Steel Solutions for Pressure Vessels
HIC Resistant Steels for the Most Demanding Pressure
Vessel Applications
Italy Seminar, 19th May 2010
Cédric Chauvy
Table of contents
• Wet hydrogen sulfide issues and definitions
• Wet H2S corrosion of C-Mn steels
• Types of damage in presence of wet H2S
• Evaluation of steels for resistance to Hydrogen Induced Cracking (HIC)
• HIC / SSC / SOHIC test facilities
• Role of metallurgical parameters on C-Mn steels behavior in wet H2S
• Parameters influencing H2S embrittlement
• Influence of cleanliness on HIC, SSC and SOHIC behavior
• Influence of microstructure (segregation, hardness variation, heat
treatment)
• Optimized metallurgical solutions for wet H2S service
• Conclusions
• CarElso® HIC Premium+
Italy Seminar, 19th May 2010
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Wet hydrogen sulfide issues and definitions
• Wet H2S corrosion of C-Mn steels
• Types of damage in presence of wet H2S
• Evaluation of steels for resistance to Hydrogen Induced Cracking (HIC)
• HIC / SSC / SOHIC test facilities
Italy Seminar, 19th May 2010
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Wet H2S corrosion of C-Mn steels
Reactions :
Oxidation:
Fe ⇒ Fe
2+ +
2
Hads
Hads
Hads
Hads
Hads
Habs
Habs
H abs
Habs
Habs
e-
Reduction:
H + + e- ⇒ Hads
Cracking
or/and
H2S + 2 e- ⇒ S2- + 2 Hads
Corrosion rate controlled by :
Hydrogen concentration profile controlled by :
pH,
corrosion rate,
presence of catalysts/inhibitors,
temperature, film formation,
partial pressure of H2S, total pressure,
gas/fluid composition ...
temperature,
material characteristics (diffusion/trapping),
plate thickness ...
Italy Seminar, 19th May 2010
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Types of damage in presence of wet H2S
HIC
SSC
SOHIC
Hydrogen Induced
Cracking
Sulfide Stress
Cracking
Stress Oriented
Hydrogen Induced
Cracking
Related phenomena
. Blistering
. Stepwise Cracking
Also called Sulfide Stress
Corrosion Cracking SSCC
SSC
SOHIC
Planar shaped defects
Parallel to plate surface
Cracks perpendicular
to the main stress
direction
Italy Seminar, 19th May 2010
Cracking aspect
intermediate between
HIC and SSC
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Wet hydrogen sulfide issues and definitions
• Wet H2S corrosion of C-Mn steels
• Types of damage in presence of wet H2S
• Evaluation of steels for resistance to Hydrogen Induced Cracking (HIC)
• HIC / SSC / SOHIC test facilities
Italy Seminar, 19th May 2010
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Hydrogen Induced Cracking (HIC) or
Stepwise Cracking
Manifests along rolling direction (surface blisters and/or internal cracks)
in the absence of an applied stress
Initiation clearly linked to presence of inclusions
Propagation (growth of defects) linked to segregation effects
Italy Seminar, 19th May 2010
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Evaluation of steels for resistance to HIC
HIC testing : NACE TM0284 - 2003 (and EN 10229)
SPECIMEN SAMPLING IN THE PLATE and TEST CONDITIONS
• According to NACE TM0284-2003 solution A:
(sometimes ordered as « TM 0284 (i.e. of 1996) with acidic solution of TM0177 »)
One test per heat on the thinnest plate
One location at one end and mid width of the plate
But extent and number of locations can depend on customer specification:
Example : three locations at one end of each plate (or even both ends !)
