Seamless steel pipe has a hollow cross-section and is used in large quantities as a pipeline for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water and certain solid materials. Steel pipe and round steel and other solid steel, compared to the same bending and torsion strength, lighter weight, is an economic cross-sectional steel, widely used in the manufacture of structural and mechanical parts, such as oil drilling rods, automotive drive shafts, bicycle frames and construction of steel scaffolding used in the manufacture of steel pipe ring parts, can improve material utilization, simplify the manufacturing process, save materials and processing time, has been widely used to manufacture steel pipe.
Mechanical properties
Steel mechanical properties is to ensure that the steel end-use properties (mechanical properties) of important indicators, it depends on the chemical composition of steel and heat treatment system. In the steel pipe standard, according to the different use requirements, specify the tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, toughness indicators, there are user requirements of high and low temperature performance, etc.
① Tensile strength (σb)
Specimen in tension, the maximum force (Fb) withstood at the time of pulling, divided by the stress (σ) obtained from the original cross-sectional area (So) of the specimen, known as tensile strength (σb), the unit is N/mm2 (MPa). It represents the maximum capacity of a metal material to resist damage in tension. The calculation formula is
Where: Fb – the maximum force sustained by the specimen when it is pulled, N (Newton); So – the original cross-sectional area of the specimen, mm2.
②Yield point (σs)
With the yield phenomenon of metal materials, the specimen in the stretching process of the force does not increase (remain constant) can continue to elongate the stress, called the yield point. If a fall in force occurs, a distinction should be made between the upper and lower yield points. The unit of yield point is N/mm2 (MPa).
The upper yield point (σsu): the maximum stress before the specimen yields and the force first falls; the lower yield point (σsl): the minimum stress in the yielding phase when the initial transient effect is not taken into account.
The formula for calculating the yield point is: formula: Fs – the yield force (constant) during the tensile process of the specimen, N (Newton) So – the original cross-sectional area of the specimen, mm2.
③ Elongation after break (σ)
In a tensile test, the percentage increase in the length of the specimen after it has been pulled from its mark to the length of the original mark is called the elongation. It is expressed as σ in %. Calculated as: formula: L1 – the length of the specimen after pulling off its mark, mm; L0 – the length of the specimen’s original mark, mm.
④ Fractional shrinkage rate (ψ)
In the tensile test, the maximum shrinkage of the cross-sectional area of the specimen at its shrinkage after pulling off as a percentage of the original cross-sectional area is called the fractional shrinkage rate. It is expressed as ψ in %. The calculation formula is as follows
Where: S0 – the original cross-sectional area of the specimen, mm2; S1 – the minimum cross-sectional area at the shrinkage after the specimen is pulled off, mm2.
⑤ Hardness index
The ability of a metal material to resist the indentation of a hard object into a surface, called hardness. Depending on the test method and the scope of application, hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, microhardness and high temperature hardness. For the tube is generally used to have Brinell, Rockwell, Vickers hardness three.
Shandong Xinjie Metal Materials Co., Ltd. is a steel pipe company integrating production, processing and operation, mainly engaged in: seamless steel pipe (thick-walled seamless steel pipe, low and medium pressure boiler tube, alloy steel pipe, square moment pipe, high pressure boiler tube, petroleum cracking pipe, chemical fertilizer pipe, special steel pipe), stainless steel (stainless steel seamless pipe, stainless steel welded pipe, stainless steel plate, imported stainless steel pipe/plate, stainless steel round bar, stainless steel square moment pipe), stainless steel Profile (I-beam, angle steel, channel steel) and other products.
Post time: Jun-01-2023