Hot-dip galvanizing (galvanizing), also known as hot-dip galvanizing and hot-dip galvanizing: is an effective method of metal anti-corrosion, mainly used in metal structural facilities in various industries. It is to immerse the rust-removed steel parts in a molten zinc solution at about 500 ° C, so that the surface of the steel parts adheres to the zinc layer, so as to achieve the purpose of anti-corrosion. Hot-dip galvanizing process: finished product pickling - water washing - adding plating solution - drying - rack plating - cooling - chemical chemical - cleaning - polishing - completion of hot-dip galvanizing It has been more than 170 years since hot-dip galvanizing was applied to the industry in France in 1836. In the past three decades, with the rapid development of cold-rolled strip, the hot-dip galvanizing industry has developed on a large scale.

Hot dip galvanized (seamless steel pipe) production process:

Loading → pickling, water washing → solvent → drying → hot-dip galvanizing → internal and external blowing → roll labeling, marking → passivation → inspection → packaging.


Feeding


Loaders should check the raw materials:


1. The outer surface of the steel pipe shall not be stuck with oil stains (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 uneven corrosion on the outer surface of the steel pipe cannot be galvanized, otherwise a large amount of hydrochloric acid will be wasted.


4. There should be no artificial bends in the steel pipe during transportation.


5. For the steel pipe used for hot-dip galvanizing, it is not allowed to stick the markers on the inner and outer walls of the steel pipe to avoid leakage of plating.


Pickling, water washing


1. Pickling of steel pipes:


1) Pickling workers must wear labor protection equipment before work, carefully check whether the work site is barrier-free and whether the sling is intact, and can work only after confirming that it is in good condition.


2) Pickling mainly adopts hydrochloric acid pickling, and water is used to prepare hydrochloric acid, and the content of hydrochloric acid is 18-20%.


3) Before the pickling worker works, first understand the acid concentration, temperature and the tonnage of the pickling pipe in this tank.


4) When hanging the pipe, the two slings should be about 1.3 meters away from the end to prevent the steel pipe from being bent and causing internal leakage of the galvanized pipe. Acid hurts.


5) For each pickling of the steel pipe, 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. During the vibration process, the steel pipe should be placed flat on the horizontal bar of the acid tank, and the sling on one side should be started repeatedly for 3 times, then the sling on the other side should be started 3 times, and then repeated twice. Lifting; the vibration rising angle is not more than 15°.


7) When the acid tank is heated, first fix the steam pipe firmly and then open the steam valve.


8) When the crane suspension pipe enters and exits the acid tank, it must not hit the tank wall to prevent damage to the acid tank.


9) The main reasons for the under-pickling of steel pipes:


(1) The steel pipe should be strictly inspected when feeding, and the unqualified steel pipe should not be put into pickling. .


(2) The steel pipe does not operate carefully when it vibrates.


(3) Insufficient pickling time and hydrochloric acid content.


10) The main reasons for the over-pickling of steel pipes:


(1) The content of hydrochloric acid is too high.


(2) The 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, and whether there is oil pollution on the surface of the steel pipe.


2. 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, the pickling sling should be loosened, and it should be lifted and lowered three to four times.


2) After washing, the water in the steel pipe should be controlled, and solvent treatment should be carried out as soon as possible to prevent the steel pipe from being oxidized.


3) The standard of iron salt content in cleaning water shall not exceed the standard, and there shall be no other sundries, and shall be kept clean and transparent.


4) When washing the pipe, it is strictly forbidden for the operator to cross the pickling tank to prevent slipping or falling into the acid tank and hurting people.


Solvent treatment


1. The steel pipe enters the solvent tank, loosen the sling until the steel pipe is completely immersed in the solvent, and the surface of the steel pipe is not allowed to expose the solvent surface. Wait until there are no bubbles at both ends of the steel pipe, then hoist one side of the steel pipe to vibrate up and down, and hoist the steel pipe to control the net solvent and enter the drying bench.


2. The inclination angle of the steel pipe during the solvent treatment process is not more than 15°.


3. The soaking time of the steel pipe in the solvent is 60 to 120 seconds, 3 to 5 minutes of immersion in the plating pipe on duty, and 5 to 10 minutes of immersion in the plating pipe after the shift.


4. Solvent temperature: room temperature Keep the solvent clean.


5. The steel pipe after solvent treatment, do not stick to other dirt, do not pour water, put it on the drying rack and level it; the steel pipe placed on the drying rack is not allowed to step on the steel pipe, if it is necessary to go up , the feet must be coated with ammonium chloride and then work on the tube.

drying

1. The steel pipe that has passed the solvent treatment is placed on the drying and receiving bench, and the flat side of the steel pipe is placed on the front side of the zinc pot and the front side of the second magnetic roller at a right angle; the pipe with larger curvature is placed at the back. Or put it on the receiving rack after straightening.

