Year1
- 规格：
- 325
- 壁厚：
- 8
- 长度：
- 12
>The mechanical properties of steel are important indicators to ensure the final performance (mechanical properties) of steel. It depends on the chemical composition and heat treatment system of the steel. 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.
> ① Tensile strength (mb) The maximum force (b) the sample endures when it breaks during the stretching process, divided by the original cross-sectional area of the sample (m), is called Tensile strength (mb), unit: /mm (M). It represents the maximum ability of a metal material to resist damage under tension. The calculation formula is: where the maximum force the sample endures when it is pulled apart, (Newton) and the original cross-sectional area of the sample, mm.
② Yield point (m) For metal materials with yield phenomenon, the stress when 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 /mm (M). Upper yield point (m): The maximum stress before the specimen yields and the force decreases for the first time. Lower yield point (m): The minimum stress in the yield stage when the initial instantaneous effect is not considered. The calculation formula of the yield point is: where: yield force (constant) during the tensile process of the specimen, (Newton) original cross-sectional area of the specimen, mm.
③ Elongation after breaking (m) In the tensile test, the percentage of the increased length of the gauge length of the sample after breaking to the original gauge length is called elongation. Expressed in m, unit is %. The calculation formula is: where: the gauge length of the sample after breaking, m the original gauge length of the sample, mm.
④ Shrinkage of area () 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 shrinkage of area. Expressed in %. The calculation formula is as follows: where: original cross-sectional area of the sample, m, minimum cross-sectional area at the reduced diameter after the sample is broken, mm.
⑤ Hardness index refers to the ability of a metal material to resist the indentation of the surface by hard objects, which is called hardness. According to different test methods and application scope, 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.
Brinell hardness (HB) uses a steel ball or cemented carbide ball of a certain diameter to press into the surface of the sample with the specified test force. After the specified holding time, remove the test force and measure the indentation on the surface of the sample. diameter. Brinell hardness value is the quotient obtained by dividing the test force by the surface area of the indented sphere. Expressed in HB (steel ball), the unit is /mm (M).
Factory inspection) The factory inspection items for anti-corrosion pipes with liquid epoxy coatings should include appearance, thickness, leakage points and adhesion. ) The random inspection ratio of the thickness of the anti-corrosion layer is %, and it shall not be less than the root. If there is any failure in the thickness inspection, double the spot check should be carried out. If the inspection is still unqualified, the entire batch will be deemed unqualified. ) The adhesion test should be carried out randomly according to the method in "Technical Conditions for Inner Coatings of Solvent-based Coatings for Petroleum Drill Pipes"/, and those above Grade B (including Grade B) are considered qualified. The sampling rate is m, and any amount less than m will be counted as m. If there are any unqualified items, the spot check should be doubled. If there are still unqualified items, the entire batch will be deemed unqualified. , Epoxy powder inner coating Epoxy powder coating has excellent anti-corrosion, insulation and reliable and durable service life. It is the preferred material for inner coating of steel pipes. It has been widely used at home and abroad and achieved ideal results. The application temperature of internal epoxy powder coating is ~℃, and the applicable media are various oils, natural gas and water.
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