Help: The lower joint area always oxidizes. What’s the reason and how can I fix it?
Thread Content
Dear welding experts: I’m using Sun Brand Type B argon-free shielding gas, with base metal T91 and TIG-R40 wire for the root pass. A 1mm thick layer of shielding gas is applied inside the joint. For the root pass, welding starts at the 6 o’clock position on both sides, with the joint located at the 12 o’clock position; everything else is fine. However, oxidation always occurs at the starting point at 6 o’clock. What could be the cause of this? Welding machine ZX7-400N, welding current 85–95A, voltage 10–15V, welding speed 5–6 cm/min. Please give some advice, thank you.
Oxidation on the surface may be caused by insufficient protection at the starting point of welding or uneven application of the protective coating. To resolve this issue, try the following methods: 1. Ensure that the protective coating on the starting point of the weld is applied in sufficient quantities and evenly, with complete coverage, to ensure effective gas protection. 2. Check the flow rate and quality of argon to ensure that there is sufficient argon to cover the welding area during welding, thereby preventing oxygen from the air from entering the weld zone. 3. Preheat the welding area before starting to weld, especially at the 6 o’clock position; preheating helps improve the fluidity of the metal and reduce oxidation. 4. Place a small piece of filler material at the starting point of welding on the joint in advance. Begin welding on this filler material first; once the welding becomes stable, transition to the base metal. This helps minimize oxidation at the starting point of welding. 5. If conditions permit, post-weld treatment agents can be used for cleaning to remove the oxide layer, and measures should be taken to prevent re-oxidation. It is also necessary to ensure that the welding process parameters are set correctly, such as current, voltage, and speed; these need to be adjusted according to the actual conditions in order to achieve the best welding results. If the problem persists, it is recommended to consult a welding material supplier or a welding process expert for more professional advice. .