Low alloy CrMo(V) petrochemical · PDF fileLow alloy CrMo(V) steel plates for petrochemical...

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Low alloy CrMo(V) steel plates for petrochemical reactors 1
LowLow alloyalloy CrMo(V)CrMo(V) steelsteel platesplates forforpetrochemicalpetrochemical reactorsreactors

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1. Introduction
2. Application trends
3. Requirements for CrMo(V) steels
4. Heat treatment - Hollomon parameter
5. General material behaviour and feasibility investigations
6. Long term embrittlement and avoidance strategies
7. The benefits of modern CrMoV steels
8. General recommendations for processing: forming+welding
9. Creep properties
10. Conclusion
Content

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Introduction
conventional CrMo steels: ASTM A387 Gr.11 Cl 1 and 2 or Gr. 22 Cl. 2 or 13CrMo4-5 or 10CrMo9-10 acc. EN 10028 part2
enhanced CrMo steels: quenched and tempered steels with increased mechanical properties, e.g. ASTM A 542A/B 3/4/4a or 12CrMo9-10 acc. EN 10028 part 2
new generation of CrMo steels: Vanadium modified CrMo-steels, e.g. ASTMA542 D4a or 13CrMoV9-10 acc. to EN 10028 part 2.
Wherever high temperatures and/or high hydrogen partial pressures in the processes are required, CrMo steels have been used for more than 50 years. Due to changing process parameters in chemical and petrochemical processes these steel grades have been developed to enhanced properties.

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1Cr Mo ASTM/ASME A/SA 387-12-1/2EN 10028-2: 1992 13CrMo4-5EN 10028-2: 2003 13CrMo4-5
1Cr Mo ASTM/ASME A/SA 387-11-1/2EN 10028-2: 2003 13CrMoSi5-5
2Cr 1Mo ASTM/ASME A/SA 387-22-1/2A/SA 542-A/B-3/4/4a
EN 10028-2: 1992 10CrMo9-1011CrMo9-10
EN 10028-2: 2003 10CrMo9-1012CrMo9-10
2Cr 1Mo V ASTM/ASME A/SA832-22VA/SA 542-D-4/4a
EN 10028-2: 2003 13CrMoV9-10
3Cr 1Mo V ASTM/ASME A/SA832-23VA/SA 542-E-4/4a
EN 10028-2: 2003 12CrMoV12-10
A broad variety of CrMo(V) steels is commercially available

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200
300
400
500
600
700
800
0 50 100 150 200 250
Hydrogen partial pressure [bar]
Tem
pera
ture
[C
]
6%Cr, 0,5%Mo
3%Cr, 0,5%Mo V
2,25%Cr, 1%Mo, V
2,25%Cr, 1%Mo
1,25%Cr, 0,5%Mo1%Cr, 0,5%Mo
Carbon steel
1%Cr, 0,5%Mo
acc. API 941, 1997
Nelson-curves

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Application and trends for the use of CrMo(V) steels
typical applications are hydrotreating reactors
operating temperatures up to 480 C
hydrogen partial pressures up to 180 bar or even more
Trends:
ever bigger and heavier reactors (already more than 1000t per unit)
higher operating temperatures and pressures resulting in higherwall thicknesses
increasing demand due to expansion or new construction of plants

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Developments in different aspects between 2000 and 2008
Example: 2Cr1Mo steels
dramatic increase of deliveries deliveries in thickness over 100mm
were increased even more than the overall deliveries for these grades
deliveries in N+AC+T conditionwere also increased dramatically
market is very tight as demand isfast rising and only few manufac-turers are able to meet the very high quality standards requested

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Factors contributing to more sophisticated steel plates
strong safety requirements for core units designed from CrMo(V) steels increasing thickness with high demand in thickness over 100mm larger dimensions to allow for more freedom in vessel design PWHT requirements including 3 or often even 4 cycles chemical restrictions exceeding those of the standards specifying J- and X-factor for ultra clean steels specifying toughness values at low temperatures in combination with PWHT additional requirements in regard to grain size hardness requirements specifying step cooling test additional tensile test at elevated temperatures ...
Many additional requirements; partly interfering each other

