Understanding hydrogen redistribution and designing a new hydrogen extraction method

Introduction
The Model
Application to real processes
Conclusion
Understanding hydrogen redistribution and
designing a new hydrogen extraction method
Daniel Gaude-Fugarolas, Ph.D, FCPS (dgaude@cantab.net)
dgaude Prime Innovation SLU
Independent Research in Physical Metallurgy and Engineering
3rd UK-China Steel Research Forum
Rutherford Appleton Laboratory (UK)
10-11 July 2014
Daniel Gaude-Fugarolas, Ph.D, FCPS (dgaude@cantab.net) Understanding hydrogen redistribution and its extraction

Introduction
The Model
Conclusion
1 Introduction
2 The Model
3 Application to real processes
Analysis of Casting (or any cooling process)
Development of a new hydrogen extraction method
Analysis of Baking
Future work
4 Conclusion

Introduction
The Model
Conclusion
Embrittlement prevention methods
At the design stage (material & component
engineering)
Extraction from liquid metal during refining
(Vacuum, AOD, et c.)
Extraction from solid at high temperature (very
slow cooling & directional cooling:
METAL2010, HSLA2011, Euromat2011, Steel &
Hydrogen2014, et c. )
Extraction by treating after cooling (Baking
treatment: METAL2014)

Introduction
The Model
Conclusion
Embrittlement prevention methods
At the design stage (material & component
engineering)
Extraction from liquid metal during refining
(Vacuum, AOD, et c.)
Extraction from solid at high temperature (very
slow cooling & directional cooling:
METAL2010, HSLA2011, Euromat2011, Steel &
Hydrogen2014, et c. )
Extraction by treating after cooling (Baking
treatment: METAL2014)
Can we still do anything else to reduce the incidence
of hydrogen embrittlement in metals?

Introduction
The Model
Conclusion
The Model
Let’s start at the beginning:
Let’s try and understand the redistribution of
interstitial elements

Introduction
The Model
Conclusion
The Model
Let’s start at the beginning:
Let’s try and understand the redistribution of
interstitial elements
An interstitial diffusion model

Introduction
The Model
Conclusion
Interstitial diffusion: Hydrogen

Introduction
The Model
Conclusion
Model: Diffusion
Characteristics of the model:
(METAL2010-2014, HSLA2011, EUROMAT2011, Steel& Hydrogen2014, et c.)

Introduction
The Model
Conclusion
Model: Diffusion
Thermal evolution and T gradients (Heat Equation)

Introduction
The Model
Conclusion
Model: Diffusion
Phase transitions from Liquid to BCC (Thermodynamic Model)

Introduction
The Model
Conclusion
Model: Diffusion
(METAL2010-2014, HSLA2011, EUROMAT2011, Steel Hydrogen2014, et c.)
Hydrogen diffusion as random walk, driven by chemical activation
gradient

Introduction
The Model
Conclusion
Model: Diffusion
gradient (... think of it as following a partial saturation gradient)

Introduction
The Model
Conclusion
Model: Diffusion
gradient (... think of it as following a partial saturation gradient)
Interstitial solubility and saturation as function of temperature and
matrix phase or trap type and distribution

Introduction
The Model
Conclusion
Model: Trapping
Each trap type characterised
by its characteristic release
energy barrier
Interaction of each of the
trap sites with lattice
Exchange with atmosphere
at free surfaces: local
equilibrium across the
surface (Sievert’s law)
E
Et
d
Trap_1 .. Trap_i .. Trap_n

Atmosphere
Lattice

Introduction
The Model
Conclusion
Analysis of Baking
Future work
What can we do with this model? (Very briefly)
Development of new H extraction method
Analysis of Baking
... and much more!!

