Method for remanufacturing ultra-large copper nut

A method for remanufacturing an ultra-large copper nut, comprising following steps of:

• step (1) coarsening treatment:
• washing an oil contamination layer on the ultra-large copper nut with diesel oil, washing a screw tooth surface and a dedendum of the ultra-large copper nut with gasoline;
• removing oil contamination in an oil hole and washing the oil hole with gasoline;
• and performing grinding and coarsening on screw teeth of the ultra-large copper nut;
• step (2) purifying treatment:
• comprising washing the screw teeth of the ultra-large copper nut with acetone or sodium hydroxide solution, and then washing the screw teeth of the ultra-large copper nut with sodium carbonate solution;
• step (3) detecting a material of the ultra-large copper nut comprising detecting materials of the ultra-large copper nut and determining chemical composition of a welding wire according to the material of the ultra-large copper nut;
• step (4) sleeving a thermal insulation device comprising sleeving the thermal insulation device outside the ultra-large copper nut;
• step (5) preheating the ultra-large copper nut comprising preheating the ultra-large copper nut by a fuel gas preheating method comprising steps of:
• step (5.1) heating the ultra-large copper nut for 4 hours at a heating rate of 20° C. per hour;
• and
• step (5.2) heating the ultra-large copper nut to a temperature at a range of 200° C.-300° C. at a heating rate of 50° C. per hour, preserving the temperature, wherein a sum of a heating time and a preserving time is 4 hours;
• step (6) melting-deposition shaping:
• comprising welding a welding wire and/or a weld assembly on a damaged region and/or a fracture of the ultra-large copper nut, so as to recover a geometrical shape of the ultra-large copper nut and achieve melting-deposition shaping, wherein the welding is performed under protection of an argon gas, and a purity of the argon gas is greater that or equal to 99.98%;
• step (7) post-processing:
• comprising performing machining and abrasive machining on the ultra-large copper to meet operating requirement and restoring oil hole which is blocked;
• and
• step (8) detecting:
• comprising performing magnetic defect detecting, ultrasonic testing, hardness detecting and geometric parameter detecting on the ultra-large copper nut.