The cold-rolling of pickled strips takes place on the reversing four-high stands with roll surface widths of 1200 mm, 1700 mm, and 1760 mm.
Cold rolling is defined as the process of forming a given metal below its typical recrystallization temperature by rolling. During cold rolling, the crystals of the metal are strongly elongated in the direction of the forming, and the so-called rolling texture is formed. The yield strength, tensile strength and hardness of the formed metal increase with the simultaneous decrease of its elongation. Forming stress is created in the metal, and its forming strength can increase to such an extent that it cannot withstand further forming without damage. Heat treatment (recrystallization annealing) is required to remove the rolling texture and restore the original mechanical properties. Heat treatment is carried out on 75 single column bell furnace positions. As a result of recrystallization annealing, the effects of cold forming are removed from the steel, and the mechanical and technological properties reach pre-cold values.
The next operation is skin-pass rolling. The aim of the 1700 mm wide four-high skin-pass rolling mill is to form the cold rolled, annealed wide strips by as much as 0.5 - 2.0%. The aim of skin-pass rolling is to terminate the phase of flowing appearing in the tensile test diagram, to avoid flow lines generated during processing, to set good mechanical properties, to produce bright or flat strip finish depending on demand, and to provide a strip with good flatness.
The Cold Rolling Mill produces cold rolled, as well as hot rolled and pickled wide and slit strips or sheets. During finishing, the coils are processed according to customer demand. During the cutting operation, the coil is cut to sheets of appropriate length.
Dimensions that can be cut are:
0.40 - 2.50 mm
550 - 1540 mm
500 - 3200 mm
On the slitting machine, strips of various types are slit to the size requested by customer, strip masses are specified, as well as narrow and wide strips, vertical and horizontal strips are produced.
Dimensions that can be slit are:
0.40 - 4.00 mm
19 - 1540 mm
The stretch-leveling line is used for the leveling of strips by stretching and bending, and it ensures the edging and oiling of the material. The equipment improves the flatness characteristics of sheet.
Dimensions that can be stretch-leveled are:
0.40 - 1.25 mm
500 - 1520 mm
During finishing, the final classification of the finished product takes place, it receives surface protection, and then it is packed.
The finished product is transferred to the warehouse and delivery workshop, from where it is eventually delivered to the customer.
Capacity of Cold Rolling Mill equipment:
- Hydrochloric acid pickling line (1200 thousand tons/year)
- 1760 mm wide four-high reversing stand (~450 thousand tons/year)
- 1700 mm wide four-high reversing stand (~280 thousand tons/year)
- 1200 mm wide four-high reversing stand (~190 thousand tons/year)
- 1700 mm wide four-high skin-pass rolling mill stand (~600 thousand tons/year)
- Bell furnace annealing (~500 thousand tons/year)
- TSheet cutting line (~150 thousand tons/year)
- 1600 mm slitting line (~158 thousand tons/year)
- 1600 mm stretch-leveling line (~158 thousand tons/year)
- 1550 mm slitting line (~150 thousand tons/year)