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Hot dip galvanizing pipe process

Hot-dip galvanizing, also known as hot-dip galvanizing and hot-dip galvanizing: is an effective metal anti-corrosion method, mainly used in metal structures in various industries. The rust-removed steel is immersed in a zinc solution melted at about 500 ° C to adhere the zinc layer to the surface of the steel member, thereby preventing corrosion. Hot-dip galvanizing process: finished pickling-washing-assisting plating-drying-hanging-cooling-pharmaceutical-cleaning-grinding-hot galvanizing is completed. Hot-dip galvanizing is a result of the older hot-dip method. Since the application of hot-dip galvanizing in France in 1836, it has been more than 170 years old. In the past three decades, with the rapid development of cold-rolled strip, the hot-dip galvanizing industry has been developed on a large scale.

Hot-dip galvanizing (steel pipe) production process:
Feeding → pickling, washing → solvent → drying → hot galvanizing → inner and outer blowing → rolling label, marking → passivation → inspection → packaging.
The material handler should check the raw materials:
1. The outer surface of the steel pipe shall not be contaminated with oil (especially oil stains such as asphalt oil blending paint), otherwise it will cause a large number of unqualified products.
2. The steel pipe must be straightened after production to eliminate the internal stress of the steel pipe.
3, the outer surface of the steel pipe is uneven and corrosion can not be galvanized, otherwise a large amount of hydrochloric acid will be wasted.
4. The steel pipe cannot be artificially bent during transportation.
5. Steel pipes used for hot-dip galvanizing are not allowed to be attached to the inner and outer walls of steel pipes to avoid leakage plating.
Pickling, washing, pickling of steel pipes:
1) The pickling worker must wear the labor protection products before work. In the work, carefully check whether the work site is barrier-free, the sling is intact, and the work can be done after the confirmation is completed.
2) Pickling is mainly carried out by pickling with hydrochloric acid, and hydrochloric acid is used to prepare hydrochloric acid. The content of hydrochloric acid is 18-20%.
3) Before the pickling work, first understand the acid concentration, temperature and the tonnage of the acid pickling pipe in the tank.
4) When the pipe is hanging, the two slings should be about 1.3 meters away from the end to prevent the steel pipe from being bent and causing leakage inside the galvanized pipe. When the pipe is to the acid tank, the steel pipe should be inclined by 15°, firstly lower the standing end to prevent spraying. Acid hurts people.
5) Each time the steel pipe is pickled, the weight is preferably 2 to 5 tons, and the time is 5 to 15 minutes.
6) The steel pipe should be vibrated frequently during pickling. In the process of vibration, the steel pipe should be placed flat on the horizontal stone of the acid tank. After the sling is repeatedly activated for 3 times, the other side sling can be started 3 times, repeating twice. Lifting; the angle of vibration rise is not more than 15°.
7) When the acid tank is warmed, first fix the steam tube and then open the steam valve.
8) When the crane pipe enters or exits the acid tank, it shall not hit the tank wall to prevent damage to the acid tank.
9) The main reason for the under-pickling of steel pipes:
(1) Steel pipes should be strictly inspected during feeding, and unqualified steel pipes should not be put into pickling. .
(2) The steel pipe is not carefully operated during vibration.
(3) The pickling time and the hydrochloric acid content are insufficient.
10) The main reason for the overheating of steel pipes:
(1) The hydrochloric acid content is too high.
(2) Pickling time is too long.
11) After pickling, check whether the outer surface of the steel pipe is smooth, whether there is residual iron oxide scale, or whether there is grease stain on the surface of the steel pipe.
Washing of steel pipes:
1) The water washing of the steel pipe should be carried out in a flowing clean water tank. When washing, the steel pipe should be completely immersed in water, and the pickling sling should be relaxed and rise and fall three to four times.
2) After washing, the water in the steel pipe should be controlled and solvent treated as soon as possible to prevent oxidation of the steel pipe.
3) The standard of washing water iron salt should not exceed the standard, no other debris, keep it clean and transparent.
4) When washing the pipe, the operator is strictly prohibited from crossing the pickling tank to prevent slipping or falling into the acid tank to injure people.
Solvent treatment 1. The steel pipe enters the solvent tank, and the sling is relaxed until the steel pipe is completely immersed in the solvent, and the surface of the steel pipe is not allowed to be exposed on the surface of the solvent. Wait until the ends of the steel pipe do not bubble, then hoist the side of the steel pipe up and down, hoist the steel pipe to control the solvent and then enter the drying gantry.
2. The inclination angle of the steel pipe during the solvent treatment is not more than 15°.
3. The immersion time of the steel pipe in the solvent is 60-120 seconds. It is immersed in the plating tube for 3 to 5 minutes, and the plating tube is immersed for 5 to 10 minutes.
4, solvent temperature: keep the solvent clean at room temperature.
