 |
|
| |
Chemical
Composition (mass %) |
C |
Si |
Mn |
Cu |
Ni |
Cr |
Mo |
Ti |
W |
Fe |
SM-2242 |
0.05 |
0.50 |
1.00 |
1.50~3.00 |
38.0
~46.0 |
19.5
~24.0 |
2.50
~4.00 |
1.20 |
— |
|
SM-2535 |
0.03 |
0.50 |
1.00 |
1.50 |
29.5
~36.5 |
23.0
~27.0 |
2.50
~4.00 |
— |
— |
— |
SM-2035 |
0.03 |
0.75 |
1.00 |
0.07 |
33.0
~38.0 |
20.5
~23.5 |
4.00
~5.00 |
— |
0.20
~0.80 |
— |
SM-2550 |
0.03 |
1.00 |
1.00 |
1.20 |
47.0
~54.0 |
23.0
~26.0 |
6.00
~9.00 |
0.69 |
3.0 |
— |
SM-2050 |
0.03 |
0.50 |
1.00 |
2.00 |
49.0
~53.0 |
19.0
~23.0 |
10.1
~12.0 |
— |
1.50 |
— |
SM-C276 |
0.01 |
0.08 |
1.00 |
Co
2.5 |
Bal |
14.5
~16.5 |
15.0
~17.0 |
V
0.35 |
3.0
~4.5 |
4.0
~7.0 |
H2S+CO2+CI - CORROSION
(NI BASE ALLOYS)
High Alloy Materials
become necessary where severe well conditions
with high concentrations of H2S, CO2
and CI- brines are encountered.
|
|
(1) |
High Ni corrosion resistant alloys
for OCTG feature a single austenitic phase. Strength
is developed through cold working.
Addition of essential alloying elements such as Cr, Ni, Mo determines the corrosion
resistance properties. |
(3) |
The effect of fundamental elements
on corrosion behaviors are shown in the following
Figures.
These can be recapped as follows.
• Application limit temperature is strongly
depending on Mo content in the Ni Base Alloys.
• In combined H2S,
CO2, Cl-
media, the basic minimal chemistry of Cr
 18%,
Ni 28%,
Mo 3%
is required.
•
Hydrogen embrittlement susceptibility increases
with material chemistries exceeding 60% Ni. |
(2) |
Resistance to general (weight loss) corrosion
and localized (pitting and crevice) corrosion
is achieved by the formation of a stable passivation
film on the material surface. |
(4) |
Elemental S is very
aggressive to SSC. SM-2050 and SM-C276 is applicable
depending on environmental temperature. |
|
|
|
Corrosion resistant region of Fe-Cr-Ni-Mo
alloy(20% NaCl+0.5%
CH3COOH, 1.0 MPa H2S-1.OMPa
CO2-pH
2) |
|
Without
CH3COOH (pH:High) |
 |
Effect
of Mo and temperature on SSC resistance
(C ring test, 20%NaCI, 1MPa H2S +1 MPa CO2, 100% YS) |
|
With 0.5%CH3COOH (pH:Low) |
 |
Effect of
Mo and temperature on SSC resistance
(C ring test, 20%NaCI, 1MPa H2S
+1 MPa CO2,
100% YS) |
|
|
The relationship
between testing temperature and Mo content
of Ni-base alloys in an S-containing sour
environment.
[25%NaCI + 1g/1S, 1.0MPaH2S +
1.0MPaCO2 Applied Stress; 110
ksi, 336h] |
|
|
| Corrosion
resistant region —pH—alloying
element |
| |
(1) |
Corrosion resistance pH2
; No SCC and C.R. <0.05 mm/y, |
| |
(2) |
Environment, SCC : 20%
NaCI + 0.5% CH3COOH—1.0
MPa H2S—1.0
MPa CO2—250°C,
HE : NACE TM01-77 solution, Iron coupling/400°C
x 1,000h aging) |
 |
Relationship between testing temperature
and Mo content of Ni Base Alloys in H2S-CL-environment
in the SSRT tests.
(SSRT test condition ; 25% NaCI-0.5% CH3COOH, 7 atm H2S, E=4.0 x 10-6S-1) |
|
|
|
|
©
2006 Sumitomo Metals - Tubular Division. All rights
reserved.
|
Website
by National Webworks
|
 |
|
|
