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Control of annealing stress (residual stress) of glass

  • Source: Unknown
  • Date: October 21, 2020
  • Number of views: two hundred and three
Glass is an amorphous inorganic non-metallic material, which is generally made of a variety of inorganic minerals (such as quartz sand, borax, boric acid, barite, barium carbonate, limestone, feldspar, soda ash, etc.) as the main raw materials, and a small amount of auxiliary raw materials are added. Its main components are silicon dioxide and other oxides.
 
The chemical composition of ordinary glass is Na2SiO3, CaSiO3, SiO2 or Na2O · CaO · 6SiO2, etc. The main component is silicate double salt, which is an amorphous solid with irregular structure. It is widely used in buildings to isolate wind and light, and belongs to mixture.
 
In addition, colored glass mixed with some metal oxides or salts to show color, and tempered glass made by physical or chemical methods. Sometimes transparent plastics (such as polymethyl methacrylate) are also called organic glass..
 
The earliest glass makers in the world were ancient Egyptians. The emergence and use of glass has a history of more than 4000 years in human life. Small glass beads have been unearthed from the ruins of Mesopotamia and ancient Egypt 4000 years ago. [3-4]
 
In the 12th century, commercial glass appeared and began to become an industrial material. In the 18th century, optical glass was made to meet the needs of telescope making. In 1874, Belgium first produced flat glass. In 1906, the introduction machine for flat glass was made in the United States. Since then, with the industrialization and large-scale production of glass, glass with various uses and properties has been produced one after another.
 
Nowadays, glass has become an important material in the fields of daily life, production and science and technology.


 
The allowable stress values of various glass products are different due to different uses, otherwise the quality will affect and cause unnecessary losses. The following table lists the control range of glass stress in the department:
 
Glass type Allowable stress/(nm/cm)
Coarse annealing of optical glass 10-30
Precision annealing of optical glass 2-5
plate glass 20-95
Glassware sixty
glass tube one hundred and twenty
Mason jar 50-400
It can be seen from the above table (nm/cm is the optical path difference -- the value can be obtained by quantitative stress meter):
 
"Optical glass" --- optical path difference will affect its optical performance, so if the allowable value is low, stress should be strictly controlled.
 
Flat glass "- the magnitude of its internal stress (i.e. the magnitude of optical path difference). If the numerical value is large enough to cause the warping of the plate surface, that is, the stress causes deformation and makes the flat glass uneven, the allowable value is also low.
 
"Glass tube" --- The allowable value of optical path is very large. If it is too large, it will also affect the mechanical strength and cause the glass tube to bend.
 
For example, "optical fiber glass tube" is mostly used for optical fiber and cable, so its stress control is more strict, so the value cannot be too large.
 
"Glass bottles and jars" - generally used as containers. Due to the complexity of the shape, it will have a certain impact on the mechanical strength, so the allowable value has a very wide range. It is necessary to develop the stress control range of your own products according to the actual situation.

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