Does "Drawn-Over-Mandrel Tube" mean SEAMLESS TUBE? 2

[unp1]

Hi All,

I have a drawing for three parts having OD ranging from .750” to 1.125”. For the material, a note says “AISI 1020, Drawn-Over-Mandrel Tube.” Does this mean SEAMLESS TUBE? My guess is yes, but still confused. Could any one please help me?

Thank you.

 

[CWIC]

To my knowledge the material would be identified as: "cold drawn seamless mechanical tubing" to be defined as seamless. This material has a higher degree of finish and closer dimensional tolerances than that of other tubing-types.

 

[mcguire]

Tubing does not have to be seamless to be DOM. You may find that welded tubing which is DOM is, however, superior to seamless if you are looking for dimensional qualities, since welded tubing has very unifrom wall thickness and concentricity.

 

[aceshigh]

yes, the typical "DOM" is in fact welded, its actually a friction pressure lap weld, there is no type of filler used, the tube is drawn over a spinning mandrel by two other spinning mandrels, the extreme pressure and friction from the spinning roller welds the pipe. true seamless is done by actually shearing a hole thru solid billet material. technically this is also "DOM". i would say find out what the part is used for, then go from there.. i would guess they would have said "seamless" of they wanted seamless.

 

[Goahead]

Shear Spinning is a fabrication technology permitting to form a tubular shape with different diameters and thicknesses along its length, on a properly shaped mandrel, by the shearing action of rotating disks on the base metal (usually a plate) deformed to envelope the central mandrel. Welding is not required.

http://www.welding-advisers.com/

 

[BillPSU]

DOM is a welded product. Flat stock is formed into a tube and then resistance welded. The weld flash both internally and externally is removed after the welding process. The tube can have further hot processess done after this process to either increase or decrease the wall thickness and O.D. size. After these processes the tube is cut to the draw length, coated with a drawing compound, one end is crimped for the draw bench grippers and finally drawn through an external die with a mandrel held in the center. DOM is a very effective tubing due to first the high strength from the cold working process, secondly tolerances are very tight on OD size, wall thickness, I.D. size and concentricity.

Costwise it is more expensive then ERW, and less expensive than seamless tubing. The disadvantage is the limited wall thickness available 5/8" maximum. DOM tubing can be other than round.

It can be oval and other special shapes depending on the volume required. The last company I worked for used 14 1/8" x 7/16" wall DOM and several other large diameter thin wall tubes.

http://www.copperweld.com/pdfs/DOMBro.pdf

http://www.steeltubeinstitute.org/domprocesses.htm

 

[EdStainless]

This is why you need materials specifications. So that these issues are defined.
For most applications the welded vs seamless discussion is meaningless. There is no advantage of one over the other. When it comes to tolerances and dimensional control it is the finishing methods that are critical.
If it is the same composition, same mechanical properties, recieved the same NDT, then use whatever gives you the dimensions that you need.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[TubeMet]

Aceshigh is correct that seamless tubes can be "drawn-over-mandrel" just as ERW welded tubes are. However, the term DOM only refers to ERW tubes drawn over mandrel as accurately explained by BillPSU. Seamless tubes that are cold drawn are always refered to as "CDS" for cold drawn seamless. Note that many companies that purchase tubing for machining applications have gone to DOM over that past 20 years because the tube production process (that is, taking flat strip, forming it round and welding it) produces a much more concentric tube than the conventional seamless process (Mannesmann piercing of a hot bar). As a result, the machining customer purchases a slightly thinner DOM wall thickness than they would in a CDS tube. There is less machining required to completely "clean-up" the DOM tube versus the CDS tube.