Outer Diameter 4-300mm Borosilicate Glass Tubing Large Glass Test Tubes ISO

Borosilicate Glass Tubing Borosilicate Glass Tubing

raw material

Including main raw materials and auxiliary raw materials. The former refers to the introduction of raw materials such as the oxides that form the network structure of the glass, the intermediate oxides and the oxides outside the network; the latter can accelerate the melting of the glass or make it obtain certain necessary properties.

main ingreadient

Depending on the nature of the oxide introduced, into an acidic oxide raw material, alkali metal oxides and alkaline earth metal oxide raw material.
① Acidic oxide raw materials: SiO2, B2O3, Al2O3 and other raw materials. SiO2 is the skeleton of the glass structure in silicate glass. It gives the glass a high strength, good chemical stability, heat resistance and low expansion properties, but will increase the melting temperature of the glass, an increase in viscosity. The listed SiO2 raw materials are silica sand, sandstone and quartzite. B2O3 in the glass can be added to reduce the thermal expansion of the glass, increasing the refractive index, thermal shock resistance and chemical resistance, lower the viscosity of the glass at higher temperature, increasing the viscosity of the glass at lower temperatures. The starting material is referenced B2O3 Borax or boric acid. Adding Al2O3 to the glass can reduce the crystallization tendency of the glass, enhance the chemical stability, increase the strength, and increase the viscosity of the glass. Starting material are generally referred feldspar and K2O or Na2O and SiO2, industrial alumina can be used. Cangzhou City Tianchang process Glassworks professional manufacturer of high borosilicate glass tube

It mainly includes the steps of batch preparation, melting, forming, annealing and post-processing.

Batch preparation

First, the raw materials are pre-processed, including the crushing of bulk raw materials, the pre-drying of wet raw materials, and the iron-removing treatment of iron-containing raw materials. The size of the crushed particles should be 0.25~0.5mm. The particles that are too coarse are not easy to be fully melted, and will form residual powder stones or silicon-rich nodules in the glass; particles that are too fine are easy to fly or agglomerate 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 material is melted and clarified at a high temperature to form a uniform glass liquid without bubbles and stones. The melting temperature of the glass batch varies with the composition, and is usually 1300 to 1600°C. The batch material undergoes a series of physical and chemical reactions at high temperature and gradually melts completely. With the increase of temperature, the viscosity decreases significantly, and a large amount of air contained therein and the gas generated by the decomposition of raw materials rise and escape from the melt, making the melt clear. While removing the bubbles at high temperature, the chemical composition of the molten glass also tends to be uniform. If necessary, mechanical external force agitation is applied. After the clarification and homogenization are completed, the temperature is lowered to make the glass liquid uniformly reach the viscosity suitable for the molding requirements.
The melting is carried out in a glass melting furnace. Continuous melting in the kiln during mass production. The batch material is added at one end of the kiln, and the formed glass liquid is discharged at the other end. In small-volume production, it is melted intermittently in a crucible kiln.