Corrosion of propeller blade edge and repair of sawtooth

Repair principle of blade edge serration and erosion
(1) The blade edge serrations or small gaps shall be repaired if they are greater than 1/2 of the blade thickness (Z depth is not more than 10mm). For small sawtooth notch, it is allowed to continue to use after grinding and smoothing.
(2) For the part beyond 0.5R of the blade, the edge erosion depth shall not exceed 1/2 of the blade thickness, and the weld repair can be carried out when the width of each side does not exceed 1/4 of the blade width. If the blade is seriously corroded and the material properties have changed after repair for many times, it should be considered to replace it.
(3) For non-serious cavitation holes and depressions, it is allowed to fill them with plastic when it is inconvenient to weld, so as to make the propeller smooth.
The repair methods for blade corrosion and wear are summarized as follows:
(1) The corrosion spot is not too deep, and its diffusion is less than three points per square centimeter. The spot shall be ground with grinding wheel until bright metal is exposed.
(2) If the depth of corrosion spots is more than 1-1.5mm and there are more than three spots per square centimeter, the spot shall be repaired and welded in batches, and then ground in batches.
(3) The cavitation corrosion depth at the blade root shall not exceed half of the blade thickness at this place, which shall be repaired by welding after being shoveled and then polished.
(4) The blade surface is deeply corroded. The depth is more than half of the blade thickness, and the diffusion area is larger or more dense and the area of dense area is more than 20% of the blade area. The diameter of corrosion depression is 20% of the blade width. For small propellers, it should be replaced. For large and medium-sized propellers, the damaged part can be cut off and welded with new plates.
(5) If the blade is partially worn and the thickness of the blade has been reduced to within 2/3 of the original thickness, this part should be cut off and welded with a new plate.
(6) The blade is severely worn in more than 1/2 of the area and should be replaced.
Partial patching and replacement of blades
When the blade tip part is broken or the cavitation corrosion of the blade tip part is serious, it is more complex to repair by welding. Some blade tips are extremely thin and crimped, and cannot be repaired by welding. In this case, the propeller can be replaced locally.
Blade patching procedure (copper)
(1) Determine the scope of patching first, and mark the cutting and changing line on the blade and punch the hole;
⑵ Then measure the actual diameter of the propeller;
(3) Cut the patching part, drill several holes outside the cutting and changing line, and then cut it, so that Z can be planed on the planer;
(4) Drill and reshape the damaged corner on the drilling machine. Then use a chisel or air shovel to level the fracture;
(5) According to the appearance of other complete leaves, make a wooden mold and fit the fracture properly, and ensure its diameter size and screw surface shape. Z good is to make wood mold inlay according to the drawing size;
(6) After casting, the patched blade shall be shaped and matched with the original blade, and the electric welding groove shall be processed at the same time;
(7) Fix the patched blade with the original blade by pressing plate and bolt;
(8) Preheating and welding;
(9) Annealing treatment after welding to eliminate stress;
(10) After Z, the weld scar protruding from the weld shall be leveled and polished.