The technical issue of the galvanized steel

5. Uniformity of galvanized coating galvanized steel pipes shall be tested for uniformity of galvanized coating. The steel pipe sample shall be continuously immersed in copper sulfate solution for 5 times and shall not turn red (copper plating color).

6. Cold bending test of the galvanized steel: galvanized steel pipe with nominal diameter not greater than 50mm shall be subject to cold bending test. The bending angle is 90 °, and the bending radius is 8 times of the outer diameter. During the test without filler, the weld of the sample shall be placed on the outside or upper part of the bending direction. After the test, the sample shall be free of cracks and spalling of zinc layer.

7. (galvanized steel)Hydrostatic test the hydrostatic test shall be conducted in the black pipe, or eddy current flaw detection can be used instead of hydrostatic test. The test pressure or the size of the comparison sample of eddy current flaw detection shall comply with the provisions of GB 3092. The mechanical property of steel is an important index to ensure the final service performance (mechanical property) of steel, which depends on the chemical composition and heat treatment system of steel. In the steel pipe standard, according to different service requirements, the tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness indexes, as well as the high and low temperature properties required by users are specified.