Acciaieria Arvedi

35% 30% 25% 20% 15% 10% 1 2 3 4 5 6 7 8 9 10 RmReL Mpa A% 550 500 450 400 350 1 2 3 4 5 6 7 8 9 10 Formability limit curve of Arvedi hot rolled strip compared with conventional cycle cold rolled strip steel grade S 420 MC gauge 1.25 mm* Mechanical characteristics, Rm ReL, edge - centre - edge over the coil length steel grade S 420 MC gauge 1.25 mm* Mechanical characteristics, A%, edge - centre - edge over the coil steel grade S 420 MC gauge 1.25 mm* 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3  0.4  0.5 > > > Ag Head End A80 Head End Ag Center A80 Center Ag Tail End A80 Tail End > > > ReL Head End Rm Head End ReL Center Rm Center ReL Tail End Rm Tail End Arvedi Cold rolled * Data from RWTH / IEHK report of 01/2006 Coil head Coil center Coil tail Coil head Coil center Coil tail Width 1250 mm <<< 30 mm from edge 30 mm from edge >>> Minor Strain Major Strain ϕ 1 = -2 ϕ 2 ϕ 1 = - ϕ 2 ϕ 1 = ϕ 2 ϕ 2 = 0 fig.2 fig.3 Arvedi ultrathin steels In the thin and ultrathin gauge range (less than 1.5 mm) the offer of Arvedi steels effectively covers a large part of those applications traditionally oriented towards the use of cold rolled strip. Thanks to ISP/ESP technology, where reduction of slab thickness is achieved with a “liquid core”, industrial production can be achieved of gauges that are unique in the world in terms of low carbon content steels for cold forming, structural steels and above all micro-alloy, high elastic limit steels. The geometrical characteristics of the ultrathin strips amply conform to the parameters set by European reference standards for cold rolled products (fig. 1). The excellent degree of cold formability, as shown by the limit curve (fig. 2) is substantially identical to that of a cold rolled product of the same steel grade and gauge (tests conducted by leading independent laboratories). Mechanical characteristics remain practically constant along the whole strip and throughout the cross-section. Homogeneousness of the mechanical characteristics, as shown by the tests conducted (fig. 3), is guaranteed by the fine-grain metallographic structure (in accordance with ASTM standards values are between 10 and 12) and by the high level of production process automation from the melt shop to casting and rolling. The reliability of the process also guarantees the repetition of the mechanical characteristics in the various production campaigns. Constant gauge for the whole coil length High precision of the cross-section fig.1 Research and development programmes conducted in collaboration with: * Data from RWTH / IEHK report of 01/2006 Coil no. 84580001 width 1,250 mm Th. 1.00 mm Longitudinal profile Cold rolled tolerance EN 10131 Coil no. 84580001 width 1,250 mm Th. 1.00 mm Cross-section (measured 25 mm from the edge) Cold rolled tolerance EN 10131 metres mm. mm. mm Gauge control The coils produced at Acciaieria Arvedi present particularly close and uniform gauge tolerances. This very important result is made possible by the integrated management of the pre-rolling and rolling phases which are governed by specific plant and software programmes, wholly developed by our technical staff. The particular conception of the process, with pre-rolling of the thin slab immediately after solidification in the continuous caster, allows precise gauge and profile control to be carried out on the slab during roughing and a semi- finished product to be prepared for finishing rolling with very precise and reliable geometrical characteristics. Subsequentfinishingrollingistherefore done on a bar starting with optimal and constant gauge conditions, at constant temperature and speed and at stable and well-controlled process conditions such as to ensure the results shown in the table “Dimensional tolerances”.