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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7

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

9

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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