annual report 2008 - continuous casting...

ANNUAL REPORT 2008UIUC, August 6, 2008

Zhaohui Yuan(MS Student)

Department of Mechanical Science and Engineering

University of Illinois at Urbana-Champaign

Thermal distortion of a slab mold with

cavity for electromagnetics

University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • BG Thomas 2

Acknowledgements

• Continuous Casting Consortium Members

• National Center for Supercomputing Applications (NCSA) at UIUC

• HKS (ABAQUS)

• Mr. Kim From POSCO provides blueprints for the model with electromagnetic brake

• Other Graduate students, especially Lance Hibbeler and Lyric Shi


Mold Construction

Conventional Mold

Mold with hollowed-out water box for EM Brake

Typical water-box

EM water-box

200mm30mm

500mm80mm

80mm

260mm


Objective

To predict distortion of slab

molds, with and without

hollowed-out region to hold

an EM Brake.


• Governing equations– Steady Heat conduction

– Mechanical equilibrium with thermal distortion

• Assumptions– 3-D elastic model

– Temperature independent material property

• Finite-element model– ABAQUS 6.7

– Standard 8-node “brick” elements

Thermal-distortion Model

0k T∇ ∇ =i

total elastic thermalε ε ε= +


Thermal Model

3D geometry Boundary conditions

27mm

0.8165m

27mm

0.122m

0.9m


Heat flux down mold

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.5

1

1.5

2

2.5

3

Hea

t flu

x (M

W/m

2)

Distance below meniscus(m)

Heat flux for this project

Li, C. and B.G. Thomas, "Analysis of the Potential Productivity of Continuous Cast Molds", The Brimacombe Memorial Symposium, (Vancouver, Canada, October 1-4), G. Irons & A. Cramb, eds., Canadian Institute of Mining, Metallurgy, and Petroleum, Montreal, Canada, 2000, pp. 595-611


Stress Model

3D geometry Boundary conditions


Mold Geometries


Material Properties and Operation Conditions


Compare with previous work

Thomas, B.G., G. Li, A. Moitra and D. Habing, "Analysis of Thermal and Mechanical Behavior of Copper Molds during Continuous Casting of Steel Slabs", Iron and Steelmaker (ISS Transactions), Iron and Steel Society, Warrendale, PA, Vol. 25, No. 10, 1998, pp. 127

30

3027

200mm

122mm

816.5mm

27

96


Heat Flux Comparison

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

0.5

1

1.5

2

2.5

3Heat flux profile

Hea

t flu

x (M

W/m

2)

Distance below meniscus(m)

Heat flux for this project

Heat flux used in the paperBG Thomas, 1998


Temperature Comparison

BG Thomas et al", ISS Transactions, 1998.


Distorted Shape Comparison

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 00

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Distortion at mold interface

Dis

tanc

e fr

om m

old

bott

om (

m)

Distortion of interface (mm)

Wide face

Narrow face

Meniscus

BG Thomas et al", ISS Transactions, 1998.


Model Validation

• Similar geometry and similar heat flux profile.

• Similar temperature contours.

• Higher heat flux near the meniscus results in a higher maximum temperature.

• Similar distortion.

• New wide face distorts more due to larger width.

• Similar gaps between WF and NF at top and bottom;

• Conclusion: New model is valid and can be used for further study.


Thermal Model

0 100 200 300 400 500 6000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Narrow face temperature distribution

Dis

tanc

e fr

om m

old

bott

om (

m)

Temperature (mm)

meniscus

x=0 (center)

x=0.0339mx=0.061m

x=0.1046m

x=0.122m

0 50 100 150 200 250 300 350 400 450 5000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Wide face temperature distribution

Dis

tanc

e fr

om m

old

bott

om (

m)

temperature( C)

z=0 (center)z=0.3474m

z=0.55m

z=0.7183m

z=0.8165m

z=0.8911mz=1.1m

Narrow Face Wide Face

Maximum temperature of the model


Thermal Model

• The highest temperature in each mold is just below meniscus.

• The maximum temperature in the whole model is at the edge narrow face just below the meniscus (owing to gap that forms between NF and WF).


Narrow Face Stress Analysis

-0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Narrow face displacement perpendicular to mold

Dis

tanc

e fr

om m

old

bott

om (

m)

Displacement (mm)

x=0 (center)

x=0.0339m

x=0.061mx=0.1046m

x=0.122m


Narrow Face Stress Analysis

• All the curves have a peak just below the meniscus (owing to the temperature peak)

• Bolts tend to lessen distortion: cause minimums in the distortion profile.

