Surface Profile Effects on AHSS processing

Presented by: Myriam Brochu and Paul MosserSupervised by: Professor Myriam Brochu

Polytechnique Montreal

WORLD-CLASS ENGINEERINGWWW.polymtl.ca

IZA Program - ZCO-72

Surface Profile Effects on AHSS processing

1Updated October 2015

1. Goal of ZCO-72 project

2. Important things since June 2015 (last GAP meeting)

2.1 NSERC Funding

2.2 Recruitment of MSc2

3. Organization & Progression

4. MSc 1: Impact of temperature deviations on the mechanical properties and zinc adhesion of AHSS

5. MSc 2: Process control and temperature variation through the study of material emissivity

6. Updated planning

7. Discussion/Questions

CONTENTS

2

Industrial Problem:

High rejection rates of Advanced High-Strength Steel (AHSS) strip processed in Continuous Galvanizing Lines (CGLs).

Hypothesis based on literature:

I. AHSS are more sensitive than conventional steels to any deviation in time and temperature (caused by emissivity variations) of the annealing and tempering cycle.

II. Variability in the surface condition (oxidation, roughness, thickness, defects, microstructure) of AHSS affects emissivity and thus process temperature and consequently mechanical properties and zinc adherence.

Ultimate goal:

Study the influence of steel strips surface characteristics on boththe mechanical properties and the coating quality of hot dipgalvanized AHSS, by focusing on emissivity variations.

1. GOAL OF ZCO-72 PROJECT

3

2.1 NSERC was approved and full funding obtained

a) Cash Budget (from 150 000 $USD to 332 527 $CAN)

b) Now signing the research agreement between Polytechnique –McMaster – Zelixir and ArcelorMittal Dofasco

2.2 MSC2 students has been recruited and will begin in W16

2. IMPORTANT THINGS SINCE JUNE 2015 (LAST GAP MEETING)

4

2015 2016 2017

IZA (Zelixir) 50 000 $US 50 000 $US 50 000 $US

NSERC 61 541 $CAN 58 363 $CAN 26 623 $CAN

TOTAL 123 541 $CAN 120 363 $CAN 88 623 $CAN

World-Class Engineering

4. DISCUSSION

5

3. Organization & Progression

3. ORGANIZATION & PROGRESSION

6

PROJECTPHASES

Description Materials studied

Preliminary

(MSC1)

Microstructural, roughness and mechanicalcharacterization of as received materials

DP980 CRDP780 CR & HRHSLA HR & CR95% COMPLETED

I(MSC1& 2)

Production and emissivitycharacterization of specimens with a variety of roughness and oxides

DP980 CRDP780 CR & HR

ON GOING

II(MSC1)

Production and mechanicalcharacterization of non galvanizedspecimens forcing temperaturedeviations

DP980 CRHSLA CRProtocol defined

IIIa(MSC2)

Production and adhesioncharacterization of galvanizedspecimens with temperature deviations

DP980 CRHSLA CRAdhesion setup

IIIb(MSC2)

Modelling temperature deviations fromthe emissivity characteristics (I)

DP980 CRStudent recruited


4. DISCUSSION

7

4. MSc 1: Impact of temperature deviations on the mechanical properties and zinc adhesion of AHSS

Objective: Study the impact of process parameters (temperature deviation and heterogeneities) on the mechanical properties and zinc adhesion of the advanced high strength steel

Research hypothesis:

• Temperature deviations and heterogeneities are causingproduct rejections due to non conformities in mechanicalproperties and zinc adhesion.

• Surface roughness and oxidation are significantparameters responsible for temperature variations andheterogeneities.

4.1. SPECIFIC OBJECTIVE OF MSC1

8

World-Class Engineering 9

4.2. PRELIMINARY PHASE

4.2.1. METHODOLOGY

10

Characterization of as received materials

DP980 CR, DP780 CR & HR and HSLA CR & HR

Tests Planned Performed

Chemical analysis per ASTM E415

5 5

Tensile per ASTM E8/A370 30 39

Hardness per ASTM E18 6 6

Roughness per ASTM D4417 30 30

Microstructure(Optical/SEM) per ASTM E3

15 10

Emissivity per ASTM E1933 15 16

Zinc adhesion 6 0

ASTM E8/A370

• Subsize specimens

• Speed rate 0,45 mm/min

• Extensometer of 25 mm

• Load cell 50 kN

4.2.2. TENSILE TESTS

11

Rolling direction

Edge1 Specimen Edge2 SpecimenCentral Specimen

Front view dimensions in mm

12

4.2.2. TENSILE TESTS - HSLA

Grade Position

Heat Treat&

GalvanizedYield(MPa)

UTS (MPa)

A% at break

HSLA HR Central No 627 667 25,4

HSLA CR Edge No 430 647 27,9

Central No 443 651 28,9

ReferenceASTM A653

- Yes 550 min. 620 min.

Mechanical properties for HSLA

The difference between edge and central specimens is not significant.

13

4.2.2. TENSILE TESTS – DP780CR & HR

Grade PositionHeat Treat

&Galvanized

Yield(MPa)

UTS (MPa)

A% at break

DP780 HREdge No 722 830 21,9

Central No 721 840 21,6

DP780 CR(Full hard)

Edge Head No 1067 1116 4,1

Central Head No 1103 1142 4,0

Edge Tail No 1010 1074 NA

Central Tail No 1060 1103 4,9

ReferenceASTM A1079

- Yes 420 min. 780 min. 14

NA : Specimen fractured outside the gage length

Mechanical properties for DP780 CR & DP780 HR

The difference between edge and central specimens is not significant

Mechanical properties for DP980 CR

14

Grade Position

Heat Treat&

GalvanizedYield(MPa)

UTS (MPa)

A% at break

DP980 CR

EdgeNo

(full hard)1334 1451 NA

CentralNo

(full hard)1373 1468 NA

Edge Yes 821 1082 13,0

Central Yes 790 1107 14,1

ReferenceASTM A1079

- Yes 550 min. 980 min. 8 min.

4.2.2. TENSILE TESTS – DP980CR

NA : specimens fractured outside gage length

The difference between edge and central specimens is not significant

15

0

200

400

600

800

1000

1200

1400

1600

Yield average UTS average

Str

ess [

MPa]

Tensile Properties DP780CR uncoated(full hard)

Tail Edge Tail Central Head Edge Head Central


Graph shows 2 trends but nothing significant:

• Edge are a bit lower than central specimens

• Tail are a bit lower than head specimens

Maximum difference:

ΔYield = 100 MPa

ΔUTS = 60 MPa

16


0

200

400

600

800

1000

1200

1400

1600


Str

ess [

MPa]

Tensile Properties DP780HR - uncoated

Edge Uncoated Central Uncoated

No significant difference between edge and central specimens.

No comparison performed between head and tail – specimen location

was not specified by the supplier.


17

0

200

400

600

800

1000

1200

1400

1600


Str

ess [

MPa]

Tensile Properties DP980 CR – coated and uncoated

Edge Galavanized

CentralGalvanized

EdgeUncoated

CentralUncoated

There is no significant difference between edge and central specimens.

Larger dispersion for uncoated specimens probably related to fractures

outside the gage length.

980MPa

18

4.2.3. CROWNING & EDGE EFFECTS

Thickness variation along the the width

SteelEdge [mm] (0 – 5mm)

Central [mm]

%Difference

DP780HR 2,45 – 2,50 2,50 – 2,55 2

DP780CR 1,25 – 1,45 1,45 – 1,55 13

DP980CR 1,05 – 1,10 1,10 – 1,20 8

Cracks perpendicular to the rollingdirection - length 1 mm

1mm

Edge defect observation (SEM) in DP980CR as received

Is this feature important for the project ?

Measured Characteristics : Ra, Rq, Rz per ISO1997

– Transverse (along the width)

– Edge : 5-10 mm from the side surfaces

– Central : >50 mm from the side surfaces

19

4.2.4. SURFACE FINISH

[μm] Ra Rq Rz

DP780 CREdge 1,87 2,32 10,74

Central 1,75 2,09 8,84

DP780 HREdge 2,76 3,38 15,34

Central 2,42 2,98 13,25

DP780 HRPickled

Central 1,98 2,91 13,98

DP980 CREdge 0,22 0,29 1,57

Central 0,25 0,33 1,83

HSLA CR Central 0,94 1,14 4,98

Rolling direction

Edge

Central

20


0

2

4

6

8

10

12

14

16

18

Ra Rq Rz

[μm]

Surface Finishing DP980CR

Edge as

received

Central as

received

0

2

4

6

8

10

12

14

16

18

Ra Rq Rz

[μm]

Surface Finishing DP780CR

Edge as

received

Central as

received

0

2

4

6

8

10

12

14

16

18

Ra Rq Rz

[μm]

Surface Finishing DP780HR

Pickled

Edge as

received

Central as

received

No significant difference between edge

and central specimens

Cold rolled are smoother than hot rolled

21


DP980CR 500x SE Position central

Surface finishing as received

DP980CR 500x SE Position edge

Surface finishing as received

Rolling direction

100μm 100μm

Similar roughness (slide 20) but SEM observations show different

textures between edge and center, for both DP CR

Reciprocal Method

Hemispherical Directional

Reflectance

Radiation

Detector

Hemi Ellipsoid

Radiation from the source uniformity illuminates sample overHemisphere; scattered radiation beam detected at angle θ

