How to choose spraying process parameters for oxy-acetylene flame spraying

       Process parameters when spraying and laying the bottom layer



    When spraying powder, the distance between the nozzle and the workpiece is about 180mm. The nozzle and the surface of the workpiece should be kept vertical and at the same level as the axis of the workpiece. When spraying to the place with grooves, the spray gun should be properly inclined, and the linear speed of the rotating workpiece should be about It is 15m/min~30m/min, and the moving speed of the spray gun is 3mm/r~5mm/r. When spraying, the flame is generally neutral flame.

    The thickness of the bottom layer does not need to be too thick, generally 0.1mm~0.15mm is appropriate. This is because the layer is only used to improve the bonding strength, and if it is sprayed too thickly, it will reduce this ability and be uneconomical.

    The nickel-clad aluminum coating of good quality is silver-white, and the surrounding smoke and dust pollution is very little.

    Process parameters when spraying working layers

    1) To choose the appropriate spraying distance. At a suitable spraying distance, the temperature, speed and deposition efficiency of the particles are the best, and the bonding strength is the highest. According to practical experience, the spraying distance can be taken as 4/5 of the total length of the flame, generally 120mm~160mm.

    2) The flame generally adopts neutral flame.

    3) Whether the heating temperature of the powder is sufficient, the flame power and powder feeding amount can be adjusted. The flame power of the powder sprayed on the working layer should be larger, and the powder output should be appropriate. The degree of powder heating can be identified by observing the color of the powder in the flame. If the powder at the end of the flame is white and bright, it means that the temperature is high; if it is dark red or red, it means that the heating is not enough. At this time, it is necessary to adjust the size of the powder feeding air flow and the flame power, so that the powder is heated to white and bright. If the powder output speed is too high, the powder color in the flame becomes darker at this time. The reason is that the heating time of the powder passing through the flame zone is not enough, and the powder temperature is not high enough, which will reduce the deposition efficiency, produce more raw powder, and have poor coating performance.

    4) The powder of the spraying working layer should be sprayed in layers, and the thickness of each coating should be controlled at about 0.1mm, and the maximum should not exceed 0.15mm. The total thickness of the working layer is generally not more than 0.8mm, too thick will reduce the bonding strength of the coating.

    5) The thickness of the sprayed layer is controlled. When repairing parts, the thickness of the sprayed layer must consider the thermal expansion of the base metal and the machining allowance.

    6) During the whole spraying process, the temperature of the workpiece should not exceed 250 degrees. When the temperature exceeds this temperature, the spraying can be suspended, and then continue after cooling down, or dry and clean cooling air (such as compressed air) can be used to cool the unsprayed parts near the spraying point.

    7) When spraying shaft parts on the lathe, the linear speed of the spraying surface is 20m/min~30m/min, and the longitudinal movement speed of the spray gun is generally 3mm/r~7mm/r.

    8) After spraying, it should be slowly cooled naturally, and rotatable parts such as shafts can be rotated and cooled on the lathe.