The process of welding tubing involves welding a seam across the length of a stainless steel strip to join two edges together to create the tube. Due to this technique, the welded tubes are produced in very long continuous lengths.
How do we make welded tubes?
The first step of making a welded tube is to send steel slabs through a hot mill (up to 800m in length) to create thin, narrow strips known as skelp. In the next step of manufacturing the shape of the tube is made by rolling out the skelp before welding a seam along the length.
The process of making a tube can be hot or cold, with the latter resulting in smoother finishes and tighter tolerances. When making the tube the thickness of the walls and the diameter is determined.
The diameter of the tubes welded can vary from small (e.g. hypodermic needles) to 3 meters (e.g. sewers). The alloy of steel that is used determines the final characteristics of the tube with respect to strength, corrosion as well as flexibility, and heat resistance.
The seam is further processed by forging and cold rolling in order to get rid of the beading. Certain welded tubes can also be deep drawn in a similar fashion to seamless tubing, to give a more precise weld seam as well as a better appearance.