By Samaneh Alibeigi Supervisor Dr. J.R. McDermid September 25, 2012 Short-Term Formation Kinetics of the Continuous Galvanizing Inhibition Layer on Mn-Containing Steels Seminar MATLS 702
By
Samaneh Alibeigi
Supervisor
Dr. J.R. McDermid
September 25, 2012
Short-Term Formation Kinetics of the
Continuous Galvanizing Inhibition Layer
on Mn-Containing Steels
Seminar MATLS 702
Zinc coating
steelInterfacial Layer
Steel
steel
Zn
Fe
Al
Al
Zn
Zn
ZnAlFe
Zinc Pot (Zn - Al)
Al Zn
Fe-Al interfacial layer
Galvanizing and Inhibition Layer
2
Zinc Coating
Interfacial Layer of Fe-Al Intermetallic Phase(s)
Minor Addition (0.16-0.20 wt%) of
Aluminum to the Zinc Bath
No Fe-Zn Intermetallic Compounds
Ductile and Adhesive Coating
Continuous Hot-Dip Galvanizing
Schematic of continuous hot-dip galvanizing process. [E.A. Silva (2007)]
Zinc Pot(Dipping)
Furnace(Annealing)
3
[Fin
e et
al.
, 1
97
9, K
ubas
chew
ski
et a
l., 1
97
7]
Mn Selective Oxidation
The presence of Mn is essential for obtaining the desired mechanical
properties, but leads to the formation of surface MnO during annealing.
4
Change in MnO layer thickness vs. reaction time.
( ) 2 3 ( )3 2 3Bath BathMnO Al Al O Mn
Aluminothermic Reduction
0 2 4 6 8 10 12 14 16 18 20 22
-250
-200
-150
-100
-50
t M
nO
(nm
)
reaction time (s)
5
initial finalΔt(MnO) t (MnO) t (MnO)
* R. Khondker et al., Mater.ials Science & Engineering A, 463 (2007) 157** R. Kavitha and J. McDermid, Surface & Coatings Technology (Accepted)
Al2O3
Research Objectives
The objectives of the present research were to investigate the
interfacial layer formation as a function of bath Al content,
substrate Mn content and reaction time (i.e. sum of dipping time
and solidification time), including the effect of the MnO layer arising
from the selective oxidation.
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Compositions of Experimental Steels (wt.%)
Alloy Name C Mn Mo Si Nb Al
0.2Mn 0.047 0.20 0.004 0.012 0.004 0.035
1.4Mn 0.066 1.40 0.003 0.085 0.071 0.036
2.5Mn 0.068 2.47 0.110 0.037 0.020 0.003
3.0Mn 0.077 2.98 0.086 0.028 0.022 0.005
Alloy
Name
PAT
[ C]
N2
[vol.%]
H2
[vol.%]
Dew
Point
[ºC]
pO2
[atm]
0.2Mn 840 95 5 -30 3.39E-22
1.4Mn 770 95 5 -30 9.22E-24
2.5Mn 724 95 5 -30 6.59E-25
3.0Mn 704 95 5 -30 1.94E-25
Bath Temperature
[ºC]460
Bath Dissolved Al
Content [wt%]0.2, 0.3
Dipping Time [s]0.5/0.7/1/1.5/
2/2.5/4/6
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Annealing ParametersDipping Parameters
Schematic Figure of Steel Panel Dimensions and Spot Cooler Position
Quench
Spot
200
mm
120 mm
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A helium jet spot cooler with a flow rate of 500L/min was used to rapidly solidify the zinc coating and arrest the interfacial reaction.
The actual reaction time was
calculated by summing the dipping
and solidification times.
Experimental Apparatus
McMaster Galvanizing Simulator
Infrared Furnace
Zinc Pot
Load steel panel / Cooling
Helium jet spot cooler
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XPS Depth Profiles of Annealed Samples
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Measured Binding Energy (eV)
State (Compound)Fe 2p/2 Mn 2p3/2 Mn 2p1/2 O 1s
706.6 641.6 653.4 530.4 MnO, Fe (metallic)
[Franzen et al., J. Solid State Chem., 18 (1976) 363.] [Foord et al., Philos. Mag. A, 49 (1984) 657.]
AES Mapping of Steels Surfaces Prior to Dipping
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1.4Mn
2.5Mn
3.0Mn
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Steel
Zinc Coating Fe-Al Inhibition
Layer
ICP
Image Analysis
ICP Analysis- Al Uptake of the Interfacial Layer
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4s reaction time
7s reaction time
2s reaction time
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ICP Analysis- Al Uptake of the Interfacial Layer
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SEM Analysis of Interfacial Layer
0.2Al
0.3Al
2.1s 7.6s
2.1s 7.6s
0.2Mn Steel
1µm 1µm
1µm 1µm18
SEM Analysis of Interfacial Layer
0.2Al
0.3Al
2.2s 7.7s
2.2s 7.7s
2.5Mn Steel
1µm 1µm
1µm 1µm19
Summary
Significant Mn segregation to the surface in the form of MnO during annealing
was observed for the 1.4–3.0 wt.%Mn steels. Mn enrichment occurred
primarily along the grain boundaries and adjacent areas. In addition, oxide
nodules with areas of metallic iron between them were observed.
The Al uptake increased with increasing reaction time for all experimental
steels. However, for 0.3Al bath, a significant increase in Al uptake was
observed for 2.5Mn and 3.0Mn steels at higher reaction times that can be
explained by aluminothermic reduction and defective-microstructure
subsurface (due to the formation of MnO).
Finer and more compact interfacial layer morphology was observed for 0.3Al
bath due to the higher nucleation rate at higher Al bath content. This, also,
can explain the lower Al uptake for 0.2Mn and 1.4Mn steels at 0.3Al bath.
20S. Alibeigi, R. Kavitha, R.J. Meguerian and J.R. McDermid, “Investigation of
Reactive Wetting of High Mn Steels during Continuous Hot Dip Galvanizing,”Acta Materialia, 59 (2011) 3537 – 3549.
Acknowledgments
Supervisory Committee Member: Dr. Joe McDermid, Dr. Ken Coley, Dr. Joey Kish
John Thomson, Mariana Budiman, Ray Fullerton, Chris Butcher, Dr. Steve Koprich,
John Rodda, Doug Culley, Fred Pearson, Julia Huang, Mark MacKenzie
U.S. Steel Canada, Xstrata Zinc, the Natural Science and Engineering Research
Council of Canada (NSERC) and the members of the McMaster Steel Research Centre
for their financial support
USSC for provision of experimental materials (IF and CMn) and the AUAF program
of MTL-CANMET for fabrication of the two high Mn steels.
Li Sun (ArcelorMittal Dofasco) for the XPS analysis
Shihong Xu (ACSES, University of Alberta) for the Auger analysis
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