The compressive strength of glass material is greater than the tensile strength, therefore, in the structural design with a glass seal, when the electric heater cools, the metal at the end of the tube which is not sealed can be free to shrink. A bending moment is generated at the intersection of the glass and metal, and because of the symmetry of the two sides, the moments cancel each other out and the seal is reliable.
Generally, glass powder and glass beads (ring) are used. Glass beads (ring) is made of proprietary glass powder pressed into a variety of shapes and sizes, sintered into a certain strength, and made easy for assembly operations. There are two kinds of common glass, one containing lead (Pb) and the other lead-free. The lead-free ones comply with ROHS directive.
This product is used for sealing the metal electric heaters.
The figure is a recommended temperature for box-type electric furnace sealing. Please pay attention to the cooling process after the sealing is completed.
If you are using a high-frequency heating machine or a flame spray gun etc., please heat until it melts and then cool down slowly (quick cooling is not suitable).
|Basic properties of sealing glass before sealing|
|Glass softening temperature||Glass transition temperature||Average coefficient of thermal expansion ( RT-300 °C)||End operating temperature||Resistivity (25 °C )|
|430~440 °C||400~410 °C||9.3±0.5×10-6 /°C||≤350 °C||109 Ω·m|
|Leakage current detection (detection voltage 1000 V)||Insulation resistance detection (detection voltage 1000 V)|
|Temperature(°C)||Leakage current (mA)||Temperature(°C)||Insulation resistance( MΩ )||Remark|
|100||0||100||2×106||Testing is performed on the insulating material itself，after packing according to the company's internal standards, which may affect the results.|
|substance||Detection value||substance||Detection value||Remark|
|Pb||not detected||Hg||not detected||Testing agency SGS, other macromolecular substances are not detected。|
|Cr6+||not detected||Cd||not detected|