What causes fractures in spiral tubes?

Release date:

2021-09-06

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Steel Pipe Knowledge

During the cold drawing of spiral‑wound tubes, cracks that arise during operation—often due to defects such as cracks in the hot‑rolled tube billet or issues with high‑precision cold‑drawn tubes used to manufacture hydraulic cylinders—are typically brittle fractures, with little to no plastic deformation. Brittle fracture in welded steel pipes can be attributed to a variety of factors.

　　 Spiral tube During cold drawing, cracks that occur during operation—often due to defects such as cracks in hot-rolled tube billets or the use of high‑precision cold‑drawn tubes to manufacture hydraulic cylinders—are typically brittle fractures, with little to no plastic deformation. Brittle fracture in welded steel pipes is caused by a variety of factors.

　　For example, when precipitates are present at grain boundaries, they can initiate cracking regardless of whether their strength is higher or lower than that of the matrix; likewise, the segregation of inclusions at grain boundaries also contributes to crack formation. In essence, this refers to cold-drawn spiral tubes: even under cyclic loading far below the yield strength, fatigue and cracking can still occur.

　　Generally speaking, from an aesthetic standpoint, the mechanical performance guidelines for hydraulic (or pneumatic) components during the design process are based on the assumption that the material is a cold-drawn helical tube—uniform, continuous, and isotropic. Adhering to this approach suggests that the design is deemed safe, though accidents may still occasionally occur.

　　During the low‑stress brittle fracture of high‑strength cold‑drawn spiral tubes, it is observed that, in welded steel pipes, the material’s microstructure is far from uniform and isotropic. Cold‑drawn spiral tubes contain defects such as cracks, inclusions, and porosity; these imperfections can be regarded as microscopic preexisting cracks. The occurrence of cracking in cold‑drawn spiral tubes is further influenced by the operating temperature of the component.

　　Guangxi Nanning Canghai Steel Co., Ltd. specializes in producing straight-seam welded pipes, steel plate‑rolled pipes, large‑diameter steel pipes, spiral pipes, spiral welded pipes, straight‑seam pipes, and steel casing pipes. As a professional manufacturer of spiral pipes, the company’s products are widely used in pipeline systems for natural gas, petroleum, chemical processing, power generation, heating, water supply and drainage, sugar production, papermaking, as well as in piling applications and steel support structures for subways.

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