You have a choice between seamless tube producers and welded tube producers.....based on your requirements. High quality seamless tube producers include Tenaris and Sumitomo while welded producers include Maverick Tube and Lone Star Steel, among others. See the following for the composite...
Another reference, at least for steels, is ASTM's Handbook of Comparative World Steel Standards:Third Edition edited by J.E.Bringas. It's available in paper or CD format. See
www.astm.org
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...
