Typical mechanical properties range of high-quality carbon steel pipes?
Taking 20# steel as an example, the tensile strength is ≥410MPa, the yield strength is ≥245MPa, and the elongation is ≥25%. The strength of 45# steel after quenching and tempering can reach more than 600MPa. Low-temperature impact energy (-20℃) needs to be ≥27J (GB/T 8163). The performance data must be tested by a universal testing machine and a report must be issued.
How to test the hardness of steel pipes?
Commonly used Brinell hardness (HBW) or Rockwell hardness (HRB/HRC) tests, 20# steel HBW is about ≤156, and 45# steel can reach HRC of 25-32 after quenching and tempering. Portable Leeb hardness tester is used for on-site testing. There is a conversion relationship between hardness and strength (such as HBW≈0.35×tensile strength). The test needs to avoid the weld area.
What is the impact toughness of steel pipes? How to test?
Impact toughness reflects the material's ability to resist brittle fracture, and the Charpy V-notch test (Charpy V) is a standard method. The specimen breaks under the impact of the pendulum, and the absorbed energy value (J) is the index. In low-temperature environments, the temperature data of -40℃ or even lower must be tested. Nuclear power steel requires AKv≥60J.
What is the purpose of the steel pipe flattening test?
To test the plastic deformation capacity of the steel pipe, the specimen should not crack when the distance between the two plates is 3 times the wall thickness. Welded steel pipes must ensure that there are no cracks in the weld area. The flattening test is a mandatory item of GB/T 8163, especially for thin-walled pipes. Failure indicates that the material ductility or welding quality does not meet the standard.
How to evaluate the fatigue life of steel pipes?
The rotating bending fatigue tester simulates alternating stress and records the number of fracture cycles. High-frequency fatigue (10^7 times) data is used for automotive drive shaft design. Surface shot peening can increase fatigue strength by more than 30%. ASTM E466 specifies the test standard, and the stress ratio (R=σmin/σmax) must be controlled.
