Views: 0 Author: Site Editor Publish Time: 2020-08-11 Origin: Site
There are many welding methods for galvanized steel. Generally, gas welding, manual arc welding, CO2 gas shielded welding, automatic submerged arc welding, and argon tungsten arc welding are commonly used in galvanized steel structures.
Gas welding was often used for welding galvanized pipes in the past. Due to the lack of concentrated heat input of gas welding, defects such as poor mechanical properties of the weld seam, etc., are basically eliminated in the installation industry. Gas welding damages the galvanized layer greatly.
CO2 gas shielded welding has good welding performance for galvanized steel. When using suitable welding specifications and matching shielding gas and welding materials, high-quality welded joints can be obtained. This method is rarely used in engineering practice.
The arc energy of argon tungsten arc welding is concentrated, which causes less damage to the galvanized layer, and is easier to form a good single-sided welding double-sided forming joint. It is a welding method that is worth using, but the welding speed is slower and the cost is relatively high. expensive.
Manual arc welding is currently the most common welding method used in pipeline installation. In the case of correct selection of electrodes, such as J421, J422, J423 and other titanium oxide type and titanium calcium type electrodes for welding, because these electrode coatings contain a large amount of rutile and ilmenite, the melting rate of the electrode is relatively large. Increased melting speed. If it can only destroy the galvanized layer at the front of the molten pool without swinging, it will generally not expand the melting area and reduce the penetration of the zinc liquid into the weld metal; if the correct operation method and welding materials are used, it can be The mechanical properties of the joint are better, and the welding quality without defects is obtained. As manual arc welding is cheaper and faster than argon tungsten arc welding, manual arc welding is used when there are skilled welders.
The pre-welding preparation of galvanized steel is the same as that of general low-carbon steel. It should be noted that the groove size and nearby galvanized layer must be carefully handled. In order to weld through, the groove size should be appropriate, generally 60-65°, and a certain gap should be left, generally 1.5-2.5mm; in order to reduce the penetration of zinc to the weld, the groove in the groove can be galvanized before welding Solder after the layer is removed. In actual work, centralized beveling is used, without blunt edge technology for centralized control, and 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, for low-carbon steel, J422 is more commonly used due to the ease of operation. Welding technique: When welding the first layer of multi-layer welding, try to melt the zinc layer and make it vaporize and evaporate to escape the weld, which can greatly reduce the liquid zinc remaining in the weld. In the fillet weld, the zinc layer should also be 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 5~7mm. When making the zinc layer After melting, return to the original position and continue welding forward. After the welding is completed, the weld seam should be cleaned in time, and the zinc-rich primer should be painted to take anticorrosion measures.