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Steel Supply
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Tube Making Processes
Seamless Tubes Manufacturing
Tube Making Processes
Hot Finishing
All our hot-finished tubes are produced either through the Assel Mill or the PQF® Mill route. Round steel blooms (billets) of specific lengths are first heated in a rotary hearth Furnace. After heating, these blooms are descaled, end-face centered and passed through a cross-roll Piercing Mill to produce rough hollow blooms. These hollow blooms are then rolled over a mandrel either through a three-roll Assel Mill or through a PQF® Mill to produce hot-finished tubes. If required, these tubes are passed through a hot-sizing mill or a stretch reducing mill to produce tubes of intermediate dimensions. Hot-finished tubes are either delivered "as is" or further cold processed.

The Assel Mill is the ideal process for producing low volume, customized tubes with high dimensional accuracy and excellent concentricity. As a result these tubes are ideal for the manufacture of items such as bearing rings, cages for constant velocity joints (CV cages), automobile parts, etc.

The PQF® Mill, on the other hand, is ideal for producing large volumes of very accurately sized tubes. This process is ideal for producing tubes for the Power Generation industry, OCTG tubes, and other applications where large volumes are required.

Cold Drawing
In the Cold Drawing process, hot-finished tubes are surface treated and then drawn through the gap between a reducing die and a central plug (or a mandrel), thereby reducing both the inside and outside diameters and polishing both internal and external surfaces of the tube to achieve close final tolerances.

Cold Pilgering
In the Cold Pilgering (Rotorolling) process the hot-finished tube is reduced by forging and elongating the tube stepwise over a stationary tapered mandrel. Two rolls, each with a tapering semi-circular groove running along the circumference embrace the tube from above and below and rock back and forth over the tube (the pass length), while a stationary tapering mandrel is held in the center of the tube. At the beginning of the stroke (pass), the circular section formed between the grooves of the two opposing rolls corresponds to the diameter of the ingoing tube and to the thickest section of the mandrel. As the rolls move forward over the tube, the circular section reduces in area until, at the end of the pass length, the circular section corresponds exactly to the finished outer diameter of the tube and the inner mandrel diameter corresponds to the finished inner diameter of the tube. The tube elongation is achieved by reduction of the outer diameter as well as the wall thickness of the in-going tubes. The Cold-Pilgered tube is characterized by very small dimensional variations and a very high surface quality. Furthermore, the high level of cold working (up to 70%) results in very high hardness levels and therefore excellent machinability.

Other Processes
Subsequent to the manufacture of tubes, ISMT uses a variety of finishing processes to produce value-added products such as near-net rings for bearings and CV cages, swaged and machined axles for trucks/trailers, couplings for OCTG products and hex-shaped drill rods for mining. Some of the processes used are:

  • Cold-Ring Rolling: We have a number of Bad Deuben machines that are capable of cold rolling rings to produce near-net shaped annular components. This process has almost zero wastage and yields a product with very tight tolerances.
  • Machining: ISMT has a variety of in-house machining facilities and has strategic manufacturing relationships with accredited vendors allowing us to meet virtually any customer requirements on short notice.
  • Heat treatment: Annealing, Hardening, Normalizing, Spherodizing
  • Peeling
  • Swaging/Upsetting