Hot-dip seamless galvanized pipe production process

1. The production process of hot-dip seamless galvanized pipe

Workpiece → Degreasing → Water Washing → Pickling → Water Washing → Dipping Assistant Coating Solvent → Drying and Preheating → Hot-dip Galvanizing → Finishing → Cooling → Passivation → Rinsing → Drying → Inspection

2. Description of the process

①Seamless steel pipe degreasing

Use chemical degreasing or water-based metal degreasing cleaning agent to degreasing until the workpiece is completely wetted by water.

②Seamless steel pipe pickling

Use H2SO4 15%, thiourea 0.1%, 40～60℃ or HCl 25%, urotropine 3～5g/L, 20～40℃ for pickling. The addition of corrosion inhibitor can prevent the matrix from over-corrosion and reduce the hydrogen absorption of the iron matrix, and at the same time, add the fog inhibitor to inhibit the escape of acid mist. Poor degreasing and pickling treatments will cause poor adhesion of the coating, no zinc coating or peeling of the zinc layer.

③Dipping flux

Also called solvent, it can keep the work piece active before immersion plating to avoid secondary oxidation, so as to enhance the bonding between the plating layer and the substrate. NH4Cl100-150g/L, ZnCl250-80g/L, 70～85℃, 1～2min. And add a certain amount of surfactant.

④Drying and preheating

In order to prevent the workpiece from deforming due to the sharp rise in temperature during immersion plating, and to remove residual moisture, to prevent zinc explosion and cause zinc liquid explosion, the preheating is generally 80 ~ 140 ℃

⑤Hot-dip galvanizing

It is necessary to control the temperature of the zinc liquid, the dipping time and the speed at which the workpiece is drawn from the zinc liquid. The extraction speed is generally 1.5 m/min. If the temperature is too low, the fluidity of the zinc liquid is poor, the coating is thick and uneven, it is prone to sag, and the appearance quality is poor; the temperature is high, the fluidity of the zinc liquid is good, and the zinc liquid is easy to leave the workpiece and reduce the flow. Hanging and wrinkle phenomenon occurs, strong adhesion, thin coating, good appearance, high production efficiency; but the temperature is too high, the workpiece and the zinc pot are seriously damaged, and a large amount of zinc dross is produced, which affects the quality of the zinc dipping layer and is easy to cause chromatic aberration to the surface The color is ugly and the zinc consumption is high.