Influence on cost and test report delivery
•
Solution B (pH5) : very « soft » testing, not recommended as a test to identify
“true” HIC resistant material
Italy Seminar, 19th May 2010
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Sampling and vocabulary for HIC test
of plates per NACE TM0284-2003
3 section faces to be examined
(x 3 for the three specimens in
this example)
this is
a sample
sometimes called coupon
Principal
Plate Rolling
Direction
this is
a section
100+/-1
20+/-1
T (<30 in this example)
this is
a specimen
T=Thickness
all dimensions in mm
Italy Seminar, 19th May 2010
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Evaluation of steels for resistance to HIC
Number and size of HIC test specimens (NACE TM 0284)
Plate thickness t, mm
Specimen thickness, mm
Number of specimen
t
3
> 30 and ≤ 88
30
3*
> 88 and ≤ 146
30
5*
> 146 and ≤ 204
30
7*
≤ 30
* specimens 30mm thick max shall cover the whole thickness of the plate with minimum 1mm overlap
For plates ≤ 30 mm thick
For plates 30 – 88 mm thick
Italy Seminar, 19th May 2010
For plates over 88 mm
thick up to 146 mm
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Evaluation of steels for resistance to HIC
HIC test results measurements
W
Test duration :
T
b
- Preparation +
- Exposure 96h = 4 days +
- Cutting +
- Polishing +
- Metallographic examination +
- Reporting
a
CSR : Crack Sensivity Ratio :
CSR =
CLR : Crack Length Ratio :
CLR =
Σ(a x b)
(W x T)
Σa
W
CTR : Crack Thickness Ratio :
CTR =
Σb
T
X
100 %
X
100 %
X
100 %
Italy Seminar, 19th May 2010
depends on the number of tests
in progress (limited availability
of test vessels) but up to about
3 weeks in worst case.
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Evaluation of steels for resistance to HIC
Levels of quality for steel plates
(averages of sample test results)
CLR, %
CTR, %
CSR, %
HIC level 1
(pressure vessel)
5
1,5
0,5
HIC level 2
("in between")
10
3
1
HIC level 3
(usual for pipes)
15
5
1,5
"HIC" level 4
CLR value is superior to 15% - NO HIC QUALITY
Italy Seminar, 19th May 2010
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Wet hydrogen sulfide issues and definitions
• Wet H2S corrosion of C-Mn steels
• Types of damage in presence of wet H2S
• Evaluation of steels for resistance to Hydrogen Induced Cracking (HIC)
• HIC / SSC / SOHIC test facilities
Italy Seminar, 19th May 2010
13
HIC / SSC / SOHIC test facilities
One of the test labs,
with SSC testing equipment
H2S
Trap
Trap
Test
Solution
Specimen
10%
NaOH
Solution
schematic diagram of typical
HIC/SOHIC test assembly
Italy Seminar, 19th May 2010
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Role of metallurgical parameters on C-Mn
steels behavior in wet H2S
• Parameters influencing H2S embrittlement
• Influence of cleanliness on HIC, SSC and SOHIC behavior
• Influence of microstructure (segregations, hardness variation, heat
treatment)
Italy Seminar, 19th May 2010
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Specification requirements for wet H2S service
SSC / HIC / SOHIC resistance
(very) Low carbon equivalent number CeqIIW
Ceq= C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
(high) PWHT temperature and (long) holding time
Charpy V impact properties at (very) low temperature
All these requirements are not always compatible, and the possible
difficulties increase as the plate thickness increases.
Italy Seminar, 19th May 2010
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Parameters influencing H2S embrittlement
CH > CK → CRACKING IN CARBON STEELS
CH – amount of hydrogen
CK – critical hydrogen concentration for cracking
Parameters
Influence on
Environmental
Partial pressure of H2S, total pressure of system
CH
pH of the solution
CH
Solution composition
CH
CH, CK
Temperature
Time
CH
Mechanical
Residual stress
CK
Applied stress
CK
Stress concentration / local plasticity
CK
Metallurgical
Inclusion content
CH, CK
Microstructure:
Segregation
Hardness variation (HAZ)
CH, CK
Italy Seminar, 19th May 2010
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Influence of cleanliness
Reduction of potential sites for crack initiation
Improvement of the cleanliness through
•
•
Reduction of sulfur content (S << 20ppm)
Reduction of oxygen content (O < 15ppm)
With such improvements
•
Only few inclusions remain and
No calcium treatment is necessary for inclusion shape control
Ca/S ratio not relevant for very low S production
Italy Seminar, 19th May 2010
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Influence of cleanliness
Reduction of the size and number of potential sites for crack
initiation (defects in the structure, non-metallic inclusions)
Influence of S content and calcium
treatment on the sulfide inclusions shape
Italy Seminar, 19th May 2010
Correlation between HIC
behavior and S content
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Influence of microstructure
Reduction of risk of crack propagation
Ceq = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
Ceq elements segregate during solidification
Ceq as low as possible
(but a minimum level is
necessary to guarantee
the required minimum tensile
mechanical properties !)
