Seam welding or Electric Resistance welding (ERW) is a process by which galvanized square tubing (SHS) is created. In this process, metal strips unwound from coils are side trimmed to control the width and prepare the edges for welding. These strips then pass through contoured rollers that cold form the material into a square shape. Using pressure the edges are forced together and welded. Once the tube has been weld tested, it is passed through a series of sizing rolls to attain precise size and then straightened and cut to a required length.
Square tubes are created from coils and then run through a series of dies. They are welded from the inside to form their shape. These tubes are used for structural and maintenance purposes. Its application would be the construction of structures, signposts, railings, fencing, furniture, gates and vehicle parts. These tubes are measured by their external dimensions and their wall thickness.
When procuring steel tubing, two variants are presented, Hot Rolled and Cold Rolled. Hot rolling involves the passing of metal through rollers that are heated and well above its crystallization temperature. These are used to mold the metal to its desired physical dimensions, which is achieved with multiple passes through the rollers.
Cold Rolled metal is that which is rolled at room temperature, and is well below its crystallization temperature. This results in an increase in its strength and hardness.
Standard: St 12 (DIN 1623), CS, DS [ASTM A1008], ASTM A500/A500M, Grade A, B & C.
When buying SHS (Square Hollow Section) or Square tubes and pipes, rest assured that: