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Good Chemical Stability 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
According to the nature of the introduced oxides, it is divided
into acidic oxide raw materials, alkali metal oxide raw materials
and alkaline earth metal oxide raw materials.
① Acidic oxide raw materials: raw materials such as SiO2, B2O3,
Al2O3, etc. SiO2 is the skeleton of the glass structure in silicate
glass. It gives the glass high strength, good chemical stability,
heat resistance and low expansion, but it will increase the melting
temperature of the glass and increase the viscosity. The cited raw
materials of SiO2 are silica sand, sandstone, and quartzite. Adding
B2O3 to the glass can reduce the thermal expansion of the glass,
increase the refractive index, thermal shock resistance and
chemical resistance, reduce the viscosity of the glass when the
temperature is higher, and increase the viscosity of the glass when
the temperature is lower. The cited raw material for B2O3 is borax
or boric acid. Adding Al2O3 to the glass can reduce the tendency of
glass to crystallize and enhance the chemical stability, increase
the strength, and increase the viscosity of the glass. The cited
raw materials are usually feldspar with K2O or Na2O and SiO2, and
industrial alumina can also be used. Cangzhou Tianchang Craft Glass
Products Factory specializes in the production of various types of
high borosilicate glass tubes
② Alkali metal oxide raw materials: raw materials with Na2O and
K2O. Adding Na2O and K2O to the glass can reduce the melting
temperature and viscosity, but it will make the chemical stability
of the glass worse. The cited raw materials are soda ash (Na2CO3)
and potash (K2CO3).
It mainly includes the steps of batch preparation, melting, forming, annealing and post-processing.
Batch preparation
First, the raw material pretreatment includes pulverization of bulk
material, pre-wetted material is dried, treated iron-containing
materials in addition to iron, and the like. The particle size
after pulverization should be 0.25 ~ 0.5mm. Too coarse particles
are not easily melted sufficiently, the remaining powder will form
stone or silicon rich nodules in the glass; too fine particles are
easily scattered or agglomerated into clumps. The particle size of
the raw materials according to a certain formula is precisely
weighed, and then mixed with a tumbler, mixer paddle or disc.
MeltingGlass batch melting and refining at an elevated temperature
to form a homogeneous molten glass free of bubbles, no stones. The
melting temperature of the glass batch varies with the composition,
and is usually 1300 to 1600°C. Batch through a series of physical
and chemical reactions, gradually completely melted at a high
temperature. With increasing temperature, the viscosity decreased
significantly large amount of gas and feed air contained therein
escapes decomposition increases the melt, the melt clear. Removing
bubbles while high temperature, the chemical composition of the
molten glass tends to be uniform. If necessary, apply mechanical
external force to stir. After completion of the clarification
homogeneous cooling, the glass was uniformly reach the desired
viscosity suitable for molding.
In glass melting furnace. Continuous melting in the kiln during
mass production. Batch kiln at one end of the addition, the
discharge of molten glass formed at the other end. In small batch,
a batch which is melted in a crucible furnace.
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