Hollow Sections Manufacturing Process

Hollow section is formed from hot-rolled coil produced in steel mill. All the incoming coils are verified based on the test certificate received from steel mill for their chemistry and mechanical properties.

The forming stage of Hollow Section begins with a single-width strip. The width of strip is roughly equal to the perimeter of the pipe to be produced. The edges of coil are sheared to pre-specified widths in slitting line.

The process involves uncoiling & leveling of coils and processing the same. The lead end of each coil is squared by shearing operation for threading into the mill. Then this end is joined with coil end of outgoing coil to maintain continuity in production and reduce losses.

To maintain continuity of production, it is accumulated in an accumulator/loop pit. It is then gradually and continuously formed into a circular shape by shaped rolls as per the required diameter in forming stands arranged in tandem. In the welding stand, edges of formed strip are pre heated by High Frequency Electrical Induction heating process to the desired temperature, which are mechanically pressed together horizontally to form continuous weld seam. This welding process does not need any filler metal. Instead, the welding pressure causes some of the metal to be squeezed from the joint, forming a bead of metal on inside and outside of the tube. This bead or welding flash is trimmed during the process. The weld seam is examined and adjusted as per the weld parameters, including temperature and outside diameters. Subsequently pipe string passes through shaping stands to produce square or rectangular section before it is cut to required length as per customer's requirement or relevant specification.

During production, online visual inspection is also carried out. Deburring of all the sections are carried out. All sections are marked and/or paint stenciled as per the order requirements, packed in bundles before shifting in the storage yard. Sections are then loaded on trailers or trucks and dispatched to the customer's site. These sections can also be supplied with black paint/oiling as per customer's requirements.