Duplex steel heat exchange tubes do not self-fuse; how can filler wire welding ensure fusion at the root?
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Dear teachers, this is from a previous experiment: if the first weld at the end of the heat exchange tube does not undergo self-fusion, wire feeding is carried out directly; as a result, the root area cannot be welded, leading to unmerged areas with \"small holes\"； Now, when dealing with double-phase steel heat exchange tubes, such steel generally does not allow for self-fusion; however, if welding is carried out by directly inserting welding wire, it results in \"holes\" at the root area that are not fully fused, as shown in the diagram. Is there any good solution to this problem?
To address this situation, the following methods can be tried to solve it: 1. Enhance preheating: Before feeding the wire, increase the preheating of the pipe ends so that their temperature rises gradually; this improves the plasticity and toughness of the steel, which is beneficial for proper welding fusion. 2. Multi-pass welding: After the first weld is completed, the second and third welds are filled and fused. By performing multiple welds, the heat can be distributed more evenly in the steel, thereby improving the quality of the weld. 3. Use filler materials with a higher temperature: During the filler application process, it is possible to use filler materials with a higher temperature, which helps to increase the temperature in the welding area and facilitates fusion at the root portion. It should be noted that before welding, it is essential to ensure the cleanliness of the pipe end surface in order to avoid issues caused by a faulty soldering iron. At the same time, it is recommended to take proper protective measures during welding to prevent the pipe ends from being affected by the external environment, which could otherwise lead to a decline in welding quality. .
Double-phase steel has a more sticky droplet behavior than 3-series stainless steels; increase the current or switch to another welder