Introduction
The Model
Conclusion
Analysis of Baking
Future work
6
5
4
3
2
1
0
Fast cooling Slow cooling
-------------center piece--------
-12.5 -5 0 5 12.5
2
1
0
H content /ppm
Thickness /cm
0s
30s
150s
600s
1200s
1700s
45
40
35
30
25
20
15
0h
1h
10
6h
5
24h
42h 0
-----------center piece-----------
-12.5 -5 0 5 12.5
15
10
5
0
H partial saturation
Thickness /cm
0s
600s
900s
1200s
1500s
1700s
0h
1h
6h
24h
42h
Steel: 25cm thick with 2ppm
Effect of cooling rate:
Fast cooling vs. Slow cooling

Introduction
The Model
Conclusion
Analysis of Baking
Future work
6
5
4
3
2
1
0
-------------center piece--------
-12.5 -5 0 5 12.5
2
1
0
H content /ppm
Thickness /cm
0s
30s
150s
600s
1200s
1700s
45
40
35
30
25
20
15
0h
1h
10
6h
5
24h
42h 0
-----------center piece-----------
-12.5 -5 0 5 12.5
15
10
5
0
Thickness /cm
0s
600s
900s
1200s
1500s
1700s
0h
1h
6h
24h
42h
Effect of cooling rate:
Fast cooling vs. Slow cooling
Effect of thickness: (5-50cm)
Effect of FCC to BCC transformation
temperature:
Steel A: 700oC vs. Steel B: 450oC
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
5 10 20 30 40 50
Max H content /ppm
Thickness /cm
Alloy A
Alloy B
Start H

Introduction
The Model
Conclusion
Analysis of Baking
Future work
“Understanding hydrogen redistribution during steel casting, and its effective extraction by
thermally induced up-hill diffusion”
D. Gaude-Fugarolas, in: Journal of Iron and Steel Research International 18 supl.1.1 (2011)
159–163.
Also at proceedings: High Strength Low Alloy (HSLA2011) International Conference, Beijing,
China, 2011.

Introduction
The Model
Conclusion
Analysis of Baking
Future work
A severe temperature gradient forces hydrogen to flow towards the core
region of a component, where it can reach severe supersaturation

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Actually, NO!!. The temperature gradient forces hydrogen to flow
towards higher temperature regions!!

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Actually, NO!!. The temperature gradient forces hydrogen to flow
towards higher temperature regions!!
Then, why don’t we try instead to redirect the hydrogen flux
towards the surface?
(and eventually get rid of it)

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Standard casting operation: Interstitial
element flux creates enriched regions at
the core of the piece
Pouring cup
Feeder
Casting
Riser

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Standard casting operation: Interstitial
element flux creates enriched regions at
the core of the piece
Pouring cup
Feeder
Casting
Riser
Modified casting operation with a severe
thermal gradient towards the surface
being imposed, eliminating interstitials
Pouring cup
Feeder
Casting
Riser
Heating Element

Introduction
The Model
Conclusion
Analysis of Baking
Future work
5
4
3
2
1
0
-12.5 -5 0 5 12.5
H content /ppm
Thickness /cm
Heated Surface
10
1
0s
60s
0.1
300s
1200s
3600s
8400s 0.01
-12.5 -5 0 5 12.5
Thickness /cm
Heated Surface
0s
60s
300s
1200s
3600s
7200s
7600s
8000s
8400s
Surface I: Fast cooling
Surface II: Kept at high temperature
(i.e. 1500oC)
Temperature gradient maintained 2h

Introduction
The Model
Conclusion
Analysis of Baking
Future work
5
4
3
2
1
0
-12.5 -5 0 5 12.5
H content /ppm
Thickness /cm
Heated Surface
10
1
0s
60s
0.1
300s
1200s
3600s
8400s 0.01
-12.5 -5 0 5 12.5
Thickness /cm
Heated Surface
0s
60s
300s
1200s
3600s
7200s
7600s
8000s
8400s
Surface I: Fast cooling
Surface II: Kept at high temperature
(i.e. 1500oC)
Temperature gradient maintained 2h
Final H content 0.99ppm!!
i.e 50% Reduction!!
Partial Saturation during
treatment below 1.0 !!

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Analysis of Baking
Analysis of Baking
“On the effectiveness of baking as hydrogen embrittlement reduction treatment”
D. Gaude-Fugarolas, in: Proceedings of METAL2014, 21-23 May, Brno, Czech Republic, 2014.