Sample Radiation source

Hemispherical emissivity :

SOC-100 + Nicolet FTIR

Wavelength : 2,4 to 25μm

Angle : 7° to 75°

ε = 1 − 𝜌

ε: emissivity

ρ: reflectance

23

4.2.5. EMISSIVITY

Source : Surface Optic Corporation

24

4.2.5. EMISSIVITY

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2 4 6 8 10 12 14

Em

issiv

ity

Wavelength (μm)

Emissivity of DP980CR without picklingSource temperature 1000F

7,0ｰ

75,0ｰ

Poly. (7,0ｰ)

Poly. (75,0ｰ)

Noise at low wavelength

Limitation

• Low precision at low wavelength

• Limited wavelength (<2,5μm)

Improvement / Future work

• Lower wavelength (1 to 2,5μm) but only 1 or 2 angle

• Use a pyrometer to measure the emissivity

25

4.2.5. EMISSIVITY

Tests will be performed per ASTM A1079

Bending : 90°

Radius of curvature : 3 x thickness of sheet

Manual

Set up is under design

26

4.2.6. ZINC ADHESION

World-Class Engineering 27

4.3. PHASE I

4.3. PHASE I - METHODOLOGY

28

Impact of roughness and oxides on spectral emissivity

Parameters:

Materials Roughness Dew Point

Gas Mixture

# Thermal cycle

DP780 CR As received

-30°C0°C

95%N2 + 5%H2

3

DP780 HRAs received1200 polished

3

DP980 CR As received 3

Status: 20th October 2015, Simulator is ready next week

29


Thermal cycle for Phase I

For HSLA CR; DP780HR; DP980CR

Duration

Temperature

Heating

Annealing

Soaking

Cooling

Interruption of thermal cycle and characterization of the surface

at every red line

30

Thermal cycle for Phase I

For DP780CR

1st heating

2nd heatingAnnealling

Interruption of thermal cycle and characterization of the surface

at every red line


Duration

Temperature

2015 2016 2017

Winter Summer Fall Winter Summer Fall Winter

Mandatory Courses x x x

Review x x x

Material incoming x x

Preliminary Phase x x

Phase I x x x

Phase II x x

Phase III x x

Gap Meeting x x x x

Progress Report x x x

4.4. TIME LINE (UPDATE FALL 2015)

31

Next Gap Meeting:

• Progress Report

• Preliminary phase & Phase I completed

• Phase II in progress


4. DISCUSSION

32

5. MSc 2: Process control and temperature variations through the study of material emissivity

Project goal:

Model temperature deviation and heterogeneities based on spectral emissivity.

General planning (delayed by 1 semester):

Will begin in January 2016 (Ending in December 2017)

Collaborators

Mary Wells and Kyle Daun from University of Waterloo accepted to co-supervised MSC2.

New idea

Use a thermomechanical simulator equipped with a pyrometer (Gleeble) to validate the model developed.

5. MSC2: PROCESS CONTROL AND TEMPERATURE VARIATIONS THROUGH THE STUDY OF MATERIAL EMISSIVITY

33

6. UPDATED PLANNINGNSERC PLANNING (SEPT. 2015 – AUG. 2018)STUDENT AGENDA (JAN. 2015 – DEC. 2017)

34

Description of milestones (overall project delay : 6 months)

Completion date

1) Design of experiments (DOE)• Confirm the grade of DP after discussions with industrial partners;• Get information from industrial partners about the available strips;• Design the plan of experiments in collaboration with an expert;• GAP meeting;• NSERC proposal;• Student recruitment.

November2014

100%April 2015

2) Acquisition of as rolled samples (hot rolled and cold rolled)• Pickup or reception of as rolled samples.• Extra samples on the way (Nucor)

February 201595 %

March 2015

3) Characterization of the as rolled samples May 201595%

Oct. 2015

4) Revision of the DOE according to the measured characteristics • Progress report + GAP meeting.

July 15October 2015

5) PHASE I : Variation in emissivity and ΔT errors• Progress report

April 2016August 2016

6) PHASE II & III: Modelling temperature variations January 2017May 2017

7) Results analysis• Progress report

January 2017August 2017

8) Redaction of final report and results dissemination + GAP meeting

May 2017October 2017



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36

PROJECTPHASES

Questions/comments Actions

0 Reference values for tensile test results of CR – uncoated specimens ?

I Pertinent parameters in the DEO:• Edges and centers ?• Crowning ?• Edge defects ?

II Use of Gleeble with pyrometer ($$)• ArcelorMital Dofasco ?• Waterloo University

Surface Profile Effects on AHSS processing

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