Hot dip galvanized (steel pipe) production technology

Feeding → pickling and washing → solvent → drying → hot dip galvanizing → internal and external blowing → label rolling and marking → passivation → inspection → packaging.

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The feeder shall check the condition of raw materials:

1. the outer surface of the steel pipe shall not be adhered to oil pollution (especially asphalt oil mixing paint and other oil pollution), 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. uneven corrosion of the outer surface of the steel pipe can not be galvanized, otherwise it will waste a lot of hydrochloric acid.

4. the steel pipe in the transportation process can not appear artificial bending pipe.

5. for hot dip galvanized steel pipe, it is not allowed to stick the marker on the inner and outer walls of the steel pipe, so as not to cause leakage plating.

Pickling, washing

1. Pickling of steel pipe:

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

2) Hydrochloric acid is mainly used for pickling. Hydrochloric acid is prepared with water, and the content of hydrochloric acid is 18-20%.

3) The pickler should first understand the acid concentration, temperature and the tonnage of the pickling pipe in this tank before working.

4) When hoisting the pipe, the two suspender straps should be about 1.3 meters away from the end to prevent bending the steel pipe and causing leakage in the galvanized pipe; When going down the pipe to the acid tank, the steel pipe should be tilted 15°, and the end that stands on its own should be lowered first to prevent acid spray from hurting people.

5) The weight of the steel pipe should be 2-5 tons each time, and the time should be 5-15 minutes.

6) The steel pipe should often vibrate during pickling. In the process of vibration, the steel pipe should be placed on the horizontal stone of the acid tank, and the suspender on one side should be started repeatedly for 3 times and then started on the other side for 3 times, and then lifted after repeated twice; Vibration rise Angle is not greater than 15°.

7) When heating the acid tank, fix the steam pipe firmly before opening the steam valve.

8) When the crane lifting pipe enters or exits the acid tank, it shall not impact the tank wall to prevent damage to the acid tank.

9) The main reasons for the underpickling of steel pipes are as follows:

(a) Steel pipe should be strictly checked when feeding, and unqualified steel pipe should not be put into pickling.

(b) The steel pipe is not operated carefully when it vibrates.

(c) Insufficient pickling time and hydrochloric acid content.

10) Main reasons for pickling steel pipe:

(a) High levels of hydrochloric acid.

(b) pickling time is too long.

11) After pickling, check whether the outer surface of the steel pipe is smooth, whether there is residual oxide sheet and whether there is oil scale pollution on the surface of the steel pipe.

2. Washing of steel pipe:

1) The water washing of the steel pipe shall be carried out in the flowing clean tank. During the water washing, the steel pipe shall be immersed in the water, the pickling sling shall be relaxed, and the hoisting and unloading shall be carried out three to four times.

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

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

4) When cleaning the pipe, the operator is strictly prohibited from crossing the pickling tank to prevent slipping or falling into the tank and hurting people.

Solvent treatment

1. the steel pipe into the solvent tank, relax the sling until the steel pipe is immersed in the solvent, do not allow the surface of the steel pipe exposed to the solvent surface. When there is no bubble at both ends of the steel pipe, the side of the steel pipe vibrates up and down, and then the steel pipe is hoisted into the drying table after the clean solvent is controlled.

2. the tilt Angle of the steel pipe in the solvent treatment process is not more than 15°.

3. The soaking time of the steel pipe in the solvent is 60~120 seconds. The plating tube is soaked for 3~5 minutes after shift, and the plating tube is soaked for 5~10 minutes after shift.

4. Solvent temperature: keep the solvent clean at room temperature.

5. after solvent treatment of steel pipe, do not stick to other dirt, do not pour water, put into the drying table to straighten; The steel pipe placed on the drying table is not allowed to step on the steel pipe. If it is necessary to go up, the feet must be coated with ammonium chloride before going to the pipe.

Dry

1. After qualified solvent treatment, the steel pipe shall be placed on the drying receiving bench, and the front side of the steel pipe shall be placed on the front side of the zinc pot and the front side of the second magnetic roll at a right Angle; The pipe with large bend should be placed behind or on the receiving rack after straightening.

