The CMB Bar Mill

Introduction

The Bar Mill was installed and commissioned in 1986. The modernisation programme which represented an initial £10m investment, involved the complete transformation and refurbishment of a redundant 4 Strand Rod Mill into a single strand continuous Bar/Light Section Mill. Utilising some of the existing equipment and new supply from Danieli & C.SpA of Italy a modern highly efficient Merchant Bar Mill was created.

Furnace An 80 tonne/hr top fired pusher furnace capable of reheating from cold 115mm square billets, 13 metres in length to a rolling temperature of 1,200 degrees centigrade with a permissible temperature difference of ± 15 degrees centigrade.

The Mill Control

 The initial installation was a fully digital ASEA Speedmaster control system which integrated with a mercury arc convertor main drive installation.

The mercury arcs have since been replaced by digital drives. This involves some of the latest technology in automatic mill control on speed matching and tension free rolling. It also has the capacity to store automatic rolling programmes. In combination with fully automatic shears and auxiliary set-ups and mill optimisation facilities it provides fully integrated operation of the 15 stands and auxiliary equipment under single operator control.

Stands and Fly Shears

 The mill train consists of 15 stands, in a continuous train, arranged in a 7 stand roughing group, 4 stand intermediate and 4 stand finishing groups. In addition to a vertical cantilever roughing stand, three new vertical stands can be interchanged with any of the horizontal stands in the intermediate and finishing groups. Two flying shears are installed for nose end and cooling bank length optimisation control. The maximum finishing speed of the mill is 14 metres/second.

Cooling Bank For efficient, controlled cooling the mill is equipped with a walking beam type cooling bed 66 metres long x 10 metres wide.

In Line Roller Straightener After cooling, all sections are straightened in pack form using an in-line roller straightener built under licence by Davy (Sheffield) from a NKK design. The unique feature of this machine is its ability to stop/start during the straightening process, delivering the required length to the cold shear which then cuts, without the need to "swing".

Cold Shear After cooling and straightening (if required) the product is cold sheared in 1.2 metre pack widths to customer lengths from 5 metres to 14 metres. It is then transported via roller tables direct to the automatic stacking station.

Automatic Stacker An automatic stacking station which can be operated as two independent 6.5 metre stations or as a single 14 metre station. It is equipped with robotic stacking heads and auto wire tying equipment, and is capable of stacking flats, angles and channels in-line at the mill rolling rate, in two tonne packs ready for despatch.