This requires that the flux must have good metallurgical and technological properties; The particle size meets the requirements (the particle size of ordinary flux is 0.45~2.50mm, the fine particles below 0.45mm shall not be more than 5%, and the coarse particles above 2.50mm shall not be more than 2%; the particle size of fine flux is 0.28~1.425mm, the fine particles below 0.28mm shall not be more than 5%, and the coarse particles above 1.425mm shall not be more than 2%); Water content w (H2O) 0.10%; The content of mechanical inclusions shall not be greater than 0.30% (mass fraction); Sulfur and phosphorus content w (S) 0.060%, w (P) 0.080%.
According to the selected welding wire material and the chemical composition of the valve body material, the high silicon melting flux or high basicity sintering flux is mostly selected.

Characteristics and Application of Steel Lined PTFE Compensator Series
1、 Product characteristics:
Compensated thermal shrinkage: non-metallic contraction joints can provide larger multi-dimensional direction compensation in a smaller size range.
Compensating device error: because system error is unavoidable in pipeline connection, non-metallic compensator can better eliminate device error.
Sound attenuation and vibration isolation: fiber fabrics and insulation cotton can absorb sound and isolate vibration transmission, which can effectively reduce the noise and vibration of boiler, fan and other systems.
No reverse thrust: as the main material is fiber fabric, the transmission is weak, and the use of non-metallic compensator can simplify the design.
High temperature and corrosion resistance: Fluoroplastics and organosilicon materials used have good performance of high temperature and corrosion resistance.
Good sealing performance: under the action of various media, it has good sealing performance.
Low price: 1/2~1/3 of imported similar products.
The device is easy to maintain.
2、 Scope of application
1. Boiler factory; 2. Cement plant; 3. Iron and steel works; Teflon compensator smelting furnace and combustion furnace; 4. Thermal power plants and nuclear power plants; 5. Air conditioning air supply system; 6. Glass and mineral wool industry; 7. Petrochemical enterprises; 8. Air and gas cleaning plant; 9. Fan factory and all in industry have high flexibility and sensitivity for pressure and request, and the center of contraction joint must be installed.
3、 Other service items:
It can be designed according to the user's special request (corrosion resistance, high temperature resistance, etc.) to manufacture various specifications of non-metallic contraction joint products and other products, repair or replace various damaged and invalid non-metallic contraction joints for the user (including the replacement and maintenance of imported non-metallic contraction joint parts), and provide the non-metallic contraction joint selection of engineering pipeline and on-site device technical guidance free of charge for the tetrafluoroethylene compensator.
4、 Main technical parameters:
Pressure: vacuum~0.1MPa
Temperature: - 20 ℃~1000 ℃
Round: DN50~DN5000
Rectangles: arbitrary sections