1. Tensile strength (σb): The maximum force (Fb) received by the sample during the stretching process, divided by the original cross-sectional area (So) of the sample (σ), is called Tensile strength (σb) in N/mm2 (MPa). It shows the maximum ability of metal data to resist damage under tensile effects. Where: Fb - the maximum force accepted when the sample is broken, N (Newton); So - the original cross-sectional area of the sample, mm2.
2. The yield point (σs): metal data with the phenomenon of yielding, the force of the sample during the stretching process is not added (maintained stable), the stress can continue to stretch, called the yield point. If the force attack declines, the upper and lower yield points should be distinguished. The unit of the yield point is N/mm2 (MPa). Upper yield point (σsu): the maximum stress before the sample is bent and the force is first lowered; the lower yield point (σsl): the minimum stress in the yielding stage when the initial transient effect is not counted. Where: Fs--the yield force (stable) 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 the tensile test, the percentage of the length added by the gauge length after the sample is broken and the length of the original gauge length is called the elongation. Indicated by σ, the unit is %. Where: L1--the length of the gauge length after the sample is broken, mm; L0--the original gauge length of the sample, mm.
4. Section shortening rate: (ψ) In the tensile test, the percentage of the maximum reduction of the cross-sectional area of the reduced diameter after the sample is broken and the original cross-sectional area is called the section shortening rate. Indicated by ψ, the unit is %. Where: S0--the original cross-sectional area of the sample, mm2; S1--the minimum cross-sectional area at the reduced diameter after the sample is broken, mm2.
5. Hardness target: metal data against the ability of hard objects to collapse the appearance of the appearance, called hardness. According to the experimental method and the scope of application, the hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, microhardness and high temperature hardness. There are three types of commonly used pipes, such as Brinell, Rockwell and Vickers hardness.
Characteristics of straight seam steel pipe
structural steel pipe planning:
(1) The pipe section has several characteristics, the pipe wall is generally thin, the section data is distributed around the centroid, the section has a large radius of gyration, and has strong torsional stiffness; as a compression, bending and bidirectional bending member, The bearing capacity is high, and the straightness and cross-sectional dimension of the cold-formed pipe are more accurate than the hot-rolled opening cross-section.
(2) In terms of anti-hydrodynamic characteristics, the cross section of the round pipe is the best, and the effect of the wind and water flow is greatly reduced. The cross section of the rectangular tube is similar to this in this respect.
(3) The steel pipe is a closed section; in the case of the same average thickness and cross-sectional area, the exposed surface product is about 50% to 60% of the opening cross section, which is advantageous for corrosion prevention and can save coating data.
(4) It is suitable to use direct welding for the connection of the nodes, which can save labor and materials without passing through the gusset plate or other connecting pieces.
(5) The shape is relatively beautiful, especially the pipe truss composed of steel pipe members, without the remaining nodes connecting, and the modern sense is strong.
(6) If necessary, concrete may be poured in the pipe to constitute a composite member.
Because of the above advantages, the steel pipe structure can save about 20% of steel in industrial buildings and 50% in tower structure compared with the structure made with open sections. The structure of the steel pipe can be selected according to the condition of the force of the component, the supply condition, the manufacturing and processing conditions, and the cost, such as a round pipe structure or a rectangular pipe structure, or a mixture of two steel pipes. When mixed, the general chord is a rectangular tube, and the web is a round tube. Sometimes, the chord can also be made of I-beam or H-shaped steel, and the rib is a rectangular tube or a round tube.