Background and General Rules
During the welding process of the condenser titanium tube, it was found that the weld seam was more oxidized and had more pores. During the coloring inspection, there were many pores and cracks. During the water filling inspection, there were many leaks. Since the titanium tube plate is a relatively active metal with poor repairability, it should not be repaired more than three times according to the instructions.
Repair Welding of Cracks
The key is to clear the cracks down to their roots. After cracks are discovered, use a forward grinder and a reamer head to completely remove the cracks; otherwise, the deep cracks after repair welding may slowly extend to the surface after a few hours, causing new cracks. The cracked area after repairing should be inspected by PT (penetrant testing), and repair welding can only be carried out after confirming that the crack has been completely removed. Before repair welding, the area should be rinsed with acetone; welding wire should be added during repair welding. The key to crack repair welding is to control the temperature to prevent oxidation and overburning of the titanium tube. After the repaired welding joint has completely cooled, PT inspection should be performed, and PT inspection should be performed again after 24 hours to determine whether there are delayed cracks.
Repair Welding of Pores
The generation of pores is mainly caused by the presence of impurities between the titanium tube and the tube sheet. The main focus should be on cleaning the tube sheet before welding, so that the generation of pores can be effectively avoided. Repair of pores generally does not require adding welding wire. During repair welding, the operation must be steady: the tip of the tungsten electrode is directly aimed at the pore area to start the arc; after the pores are melted, the arc is stopped immediately. When the arc is stopped, the decay time should be greater than 4 seconds, and the argon torch should not be taken away immediately; use argon gas to cool down the repaired solder joint for a few seconds before removing the torch. 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 was too high, and crack defects are easy to be found during PT inspection.
Frequently Asked Questions
How many times can titanium tube plates be repaired? Not more than three times according to the instructions.
Why must cracks be fully removed? Deep cracks after repair welding may slowly extend to the surface after a few hours, causing new cracks.
What color indicates correct repair welding temperature? Bright white with metallic luster; blue or silver gray indicates excessive temperature.
How should the cracked area be prepared before repair welding? Use a forward grinder and a reamer head to completely remove the crack, confirm complete removal by PT (penetrant testing), and rinse the area with acetone before repair welding.
Why is the arc decay time important when repairing pores? When the arc is stopped, the decay time should be greater than 4 seconds and the argon torch should not be taken away immediately; use argon gas to cool down the repaired joint for a few seconds before removing the torch.