5, the steel pipe after solvent treatment, do not stick to other dirt, do not pour water, put it into the drying rack to flatten; put the steel pipe on the drying stand, do not allow people to step on the steel pipe, if you must go up The feet must be coated with ammonium chloride before going to the tube to work.
Drying 1. The steel pipe after passing the solvent treatment is placed on the drying receiving frame, and the side of the steel pipe is placed on the front side of the zinc pot and the front side of the second magnetic roller is placed at a right angle; the tube with a large curvature is placed. Place it on the receiving frame at the back or after straightening.
2, the main function of drying 炕 is to dry the water on the surface of the steel pipe, on the other hand, to raise the temperature of the steel pipe itself, to prevent splashing of zinc, and not to take away the heat energy in the zinc pot, so as to accelerate the formation of the zinc-iron alloy layer. .
3, drying 炕 temperature is 80 ° C ~ 180 ° C, steel pipe drying time is 3 ~ 7 minutes, can also be based on the specifications of the steel pipe, wall thickness to grasp the drying temperature; dry workers should always check the dryness of the steel pipe, prevent time Insufficient to enter the zinc solution to splash zinc; in the drying, do not overheat, to prevent the solvent from being baked.
Hot-dip galvanizing of hot-dip galvanized steel pipe adopts the mechanical principle of dialing, pressing, spiraling, pulling out and lifting of the full-immersion semi-automatic galvanizing of the toothed disc to complete the hot-dip galvanizing process.
1. Control of process parameters: the temperature of zinc solution should be controlled between 440-460 °C; the time of zinc immersion should be controlled between 30-60 seconds; the amount of aluminum added (0.01-0.02% aluminum content of zinc liquid surface)
2. The zinc ingot should be used as the national standard Zn0-3 zinc ingot.
3. Always maintain and control the reliability of pulling the screw down and pulling out the lifting device, strengthen the lubrication of the cylinder, adjust the height and angle of the galvanized pipe distributor, and adjust the equipment to the best condition.
4. The placement position of the proximity switch should be accurate; the thermocouple wire and the watch should be used in a unified model. Otherwise, the temperature error is large, and the protective sleeve of the thermocouple should be checked and replaced frequently.
5. The operator of the console should manually adjust the speed to prevent the card tube phenomenon according to the operation of the equipment in front of the furnace and the gesture command.
6, the furnace before the use of tools must be preheated and then used to prevent splashing zinc to hurt people; often check whether the steel pipe fell into the pot, if necessary to clear out in time; to adjust the equipment in time to avoid the equipment to protect the equipment Safety.
7. When zinc is added to the zinc pot, the zinc ingot should be preheated first. When adding zinc, a bundle of zinc should not be allowed. When adding zinc, the maximum amount is not more than five. The zinc ingot should be longitudinally attached to the wall of the zinc pot. Slowly draw down, so as not to damage the zinc pot and splash a lot of zinc to hurt people; iron substances are not allowed to fall into the zinc liquid to prevent the production of a large amount of zinc residue.
8. When melting zinc, it should be heated slowly. Do not burn the fire. Otherwise, the life of the galvanizing pot will be damaged, and a large amount of zinc vapor will evaporate. When this harmful gas is inhaled by the human body, it will suffer from a "casting heat" condition. In the process of zinc melting, once the zinc has a higher temperature, do not use the hand to move the zinc block to avoid burns. Use appropriate tools to move it.
9, to clear out the zinc ash on the surface of the zinc liquid. When scraping ash, it should be gently wiped on the surface of zinc liquid with a scraping board. It should not be stirred too much, so as to avoid the zinc ash rising. The scraping board should not touch the steel pipe which is being immersed or discharged, so as to avoid rolling. There is a personal accident or equipment accident.
10. The zinc block on the ground in front of the furnace, the zinc smelting, the zinc brought out during galvanizing, and the zinc flowing out of the steel pipe should be recycled back to the pot at any time to reduce the heat loss of the zinc pot.
11. When adding aluminum ingot to the surface of zinc liquid, it must be acted several times before and after to ensure uniform aluminum content on the surface of zinc liquid.
12. In order to facilitate the slag and zinc extraction, 20 tons of lead should be placed inside the zinc pot.
13. When slag is used, the slag machine should be preheated first. The slag should be stored in large and small blocks. The slag temperature should be controlled above 455 °C. When smashing the slag machine, special tools must be used to leave the zinc pot 1 meter. The feet should stand in a T-shape.
14. The hot-dip galvanizing process requires stricter work. Therefore, in the hot-dip galvanizing production process, the work station must be dry, that is, the more the number of roots or tonnage per unit time, the lower the cost, and vice versa.
After the lead-out and outer-blowing 1, the galvanized pipe is put forward, the galvanized pipe is taken out by the magnetic roller, and the number of revolutions of the lead-out machine is not too fast, so that the zinc flows before the inner blow.
2. The angle of the outer blow ring should be parallel to the magnetic roller, and the longitudinal and lateral positions should be positive to ensure that the galvanized pipe passes through the middle of the wind ring.
