This process occurs after the mild strips have been slitted by the slitting line machine using a cold rolling mill. In this process, the largest strip would be 670mm with a thickness of 5.0 to 6.0mm for making a rectangular structural hollow section of 200 by 150mm. The smallest strip width is 47 to 48mm with a thickness of 1.0mm for making 12 by 12mm square hollow section.
Machines to be used may defer depending on the width of the strips. Larger strips like 670mm may have to use a bigger mill than that to be used on a 47mm strip width. Before beginning the process, ensure that the strips are free from any damages or defects such as burrs, lamination, dents, waviness, and unstilted parts. These damages and defects may cause poor welding resulting in openings or leakages in the circular hollow sections or pipes. In case any defects and damages occur, the deformed parts should be cut off and the good parts rejoined by welding. Once everything is in order, you lift the strips using an overhead crane and load them into the uncoiler, unsealed. The pinch roll-up should be positioned downwards to support the strip to be moved to the leveler rollers. Note that large width strips of 670mm with the thickness of 5.0 to 6.0 are supported by pinch roll up but for those of width of 47mm and thickness of 1.0, the pinch roll up may not be needed.
If the process is a continuation and the strip is not flat, it should be cut off at the beginning by the shearing machine and joined to the other strips. However, if it is the first time, you should pass it through rollers that will have to be adjusted to fit the strip’s width through the hoop cage. The hoop cage enables the loading of many strips as possible to enable the continuation of the process. From the hoop cage, the strip is moved to the forming rollers which is adjusted to the type of tube to be produced. It is then moved to the fin pass then to the weld and lastly to the scarfing post where excess material formed by the weld is trimmed off by the carbide tip tool which is rolled and attached to the scrap winder. From the scarfing post, the material goes through the main pass to the side rolls that are moulding the tubes into the desired final products.
You should now be able to move it through the turks-head to the cut-off carriage which is set to the length of the tube desired. Coolant water from the leveler should be used to help cool the welding so that it will not get damaged due to overheating as forming rolls moved to welding lastly to finalized at the side rolls. The coolant water also helps in preventing the rollers from slowly wearing off due to friction as well as in keeping the material straightened so that it does not bend due to the expansion and contraction of metal.
