Today, we’d like to share the differences between ERW and DOM steel pipe with you.

ERW Steel Pipe

The nomenclature ERW (Electric Resistance Welded) refers to a specific type of welding process that involves both spot and seam welding. Seam welding is commonly used during the manufacturing of round, square and rectangular steel tube. The steel strip is unwound from coils and side-trimmed to control the width and condition the edges for welding. The strip then passes through a series of contoured rollers that cold-form the material into a circular (square or rectangular) shape. The edges are forced together under pressure as a butt joint and then welded by heating the material to temperatures above 2000° F. The flash weld that has formed is now removed from the outside diameter of the tube. Once the weld has been tested the tube then passes through a series of sizing rolls to attain its precise finished size, after which the tube is then straightened and cut to length.

The material used in the manufacturing process is typically SAE 1010. This product is typically available in Cold Rolled steel (CREW) for 0.060” wall and lighter and Hot Rolled steel  (HREW) for 0.083” wall and heavier. The product will come in an “as-welded” condition, (often called – flash-in condition) referring to when the flash from the weld is left on the inside of the tubing, it is not normally removed or controlled during the ERW tube production process.

(DOM) Drawn Over Mandrel

Technically, DOM is not a type of steel tube, but rather the process in which the tube is finished. It is considered a high-quality tube and is normally constructed from SAE 1020 or 1026 steel. The first stages of manufacturing are identical to ones used to make an electric resistance welded tube, but in the finishing stages the entire flash weld is removed and the tube is cold drawn over a mandrel. The cold drawn process provides the tube with better dimensional tolerances, improved surface finish and the strongest weld strength achievable. DOM is often incorrectly referenced as a “seamless tube” when it actually does have a seam (although it is almost invisible).