Cold Rolling

NSAIL’s state-of-the-art cold rolling unit uses Canadian and Japanese equipment to manufacture annealed and galvanised cold rolled steel that is the best in its class, and adheres to global standards.

Cold rolling is done from hot rolled coil that has been trimmed and pickled before being rolled. The cold rolling process reduces the thickness of the steel and simultaneously changes/enhance the mechanical properties of the steel.

The cold rolled steel coils can then be annealed (heated in a controlled atmosphere) to make the steel more formable (cold rolled annealing) or further processed on the metallic coating line, with a coating of zinc (galvanising). Cold rolled steel is available in numerous grades, each with a variety of properties for different applications.

The resultant products are far superior in terms of adherence to zinc coating and surface finish. Furthermore, they meet international standards such as ASTM, JIS, EN and Australian as well as Indian standards.

As a part of backward integration NSAIL set up a Cold Rolling Mill Complex and further added capacity in 2004 with total production of 300,000 TPA. A HR band slitter, a push pull pickling line with shallow bath technology from Keram Chemie, precision Roll grinder where trimming cum slitting linear the auxillary units of the CRM Complex. The heart of the complex is the modern high speed, 4 Hi Cold reversing mill imported from Canada. It has digital drives, computerised mill management system and H.A.G.C. (Hydraulic Automatic Gauge Control). Initial capacity of 60,000 MT per annum was doubled to 120,000 MT through upgradation - QWRC (Quick Work Roll Change), Auto pass line adjustment and pay off speed increase. CRM provides a consistent clean substrate with dimensional tolerances to its Galvanising Lines.

National Steel's fully computerised galvanising line incorporates the world's latest NON-OX process comprising superior surface cleaning and preparation techniques, along with computer-aided annealing followed by hot dip galvanising in a zinc bath.

Finally the steel sheets and coils undergo water quenching with D.M. water and skinpassing with Tension Leveler to give surface suitable for colour coating with excellent flatness. Post-surface treatment known as chromating is done to retain its shine, brightness and improved corrosion resistance.

The resultant products are far superior in terms of adherence of zinc coating and surface finish and meet international standards such as ASTM, JIS, DIN and Ethopian as well as Indian standards.