3. When installing the magnetic roller, the five magnetic rollers must be on the center line up and down, to ensure that the zinc coating of the galvanized tube after the external blowing is uniform.
4. The external blowing is performed by using compressed air for external blowing, preferably at 70 ° C or higher and pressure at 0.2-0.4 Mpa.
5. The wind pressure should be adjusted under the following conditions:
(1) The zinc layer on the outer surface of the galvanized pipe is too thick.
(2) The surface of the zinc layer is dark after the external blowing.
(3) After the external blowing, the surface of the zinc layer is adhered with debris and strips of dirty materials, and the air volume should be adjusted.
6. Replace the wind ring of the same specification according to the specifications of the galvanized steel pipe. The wind ring cannot be replaced by other specifications.
7. The outer air ring is prohibited from passing through the galvanized pipe under the condition of no wind, so as to avoid the blockage of the air hole and affect the quality of the outer blow.
8. Always check whether the outer ring is clean, whether there is zinc hanging, whether the outer surface of the galvanized pipe is smooth, whether it is scratched or not; whether the surface of the magnetic roller and the chain are zinc-plated, if there is zinc hanging, it should be cleaned in time.
9. Leading the roller path Because there is no magnetic roller, the zinc layer is not firmly fixed, the surface of the zinc layer is most easily scratched, and the speed of the upper roller is matched with the speed of the magnetic roller.

Internal blowing, traverse and water cooling 1. The hot-dip galvanized pipe is sent to the inner blower by the upper device to complete the traverse through the proximity switch, press the inner blow, the ram is lifted, and the traverse is completed to complete the inner blow and the lower pipe action. Move the hot dip galvanized tube into the cooling water tank.
2. The hot-dip tube is the most easily scratched on the upper roller, mainly because the steel has not completely solidified during operation.
3. The inner blow is purged with steam, and the inner blow pressure is 0.4-1.0 Mpa; the inner surface of the galvanized pipe after the inner blow must be smooth.
4. The galvanized pipe should maintain a certain angle of inclination on the chain to keep the cooling water flowing.
5, the internal blow job site is steep, the working space is small, must be carefully operated to prevent slipping and falling, and the bent pipe hurts; prohibit any part of the body, directly contact with high-temperature galvanized pipe, so as not to hurt people .
6. When working in the sink, pay attention to whether the foot is stable, whether there are other obstacles, and prevent it from falling into the sink; the chain runs on the sink, it is easy to leave it alone, to prevent the flying tube from injuring people.
Passivation meaning: When the parts need to be stored and transported for a long time, they should be passivated between them to prevent corrosion during storage and transportation. The corrosion product is often referred to as white rust. Commonly used passivation methods are the chromate and phosphate methods.
1. Passivation method Use hot-dip galvanizing pipe to directly spray the passivation liquid on the runway. At a distance of one meter from the spray position, wipe the liquid with a steam knife and wipe it off. Be sure to blow it off.
2. Use a compressed air-cleaning wipe to blow off the liquid on the surface of the steel pipe and make the coating uniform. By adjusting the thickness of the coating to adjust the thickness of the coating, there must be no excess beads attached to the surface of the zinc tube.
Roller, Roller and Packing 1, Roller, Roller:
1) When the roller marking machine is working, it is strictly forbidden to touch the roller roller by hand to prevent pressing; it is strictly forbidden to pass the roller to prevent the roller from being damaged.
2) The galvanized pipe is rolled in the running roller conveyor. The roller marking machine should change the note according to different specifications. To change the specification once, adjust the height of the pressing wheel, and add oil frequently.
3) The rubber ring of the roller marking machine should be inspected frequently, and cracks should be replaced in time.
4) The rubber wheel should be pressed on the center line of the steel pipe, and the upper and lower fixing bolts of the pressure angle should be adjusted.
5) When printing the marking ring, the two people should roll at the same time. The rolling steel pipe must be filled with ink frequently, but the ink is not too much.
2, packaging:
1) The baler uses air compressor gas at a pressure of 0.4-0.8 MPa. It is forbidden to touch the action part of the baler by hand when the baler is working to avoid hurting the hand.
2) When packing, first put the buckle on the packaging tape, then wrap the packaging tape around the steel pipe, insert the other end into the buckle, press the baler on the packing belt, and open the baler damper to pack and press the buckle. The thick part of the packing belt is 1.0-1.2mm, the packing belt is required to be 100mm from the end, the second is 300mm, and the blue bar mark should be 400mm away from the end.
3) When smelting the same size of galvanized pipe, select the same size of the packaging frame, and put the galvanized pipe into a hexagonal shape and reach one end.
4) Once the outer surface of the packaged steel pipe is contaminated, it should be cleaned with clean cotton sand before it can be lifted. If there is condition, the small pipe should be controlled by the water inside the pipe; no one should be allowed to use the foot to control the pipe. quality.