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.

Maintenance and commissioning of pneumatic butterfly valve
1. The inspection and maintenance plan of the cylinder is to clean the cylinder surface and add oil to the cylinder shaft circlip at ordinary times, and open the cylinder end cover regularly every 6 months to check whether there are sundries and moisture in the cylinder and whether the lubricating grease is in good condition. If the grease is insufficient or dry, the cylinder shall be disassembled for comprehensive maintenance and cleaning before adding grease.