유리병 및 유리 용기: 열 응력과 어닐링

Glass in the molding process and mold contact, as well as by the cooling wind, the rapid cooling of the glass (such as in 10 seconds from 1100 ℃ down to 600 ℃), the glass inside and outside will produce a large temperature difference, due to the temperature difference of the stress produced is called thermal stress. (The force remaining inside the glass puts the structure of the molecules in a state of deformation)

Thermal stress, if not eliminated, will seriously reduce the mechanical strength and thermal stability of the products, and even the phenomenon of self-cracking. Therefore, we should raise the products into the furnace to the annealing temperature, and then keep them for a certain period of time, after removing the thermal stress, anneal them slowly, so that the residual stress does not exceed a certain value, in order to ensure the safe use of the products.

The essence of annealing is to reduce or eliminate stresses and prevent new ones from arising.

The internal stress of beer bottles is ≤4, less than 30.0^o. It is recommended to control the internal stress of small mouth pressure blowing lightweight bottles ≤ 2 levels, less than 15.0^o.

The stress of the product can be detected by the stress meter, and the angle of rotation of the polarizer corresponds to the stress level of the product: Level 1 0.0^{(o) -7}.4^o, Level 2 7.5^o-14.9^o, Level 3 15.0^o-22.4^o, Level 4 22.5^{(o) -29.9(o)}, Level 5 30.0(^{o) -37.4(o), and}Level 5 30.0(^{o) -37.4(o).}-29.9^o, Level 5 30.0^o-37.4^o.

에메랄드 그린 소재 병 바닥 응력 레벨 4 사진

Annealing point Ta: means that 95% of the stress can be removed after three minutes at this temperature, also called the upper limit of annealing temperature. (approximately 555°C)

Transition point Tg: Between the annealing point Ta and the strain point Ts. Glasses near this temperature are viscoelastic, and the plasmas can undergo viscous flow to remove the temperature gradient in various parts of the glass. (about 530°C)

Strain point Ts: means that only 5% of the stress can be removed after three minutes at this temperature, also called the lower limit of the annealing temperature. (approximately 515°C)

The theoretical values of annealing point Ta and strain point Ts can be calculated by referring to the following equations:

Annealing point Ta = 0.8381 x SP-44.223 (°C)

Strain point Ts = 0.8094 x SP-52.062 (°C)

Here SP is the softening point of the glass, and when the softening point of the glass changes, the annealing point and strain point also change.

The annealing temperature, which refers to the temperature at which the product can be stress relieved by 15 minutes, is generally 20℃~30℃ lower than the theoretical value. Most of the annealing temperature of soda-lime glass is 510℃~550℃.

Due to the annealing furnace thermocouple installation position, insertion depth, instrumentation and other possible differences, even if the same type of annealing furnace, but also according to the product measured stress results to set a reasonable annealing temperature and annealing speed, do not rigid.

In stress relief, usually the higher the annealing temperature, the longer the holding time, the better the effect. The thicker the glass and the more complex the shape of the product, the stress is more likely to be concentrated, to increase the annealing temperature and extend the time (slow down the speed of the large mesh belt) to eliminate the stress.

Keeping the glass bottles and jars on the large mesh belt neatly arranged and properly spaced is conducive to stress relief. How to make the spacing of glass bottles and jars suitable, so that the cold spray gun can sink below the bottle mouth surface, and at the same time to avoid the large mesh belt speed is too fast resulting in stress failure? In the new construction or overhaul should be based on the type of products produced by the molding machine, specifications, machine speed to calculate the selection of the appropriate annealing furnace.

In the production process, if the product stress is unqualified, the annealing equipment and annealing process to find the reasons. Common causes include annealing furnace heater failure, top circulating fan stop, inaccurate display of annealing temperature, low temperature of incoming products, unreasonable setting of annealing temperature and annealing curve, and insufficient annealing time. Find the real and accurate reasons, countermeasures will naturally have.