Tubing and Pipe Finishes

Hot-finished tubular products produced by the seamless processes have a surface finish comparable to hot-rolled bars. Welded tubular products produced from hot-rolled sheets, strip, or plate retain the general surface finish of those flat rolled products. Thin-wall tubular products, due to greater reduction during the rolling operation and the lower finishing temperatures, may have a smoother surface than those with heavy walls.

Stainless steel tubular products are cold worked to improve dimensional limits or--in the case of welded tubing--to control the weld bead on the inside, or to condition the weld for grain refinement during the annealing operation. Cold finishing may include cold drawing, tube reducing, or swaging. Tubes may also be rough turned (machined) or honed, such as for hydraulic cylinders.

Tubular products may be polished, but instead of "typical" finish designations, the polished finishes for tubing are usually indicated by the grit size, such as 80, 120, 180, or 320 grit. Note that for the exterior surface of round tubing, grit lines are longitudinal. Tubing may be specified polished on the outside, the inside, or both surfaces. Welded and cold-finished seamless tubing is suitable for grinding or polishing and is produced in sizes up to 168 mm (6 -in.) OD with polished

outside surfaces. It is not practical to polish interior surfaces or tubes with an inner diameter of less than 19 mm (^ in.).

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