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Seamless Steel Pipe According To Different Requirements
Aug 10, 2017

Seamless Steel Pipe According to different requirements

Seamless steel pipe has become a part of people's lives, essential parts of the seamless steel pipe is related to people's quality of life, to promote national finance. So what is the seamless steel pipe in the end?

    The mechanical properties of steel are important indicators to ensure the ultimate use of steel (mechanical properties), which depends on the chemical composition of steel and heat treatment system. In the steel pipe standard, according to the 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.

    ① Tensile strength (σb)

    The maximum force (Fb) of the specimen in the drawing process, divided by the original cross-sectional area (So) of the specimen, is called the tensile strength (σb) in units of N / mm2 (MPa). It represents the maximum capacity of metal materials to resist damage under tension.

    ② yield point (σs)

    With the yield phenomenon of the metal material, the sample in the tensile process does not increase (to maintain a constant) can continue to stretch the stress, called the yield point. If the force falls, it should distinguish between the upper and lower yield points. The unit of yield point is N / mm2 (MPa).

    (Σs): the maximum stress before the first drop of the specimen; the lower yield point (σsl): the minimum stress in the yield phase when the initial transient effect is not counted.

    The yield point is calculated as:

    Where: Fs - the tensile strength of the sample during the test (constant), N (Newton) So - the original sample cross-sectional area, mm2.

    ③ elongation after breaking (σ)

    In the tensile test, the length of the gauge length after the specimen is pulled off is the percentage of the length of the original gauge length, called the elongation. Expressed in σ, in%. The formula is: σ = (Lh-Lo) / L0 * 100% where: Lh - gauge length after specimen withdrawal, mm; L0 - original gauge length, mm.

    ④ section shrinkage (ψ)

In the tensile test, the maximum reduction in the cross-sectional area at the reduced diameter and the percentage of the original cross-sectional area after the specimen is broken is called the section shrinkage. Expressed in ψ, in%. Calculated as follows:

     Where: S0 - the original cross-sectional area of the sample, mm2; S1 - the minimum cross-sectional area of the specimen after the break, mm2.

     ⑤ hardness indicators

     The ability of a metal material to resist the surface of a hard object is called hardness. According to the test method and the scope of application, the hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, micro hardness and high temperature hardness. For the pipe commonly used are Brinell, Rockwell, Vickers hardness of three.

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