Reasons For Black Spots On The Surface Of Steel Strapping

　　The main reason for black spots on the surface of cold-rolled steel strapping is that the emulsion is not removed cleanly enough, so black spots will appear after annealing.

　　Causes of black spots on the surface of steel strapping

　　1. Steel strapping surface roughness: If the surface roughness is obvious, the gap between the steel coil layer and the layer interface will increase, which is conducive to the evaporation of the emulsion.

　　2. Annealed substrate chilled coil type: The evaporation of the emulsification during the annealing heating process will seriously affect the quality of the chilled coil. If there are waves in the steel strapping, it will also have a certain impact on the volatilization of the interlayer emulsion.

　　3. Residual chloride ions on the steel strapping surface: If the rinsing is not clean, the chloride ions will remain on the steel strapping surface, causing electrochemical corrosion and producing black Fe 304.

　　4. Emulsion volatility: high-quality emulsification heat evaporation can reduce the shortcomings of cold-rolled coil black spots.

　　5. Coiling tension of rolled products: reduce the coiling tension, increase the gap between the coil layers, make the distance between the coil layers flow, and fully volatilize and emulsify.