Seamless steel tube is a hollow section with no seams around the strip steel. Seamless steel tube has a hollow section, a large number of pipelines used for conveying fluids, such as oil, gas, gas, water and some solid materials pipeline. Seamless steel tubes and round steel and other solid, Seamless Steel Pipes in contrast to flexural and torsional strength, light weight, is an economic cross-section of steel, widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipe, automobile propeller shaft, bicycle racks and steel scaffolding used in construction and so on. The use of seamless steel tubes to make ring parts, can improve the utilization of materials, simplify the manufacturing process, saving materials and processing hours, such as rolling bearing rings, Jack sets, etc., has been widely used seamless steel tube to make. Seamless steel tube or a variety of conventional weapons indispensable materials, barrel, barrel, etc. seamless steel pipe to make. Seamless steel tube According to the cross-section of the shape of the different area can be divided into round pipe and shaped tube. As the circumference is equal, Seamless Steel Pipes the circle area is the largest, and more fluids can be transported with a circular tube. In addition, the ring section under the internal or external radial pressure, the force is more uniform, Seamless Steel Pipes so most of the seamless steel tube is round pipe.
Seamless steel tubes are now used in the field is really very extensive, for example, in terms of construction, transport and so on, the reason seamless steel tube can be so many hours, Seamless Steel Pipes it must have its own strengths and advantages. Compared with the general use of the kind of steel pipe, seamless steel tube used a series of high-tech manufacturing technology, and then also seamless steel pipe has a perfect quality.
Seamless steel tube Performance characteristics
The mechanical property of steel is an important index to ensure the final use performance (mechanical properties) of steel, Seamless Steel Pipes which depends on the chemical composition and heat treatment system. In the steel pipe standard, according to different use requirements, the tensile performance (tensile strength, yield strength or yield point, elongation) and hardness, toughness index, as well as user requirements of high, Seamless Steel Pipes low temperature performance.
① tensile strength (σb)
During the tensile process, the specimen is subjected to a larger force (FB), divided by the stress (σ) obtained by the original cross-sectional area (so) of the specimen, called the tensile strength (σb), and the Unit is n/mm2 (MPa). Seamless Steel Pipes It indicates that the metal material can resist the damage under the tensile force.
② yield Point (σs)
In the case of metallic materials with yielding phenomena, the stress of the specimen during the tensile process is not increased (constant), and the yield point is also maintained. If the force is reduced, Seamless Steel Pipes the upper and lower yield points should be differentiated. The unit of the yield point is n/mm2 (MPa).
The upper yielding point (ΣSU): The larger stress before the specimen is yielded and the force first decreases; the lower yield point (ΣSL): When the initial instantaneous effect is disregarded, Seamless Steel Pipes the minimum stress in the yield phase is taken.
The formula for the yield point is:
In the formula: The yield force (constant) in the tensile process of fs--specimen, the original cross-sectional area of N (Newton) so--specimen, mm2.
Elongation rate (σ) after ③
In tensile test, the percentage of the length of the specimen and the length of the original standard distance is called elongation rate. In σ, the unit is%. The formula is: σ= (Lh-lo)/l0*100%
In the formula: lh--specimen pull the mark distance length, mm; Seamless Steel Pipes l0--specimen original standard distance length, MM.
④ section Shrinkage Rate (PSI)
In tensile test, the reduction of the cross-sectional area of the specimen and the percentage of the original cross-sectional area are called the sectional shrinkage rate. In the case of PSI, the unit is%. The calculation formula is as follows:
In the formula: the original cross-sectional area of the s0--specimen, the mm2, Seamless Steel Pipes the minimum cross-sectional area of the s1--specimen, and the mm2.
⑤ Hardness Index
The ability of metal materials to withstand hard surfaces is called hardness. According to 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 general use of pipe has Brinell, Rockwell, Vickers hardness three kinds.
A, Brinell hardness (HB)
With a certain diameter of steel ball or cemented carbide ball, the specified test force (F) is pressed into the design surface, the test force is removed after the prescribed retention time, and the indentation diameter of the specimen surface is measured (L). Brinell hardness is the quotient of the experimental force divided by the spherical surface area of the indentation. With HBS (steel ball) indicated, the unit is n/mm2 (MPa).
The calculation formula is:
In the formula:-pressure into the surface of the metal specimen test Force, N; d test with the diameter of steel ball, MM, D indentation mean diameter, mm.
The determination of Brinell hardness is more accurate and reliable, but general HBS is only applicable to 450n/mm2 (MPa) of the following metal materials, Seamless Steel Pipes for the harder steel or thin plate does not apply. In the steel pipe standard, Brinell hardness is the most widely used, often with indentation diameter d to indicate the hardness of the material, both intuitive and convenient.