Surface Profile Effects on AHSS processing
Transcript of 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
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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)
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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
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4. DISCUSSION
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3. Organization & Progression
3. ORGANIZATION & PROGRESSION
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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
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4. DISCUSSION
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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
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4.2. PRELIMINARY PHASE
4.2.1. METHODOLOGY
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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
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Rolling direction
Edge1 Specimen Edge2 SpecimenCentral Specimen
Front view dimensions in mm
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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.
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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
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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
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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
4.2.2. TENSILE TESTS
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
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4.2.2. TENSILE TESTS
0
200
400
600
800
1000
1200
1400
1600
Yield average UTS average
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.
4.2.2. TENSILE TESTS
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0
200
400
600
800
1000
1200
1400
1600
Yield average UTS average
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
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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
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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
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4.2.4. SURFACE FINISH
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
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4.2.4. SURFACE FINISH
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
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4.2.5. EMISSIVITY
Source : Surface Optic Corporation
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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
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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
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4.2.6. ZINC ADHESION
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4.3. PHASE I
4.3. PHASE I - METHODOLOGY
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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
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4.3. PHASE I - METHODOLOGY
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
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Thermal cycle for Phase I
For DP780CR
1st heating
2nd heatingAnnealling
Interruption of thermal cycle and characterization of the surface
at every red line
4.3. PHASE I - METHODOLOGY
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)
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Next Gap Meeting:
• Progress Report
• Preliminary phase & Phase I completed
• Phase II in progress
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4. DISCUSSION
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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
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6. UPDATED PLANNINGNSERC PLANNING (SEPT. 2015 – AUG. 2018)STUDENT AGENDA (JAN. 2015 – DEC. 2017)
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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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7. Discussion/Questions
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7. Discussion/Questions
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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