Repair welding technology of ship propeller
1. Choose proper welding joints for cracks and broken leaves. When blades are broken in zone C and new fractured blocks are used for butt welding, the chemical B composition and mechanical performance test reports of the newly cast and welded fractured blocks must be approved by the surveyor. The pressure of the blades should be face down during welding. , The underside of the matching port should be lined with a cladding plate, and the welding port should be double-sided U-shaped or V-shaped, and should be welded through. The welding should be carried out from the center to the two edges respectively.
2. Corresponding measures should be adopted to reduce the welding temperature during welding, and the interlayer temperature at the molten pool should be kept at about 300℃ to reduce the evaporation and oxidation of zinc. During welding, the weld meat should be continuously and evenly tapped to extend it and reduce the shrinkage of the weld joint to ensure that there will be no cracks between the weld meat and the base metal.
3. The propeller after repair welding should be annealed. Area A, B or other large areas should be repaired. When conditions permit, heat it at a speed of no more than 100°C per hour and rise to the annealing temperature. The heat preservation time of the entire propeller is according to the propeller. The size is 4~8 hours, the cooling rate does not exceed 55℃ per hour, and the furnace can be opened and cooled after cooling to below 200℃.
4. If it is a blade or partial repair welding, when the annealing conditions in the furnace are not available, the heat preservation time can be calculated according to the maximum section thickness of the weld repaired part of 20min/25mm, but it should not be less than 1 hour, and then use insulation materials For bandaging, as the room temperature drops by itself, do natural annealing treatment. After annealing, the welding surface shall be polished and inspected for coloring flaw detection. There shall be no cracks, pores, slag inclusions, looseness, etc.