• More bolts and even distribution would reduce the distortion

• More bolts and even distribution would reduce the stress (the maximum stress is 1.51GPa, causing yielding of the copper)


Narrow Face Shape

-0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Narrow face displacement perpendicular to mold

Dis

tanc

e fr

om m

old

bott

om (

m)

Displacement (mm)

mold hot face

mold cold facewater jacket surface

meniscus

Gap


Narrow Face Gap

-0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Narrow face gap

Dis

tanc

e fr

om m

old

bott

om (

m)

gap (mm)

gap

meniscus


Narrow Face Shape

• Gap forms between the narrow face mold and water box.

• Water box thickness increases due to temperature increase, which stretches the bolts.


Wide Face Stress Analysis

-2 -1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Wide face displacement perpendicular to mold

Dis

tanc

e fr

om m

old

bott

om (

m)

Displacement (mm)


z=0.55m

z=0.7183m

z=0.8165m(corner)

z=0.8911mz=1.1m

-2 -1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Wide face displacement perpendicular to mold

Dis

tanc

e fr

om m

old

bott

om (

m)

Displacement (mm)


z=0.55m

z=0.7183m

z=0.8165m(corner)

z=0.8911mz=1.1m

Model with typical water box Model with EM water box


Wide Face Stress Analysis

• The whole wide face mold is tilted.

• Assuming mold shape is kept more vertical, plots are redrawn to show the thermal distortion.


Distorted shape after tilted

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9adjusted wide face distortion

Dis

tanc

e fr

om m

old

bott

om (

m)

Displacement (mm)


z=0.55m

z=0.7183m

z=0.8165m(corner)

z=0.8911mz=1.1m

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.60

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9adjusted wide face distortion

Dis

tanc

e fr

om m

old

bott

om (

m)

Displacement (mm)


z=0.55m

z=0.7183m

z=0.8165m(corner)

z=0.8911mz=1.1m



Distorted shape after tilted

• Mold for EM Brake has less distortion!

• The thicker the water box plate is, the more rigid, and less it bends.

• The shorter the bolts are, the harder for them to elongate.

• A thicker plate and shorter bolts will lead to a flatter mold (less distortion).


Wide Face Shape

-1.8 -1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Wide face distortion

Dis

tanc

e fr

om m

old

bott

om (

m)

Distortion (mm)

mold cold face

water box surfacemeniscus

-1.3 -1.2 -1.1 -1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.30

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Wide face distortion

Dis

tanc

e fr

om m

old

bott

om (

m)

Distortion (mm)

mold cold face

water box surfacemeniscus



Wide Face Shape

• No gap for the wide face model with typical water box

• Constraints will not change the edge shape, just lead to transportation and rotation;

• Gap exists in the wide face mold model for the EM brake. Because the water box plate is too thick to bend.

• thick water box plate has both good and bad effects.


Mold interface

-1.2 -1 -0.8 -0.6 -0.4 -0.2 00

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8


Dis

tanc

e fr

om m

old

bott

om (

m)


narrow face displacement along the corner

wide face displacement along the cornermeniscus

-1.2 -1 -0.8 -0.6 -0.4 -0.2 00

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8


Dis

tanc

e fr

om m

old

bott

om (

m)


narrow face displacement along the corner

wide face displacement along the cornermeniscus

gap


Ferrostatic Pressure effect

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 00

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8


Dis

tanc

e fr

om m

old

bott

om (

m)


narrow face with ferrostatic pressure

wide face wich ferrostatic pressurenarrow face without ferrostatic pressure

wide face without ferrostatic pressure

IDENTICAL

(effect is negligible)


Constraints

-1.6 -1.4 -1.2 -1 -0.8 -0.6 -0.4 -0.2 00

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8


Dis

tanc

e fr

om m

old

bott

om (

m)


narrow face with contact

wide face wich contactnarrow face with constraints

wide face with constraints

Two restricted points


Mold Interface

• The gap is not caused by the ferrostaticpressure

• Constraints will not change the shape of the interface.

• The achieve the balance, the mold must rotate to get the two points to contact.


Conclusions• Water box for EM brake has thicker plate, shorter bolts and

longer frame, which leads to less distortion.

• Evenly distributed bolts could better limit mold distortion, as well as derive a flatten surface and avoid stress concentration.

• Enough bolts should be assigned to avoid stress concentration.

• The thickness of the water box plate will greatly influent the mold distortion. A thicker plate would lead to a flatter mold.

• Gap might exist at the middle region of the corner, not only at the top and bottom.

• Depending on the water box structure and bolt distribution, gap may be created between the mold and water box.

annual report 2008 - continuous casting...

Documents