TPT July 2007

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• Minimise the surface strain due to the torsion and

circumferential shear deformation

• Suppress the ‘forging’ effect (by increasing roll velocity the

shell is pulled in the direction of rolling)

• Improves the shell OD surface (due to the speed match

between roll and shell)

The cone-type cross roll piercing characteristics are:

• High elongation

• High expansion levels

• Capacity to pierce a wide range of steel grades

• High concentricity and wall uniformity

• Excellent inner and outer surface quality

After the piercing of the billet, the shell is rolled in the FQM™ and

the finishing of the tubes into the required final sizes is performed in

a sizing or a stretch-reducing block. It is here that the reduction of

the outer diameter takes place with a simultaneous wall thickness

variation.

The change of the wall thickness depends on the longitudinal tension

(stretching) acting on the tube during reduction. The mill is equipped

with a series of closely spaced three-roll stands (in accordance with

the required OD reduction). The three rolls, individually driven and

with adjustable roll stands, are used in the last stand position.

The Kocks sizing or stretch reducing blocks are the state-of-the-art

in 3-roll technology for tube rolling, with stands featuring three input

drive shafts, and radially adjustable or non-adjustable rolls with quick

roll change. Restrictions normally experienced with conventional

stretch reducing mills are completely eliminated and overcome in

the Kocks design. This leads to the following improvements:

• Higher rolling forces and torque

• Shorter stand spacing

• Quick roll changing (30 min per stand)

• Radial adjustment of rolls

• No special roll lathe is required

• Investment is considerably reduced

7. Conclusion

FQM™ is the core of the seamless pipe production process selected

by Danieli. The innovative features of the mill are fully integrated

in the deformation path of the complete rolling line, either for new

installation or for revamping of an existing installation.

The best result is achieved when a complete new rolling line, from

the billet re-heating furnace, usually rotating hearth type, to cooling

bed is installed, allowing Danieli to balance the deformation path

among the piercing mill, the RMM and the sizing/stretch reducing

mill.

Figure 13

A complete view of a five-stand FQM™ (Fine Quality Mill) for a

350,000t/y 7" seamless pipe mill (Buttrio, Italy)

›

Figure 11 (above left)

Into the heart of the FQM process;

Figure 12 (above right):

a diagram displaying the FQM’s automatic mandrel cycle

Danieli Centro Tube

– Italy

Fax

: +39 02 2624 5486

Email

r.giannatasio@danieli.it

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