How to choose the process parameters of oxygen-acetylene flame wire spraying

       1) Selection of spraying distance



     Choosing a suitable spraying distance has a great influence on the quality of the coating. If the spraying distance is too small, the droplet temperature of the wire will be high, and the kinetic energy will also be large, which is conducive to improving the bonding strength of the coating and the surface of the substrate; but the oxygen-acetylene flame The temperature transferred to the surface of the substrate increases, which is easy to cause thermal deformation of the substrate, and the heating of the substrate will also cause new stress in the coating due to the difference in thermal expansion coefficient between the coating and the substrate, which will lead to cracking and peeling of the coating. . When the spraying distance is too large, the temperature and kinetic energy of the wire droplets will drop, which will reduce the bonding strength between the coating and the substrate and the density of the coating.

     When the compressed air is a fixed value, the maximum speed of the wire droplet flying is at the spraying distance of about 100mm. For this reason, the spraying distance of oxygen-acetylene flame wire is generally selected as 100mm~150mm. For exothermic composite wire, the spraying distance can be increased to 150mm~180mm.

     2) Selection of wire diameter and feeding speed

     In oxygen-acetylene flame wire spraying, the larger the diameter of the wire selected, the lower the oxygen content of the coating, which can further improve the quality of the coating and the spraying efficiency. However, when large-diameter wire is used for spraying, it will be limited by the power of the spray gun. The domestic SQP-1 oxygen-acetylene flame wire spray gun uses two wire diameters of 2.3mm and 3mm, and the US-made 12E oxygen-acetylene flame wire spray gun generally uses two wire diameters of 3.77mm and 4.7mm.

     The wire feeding speed depends on the melting point of the wire itself and the optimum conditions for the oxygen-acetylene flame parameters. When the oxygen-acetylene flame parameters are the best conditions, due to the good flame stability, the wire can be in a state of high heat capacity, and the feeding speed of the wire can be higher. However, when the feeding speed of the wire is high, it will cause uneven melting of the wire droplets. When the feeding speed of the wire is too low, fine particles appear in the wire droplets, causing the coating to contain more oxides, which will reduce the performance of the coating and the spraying efficiency. On the premise of ensuring the quality of the coating, a higher wire feeding speed should be selected to improve the spraying efficiency.

     The domestic SQP-1 oxygen-acetylene flame wire spray gun has two feeding speeds of medium speed and high speed. For high melting point wire and oxide wire, when the diameter is 2.3mm, the medium speed gear is generally used; for the metal wire with lower melting point, when the diameter is 3mm, the high speed gear is generally used.

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