Corus 2 - roughing mill Lanwern, stand m/cing

To restore stands R2 and R3 of the roughing mill to their original manufacturing tolerances for squareness,straightness and dimensional accuracy and eliminate risk of cambered bars at Corus Llanwern hot strip mill,Metalock Engineering UK, Coventry in conjunction with the mill management, carried out extensive in-situmachining work during a recent shutdown. Metalock has a wealth of experience in this type of work and hasdeveloped equipment and expertise enabling it to undertake such projects effectively.

Llanwern is an integrated steel plant producing strip products. The roughing mill is the first rolling stage of thehot strip mill.

The project involved machining the vertical wear plate faces(windows) and wrap around edges on R2 and R3mill housings. The 1.7m wide x 6m high vertical windows and new wrap around edges on each of the fourcolumns required machining to full height. This allowed oversize hardened wear plates to be fitted and originaldimensions restored. Additionally, over 200 1¼-inch BSW holes were to be refurbished by drilling and tappingoversize to M48 holes, then fitting screwed inserts with a central 1¼-inch BSW tapped hole.

Wear plate securing holes tend to become damaged during routine roll changes due to the 30-ton roll andchock assemblies sometimes colliding with the edges of the wear plate. Corus’s solution to this problem hasbeen to redesign the wear plates to incorporate wrap around edges to closely position the plates thus preventingsideways movement in the event of a collision with the roll chocks.

From information collected during a series of pre shutdown surveys it was evident that the vertical wear platefaces had worn and would require each face to be machined to clean up and at the same time to ensure squareand true surfaces to the mill centreline axis.

For the vertical wear plate faces and wrap around edges machining operations, special purpose milling machines,designed and built previously by Metalock, were adapted to suit the larger mill housings at the Llanwern plant.To drill and tap the a large number of M48 holes on the wear plate faces Metalock engineers designed andmanufactured two special-purpose drilling machines mounted on 6m long jig plates that covered the full faceand facilitated rapid access to every hole.

By using two special purpose milling machines, the operator side windows on both stands were machinedconcurrently. At the same time, two drilling rigs were used to drill and tap the holes in the drive sides of bothstands. On completion of those four operations, the machines were changed over to drill and tap the operatorsides and machine both drive side windows. Organizing concurrent operations on each stand this way enabledthe project to be completed well within programme and budget.

Stands R2 and R3 of the roughing mill at CorusLlanwern’s hot stip mill were restored to originaltolerances using in-situ machining expertise byMetalock