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Steel mechanical properties is an important index to ensure that the steel eventually use performance, it depends on the chemical composition of the steel and heat treatment system

The technical requirements galvanized steel pipe should reach.

• Grades and chemical composition. Galvanized steel grades and chemical composition shall comply with the stipulated GB3092 standard of black steel pipe steel.

• the manufacture method: the manufacturing method of black steel pipe (furnace or electric welding) should be selected by the factory. Galvanized by hot dip galvanizing.

• thread and pipe joint

  1. delivery of galvanized steel pipe with screws, screw thread should be done after galvanizing. And the thread should comply with the provisions of the YB822.

  2. steel pipe joint shall comply with the terms of YB238; Malleable iron pipe fittings shall comply with the terms of YB230.

• the mechanics properties: the mechanical properties of steel tube before galvanized should comply with the provisions of the GB3092.

• the uniformity of the galvanized layer: the galvanized steel pipe should be carried out galvanized layer uniformity test. Steel tube specimens in the copper sulfate solution dipping 5 consecutive shall not become red (copper plating color).

• the nominal diameter of cold bending test no greater than 50 mm galvanized steel pipe should carry out cold bending test. Bending angle is 90°, bending radius is 8 times the diameter. Without padding when testing, sample welds should be placed in the bending direction of the lateral or upper. After the testing, the sample should not have cracks and zinc layer peeling off with the elephant.

• hydrostatic test: water pressure test should be performed in the black steel pipe, eddy current flaw detection can also take place of hydrostatic test. Test pressure or eddy current inspection shall comply with the terms of GB3092 contrast sample size.

In the steel tube standard, according to different application requirements, the tensile strength, yield strength or yield point, elongation and hardness, toughness index are all stimulated, and even the user's high, low temperature performance, etc.