1, Grade and chemical composition
The grades and chemical compositions of hot-dip galvanized steel strip shall comply with the grades and chemical composition of the black tube for GB 3092.
2, Manufacturing methods
The manufacturing method of the black tube (furnace welding or welding) is selected by the manufacturer. Galvanized by hot dip galvanizing method.
3, Thread and pipe joints
1) With the delivery of galvanized steel pipe
, the thread should be in the galvanized car system. The thread should be in accordance with YB 822.
2) Steel pipe fittings shall comply with YB 238; malleable cast iron fittings shall comply with the requirements of YB 230.
4, Mechanical properties
Steel pipe galvanized before the mechanical properties should be consistent with the provisions of GB 3092.
5, Galvanized layer uniformity galvanized steel pipe should be galvanized layer uniformity test. Steel samples in the copper sulfate solution for 5 times can not be red (copper).
6, Cold bending test nominal diameter is not more than 50mm galvanized steel pipe should be cold bending test. The bending angle is 90 ° and the bending radius is 8 times the outer diameter. The test shall be filled with no filler, and the specimen shall be placed in the outer or upper part of the bending direction. After the test, there should be no cracks and cracks on the sample.
7, Hydraulic pressure test should be carried out in the black tube, eddy current can also be used instead of hydraulic test. Test pressure or eddy current testing Contrast sample size should be in accordance with GB 3092.
Hot-dip galvanized steel pipe mechanical properties is to ensure that the final use of galvanized pipe performance (mechanical properties) an important indicator, it depends on the chemical composition of galvanized pipe and heat treatment system. In the galvanized pipe standard, according to different requirements, the tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, toughness indicators, as well as the user requirements of high and low temperature performance.