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. Steel standards, 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.
① tensile strength (σb)
Sample during stretching, pull off to withstand the maximum force (Fb), divided by the original specimen cross-sectional area (So) from the stress (σ), known as the tensile strength (σb) unit for N/mm2 (MPa). It said the maximum capacity to resist destruction of metallic materials under tension. The formula is:
Where: Fb - sample pulled off to bear most strongly, N (Newton); So - the original specimen cross-sectional area mm2.
② the yield point (σs)
Yield the 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).
Yield point (σsu): specimen occurred to yield the maximum stress and force the first drop; yield point (σsl): yield minimum stress in the stage when excluding the initial transient effect.
Yield point is calculated as follows:
Where: Fs in - sample the stretching process yield force (constant), N (Newton) So - the original specimen cross-sectional area, mm2.
The ③ Elongation (σ)
In the tensile test, the specimen fractured a percentage of the gauge to increase the length of the original gauge length, called elongation. Σ, said the unit is%. The formula is:
Where: L1 - sample pull up the rear of the standard gauge length, mm; of L0 - the original specimen gauge length, mm.
(4) cross-section contraction rate (ψ)
In the tensile test, the specimen fractured its shrink the diameter at the cross-sectional area of the maximum reduction in the percentage of the original cross-sectional area, known as section shrinkage. Ψ expressed in%. Calculated as follows:
Where: S0 - the original specimen cross-sectional area, mm2; S1 - the specimen fractured necking at least cross-sectional area mm2.
⑤ hardness index
Metallic materials against hard objects indentation 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. Commonly used for pipe, Brinell, Rockwell, Vickers hardness of three kinds.
A Brinell hardness (HB)
A certain diameter ball or carbide ball pressed into the required test force (F) pattern surface, removable by the provisions of time after the test force, indentation diameter measurement surface of the specimen (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).
The formula is:
Where: F - pressed into the metal surface of the specimen test force, N; - test ball diameter, mm; d - indentation average diameter, mm.
Determination of the Brinell hardness is more accurate and reliable, but generally HBS applies only to 450N/mm2 (MPa) below the metal materials, NA hard steel or thin plate. Steel standards, the Brinell hardness of the most widely used, often to the indentation diameter d to represent the hardness of the material, intuitive, and convenient.
Example: 120HBS10/1000130: with diameter 10mm steel ball under the action of the test force 1000Kgf (9.807KN), keeping the 30s (seconds) measured the Brinell hardness value of 120N / mm2 (MPa).
Formula
Seamless steel pipe per meter weight formula: 0.02466 * wall thickness * (OD - Wall Thickness)
Stainless steel tube per meter weight formula is: 0.02491 * thickness * (OD - Wall Thickness)
Alloy tube per meter weight formula is: 0.02483 * thickness (OD - Wall Thickness)
Seamless steel tubes for mechanical properties
time：2017-03-07 14:51:03 hits：second
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