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Production Process of Hot-dip Galvanized Seamless Steel Pipe

Date:2023-03-22    keywords: hot-dip galvanized seamless steel pipe, galvanized pipe production process
Hot-dip galvanized seamless steel pipe has strong corrosion resistance, strength and rigidity, and is widely used in gas, heating and water pipelines.

The production process flow of hot-dip galvanized seamless steel pipe is:

Black pipe—Alkali cleaning—Water washing—Pickling—Water rinsing—Immersion aid—Drying—Hot dip galvanizing—Outside blowing—Inside blowing—Air cooling—Water cooling—Passivation—Water rinsing— Inspection—Weighing—Storage. 


 hot-dip galvanized seamless steel pipe

1. Pre-galvanizing process
There are 5 processes of alkali washing, pickling, rinsing, soaking aid, and drying.

1) The surface of some steel pipes has oil stains and needs to be washed with alkali.
2) Use hydrochloric acid for pickling to remove the scale on the surface of the steel pipe.
3) In order to remove the residual acid and iron salt attached to the surface of the steel pipe, the steel pipe needs to be rinsed twice.
4) The role of the flux is to remove all impurities from the surface of the steel pipe to ensure clean contact between the steel pipe and the zinc liquid to form a good coating.

5) In order to prevent the steel pipe from being immersed in the zinc pot and blasting, it is necessary to dry the steel pipe coated with flux. The drying temperature is 120-200°C and the drying time is not less than 150s.

2. Hot-dip galvanizing process

1) The temperature of the zinc liquid in the zinc pot is strictly controlled at 450±5°C.
2) The dried steel pipes are removed one by one through the chain of the drying furnace, immersed in the roller table of the furnace, then transported to the galvanizing furnace, and rolled into the three galvanizing spirals in the galvanizing machine.
3) The phases of the three helices are different, so that the steel pipe is in an inclined state on the helix. With the rotation of the helix, the steel pipe moves downward on one side and forms an inclination angle, then enters the zinc liquid, and continues to move downward.
4) The steel pipe automatically falls on the slide rail in the zinc pot, and is pushed to the outside by the material shifting mechanism, and then the zinc liquid is lifted out by the pipe lifter.
5) When the steel pipe is lifted to the surface of the magnetic roller, it is sucked and moved to the pull-out roller table.

3. Post-galvanizing treatment process

The post-plating treatment process includes: external blowing, pulling out, internal blowing, water cooling, inspection, passivation, and printing.
1) The steel pipe passes through the outer blowing ring, which has a row of small holes, and the excess zinc liquid of the steel pipe is blown away by compressed air to obtain a smooth appearance.
2) Under the condition of meeting the production rhythm, reducing the dragging speed can control the amount of zinc added and reduce zinc consumption.
3) Internal blowing can remove excess zinc liquid on the inner surface of the steel pipe to obtain a smooth inner surface. The removed zinc liquid forms zinc powder and is recycled.
4) The temperature of the water cooling tank is controlled at 80°C, and the cooling water is pumped to the cooling tower for cooling and then recycled.
5) After water-cooling, move out of the water-cooling tank and drop it on the inspection bench. After inspection, put the missed plating tubes into the waste basket, and the finished tubes are sent to the output roller table.
6) Spray and blow the finished tube with passivation solution during transportation to passivate the surface of the tube, and blow off excess passivation solution with compressed air after blowing the ring outside.

7) During the transportation, it passes through the drying bench laid with steam heating pipe rows, and after drying, it is printed and packaged.

Go here to learn more about " How to Carry Out the Pickling Process for Seamless Steel Pipes?"

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