2. The main function of drying kang is to dry the water on the surface of the steel pipe. On the other hand, it is to raise the temperature of the steel pipe itself, prevent zinc sputtering from hurting people, and do not take away the heat energy in the zinc pot, so as to accelerate the formation of the zinc-iron alloy layer.

3. The drying temperature of kang is 80℃~180℃, and the drying time of steel pipe is 3~7 minutes. The drying temperature can also be controlled according to the specifications and wall thickness of steel pipe. The dryer should check the dryness of the steel pipe at any time to prevent the lack of time into the zinc liquid zinc spatter injury; Do not overheat when drying to prevent the solvent from burning.

Hot-dip galvanizing

The hot dip galvanizing of steel pipe adopts the mechanical principle of full dip semi-automatic galvanizing with tooth disk to pull in, press down, screw, pull out and lift to complete the hot dip galvanizing process.

1. Process parameter control: zinc liquid temperature should be controlled between 440-460℃; Zinc dipping time should be controlled between 30-60 seconds; Aluminum content (zinc liquid level aluminum content 0.01-0.02%).

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

3. It is necessary to regularly maintain and control the reliable performance of pulling in and pressing down the screw 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 state.

4. The location of the proximity switch should be accurate; Thermocouple wire and table should be used in the same model, otherwise, the temperature error is large, thermocouple protection sleeve, to check and replace often.

5. The operator of the operating platform should manually adjust the speed to prevent pipe sticking according to the operation condition of the equipment in front of the furnace and the hand command.

6. the use of tools to preheat before use, in order to prevent zinc spatter hurt people; Often check whether the steel pipe falls into the pot, if there is to clear out in time; It is necessary to adjust the pipe of the equipment in time to ensure the safety of the equipment.

7. add zinc to the zinc pot, zinc ingot to preheat first, add zinc is not allowed to bundle zinc, add zinc at most five pieces each time, the zinc ingot longitudinal stick to the zinc pot wall slowly row down, so as not to damage the impact of zinc pot and splash a lot of zinc hurt; Iron substances are strictly prohibited from falling into the zinc liquid to prevent a large amount of zinc slag.

8. melting zinc should be slow heating, not burning fire, otherwise it will damage the life of galvanized pot, and there are a lot of zinc steam volatilized out. This harmful gas is inhaled in excess, will suffer from a "foundry fever" disease. In the process of zinc melting, once the zinc has a high temperature, do not use hands to move the zinc block, so as to avoid burning, should use appropriate tools to move it.

9. To clear the zinc ash on the surface of the zinc liquid regularly. When scraping ash, it should be gently scraped on the surface of the zinc liquid with a scraping plate. It should not be stirred too much to avoid the raising of zinc ash. The scraping plate should not collide with the steel pipe when zinc is dipping or out of the pipe, so as to avoid the occurrence of personal accident or equipment accident.

10. in front of the zinc block on the ground, broken zinc, galvanized zinc, steel pipe flow to the outside of the zinc should be recovered at any time to reduce the heat loss of the zinc pot.

11. When aluminum ingots are added to the surface of zinc liquid, it is necessary to move several times before and after to ensure uniform aluminum content on the surface of zinc liquid.

12. in order to facilitate waterlogging slag and zinc pumping, zinc pot inside to put 20 tons of lead.

13. When dregs are scooping, the dregs should be preheated first, zinc slag should be stored in large and small blocks, and the temperature of waterlogging slag should be controlled at more than 455℃. Special tools must be used when the slag grabbing machine is swing, and the feet should stand in a T-shape.

14. hot dip galvanizing process requirements are strict, so in the process of hot dip galvanizing production, it is necessary to dry the station, that is, the more root number or tonnage in the unit time, the lower the cost, and the higher the vice versa.

Lead out and blow out

1. After the galvanized pipe is put forward, the magnetic roller table is used to draw out the galvanized pipe, and the revolution of the extraction machine is not too fast, so that the zinc flows clean before blowing inside.

