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Galvanized steel pipe is a steel pipe that has been coated with a zinc layer. The zinc layer coating protects the steel pipe from corrosion and rust. The zinc layer provides a barrier against corrosion so that the pipe can be used in the outdoor environmental conditions with satisfied service life. It is most commonly used for outdoor construction like fences and handrails, or for some interior ducts. It sometimes can be used to manufacture the scaffolding system. For example, the components of the scaffolding system like scaffolding pipes. The protective barrier proves equally effective against damage from indoor humidity and outdoor corrosion.
To create a hot-dipped galvanized steel pipe, the steel pipes should be placed into a molten bath of zinc. This process is also called hot-dipped galvanization. The two metals are chemically attached to each another in this process, resulting in a more resistant and longer-lasting version of steel.
Production steps
The process flow is: black tube-alkaline washing-water washing-pickling-water rinsing-soaking aid-drying-hot dip galvanizing-external blowing-internal blowing-air cooling-water cooling -Passivation-water rinsing-inspection-weighing-storage.
skills requirement
1. Brand and chemical composition
The grade and chemical composition of the steel for galvanized steel pipes should comply with the grade and chemical composition of the steel for clarinet specified in GB/T3091.
2. Manufacturing method
The manufacturing method of the black pipe (furnace welding or electric welding) is selected by the manufacturer. Hot-dip galvanizing is used for galvanizing.
3. Thread and pipe joints
(A) For galvanized steel pipes delivered with threads, the threads should be machined after galvanizing. The thread should comply with YB 822 regulations.
(B) Steel pipe joints should comply with YB 238; malleable cast iron pipe joints should comply with YB 230.
4. Mechanical properties The mechanical properties of steel pipes before galvanizing should meet the requirements of GB 3091.
5. Uniformity of the galvanized layer Galvanized steel pipe should be tested for the uniformity of the galvanized layer. The steel pipe sample shall not become red (copper-plated) after being immersed in copper sulfate solution for 5 consecutive times.
6. Cold bend test The galvanized steel pipe with a nominal diameter of not more than 50mm should be subjected to a cold bend test. The bending angle is 90°, and the bending radius is 8 times the outer diameter. There is no filler during the test, and the weld of the sample should be placed on the outside or upper part of the bending direction. After the test, there should be no cracks and peeling of the zinc layer on the sample.
7. Water pressure test The water pressure test should be carried out in the clarinet. Eddy current flaw detection can also be used instead of the water pressure test. The test pressure or the size of the comparison sample for eddy current testing shall meet the requirements of GB 3092. The mechanical properties of steel are important indicators to ensure the final use performance (mechanical properties) of the steel.
