The galvanized steel pipe is a kind of pipe with a layer of zinc on the surface. The galvanizing treatment can improve the corrosion resistance of the steel pipe, extend its service life, and give it a certain aesthetic appeal. The base material of galvanized steel pipes is usually carbon steel, and common grades include Q195, Q215, Q235 and other carbon structural steels. These carbon steels have certain strength and toughness, and can meet the use requirements of general construction, water supply and drainage and other fields.
Can galvanized steel pipes be welded?
Galvanized steel pipes are quite common in daily life. They are generally used to transport low-pressure fluids such as gas and heating. They can also be used for trestle pipe piles, support frame pipes for mine tunnels, oil well pipes in oil fields, oil pipelines, etc. So, can galvanized steel pipes be welded?
Generally speaking, galvanized steel pipes can be welded. Ordinary galvanized pipes have a relatively thin galvanized layer, so ordinary electric welding or gas shielded welding can be used. Gas shielded welding is mainly suitable for situations where grinding is inconvenient and welding with a galvanized layer is required. If the galvanized layer is thick, argon arc welding can be considered.
How to weld galvanized steel pipes?
Galvanized steel pipes are corrosion-resistant, have a long service life, and are relatively inexpensive, so they are widely used. When welding galvanized pipes, we must pay attention to the correct galvanized pipe welding method and some matters that need attention:
1. Before welding
The preparation before welding of galvanized steel is the same as that of ordinary low-carbon steel. It mainly deals with the groove size and the galvanized layer nearby. The groove size is generally 60-65°, leaving a certain gap, generally 1.5~2.5mm; before welding, in order to reduce the penetration of zinc into the weld, the galvanized layer in the groove should be removed before welding.
2. When welding
The welding technique uses centralized beveling, and the process of not leaving a blunt edge is centrally controlled. The two-layer welding process reduces the possibility of incomplete penetration. When welding, you should also pay attention to:
(1) When welding the first layer of a multi-layer weld, try to melt the zinc layer and allow it to vaporize and evaporate to escape from the weld, which can greatly reduce the amount of liquid zinc left in the weld.
(2) When welding fillet welds, try to melt the zinc layer in the first layer and make it vaporize and evaporate to escape from the weld. The method is to first move the end of the electrode forward about 5 to 7 mm, and then return to the original position and continue welding forward after the zinc layer is melted.
3) When welding horizontally or vertically, it is recommended to use short-slag electrodes such as J427, which will reduce the tendency of undercutting. The back-and-forth electrode movement technology will improve the welding quality.
3. After welding
After welding, the galvanized layer of the galvanized pipe must be polished off, otherwise it will cause bubbles, sand holes, false welding and other problems, and will also make the weld brittle and reduce rigidity.
Read more: Production Process of Hot-dip Galvanized Steel Pipes
