What aspects should be paid attention to in the production of precision spiral welded pipes?

Release date:

2021-04-12

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In general, the tools used in the production of cold-drawn precision spiral-welded pipes must have a surface finish better than Ra 0.4, dimensional accuracy at least to H3 grade, and a hardness exceeding HRC 70. Additionally, during the drawing process, neither the die tip nor the die itself should exhibit steel sticking.

　　Cold-drawn precision Spiral welded pipe Key control points to be observed in production:

　　1. Capillary tube

　　The capillary wall thickness shall be uniform, with minimal defects on both the inner and outer surfaces. Equipment for polishing the outer surface and removing defects from the inner bore must be provided.

　　2. Reinspection

　　Compared with ordinary cold-drawn steel tubes, the production of cold-drawn precision seamless tubes incorporates an additional hot-rolled billet pickling and re‑inspection step, primarily to ensure that the outer surface of the billet is free from defects such as folds and cracks. Billets exhibiting defects on the inner surface—such as folds, severe scratches, or a pitted finish—are rejected.

　　3. Tools

　　In general, the tools used in the production of cold-drawn precision spiral welded pipes must have a surface finish of Ra 0.4 or better, dimensional accuracy to H3 or higher, and a hardness of HRC 70 or greater. Additionally, during the drawing process, neither the mandrel nor the die should exhibit steel sticking.

　　4. Annealing

　　Annealing is a critical process in the production of all cold-drawn tubes; its quality directly affects both the mechanical properties of the steel pipe and the removal of iron oxide scale. Cold-drawn precision steel tubes require dedicated equipment, such as an oxidation‑free bright‑annealing furnace.

　　5. Pickling

　　During the sulfuric acid pickling process, precision spiral welded pipes tend to form “black dross” primarily composed of Fe₂O₃ and Fe₃O₄, which subsequently leads to surface black spots in downstream production. Since Fe₂O₃ and Fe₃O₄ are readily soluble in hydrochloric acid, to prevent the formation of these black spots, 5–10 g/L of NaCl is added to the acid bath.

　　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, spiral steel pipes, and steel casing tubes. As a professional manufacturer of spiral pipes, our products are widely used in pipeline systems for natural gas, petroleum, chemicals, 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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