Galvanized steel pipes are divided into cold galvanized steel pipes and hot galvanized steel pipes. Cold galvanized steel pipes have been banned, and the state advocates the temporary use of the latter. In 1960s and 1970s, developed countries began to develop new pipes and gradually banned galvanized pipes.
China Ministry of Construction and other four ministries and commissions also issued resolutions in 2000 to prohibit the use of galvanized pipes as water supply pipes. Galvanized pipes are rarely used for cold water pipes in new residential areas, and galvanized pipes are used for hot water pipes in some residential areas. Hot dip galvanized steel pipe is widely used in fire protection, electric power, highway and other industries.
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Precautions:
First of all, the weld must be polished before welding, and the galvanized layer must be polished off, otherwise there will be bubbles, sand holes and virtual welding. It will also make the weld brittle and reduce the rigidity.
Secondly, the introduction of welding technology: when the first layer is welded, the zinc layer should be melted, evaporated and escaped from the weld as much as possible, which can greatly reduce the residual liquid zinc in the weld. When fillet welding, the zinc layer should melt and evaporate in the first layer as much as possible and escape from the weld. The method is to move the electrode tip forward about 5 ~ 7 mm, and after the zinc layer melts, it should return to its original position to continue welding forward.
Thirdly, when welding horizontally and vertically again, if a short slag covered electrode like J427 is selected, the tendency of undercut will be very small; If reciprocating rod conveying technology is adopted, defect-free welding quality can be obtained.
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