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Treatment after cooling: Baking
Storage of the metal components in over at low warm
temperature (typically 150-230 oC) for a long period,
up to 24-48 hours.
The treatment aims to reduce internal stresses and to
reduce hydrogen content.
If treatment is not performed immediately after
casting and cooling, it might become ineffective.
Effectiveness of treatment varies.
Why does effectiveness of baking vary so much?

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Analysis of Baking
Hydrogen content: 1 ppm
Baking: 12h at 190oC or 300oC
Sites: Lattice, Dislocation, Grain boundary,
Precipitate ( Desorption to atmosphere)
Steel A: Allotriomorphic Ferrite (725oC), large
grain, low dislocation density
Steel B: Bainitic/Martensitic Ferrite (450oC),
small grain, high dislocation density

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Analysis of Baking
Hydrogen content: 1 ppm
Baking: 12h at 190oC or 300oC
Sites: Lattice, Dislocation, Grain boundary,
Precipitate ( Desorption to atmosphere)
Steel A: Allotriomorphic Ferrite (725oC), large
grain, low dislocation density
Steel B: Bainitic/Martensitic Ferrite (450oC),
small grain, high dislocation density
LATTICE Steel A
0.625
0.125
0.025
0.005
0.001
0 6 h 12 h
H conc /ppm
Time /s
(a0)
0.625
0.125
0.025
0.005
0.001
Steel B
0 6 h 12 h
H conc /ppm
Time /s
(b0)
0.625
0.125
0.025
0.005
0.001
0 6 h 12 h
H conc /ppm
Time /s
(a1)
DISLOCATION
0.625
0.125
0.025
0.005
0.001
0 6 h 12 h
H conc /ppm
Time /s
(b1)
GRAIN Steel A
0.1000
0.0100
0.0010
0.0001
0.0000
0 6 h 12 h
H conc /ppm
Time /s
(a2)
0.1000
0.0100
0.0010
0.0001
0.0000
Steel B
0 6 h 12 h
H conc /ppm
Time /s
(b2)
0.55
0.50
0.45
0.40
0.35
0 6 h 12 h
H conc /ppm
Time /s
(a3)
PRECIPITATE
0.55
0.50
0.45
0.40
0.35
0 6 h 12 h
H conc /ppm
Time /s
(b3)
“On the effectiveness of baking as hydrogen embrittlement reduction treatment”
D. Gaude-Fugarolas, in: Proceedings of METAL2014, 21-23 May, Brno, Czech Republic, 2014.

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Conclusions on Baking
The success of baking depends of the interaction of hydrogen
content, microstructure and trap distribution.
Some microstructures already saturate with low hydrogen contents,
making baking useless.
In general, baking is only effective when the microstructure is far
below saturation.
The baking temperature needs to be tailored to trap type and H
distribution.
Some defects may even increase their H content during baking.

Introduction
The Model
Conclusion
Analysis of Baking
Future work
Future work
This is still work in progress...
Surface defects
Crack initiation
H absorption from atmosphere
To be presented at, may be, METAL2015, Brno, Czech Republic, May 2015.

Introduction
The Model
Conclusion
Conclusion
Conclusion

Introduction
The Model
Conclusion
Conclusion
To summarise...
Small amounts of hydrogen can endanger the integrity of critical
metal components.
A physical model has been presented offering a correct description of
hydrogen redistribution during manufacturing operations.
Several methods exist to reduce hydrogen embrittlement in metal,
but not always successful.
A new method has been presented to reduce hydrogen content using
of imposed temperature gradients.
(Patent filed in US, Europe, China, et c., Already awarded or in
process, and open for licensing).

Introduction
The Model
Conclusion
Thanks
Thank you for your attention!!
For more information, please visit (or email):
primeinnovation.net
dgaude@cantab.net

Understanding hydrogen redistribution and designing a new hydrogen extraction method

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (19)

Similar to Understanding hydrogen redistribution and designing a new hydrogen extraction method

Similar to Understanding hydrogen redistribution and designing a new hydrogen extraction method (20)

Recently uploaded

Recently uploaded (20)

Understanding hydrogen redistribution and designing a new hydrogen extraction method