully controlled. During the process, dedicated personnel should be assigned to monitor the condition of the glass bottles in real time. Once any abnormalities such as cracks are detected, the cooling parameters should be adjusted immediately to ensure product quality.