The wall thickness, diameter or shape of tubes that have been produced by extrusion or other hot-working processes of making seamless or welded tubes can be further reduced by the tube drawing process. Tubes as large as 0.3 metre diameter can be drawn using mandrels of various profiles. Mandrel provides proper internal diameter to the drawn tube. Tubes are drawn with or without the use of mandrel. Tubes with
Cold drawing of tubes. The set-up for cold drawing of extruded seamless tube (A) is shown at (a) wherein the small drawn end (B) of the tube is grasped and pulled further by the tongs of the draw bench operated with the help of a chain-sprocket system. Examples of tube drawing with and without an internal mandrel are shown at (b) wherein tube drawing. without mandrel is shown at (i), and with mandrel at (ii).
small bores or those in which internal diameter is not of great importance may be drawn without the use of mandrel. Reduction in one pass through the die is not more than 40% Several passes may be required for heavy reduction.
To remove the work hardening or strain hardening effect and to improve ductility, metal is annealed in between passes. In tube drawing, tubes are first pickled and cleaned of scale, etc. and later a thick lubricant film is applied on the tube and also maintained during drawing at the mandrel-tube interface to reduce friction.
See More: Wire Drawing
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