optimisation of the mannesmann effect by process simulation
TRANSCRIPT
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
Analytical prediction of the central ruptureof billets during piercing in a cross-rollpiercer due to the Mannesmann effect
Elisabetta Ceretti, Claudio Giardini, Ferdinando BrisottoUniversità degli Studi di Brescia - Dipartimento di Ingegneria Meccanica
Raul [email protected]
Centro Sviluppo Materiali SpA
Luca [email protected]
Tenaris Dalmine SpA
presented atInnovations in metal forming - an international Conference
September 23-24, 2004 - Brescia, Italy
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
Contents
• the Rotary Piercing Process– general description– the Mannesmann effect
• FEM simulation of the Mannesmann effect– FE model basics– results validation through industrial trials
• on-line application of the results of the FE model into theprocess control systems at the Tenaris tube rolling plants
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
Production steps of seamless steel tubes(hot rolling cycle)
• heating of round billetsup to rollingtemperature
• piercing of the billetinto a hollow shell
• elongation of the shellinto a mother tube
• final rolling of themother tube to the finaldimensions
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Rotary Piercing Process
piercerplug
left roll
right roll
billet
roll-billettouchpoint
position ofthe plug nose
void reductionlength
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Rotary Piercing Process
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Rotary Piercing Process
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
Basic schematization of the forces exerted by the piercer rolls on thebillet in the inlet cone of the piercing mill
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
piercerplug
central rupture produced by theMannesmann effect
(as seen on the longitudinal section ofthe semipierced hollow)
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
central ruptureproduced by the
Mannesmann effecton a billet rolled in
the piercing millwithout plug
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
• strongly beneficial to:– shell concentricity (uniform wall thickness on the cross
section)– lifetime of the piercer plugs
• if not controlled, may produce internal defects on thepierced shell, due to oxidation of the internal surface
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
Pierced shell tail with square end The non-squareness of the tailend of the pierced shell indicateswall thickness eccentricity of the
cross section
square tail end ofthe pierced shell
non- square tail end(eccentric shell)
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
Internal defects (as seen on the finished tube) generated by oxidation ofthe broken surface at the billet center, and subsequent rolling by the
piercer plug
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
Normal wear pattern on thepiercer plug (proper piercer
settings)
Abnormal wear on the nose of thepiercer plug, generated by absentor insufficient centeral rupture on
the billet
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
normal wearpattern of worn
piercer plug
worn plug withdeformed shape(central cavity
too large)
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Mannesmann effect
It can be concluded that:• the Mannesmann effect should be regarded as a basic
feature of the rotary piercing process• its control is important to assure an acceptable level of
dimensional and surface quality to the rolled product• in consideration of the 3-dimensional complexity of the
piercer machine, it is sometimes difficult to predict the realactual extention of the rupture cone in the billet
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The FEM approach to in-line control of theMannesmann effect
• calculation (with FE model) of the stress and strainconditions in the billet as a function of time during thepiercing process
• determination of the axial position where the materialreaches a treshold value for central rupture (depending onsteel grade, temperature and deformation conditions)
• validation of such theoretical approach with full-scaleexperimental tests (at rolling plant)
• theoretical simulation of possible rolling conditions andextrapolation of the results with artificial neural networktechniques
• implementation in the process control of the rolling plants
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Finite Element modelDescription of the problem
• as previously described, in the rotary tube piercing processthe round bar rotates around its axis, and the fracture islocated on a plane perpendicular to the rotation axis of theround bar
• the influence of the axial stress in the hole formationmechanism has been investigated with a 3D model
• the FEM calculated value of the axial stress generatedduring the process has been found to be constant along thebillet axis and only 10% of the transversal stresses
• it was then decided to approach the problem with a 2-dimensional FE model, neglecting the influence of axialstresses on the hole formation and considering only thestresses acting on the transversal cross section of the billet
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Finite Element modelCalculation of stress and strain distribution
(step 1) - CAD schematization of the 3-dimensional geometry ofthe piercer mill
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Finite Element modelCalculation of stress and strain distribution
(step 2) - determination of the contact points between the billetand the piercer rolls on the void reduction length
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Finite Element modelCalculation of stress and strain distribution
(step 3) - the 3-dimensional geometry is analyzed with a 2-Dapproach by neglecting axial stresses and reproducing the rolls-
material contact with a spiral
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Finite Element modelDetermination of the breaking point
• The axial position where the center of the material breaks isdetermined with the Cockroft-Latham criterion of themaximum cumulated energy:
• The damage index C(x) is calculated along the longitudinalaxis (x) of the billet center
• The starting point of the central crack is then determined asthe point where the calculated damage index C(x) becomesgreater than the characteristic value for the rolled material,at the piercing temperature
∫ ⋅
=
f
dCiε
εσσσ
0
*
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
The Finite Element modelDetermination of the breaking point
Damage on the billet cross section for a given piercing condition
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
-450 -400 -350 -300 -250Axial coordinate
CumulateddamageLimit damagefor the material
The Finite Element modelModel validation
Position ofthe nose of
the plug
Position wherethe breakage
occurs
B = Length of the Mannesmann effect
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
In-line algorithms for the prediction of theoccurrence of the Mannesmann effect
• FEM simulations and operationalexperience indicate that theoccurrence and extention of theMannesmann effect depends onthe following main factors:– steel grade– piercing temperature– geometry of the contact with
the rolls (spiral), expressedthrough the parameters M, Qand a, where:
M = arctan ( )Q
dQ*α
Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
In-line algorithms for the prediction of theoccurrence of the Mannesmann effect
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Analytical prediction of the central rupture of billets duringpiercing in a cross-roll piercer due to the Mannesmann effectInnovations in metal forming - an international ConferenceSeptember 23-24, 2004 - Brescia, Italy
Conclusions
• the FE model of the Mannesmann effect has been realizedto exhaustively approach a well-known everyday problemof the tube rolling process
• the results provided by this model have fully matched theevidence of long-term operational experience, and havebeen also verified with specific and dedicated rolling tests
• the implementation of the results of the model in theprocess control of the Tenaris rolling lines will providesupport to the operators of the mills in the decision-takingprocess, with expectations of specific improvements on:– internal surface quality of the pipes– plug life– dimensional quality of the rolled product