2. The main function of the drying kang is to dry the water on the surface of the steel pipe. On the other hand, it is to increase the temperature of the steel pipe itself to prevent splashing zinc from hurting people, and it does not take away the heat energy in the zinc pot, which promotes the accelerated formation of the zinc-iron alloy layer. .


3. The drying temperature of the kang is 80℃～180℃, and the drying time of the steel pipe is 3 to 7 minutes. The drying temperature can also be controlled according to the specification and wall thickness of the steel pipe; the drying worker should check the drying degree of the steel pipe at any time to prevent time Insufficient to splash zinc into the zinc solution to hurt people; do not overheat when drying to prevent the solvent from being scorched.

hot dip galvanized

The hot-dip galvanizing of steel pipes adopts the mechanical principle of dialing in, pressing down, screwing, pulling out and lifting in the fully immersed semi-automatic galvanizing method of the toothed disc to complete the hot-dip galvanizing process.


1. Process parameter control: the temperature of the zinc liquid should be controlled between 440-460 °C; the zinc immersion time should be controlled between 30-60 seconds; the amount of aluminum added (the aluminum content of the zinc liquid surface is 0.01-0.02%)


2. The use of zinc ingots should be the national standard Zn0-3 zinc ingots.


3. It is necessary to regularly maintain and control the reliable performance of the pull-in and push-down screw and pull-out 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 state.


4. The placement position of the proximity switch should be accurate; the thermocouple wire and the meter should be used in the same model, otherwise, the temperature error will be 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 according to the operation of the equipment in front of the furnace and the gesture command to prevent the pipe stuck.


6. The tools used by the workers in front of the furnace should be preheated before use to prevent zinc splashing from hurting people; always check whether the steel pipe has fallen into the pot, and if so, it should be removed in time; the equipment should be adjusted in time to prevent the pipe from being stuck to ensure the safety of the equipment. Safety.


7. When adding zinc to the zinc pot, the zinc ingots should be preheated first. When adding zinc, it is not allowed to add zinc in bundles. The maximum number of zinc ingots should be no more than five pieces at a time. The zinc ingots should be longitudinally attached to the wall of the zinc pot. Swipe down slowly to avoid impact damage to the zinc pot and splashing a lot of zinc to hurt people; it is strictly forbidden to drop iron substances into the zinc liquid to prevent a large amount of zinc slag.


8. When melting zinc, it should be heated slowly, and the fire should not be burned quickly, otherwise the life of the galvanizing pot will be damaged, and a large amount of zinc vapor will be volatilized. When this harmful gas is inhaled in excess by the human body, it will suffer from a "caster's fever" disease. In the process of melting zinc, once the zinc has a high temperature, the zinc block must not be moved by hand to avoid burns, and appropriate tools should be used to move it.


9. The zinc dust on the surface of the zinc liquid should be removed regularly. When scraping the ash, it should be gently scraped on the surface of the zinc liquid with a ash scraper, and it should not be stirred too much to prevent the zinc ash from rising. personal accident or equipment accident.


10. The zinc blocks, broken zinc, zinc brought out during galvanizing, and zinc flowing from the steel pipe to the outside should be recovered and returned to the pot at any time to reduce the heat loss of the zinc pot.


11. When adding aluminum ingots on the surface of the zinc liquid, be sure to move back and forth several times to ensure that the aluminum content on the zinc liquid surface is uniform.


12. In order to facilitate waterlogging and zinc extraction, 20 tons of lead should be placed inside the zinc pot.


13. The slag catcher should be preheated first, and the zinc slag should be stored in large and small pieces. The temperature of the waterlogged slag should be controlled above 455°C. When swinging the slag catcher, special tools must be used, and it should be 1 meter away from the zinc pot. The feet should stand in a T-shape.


14. The requirements of hot-dip galvanizing process are relatively strict, so in the process of hot-dip galvanizing production, it is necessary to do enough work, that is to say, the more the number or tonnage per unit time, the lower the cost, and vice versa.


lead out and blow out


1. After the galvanized pipe is put out, the galvanized pipe is drawn out by the magnetic roller table. The rotation of the drawing machine should not be too fast, so that the zinc can flow cleanly before blowing inside.


2. The angle of the outer blowing ring should be parallel to the magnetic roller, and the vertical and horizontal positions should be positive to ensure that the galvanized pipe passes through the middle of the wind ring.


3. When installing the magnetic rollers, the five magnetic rollers must be on a center line up and down, left and right, to ensure that the zinc layer of the galvanized pipe after blowing is uniform.


