Repair welding for cracks of condenser titanium pipe:
The key is to remove the crack to the root. the cracks should be completely eliminated by using a forward polisher and reamer head first after they are found, otherwise the deep cracks after repair welding will slowly extend to the scarce surface after several hours, causing new cracks.PT inspection is carried out on the crack area after excavation and repairing, and repairing welding can be carried out only after it has been completely cleared: the crack area should also be cleaned with done before repairing welding; Add welding wire for a time lag of repair welding. the key to crack repair welding is to control temperature, stop oxidation and overheating of titanium pipe, check PT after complete cooling of the weld joint, and check PT again after 24 hours to determine whether there is a delayed crack.
Repair welding of air holes:
Pore formation is mainly caused by impurities between the condenser titanium pipe and the tube sheet. The main attention should be paid to tube sheet management before welding so that the generation of the pore can be effectively avoided. welding wire is generally not required for the repair of air holes. stable operation is required during repairing welding. The tungsten tip is directly aligned with the arcing in the pore area. The arc stops immediately after the pore melts. The attenuation time during the arc stop should be more than 4S and the arc stopping/T.do not remove the argon arc immediately. Apply argon to cool the weld joint for a few seconds before removing the argon arc. the spot after repair welding should be bright white with metallic gloss. If the color becomes blue or silver grey, it indicates that the temperature is too high during repair welding and cracks are easy to be found during PT inspection.
Treatment of weld beading and incomplete fusion defects:
It is mainly caused by the loose expansion of the condenser titanium pipe or the insufficient coaxiality of the welding machine, and the deviation of the welding gun from the center line of the titanium tube. the location of welding pain and incomplete fusion defects is generally deep. Some weld beads are 3.5mm away from the pipe orifice, so the repair welding location is difficult. And because the titanium pipe is thin, it is easy to burn the titanium pipe during repair welding, resulting in the result that the more repair, the more difficult repair welding. Before repair welding of incomplete fusion defects of weld beading, the weld beading shall be ground off with a cemented carbide rotary file, and then the pipe shall be expanded again with a pipe expander, and then the repair welding shall be carried out after cleaning with internal ketone. This repair welding requires high welding technology for the operator. In the operation, we should fully grasp the operation essentials of "stability, accuracy, and ruthlessness", that is, the operation should be stable, the wire feeding should be accurate, and the judgment should be decisive.
During repair welding, the operator shall hold the welding gun and lean on the tube plate to avoid instability of the welding gun and arc burning of other parts of the titanium tube. during wire feeding, each drop of welding wire must be accurately sent to the defect, and the position to be fed must be determined without hesitation, so as to prevent oxidation caused by too high temperature. some defects are far away from the surface of the tube sheet, so it is difficult to feed wire during repair welding. In order to prevent the defects from getting bigger and bigger due to the untimely feeding of lines, a drop of welding wire can be melted at the edge of the defect before repairing the welding.