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CrMo-plate delivery dimensions of Dillinger Htte GTS
Maximum thickness is often limited by requirements from specifications
0
25
50
75
100
125
150
175
200
225
250
1.500 1.750 2.000 2.250 2.500 2.750 3.000 3.250 3.500 3.750 4.000 4.250 4.500 4.750 5.000 5.250
N + AC + T( Q + T)
N + T
up to 28 t
up to 37 t
depending on grade & thickness up to 37 t
upon agreement
up to 42 t
up to 37 t
width [mm]
thic
knes
s [m
m]

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Common additional requirements for different CrMo(V) grades
> 100 mm
Ch-V + PWHT
Step CoolingHardness
J- / X-Factor
1Cr Mo1Cr Mo2Cr 1Mo2Cr 1Mo V
100 %
80 %
60 %
40%
20%

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Concept of the Hollomon-Parameter (HP)
The metallurgical effect of tempering and PWHT on the mechanical properties of steel can be combined by the HP-Parameter (T

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Description of a heat treatment cycle by the Hollomon Parameter:
Time [h]
Tem
pera
ture
[C
]
t +
holding
T Holding
Temperature[C]
[HP = T (+ 273) log ( T (+ 273) 2,3 * Kh ( 20 - log Kh )
heating
Kh heating rate
[C/h]
2,3 * Kc ( 20 -log Kc )
T (+ 273) ) + 20 ] * 10 -3
cooling
Kc cooling rate
[C/h]
t Holding time
[h]*
*) holding time starts whenreaching temperatureover the whole cross section
+

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Tempering PWHT HP700C/300Min. 20.15700C/250Min. 670C/180Min. 20.15680C/250Min. 680C/600Min. 20.15680C/60Min. 690C/300Min.+700C/90Min. 20.15680C/60Min. 675C/600Min.+680C/300Min. 20.15
Equivalence of Tempering and PWHT on Hollomon Parameter:

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General influence of heat treatment on mechanical properties
AfterPWHT
Av,
Rm
, Rp0
.2
Hollomon parameter
HB before
HB after
BeforePWHT

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Tensile strength in dependence of HP for CrMo and CrMoV steels
500
600
700
800
900
1000
1100
19,00 19,20 19,40 19,60 19,80 20,00 20,20 20,40 20,60 20,80 21,00 21,20 21,40
Rm
[MPa
]
400
HP
12CrMo 910 acc. EN 10028-2:2003
CrMoV: acc.SA 542-D-4a
2,25CrMoV, t/42,25CrMoV, t/23CrMoV, t/43CrMoV, t/212CrMo 910
HP 20,8: Tempering+705 C/10h
thickness: 200 mmcondition: N+AC+T

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Yield strength for CrMo and CrMoV steels
19,2 19,4 19,6300
400
500
600
700
800
900
1000
19 19,8 20 20,2 20,4 20,6 20,8 21 21,2 21,4HP
Rp0
2[M
Pa]
12CrMo 910 acc. EN10028-2:2003
2CrMoV, t/42 CrMoV, t/23CrMoV, t/43CrMoV, t/212CrMo 910 (2CrMo)
CrMoV acc. SA 542-D-4a
thickness: 200 mmcondition: N+AC+T

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HP
0
50
100
150
200
250
300
350
400
19,00 19,20 19,40 19,60 19,80 20,00 20,20 20,40 20,60 20,80 21,00 21,20 21,40
Cha
rpy-
V-tr
ansv
erse
,A
vm
ean
[J]
2CrMoV, t/4
3CrMoV, t/4
12CrMo 910 (2CrMo)
test temperature: -60C
CH-V-results vs HP compared between CrMo and CrMoV steels
thickness: 200 mmcondition: N+AC+T test location: t/4

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General observations when dealing with transition curves

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SA 387-11-2: Feasibility in dependence of HP, Rm, Re, Ch-V, hardness and plate thickness of 1Cr steel
0 20 40 60 80 100 120 140 160 180 200
plate thickness [mm]

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