Unlike seamless steel tubes, the pre-weld preparation of galvanized steel pipes is the same as that of ordinary mild steel. It is necessary to pay attention to the groove size and the nearby galvanized layer.
For the penetration, the groove size should be appropriate, generally 60~65°, to leave a certain gap, generally 1.5~2.5mm; in order to reduce the penetration of zinc into the weld, the galvanization in the groove can be done before welding.
After the layer is removed, it is soldered again. In the actual work, the centralized beveling is adopted, and the blunt edge process is not used for centralized control. The two-layer welding process reduces the possibility of incomplete penetration.The electrode should be selected according to the base material of the galvanized pipe. Generally, the low carbon steel is considered to be easy to handle.
When welding the first layer of welds of multi-layer welding, the zinc layer is melted as much as possible and vaporized and evaporated to escape the weld seam, which can greatly reduce the liquid zinc remaining in the weld.
In the welding of the fillet weld, the zinc layer is also melted as much as possible in the first layer and vaporized and evaporated to escape the weld. The method is to first move the end of the electrode forward about 5~7 mm, when the zinc layer is made. After melting, return to the original position and continue to weld forward. After the welding is completed, the welds should be cleaned in time, and the zinc-rich primer should be brushed to prevent corrosion.
Welding quality assurance measures are controlled from five aspects: human, material, machine, law and ring.
The one-person factor is the focus of the welding control. Therefore, before the welding, the skilled welder who holds the welder’s certificate should be selected to carry out the necessary technical training and delivery. It is not allowed to be replaced at will, to ensure that the pipe welder is relatively stable.
2. Control of welding consumables
Ensure that the procurement materials are regular channels of welding consumables, have quality assurance books, certificates, and meet the process requirements; the welding heads are strictly controlled to ensure the flow direction and dosage; the welding consumables must be baked strictly according to the process, and once Disbursement for no more than half a day.
3. Have a reliable welder
The welder must ensure reliable performance and meet the needs of the process; the welder must have a qualified current and voltmeter to ensure the correct implementation of the welding process. The welding cable should not be too long, and the welding parameters should be adjusted when it is long.
4. Welding process
Ensure the strict implementation of the special operation method of galvanized pipe, weld process pre-weld groove inspection, welding process parameters, operation method control, post-weld appearance quality inspection, and increase non-destructive testing after welding if necessary. Control the welding level and the amount of welding consumables per pass.
5. Welding environment control
Ensure that the temperature, humidity and wind speed during welding meet the process requirements. The hot-dip galvanized pipe welding adopts the correct welding process in the construction, and carries out inspection and acceptance in strict accordance with the specifications. After the welding is completed, the anti-corrosion treatment of the weld seam (zinc-rich paint) is carried out in time, and it is applied in the air-conditioner open and closed system.
The process has certain feasibility, which can improve the construction speed and improve the firmness of the pipeline connection. Therefore, under the premise of construction conditions, the hot-dip galvanized pipe can be welded and welded under the premise of relevant protection and anti-corrosion measures.