4. Compressed air is used for external blowing, preferably above 70°C and the pressure is 0.2-0.4Mpa.


5. The wind pressure should be adjusted in the following cases:


(1) The zinc layer on the outer surface of the galvanized pipe is too thick.


(2) The surface of the zinc layer becomes dark after blowing out.


(3) After the external blowing, the sundries and strips of unclean objects adhere to the surface of the zinc layer, and the air volume should be adjusted.


6. Replace the air ring of the same specification according to the specification of the galvanized steel pipe. The air ring cannot be replaced by other specifications.


7. It is forbidden for the galvanized pipe to pass through the outer blowing ring under no wind conditions, so as to avoid blockage of the air holes and affect the quality of the outer blowing.


8. Always check whether the inside of the outer blowing ring is clean, whether there is hanging zinc, whether the outer surface of the galvanized pipe is smooth and whether there is any scratch; whether the surface of the magnetic roller and the chain are hung with zinc, and if there is any hanging zinc, it should be cleaned in time.


9. Since there is no magnetic roller on the lead-up roller table, the zinc layer is not firm, and the surface of the zinc layer is most likely to be scratched. The speed of the lead-up roller should match the speed of the magnetic roller.


Internal blow, traverse and water cooling


1. The hot-dip galvanized pipe is sent to the side of the internal blowing machine through the lead-up device, and the horizontal movement is completed by the proximity switch, the internal blowing is pressed down, the pressure head is raised, and the traversing movement is completed, and the hot-dip galvanized pipe is moved into Cooling tank.


2. The hot-dip galvanized pipe is most easily scratched on the lead-up roller table, mainly because the zinc of the steel pipe has not completely solidified during operation.


3. Steam is used for internal blowing, and the internal blowing pressure is 0.4-1.0Mpa; the inner surface of the galvanized pipe after internal blowing must be smooth.


4. The galvanized pipe should maintain a certain inclination angle on the chain to allow the cooling water to flow cleanly.


5. The terrain of the internal blowing work site is steep and the working space is small. It must be operated carefully to prevent slipping and falling, and bending the pipe to hurt people; it is strictly forbidden to directly contact any part of the body with the high-temperature galvanized pipe to avoid hurting people. .


6. When working in the sink, pay attention to whether the feet are standing firmly and whether there are other obstacles to prevent falling into the sink; the chain runs on the sink, it is easy to leave it alone, to prevent the flying tube from hurting people.


passivation


Meaning: When the parts need to be stored and transported for a long time, passivation treatment should be carried out between them to prevent corrosion during storage and transportation. Its corrosion products are often referred to as white rust. Commonly used passivation methods are chromate and phosphate methods.


1. In the passivation method, the hot-dip galvanized pipe is used to spray the passivation liquid directly on the runway, and the attached liquid is wiped and blown off by a steam knife at a distance of one meter from the spray position. Be careful to blow it off.


2. Wipe with compressed cold air to blow off the liquid attached on the surface of the steel pipe and make the coating uniform. Adjust the thickness of the coating by adjusting the air pressure, and there must be no excess liquid droplets attached to the surface of the zinc tube.


Roller Labels, Rollers and Packaging


1. Roller, Roller:


1) When the roller labeling machine is working, it is strictly forbidden to touch the roller labeling roller with hands to prevent pressing hands; it is strictly forbidden for the double tube to pass through the labeling roller to prevent the roller from being damaged.


2) The galvanized pipe rolls the label during the operation of the conveying roller table. The labeling machine should replace the note according to different specifications. Once the specification is changed, the height of the pressure roller should be adjusted once, and oil should be added frequently.


3) The rubber ring of the roller labeling machine should be checked frequently, and any 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 pressing angle should be adjusted.


5) When printing the logo ring, the two should roll at the same time, and the felt for rolling the steel pipe should be often filled with ink, but the ink is not easy to be too much.


2. Packaging:


1) The baler uses air compressor gas with a pressure of 0.4-0.8Mpa. In the working state of the baler, it is forbidden to touch the action part of the baler with your hands to avoid injury to your hands.


2) When packing, first put the buckle on the packaging tape, then pass the packaging tape around the steel pipe, insert the other end into the buckle, press the baler on the packaging tape, and open the air valve of the baler to pack and press the buckle. The thickness of the packing belt is 1.0-1.2mm, the packing belt should be 100mm away from the end, the second is 300mm, and the blue bar mark should be 400mm away from the end.


3) When packaging the galvanized pipes of the same specification, choose the same specification of the packaging rack, and arrange the galvanized pipes into a hexagonal shape, and make them even at one end.


4) Once the outer surface of the packaged steel pipe is polluted, it should be wiped with clean cotton sand before stacking. If the conditions are met, the water in the pipe should be controlled; no one is allowed to step on the pipe with their feet, and the appearance of the galvanized pipe should be maintained. quality.