Detailed Explanation of The Performance of Large Diameter Spiral Steel Pipes

Detailed explanation of the performance of large-diameter spiral steel pipes. In the steel pipe standards, tensile properties (tensile strength, yield strength or yield point, elongation) as well as hardness and toughness indicators are specified according to different usage requirements, as well as user requirements. High and low-temperature performance, etc.

①Hardness index

The ability of a metal material to resist the indentation of the surface by hard objects is called hardness. According to different test methods and application scopes, hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, microhardness, and high-temperature hardness. There are three commonly used hardnesses for pipes: Brinell, Rockwell, and Vickers hardness.

②Yield point (σs)

For metal materials with yield phenomenon, the stress at which the sample can continue to elongate without increasing the force (remaining constant) during the stretching process is called the yield point. If the force decreases, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa).

Upper yield point (σsu): the maximum stress before the force of the installation and removal of net sample yields for the first time; lower yield point (σsl): the minimum stress in the yield stage when the initial instantaneous effect is not considered.

③Area shrinkage (ψ)

In the tensile test, the percentage of the maximum reduction in the cross-sectional area at the reduced diameter after the specimen is broken and the original cross-sectional area is called the reduction of area. Expressed by ψ, the unit is %.

④Elongation after a break (σ)

In the tensile test, the percentage of the increased length of the gauge length of the specimen after it is broken to the original gauge length is called elongation. Expressed by σ, the unit is %.

⑤Tensile strength (σb)

During the stretching process, the maximum force (Fb) the sample endures when it breaks is the stress (σ) obtained by the original cross-sectional area (So) of the sample, which is called tensile strength (σb). The unit is N/mm2(MPa). It represents the maximum ability of a metal material to resist damage under tension.

The mechanical properties of large-diameter spiral steel pipes are important indicators to ensure the final performance (mechanical properties) of large-diameter spiral steel pipes. It depends on the chemical composition and heat treatment system of the steel pipes. In steel pipe standards, tensile properties (tensile strength, yield strength or yield point, elongation), hardness, and toughness indicators are specified according to different usage requirements, as well as high and low-temperature properties required by users.