technical requirement
1. Brand and chemical composition The grade and chemical composition of steel used for galvanized steel pipes should comply with the grade and chemical composition of black pipe steel specified in GB/T30912. Manufacturing methods The manufacturing method of the black tube (furnace welding or electric welding) is chosen by the manufacturer. Galvanizing adopts the hot-dip galvanizing method.
3. Thread and pipe joint (a) For galvanized steel pipes delivered with threads, the threads should be turned after galvanizing. The thread should comply with the provisions of YB 822. (b) Steel pipe joints should comply with the provisions of YB 238; Malleable cast iron pipe joints shall comply with the provisions of YB 230.
4. The mechanical properties of steel pipes before galvanizing should comply with the provisions of GB 3091. 5. The uniformity of the galvanized layer should be tested on galvanized steel pipes. The steel pipe sample shall not turn red (copper plated) after continuous immersion in copper sulfate solution for
5 times.
6. Galvanized steel pipes with a nominal diameter of no more than 50mm shall undergo a cold bending test. The bending angle is 90 °, and the bending radius is 8 times the outer diameter. During the test, there should be no filler, and the weld seam of the sample should be placed on the outer or upper side of the bending direction. After the test, there should be no cracks or zinc layer peeling on the sample.
7. The hydraulic test should be conducted on a black tube, or eddy current testing can be used instead of the hydraulic test. The test pressure or eddy current flaw detection comparison sample size should comply with the provisions of GB 3092. The mechanical properties of steel are important indicators to ensure the ultimate performance (mechanical properties) of steel,
