Coupled experimental-numerical analysis of wear in hot-rolling...

Coupled experimental-numerical analysis of wear

in hot-rolling rolls

L.G.D.B.S. Lima(1), A. Gonçalves(2), A.P.V. Braga(2), R.M. Souza(1), M. Boccalini Jr. (2)

(1) Surface Phenomena Laboratory, Department of Mechanical Engineering, Polytechnic School, University of São Paulo, Brazil (LFS-USP)

2 Institute for Technological Research, São Paulo, Brazil (IPT)

[email protected]

10th International TOOL Conference 2016 - 05/10/2016

Motivation

Project: Advanced system for design of alloys for hot forming tools

Partnership:

Support:

Scope: Development of a numerical system to allow alloy selection based on analysis of damage on micro scales.

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Motivation > Summary > Experimental setup > Numerical model > Preliminary results > Improved model > Current results > Next steps > Conclusions > End of presentation

FORGING ROLLING INJECTION

10th International TOOL Conference 2016 – 05/10/2016 Luiz Lima – [email protected]

Summary

Specific objectives: development of a numerical subsystem capable of predicting wear in hot rolling

based on general process parameters and material modeling

In this presentation:

• Description of the pilot scale mill in operation

• Description of the numerical model developed to reproduce pilot scale rolling

• Comments on preliminary results and improvement of the models

• Discussion of current results

• Next steps in this subject

• Main conclusions



Experimental setup – pilot scale mill

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Instrumented, pilot-scale mill

Roll data:

–AISI H13, quenched and tempered to 46 HRC

–Dimensions (mm): Ø 126.77 x 203 (working region)

–Angular velocity: 27 RPM

Slab data:

–AISI 1045

–Dimensions (mm): 19.05 (thickness) x 92 x 280

– Initial temperature: 1300ºC

Process data:

–5 passes, alternate

–Reduction per pass: 15%

–Time between sucessive slabs: ~ 120 seconds

–Alternate cooling, always on exit side, water

–No descaling



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Measurements:

• Rolling loads (load cells)

• Temperature (thermocouples on surface and at several depths)

• Wear (roll profile after rolling campaings)


Numerical model

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Software ABAQUS/Explicit

• 2D, plane strain conditions (central cross-section)

• Thermal and mechanical results, coupled

• Roll material data measured

• Slab material data obtained from manufacturer and literature


Numerical model

Wear estimation:

• During each time increment of the numerical analysis, wear is calculated locally, based on a

modified Archard equation:

Where

• dt is the local thickness of material removed

• k is the adimensional wear coefficient

• p is the local contact pressure

• dl is the local sliding between roll and slab

• H(T) is the roll hardness, function of local roll temperature

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Numerical model

Wear estimation:

• The local values for each time increment are integrated over the whole slab rolling, resulting in wear

thicknesses per slab rolled, for every position in the roll surface

• As it is impracticable to perform a simulation covering the whole experiment (~1600 slabs), wear is

calculated on a group of slabs basis – values for a single slab are multiplied by a given number of

slabs.

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Wear ismultiplied by N slabs


Preliminary results - temperatures

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Numerical Experimental

1st rolling pass

Preliminary results – rolling loads

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1st pass2nd pass

3rd pass

4th pass5th pass

Numerically calculated temperatures and forces are in accordance with measured values. However...

Preliminary results – wear

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Measured Comparison

... values obtained by the numerical models are far higher than the measured in the roll, demanding

further investigation.

Improved model

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Wear coefficient is not a constant k = k(P,N)

Solution Investigation of wear evolution in a reciprocating machine with different normal loads


Current results

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Numerical procedure for wear shown before updated with values of k

Results:


Next steps

• Correction of slab properties to fine tune rolling loads:

• Incorporation of other wear mechanisms apart from abrasion:

– Thermal fatigue

– Adhesion

– Oxidation

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Conclusions

• Good results were obtained using a local approach for wear calculation in hot rolling using numerical

models.

• This strategy also allows the identification of the wear intensity in different moments of the process.

• Selection of wear coefficient is critical to the accuracy of the procedure.

• Results are closer for the first group of slabs, after which other mechanisms seem to compete with

abrasion in damaging the rolls.

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Coupled experimental-numerical analysis of wear in hot-rolling...

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