What is Cold Drawn Seamless Steel Tubes?

 

What is CDS tube?

Cold Drawn Seamless Mechanical Tubing (CDS) is a cold drawn 1018/1026 steel tube which offers uniform tolerances, enhanced machinability and increased strength and tolerances compared to hot-rolled products.

 

What is Drawing Process?

Floating/Drawing process of pulling a metal bar, rod, or wire through the whole of a die to alter its finish, shape, size, and/or mechanical properties. The tube drawing technique reduces the outer diameter, inner diameter, and wall thickness of the tube. The integrity of the surface of the tube is maintained, ideal for stainless steel tubes.

 

How much Drawing Process?

Typically used as the first form of size reduction for seamless tubes, cold drawing reduces the diameter by pulling the tube through a die that is smaller than the tube. In order to fit the tube into the die, one end is swaged or tagged thereby reducing the diameter of the leading end before drawing. Next, the narrowed end is passed through the die and clamped to a drawing trolley which pulls the tube through the die. After drawing the tag is cropped from the tube end prior to cleaning. Superior Tube employs three types of cold drawing techniques:

 

Sink drawing

This is the simplest of the three drawing methods, as there is no tooling to support the ID surface. The tube is drawn through a die made of polished tool steel or industrial diamond, thereby reducing its inside and outside diameters. Our specialized lubrication and application techniques, combined with our proprietary die profiles, enable the OD surface to become smoother as the tube is drawn. Since the inside diameter is not constrained, the wall thickness of the tube will normally increase during drawing, and the ID surface finish will normally become rougher during a sink draw.

 

Rod drawing

Rod drawing is our most commonly used cold draw method, primarily for intermediate or in-process drawing stages, where both the outside diameter and wall thickness are reduced at the same time.

 

The tube is loaded over a hardened steel mandrel rod and both are then drawn through a die. This squeezes the tube onto the rod, reducing the outside diameter and thinning the wall simultaneously. The die and mandrel determine the size of the drawn tube, which is then slightly expanded by applying pressure to the outside of the tube so that the rod can be removed. Since larger reductions in cross-sectional area can be achieved by rod drawing, this method is used for mid-process stages to reduce tube sizes prior to the final drawing cycle.

 

Plug drawing

This type of drawing is used to achieve the best possible surface finish and the greatest control over both dimensions and final temper. The outside diameter and wall thickness of the tube are both reduced during plug drawing, as the tube travels through a die and over a stationary plug/mandrel made of high grade tool steel. The plug or mandrel has a polished surface and is attached to a fixed back rod, which is carefully positioned within the drawing die. The tube is loaded over the mandrel/back rod. As the tube passes through the die, the burnishing action of the metal flowing over the stationary plug imparts a high tolerance surface finish inside the tube.

 

When properly lubricated and prepared, the ID will show very few flaws and finishes of 16 RMS or better can be achieved. Plug drawing is normally chosen for the final draw stage because it achieves a high quality surface finish, exceptional dimensional control, and positive influence on tensile strength requirements.

 

Contact Fushun for CDS Steel Tubing Today

Contact us for more information regarding precision steel tubing specifications and product options, or request a quote for further pricing details today.