Production process

Report

Editor

Mainly includes the steps of batch preparation, melting, molding, annealing and post-processing.

Batch preparation

First, pre-process the raw materials, including crushing the block raw materials, pre-drying the wet raw materials and removing the iron from the iron-containing raw materials. The crushed particle size is preferably 0.25-0.5mm. Too coarse particles are not easy to fully melt, and residual material powder stones or silicon-rich nodules will be formed in the glass; too fine particles are easy to fly or gather into agglomerates. The raw materials with a certain particle size are accurately weighed according to the formula, and then mixed with a drum, paddle or disc mixer.

Melting

The glass batch is melted and clarified at high temperature to form a uniform glass liquid without bubbles and stones. The melting temperature of the glass batch varies with the composition, usually 1300-1600℃. The batch undergoes a series of physical and chemical reactions at high temperature and gradually melts completely. As the temperature rises, the viscosity decreases significantly, and a large amount of air and gas produced by the decomposition of raw materials rise and escape from the molten liquid, making the melt clear. While the bubbles are eliminated at high temperature, the chemical composition of the glass liquid tends to be uniform. If necessary, mechanical external force is added to stir it. After clarification and homogenization, the temperature is lowered so that the glass liquid can reach a viscosity suitable for molding requirements uniformly.

Melting is carried out in a glass melting furnace. In large-scale production, it is continuously melted in a pool kiln. The batch material is added at one end of the kiln, and the glass liquid for molding is discharged at the other end. In small-scale production, it is melted intermittently in a crucible kiln.

Molding

Processing the glass liquid into products with fixed geometric shapes. When the glass is cooled, it changes from liquid, plastic to solid, connecting the production stages of glass feeding, shaping and finalization. When the material is picked manually, the viscosity of the glass liquid is usually 102.2Pa•s; when the material is automatically fed mechanically, it is 102~103Pa•s, which is equivalent to 10~100 times the viscosity of the glass liquid when it is clarified. The appropriate viscosity of the glass liquid when dripping into the mold is usually 103.5Pa•s, and the viscosity should be 106Pa•s when demolding. Within this plastic range, the glass material is sheared, bonded, blown, expanded, and rolled. If the production time is long, the glass composition must be adjusted to slow down the viscosity change and reduce the tendency of crystallization, so as to avoid hardening too quickly and crystallization during the molding process. Common glass molding methods include blowing, pressing, pulling, pouring, and rolling.

 

Glass tube blowing method: used to make hollow glass products, such as water cups, utensils, bottles, cans, light bulbs, etc. When blowing manually, a hollow iron blowpipe about 1.5m long is used, one end is dipped in glass liquid (pick material), and the other end is a blowing nozzle. After picking the material, roll it evenly on the rolling plate (bowl) and blow it to form a glass bubble, which is blown into a product in the mold; it can also be blown freely without a mold and finally knocked off the blowpipe. When molding large products, it is necessary to repeatedly pick and roll the material evenly to collect enough material. During mechanical blowing, the glass liquid flows out from the outlet of the glass melting furnace, and is formed into droplets of set weight and shape by the feeder, which are cut into the initial mold and blown or pressed into the initial mold, and then transferred to the forming mold to be blown into the product. The blow-blow method, which is used to blow the initial mold and then blow the product, is suitable for making small-mouthed vessels and bottles. The press-blow method, which is used to press the initial mold and then blow the product, is suitable for making large-mouthed vessels and thin-walled bottles.