5. Warming up the workpiece before spraying
The pre-heating of the workpiece before spraying has great practical significance. It can remove the moisture on the surface and reduce the stress accumulation of the coating. Especially for shaft parts of the size like our factory, the pre-heating temperature is about 100 ° C. Spray the aluminum-coated nickel composite powder F505 as the bonding layer on the surface of the treated journal. The thickness of the bonding layer can be 0.10-0.15mm. This layer is only used in combination, so it is not necessary to spray too thick. After spraying the bonding layer, spray the G101 powder working layer. The G101 powder must be preheated and baked at a temperature of 105-250 ° C before use to ensure the fluidity of the powder spray and prevent the agglomeration from blocking the spray path. During the spraying process, the gas pressure, flame temperature, spraying distance, spraying angle, and speed of movement are strictly controlled, so that the coating is even and flat, and the bonding is firm. The specific control parameters are as follows: the coating position is the outer arc surface; the preheating temperature is 100-200 ° C. The spraying distance is 180-200mm; the spraying angle is 90 °; the moving speed of the spray gun is 6-12mm / min; the linear speed of the roll is 8-12m / min.
When spraying the working layer, a neutral flame is used. The powder can be observed from the flame. The powder is white and bright at the end of the flame. This indicates that the temperature is high if the temperature is dark red or red. And the flame energy rate, it is appropriate to heat the powder to white light. At this time, the powder temperature is high, the speed is fast, and the deposition effect is good.

6. Metal processing after spraying
After spraying, use asbestos to wrap up the sprayed parts to make them cool slowly to avoid cracks. When it is cooled to room temperature, rough turning can be performed, leaving grinding allowance (about 0.3 to 0.5 mm) before grinding. Grind according to the size required by the drawing and the specified roughness. This completes the repair of the roll. The repair cost of the roll is about 10,000 yuan, which can save more than 100,000 yuan in the factory (the finished product of the roll is 30,000 yuan per ton and the weight of each roll is 3 tons).