Quality control and production process of zinc coating
Galvanizing is one of the effective methods to prevent steel wire corrosion. There are generally two methods of galvanizing, one is galvanizing, the other is hot galvanizing. The disadvantage of hot galvanizing is that the strength loss is large. In the production process of small size steel wire rope, electro galvanizing is mostly used as the raw material for wire rope coating processing. The advantages of electro galvanizing are that the thickness of steel wire coating is uniform and dense, and the mechanical properties of steel wire before and after plating change little, which can also be adjusted according to the requirements; the disadvantage is that if the steel wire is not cleaned before plating, the adhesion between the coating and the steel wire substrate is poor, and dezincification is easy to occur. Therefore, the quality control of galvanized steel wire is very important.
The production process of electro galvanizing is as follows: setting out → pickling → washing → galvanizing → cold washing → hot water washing → drying → winding up. Zinc sulfate was used for electroplating. The mass concentration of zinc sulfate was 400-600 g / L, and the pH value of electroplating solution was 2-4. In the process of electro galvanizing, the key factors affecting the quality of galvanizing are the cleanliness of steel wire pickling before electroplating, the concentration of electroplating solution, the control of pH value and the size of single wire current. The quality of pickling directly affects the bonding strength between the coating and the substrate, and the mass concentration of the plating solution directly determines the ion replenishment speed in the solution after ion migration, thus eliminating the phenomenon of concentration polarization.
1. Adjust electroplating process parameters. (1) Strictly control the pH value of the plating solution. The research shows that the pH value of the plating solution directly affects the quality of the steel wire coating. If the pH value is not controlled properly, the coating will be loose. When the pH value is greater than 3, the steel wire coating has burr caused by fine dendrite, and the surface is not smooth. (2) The current density should be strictly controlled. From the micro morphology, the higher the current density is, the larger the grain deposition of zinc layer is, and the less dense the corresponding zinc layer is. On the contrary, the denser the ion deposition, the better the quality of zinc layer. Under the condition that the surface zinc layer is compact and bright, the process parameters should be optimized as follows: current density is 16 ~ 20A / DM2, mass concentration of zinc sulfate solution is 500 g / L, pH value is 2.5 ~ 3.0.
Second, adjust the water tank drawing process parameters. (1) The total compression ratio is 96.48% and the scraping of zinc layer is reduced. (2) The material of the whole drawing die is composed of tungsten steel die and polycrystalline die. The angle of working cone of drawing die is 12 ° to 16 ° and the length of sizing belt is 0.15 of steel wire diameter, so as to ensure the deformation of zinc layer and steel wire matrix are basically synchronized. (3) The cooling circulation system uses spray method to cool the drawing die, and take away a large amount of heat generated by the wire drawing machine in high-speed drawing, so as to ensure the quality of steel wire. (4) Control drawing process parameters: take-up speed 10-12 MGS; take-up tension 8-10n; fixed length 30km; lubricant mass fraction 3.5-4.5%; lubricant pH 7-8; lubricant temperature 30-40 ℃.
After process optimization, the mass production of galvanized steel wire with diameter of 0.80 mm is controlled in 80-90 g / m2, and the quality difference of zinc layer is very small; the zinc layer detection is carried out on the subsequent steel wire for rope drawing in water tank, and the results show that the average zinc layer mass is 14.5 g / m2, the loss of zinc layer is less than 5%, and the tensile strength of steel wire is 2300-2500 MPa. It not only effectively controls the quality of zinc layer of raw steel wire for galvanizing rope, but also reduces unnecessary waste and production cost.
Release time : 2020-04-08
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