Compression sealing technology
The compressive strength of Glass is much larger than that of the tensile strength (Glass DM-308 is 108kg/mm2 and the tensile strength is only 7.7kg/mm2, which is about 15 times as much as that between the two). The expansion coefficient of the external metal should be much larger than that of the intermediate glass when the sealing material is not matched. The intermediate glass expansion coefficient and internal metal expansion coefficient is used to match state, resulting in the sealing process with temperature decreased, especially in the annealing temperature to room temperature stage, the expansion coefficient of the metal material to produce a certain pressure on the stress of Glass, the Glass is in a compressed state in the contracting process. The basic principle of the compression seal.
If the choice of metal is 45 or 10 low carbon steel case, can choose high melting point silicate based iron alloy sealing glass powder, and iron nickel expansion alloy (4J50) pin for sealing. The expansion coefficient of the coating to pin the thermal expansion coefficient of glass sealed iron heat (e.g. 4J50: 9.2-10x10-6/oC), but less than the metal shell is coated with thermal expansion coefficient (such as 45#:13.09x10-6/oC), in order to achieve compression sealing.
It is worth noting that, with the continuous improvement of materials and technology, compression sealing technology has been quite stable, but also has a good control of the cost of products.