Influence of C content on
segregation ratio of Mn
Italy Seminar, 19th May 2010
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Influence of microstructure
Reduction of P content : P has a very high segregation rate
and strongly increase the cracking sensitivity
HIC test specimen microprobe
profiles of P segregation
Influence of C and Mn
contents on P segregation
Influence of P Content on HIC level
4
30
Cracked
20
10
0
P content (10-3%)
0
50
100
150
200
250
profile (microns)
300
350
400
30
Average CLR value, %
P content (10-3%)
40
3
2
1
0
20
GUARANTEE
LEVEL
Uncracked
10
<6
[6;7[
[7;8[
[8;9[
>9
P 10-3 weight, %
0
0
50
100
150
200
250
profile (microns)
300
350
400
aim P < 0.008%
(average < 0.006%)
Italy Seminar, 19th May 2010
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Influence of microstructure
Solutions to achieve 248HV10 in HAZ :
- Post Weld Heat Treatment (strong effect of steel grade on PWHT behavior!)
microalloying with Nb (or V) to improve the tensile properties will increase HAZ hardness after
PWHT High PWHT temperature necessary, possibly leading to low charpy impact values !
Influence of PWHT conditions on HAZ maximum
hardness of (good) A516 grade 70 steel
Influence of PWHT conditions on HAZ maximum
hardness of BS 1501-225 (alloyed with Nb)
340
0,99kJ/mm
1,98kJ/mm
2,78kJ/mm
Max allowed HV
300
260
248HV
220
180
380
HAZ max hardness (HV5)
HAZ max hardness (HV5)
380
340
1,35kJ/mm
1,85kJ/mm
2,7kJ/mm
Max allowed HV
300
260
248HV
220
180
As welded
600°C/3h
625°C/3h
PWHT conditions
650°C/3h
As welded
600°C/3h
625°C/3h
PWHT conditions
650°C/3h
It is better to obtain the 248HV10 hardness level by using a non micro-alloyed steel with a lower PWHT
temperature ; e.g. it is possible to meet the required tensile and impact properties of A516 grade70,
with a Ceq of 0.43 and a PWHT at 600°°C
Italy Seminar, 19th May 2010
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Optimized metallurgical solutions for
wet H2S service
Italy Seminar, 19th May 2010
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Optimized solutions for wet H2S service
Very clean high quality C-Mn steel grades CarElso® according to ASTM
A516 standard specification (and others)
Guarantee of :
•
Chemical composition according to ASTM A516
•
Cleanliness (S << 20ppm; O < 15ppm; P < 0,007%)
•
Very low inclusion content
•
No microalloying elements (V, Nb)
•
Weldability
•
Perfectly balanced low Ceq (0,38 to 0,45)
Thickness, mm
Ceq maximal value
0.41
< 100
Grade 65 HIC
Grade 70 SOHIC
100 - 200
Grade 60 HIC
0.43
0.45
Grade 70 HIC
Grade 65 HIC
Grade 70 SOHIC
Italy Seminar, 19th May 2010
Grade 70 HIC
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HIC tests results statistics
• Premium level of HIC quality (average CLR < 5%)
Statistic HIC test results for A516 C-Mn ingot and continuous cast steel plates
80,0
70,0
% of values
60,0
Results on 1048 plates with
gage from 5 to 276mm
50,0
40,0
30,0
20,0
10,0
0,0
0
]0;1]
]1;2]
CLR max per specimen
]2;3]
]3;4]
CLR range
]4;5]
]5;7]
Italy Seminar, 19th May 2010
Average CLR values
]7;10]
>10
25
HIC tests results statistics
• Premium level of HIC quality (average CLR < 5%)
Statistic average CLR HIC test results' values for A516 C-Mn
ingot and continuous cast steel plates
90,0
80,0
70,0
Results on 1048 plates with
gage from 5 to 276mm
% of values
60,0
50,0
40,0
30,0
20,0
10,0
0,0
0
]0;1]
]1;2]
]2;3]
A516 Grade 60 - 412 plates
A516 Grade 65 - 140 plates
]3;4]
CLR range
]4;5]
]5;7]
A516 Grade 70 - 496 plates
]7;10]
Italy Seminar, 19th May 2010
>10
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SSC tests results statistics
Statistic SSC test results for A516 C-Mn ingot cast steel plates
with thickness range from 60 to 177mm
% of values
100,00
92,13
80,00
Results on 127 plates
60,00
With applied stress for SSC test
at least equal to 80% of SMYS
40,00
20,00
0,00
7,87
A516 grades 60 and 70
No failure in 720h
Failure before 720h
Italy Seminar, 19th May 2010
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SSC tests results statistics
Statistic SSC test results for A516 C-Mn ingot cast steel plates
with thickness range from 60 to 177mm
95,92
100,00
% of values
80,00
Results on 127 plates
With applied stress for SSC test
at least equal to 80% of SMYS
79,31
Grades 60 and 70 – better SSC
performance of Grade 70
60,00
40,00
20,00
20,69
4,08
A516 Grade 70
0,00
A516 Grade 60
No failure in 720h
Failure before 720h
Italy Seminar, 19th May 2010
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Conclusions
Italy Seminar, 19th May 2010
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Conclusions : steel specification
• For better resistance of pressure vessels to the embrittlement
phenomena such as HIC, SSC and SOHIC in wet H2S, a lot of
metallurgical parameters must be taken into account by the steelmaker.
