The technical galvanized steel pipe achieved

The technical requirements of galvanized steel should be achieved
1, grade and chemical composition
 Steel grades and chemical composition of galvanized steel should be consistent with the GB 3092 clarinet steel grades and chemical composition.
 2, the manufacturing methods
 The manufacturing method of the clarinet (furnace welding or welding) is selected by the manufacturer. Galvanized by hot dip galvanizing.
 3 threads and pipe joints

 a: galvanized steel pipe with threaded delivery, threaded galvanized after car system. The thread should be consistent with the provisions of YB 822.
 b: steel fittings shall comply with the provisions of YB 238; malleable iron pipe fittings shall comply with the provisions of the YB 230.
 4, the mechanical properties of the mechanical properties of galvanized steel should be consistent with the provisions of GB 3092.
 5, the zinc coating uniformity of galvanized steel should be a test of the zinc coating uniformity. Steel pipe sample dipping five times in a copper sulfate solution may not be red (copper color).
 6, cold bending test nominal diameter not greater than 50mm in galvanized steel for cold bending test. The bending angle is 90 °, the bending radius of 8 times the outer diameter. Test without filler, sample weld should be placed in the bending direction of the lateral or upper. After the test, the specimen should not have cracks and zinc layer peeling off with like.
 7, hydrostatic test hydrostatic test should be in the clarinet, eddy current flaw detection can also be used instead of the hydrostatic test. The test pressure or eddy current testing comparison sample size should be consistent with the provisions of GB 3092. The mechanical properties of steel is to ensure that an important indicator of the steel end-use properties (mechanical properties), it depends on the chemical composition and heat treatment of steel. Galvanized steel standard, according to different requirements, the provisions of the tensile properties (tensile strength, yield strength or yield point elongation) and hardness, toughness, user requirements, high and low temperature performance.
 The ① tensile strength (σb): the sample during the tensile pull off withstand maximum force (Fb), the obtained sample of the original cross-sectional area (So), stress (σ), called anti- tensile strength (σb), N/mm2 (MPa). It said the maximum capacity to resist destruction of metallic materials under tension. Where: Fb - sample pulled off to bear most strongly, N (Newton); So - the original specimen cross-sectional area mm2.
 ② yield point (σs): yield phenomenon of metal materials, the sample does not increase during the tensile force (remains constant) can continue elongation when the stress known as the yield point. If the force drop occurred, you should distinguish between upper and lower yield point. The yield point N/mm2 (MPa). Upper yield point (σsu): the specimen to yield the maximum stress and force the first drop; lower yield point (σsl): galvanized steel yield minimum stress in the stage when excluding the initial transient effect. Where: Fs in - sample the stretching process yield force (constant), N (Newton) So - the original specimen cross-sectional area, mm2.
 ③ elongation rate: (σ) in the tensile test, the fractured a percentage  galvanized steel pipe  of its gauge the increase in the length of the original standard gauge length, called elongation. Σ, said the unit is%. Where: L1 - sample pull up the rear of the standard gauge length, mm; of L0 - the original specimen gauge length, mm.
 ④ section shrinkage rate: (ψ) in the tensile test, the specimen fractured shrink the diameter at the cross-sectional area of the largest reduction in the percentage of the original cross-sectional area, known as section shrinkage. Ψ expressed in%. Where: S0 - the original specimen cross-sectional area, mm2; S1 - the specimen fractured necking at least cross-sectional area mm2.
 The ⑤ hardness index: hard objects of metal material to resist indentation of the ability of the surface, known as hardness. Depending on the test method and scope of application, the hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, hardness and high temperature hardness. Galvanized steel pipe commonly used Brinell, Rockwell, Vickers hardness of three kinds.
 Brinell hardness (HB): ball or carbide ball of a certain diameter, the pressure to the required test force (F) into the pattern surface and removable test force, by the provisions of the time, measuring the surface of the sample pressure scar diameter (L). Brinell hardness value is the test force divided by the quotient of indentation of spherical surface area. HBS (ball), the units of N/mm2 (MPa).

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