Steel mechanical properties are guaranteed final performance (mechanical properties), an important indicator, it depends on the chemical composition and the heat treatment of steel. In the standards of seamless steel pipes, according to different requirements, providing tensile properties (yield strength or yield point, tensile strength, elongation) and hardness, toughness, and user requirements, such as high and low temperature performance.
① tensile strength (σ b)
In the sample during the drawing process, pull off the maximum force (Fb), to sample the original cross-sectional area (So) the stress (σ), known as tensile strength (σ b), N/mm2 (MPa). It represents the maximum tension resistance of metallic materials destruction capacity.
② the yield point (σ, s)
Yield phenomena of metal materials, samples in the tensile force in the process does not increase (constant) can still stretch the stress, said the yield point. Drops, you should distinguish between upper and lower yield point. Yield point is in N/mm2 (MPa).
Upper yield point (σ Su): sample yield and reduced the maximum stress for the first time;
Yield point (σ SL): regardless of the initial transient effects, yield the smallest stage in stress.
③ elongation (σ)
Tensile test specimen after the gauge added length and the percentage of the original gauge length, called elongation. Expressed as σ, the unit is%.
④ section shrinkage (ψ)
Tensile test specimen after the reduction maximum reduction of cross sectional area and the percentages of the original cross-sectional area, known as the contraction of cross sectional area. Expressed in ψ, expressed in%.
⑤ hardness index
Metal material's ability to resist compressive stress of hard objects surfaces, called hardness. According to the test methods and the scope of different hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, hardness, hardness and high temperature hardness. For pipes commonly Brinell, Rockwell, Vickers hardness of three.