In the welding process of the titanium tube of the condenser, it is found that the welding seam is more oxidized and the porosity is more. There are many porosity and cracks during the color inspection and there are more than 50 leaks during the irrigation inspection. Active metals have poor repairability, and should not be repaired more than three times according to the instructions. In view of this situation, the company conducted a careful and careful analysis of the problems that occurred, first found the causes of various quality problems, and found corresponding countermeasures and effective remedies, and then carried out on-hand welding training and finally went to A formal manual welding repair is performed to ensure the success of the second welding.
Repair welding of cracks
The key is to remove the crack to the root. After finding the crack, first use a forward grinder and a reamer head to completely remove the crack, otherwise the deep crack after repair welding U * can slowly extend to the surface after a few hours, causing a new crack. Perform PT inspection on the cracked area after excavation, and confirm that it has been completely removed before repair welding: before repairing, first wash with internal ketone; add welding wire after welding delay. The key to crack repair welding is to control the temperature to prevent oxidative overheating of the titanium tube, complete the welded joints and so on after cooling down, and then carry out PT inspection, and PT inspection should be conducted again after 24 hours to determine whether there is delayed crack Of generation.
Repair welding of air holes
The generation of air holes is mainly caused by the existence of impurities between the titanium tube and the tube plate. The main energy should be focused on the tube plate before welding, so that the generation of air holes can be effectively avoided. The repair of air holes generally does not require the addition of welding wire. The operation should be stable during the repair welding. The tungsten pole tip is directly aligned with the air hole area to start the arc, and the arc is stopped immediately after the air hole is melted. After the gas cools the repaired solder joint for a few seconds, the argon arc is removed. The parts after repair welding should be bright white with metallic luster. If the color changes to blue or silver gray, it indicates that the temperature during repair welding is too high, and crack defects are easy to find during PT inspection.
Treatment of welding lumps and unfused defects
The main reason is that the expansion of the titanium tube is not strict or the coaxiality of the zero-motion welding machine is not enough, and the welding gun deviates from the center line of the titanium tube. The position of welding pain and unmelted defects is generally deep. Some weld nodules are 3 to 5 mm away from the tube mouth. The repair welding position is difficult. Because the titanium tube is thin, it is easy to burn the titanium tube during repair welding. The more the repair, the more the position is f. The more difficult the result of repair welding. Before welding repairing welding defects at the end of welding edge 5, the welding edge should be ground away with a cemented carbide rotating file, then the tube should be re-expanded with a tube expander, and then repaired with internal ketone after welding. This repair welding has relatively high requirements for the operator’s welding technology. In the operation, the operation principle of “stable, accurate and ruthless” must be fully grasped, that is, the operation must be stable, the wire feeding should be accurate, and the judgment must be decisive. During repair welding, the operator should lean against the tube plate while holding the welding torch to avoid instability of the welding torch and arc burns to other parts of the titanium tube. When feeding the wire, each drop of welding wire must be accurately delivered to the defect, and the position of the wire to be fed must be determined decisively. + Can hesitate to prevent oxidation caused by excessive temperature. Some defects are far away from the surface curvature of the tube sheet, and it is difficult to feed the wire during repair welding. In order to prevent the defect from being burned in time, the drop of welding wire can be melted on the edge of the defect before repair welding.
