Factors affecting the fatigue strength of seamless steel pipe materials: inclusions.
The inclusion itself or the hole created by it is equivalent to a tiny gap, which will produce stress concentration and strain concentration under the action of alternating load, which will become the source of fatigue fracture and have a negative impact on the fatigue performance of the material. The influence of inclusions on fatigue strength not only depends on the type, nature, shape, size, number and distribution of inclusions, but also depends on the strength level of the material, the level and state of applied stress and other factors.
The tightness of the combination of inclusions and base metal will also affect the fatigue strength. Sulfides are easy to deform and are tightly bonded to the base material, while oxides are easy to separate from the base material, causing stress concentration. It can be seen that from the type of inclusions, sulfides have less influence, while oxides, nitrides and silicates are more harmful.
Tips: ASTM A53 covers welded and seamless steel pipe with nominal wall thickness. The surface condition is usually black and hot-dipped galvanized. ASTM A53 is produced mainly for pressure and mechanical applications, and is also used for transport of steam, water, gas line pipes.