2. The Angle of the outer blowing ring should be at a right Angle parallel to the magnetic roll, and the longitudinal and transverse 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 a center line to ensure the uniform zinc layer of the galvanized pipe after blowing.

4, the use of compressed air blowing outside, the best use of 70℃ above, the pressure in 0.2-0.4Mpa condition.

5. The wind pressure should be adjusted under the following circumstances:

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

(2) After blowing out the surface of the zinc layer dark.

(3) After blowing outside the surface of the zinc layer adhering to debris and strip unclean matter should adjust the air volume.

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

7. Galvanized pipe is prohibited from passing through the external blowing ring under the condition of no wind, so as not to cause the blockage of the air hole and affect the quality of the external blowing.

8. often check whether the blowing ring is clean, whether there is hanging zinc, galvanized pipe surface is smooth, there is no scratch; Magnetic roller surface, chain whether hanging zinc, if hanging zinc should be cleaned in time.

9. As there is no magnetic roll and zinc layer is not solid, the surface of zinc layer is most likely to be scratched. The speed of the drawing roll should match the speed of the magnetic roll.

Internal blowing, transverse movement and water cooling

1. The hot-dip galvanized pipe is sent to the internal blower by the draw-up device through the proximity switch to complete the transverse movement, press down the internal blowing, the pressure head is raised, and the transverse movement is completed, and the hot-dip galvanized pipe is moved into the cooling tank.

2. The hot plated tube is the most likely to be scratched on the upper roller table, mainly because the zinc has not completely solidified in the operation of the steel tube.

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

4, galvanized pipe in the chain to maintain a certain tilt Angle, so that the cooling water net.

5. The terrain of the internal blowing workplace is steep and the working space is small. It must be operated carefully to prevent slipping and falling injuries, as well as bending injuries; It is strictly prohibited to contact any part of the body directly with high temperature galvanized pipe, so as not to hurt.

6, in the sink operation should pay attention to whether the foot is firm, there are no other obstacles, to prevent falling into the sink; The chain on the sink runs, it is easy to leave it alone, to prevent the flying pipe from hurting people.

Passivation

Meaning: When the parts need to be stored and transported for a long time, passivation should be carried out between them to prevent corrosion in the process of storage and transportation. The corrosion product is often called white rust. The commonly used passivation methods are chromate and phosphate.

1. Passivation method uses hot-dip galvanized pipe to spray passivation liquid directly on the runway. In the place one meter away from the spray position, the steam knife is wiped to clean the liquid.

2. Use compressed air to wipe, blow off the liquid on the surface of the steel pipe and make the coating uniform. The thickness of the coating is adjusted by adjusting the pressure, so that no excess liquid beads can be attached to the surface of the zinc tube.

Rollers, rollers and packaging

1. Roller mark and roller:

1) When the mark roller is working, it is forbidden to touch the mark roller with your hand to prevent hand pressure; It is forbidden to pass the double pipe through the marking machine to prevent damage to the press roll.

2) Galvanized pipe should be rolled in the running of the conveying roller table. The rolling machine should replace the note according to different specifications. Once the specification is replaced, the height of the press wheel should be adjusted and oil should be added frequently.

3) The rubber ring of the marking machine should be checked frequently, and the 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 mark ring, two people should roll at the same time, and the felt of the steel pipe should be often added with ink, but the ink is not easy to be too much.

2. Packaging:

1) The baling machine uses air compressor gas, and the pressure is 0.4-0.8Mpa. Do not touch the action part of the baler with your hands to avoid hand injury when the baler is working.

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

3) When packaging galvanized pipes of the same specification, select the packaging rack of the same specification, place the galvanized pipes into hexagonal shape, and reach one end.

4) Once the outer surface of the packed steel pipe is polluted, it should be cleaned with clean cotton sand before it can be stacked. If conditions permit, the tube should control the water inside the tube. No one is allowed to step on the pipe with their feet, and the outer quality of the galvanized pipe should be maintained.