• The real improvement of H2S resistance of C-Mn steels can be
provided by :
Improvement of the cleanliness
(S << 20ppm; O < 15ppm; P < 0,007%)
Improvement of the steel chemical composition homogeneity
(reduction of segregations) and steel microstructure (proper PWHT
in order to avoid any hard structures and keep the hardness below
248HV)
Italy Seminar, 19th May 2010
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Conclusions : steel specification
• Ceq 0.38 to 0.43 max depending on thickness and grade (very thick
plates may go up to 0.45)
• HIC 1 (CLR max 5%) guarantee
• PWHT at 600°C to 610°C nominal (needed for HIC resistance)
• SSC resistance guarantee (max 248Hv in HAZ after PWHT)
• SOHIC resistance only available through NACT (i.e. QT) in higher
strength grade, with lower Ceq
Italy Seminar, 19th May 2010
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CarElso® HIC Premium +
Italy Seminar, 19th May 2010
32
The core of the offer
typical competition
typical Industeel
In the past...
"We meet the spec
but
you have to wait"
" The material is there
but
we don't meet the spec "
Industeel CarElso® HIC Premium+
The new deal...
"We meet the spec
AND
the material is there"
there
Italy Seminar, 19th May 2010
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CarElso® HIC Premium +
• HIC test after PWHT (properties guaranteed up to max 3 cycles)
CAUTION! H2S service resistance guaranteed ONLY in stress relieved condition
provided with tempering or PWHT
(HIC, SSC guaranteed, but NOT SOHIC which needs NACT / QT)
• Compatibility with most demanding specs like
Axens IN-43, EEMUA179, ENI CAL501S, Petrobras N-1706,
Saudi Aramco 01-SAMSS-016, SHELL MESC74/125,
SHELL DEP31.22.10.32, etc...
Material able to pass HIC re-test using dummy samples and several sampling locations
(after PWHT), UT quality compatible with EN 10160 S2E2, HIC and other properties
guaranteed by Industeel on full lots covered by the certification
Italy Seminar, 19th May 2010
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CarElso® HIC Premium +
• Certificate 3.2 as per EN 10204 :
– Industeel CarElso HIC Premium+ ASTM/ASME A/SA 516 grade
60/65/70 – triple separate certificates
– third party is an internationally recognised body like Lloyd's, Bureau
Veritas, DNV, etc...
• EAF steel making route, fully killed, vacuum degassed, fine grain
practice
• According to MR0175/ISO15156-2 and MR0103
(hardness <22HRC / 248HV10)
• Chemistry
– max Ceq 0.41% up to 50mm, 0.43% above
– max S .001%; P .008%; Nb .015%; V.005%; O .002%
Italy Seminar, 19th May 2010
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CarElso® HIC Premium +
• Mechanical test after 1 cycle of PWHT 610°C 2min/mm (guarantee up
to three cycles) – minimum 1h
– ambient tensile properties : as per standard
– Charpy impact test longitudinal and transverse direction
• at -51°C for thickness<=25 mm (20J average/16J mini)
• at -46°C for thickness>25 mm (41J average/34J mini);
• E1268 microexamination (banding index):
on each plate that is HIC tested
• Ultrasonic Testing as per SA 578 level C with max acceptable defect
area reduced to 100mm2 and scanning along 75mm parallel paths
Italy Seminar, 19th May 2010
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CarElso® HIC Premium +
• normalized 920°C
• thickness 8mm to 105mm (all positive tolerance)
6mm possible on request
• width up to 4000mm
• length up to 14000mm
• surface shotblasted to SA2.5
• low-stress die stamping 2 locations:
head and foot of plate
• identification paint marking one end + eventual shipping marks
• continuous brand marked 2 long edges :
INDUSTEEL CARELSO HIC PREMIUM+
• generalities as per ASME SA20
Italy Seminar, 19th May 2010
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