Alloy Steel Used in Power Plant &

Precautions during its Welding

By
Prashant Kumar
Sr.Manager,QA
Objective Of the Session

1.Familiarisation with Alloy Steels Components used

in Power Plant
2.Precautions during Alloy Steel Welding
 ALLOY STEELS
Steels that derive their properties primarily from the presence
of some alloying element other than C & the commonly
accepted amounts of Mn, Cu, Si, S & P are called ALLOYS or
ALLOY STEELS.

The principal alloying elements are nickel, chromium,

manganese, molybdenum, vanadium, silicon and cobalt.

Low Alloy steels: Alloy content less than 5%

High Alloy steels: Alloy content more than 5%

 REASONS FOR CHOOSING
ALLOYING ELEMENTS
• Increased Hardenability.
• Reduced danger of warpage
• Improved strength at high & low
temperature
• Resistance to grains growth at elevated
temperature
• Improved corrosion and heat resistance
 REASONS FOR CHOOSING
ALLOYING ELEMENTS
• Improved magnetic properties
• Improved fatigue resistance
• Improved machine-ability
• Improved Creep properties at high temp.
• Full value of Alloy steels can be gained
through heat treated conditions
 HARDENABILITY
• The depth up to which a material is
hardened after putting through a heat
treatment process is known as
Hardenability.
• It is easier to harden alloy steels than plain
carbon steel
• Because of this ease of hardening and
greater uniformity in any heat-treatment
operation, alloy steels are often selected
for a job in presence to the plain carbon
steel.
 Alloy Steels Service Temperature Application

Grade Application
C Cr Mo V Nb W Structure
P/ T Range [°C]

11 0,1 1,25 0,5 B 520

22 0,1 2,25 1,0 B 550

23 0,1 2,5 0,3 0,3 0,08 1,75 B 600

24 0,1 2,5 1,0 0,3 0,1(Ti) - B 600

91 0,1 9,0 1,0 0,2 0,1 - TM 650

92 0,1 9,0 0,5 0,2 0,09 2,0 TM 650

TM = Tempered Martensite
B = Bainite
DEVELOPMENT OF 9-12% Cr STEELS

IMPORTANCE OF
MICROSTRUCTURAL
STUDY

KEY
QUESTIONS
TO BE
ANSWERED

8
 Influence of Alloy elements on Strength

strength MPa

temperature °C

Influence of the different elements by adding 0,50% of the

Element.
 2.25 Cr

12 Cr

A comparative Creep Vs Temp. graph for different grades of Steel

LIST OF ALLOY STEEL MATERIALS WITH THEIR APPLICATION

SG (BHEL-ALSTOM- 800MW-GSTPP):
MATERIAL AREA OF USE REFERENCE
GRADE STANDARD

1. T11 LTRH COILS SA 213

2. T12 SH FURN. ROOF TUBES / BP EXT. SIDE WALL / BP EXT. SIDE FLOOR / BP SIDE WALL / BP FRONT / BP FRONT SA 213
SCREEN / BP REAR / BP ROOF
3. T22 ECONOMISER HANGER TUBES/ WATER WALL SPIRAL AND STRAIGHT TUBES/ SH PLATEN COILS / LTRH COILS SA 213
/ FINISHING RH COILS / STEAM COOLED SPACERS
4. T23 LTRH COILS / LTRH PENDANT COILS SA 213
5. T91 SH PLATEN COILS / FINISH SH / LTRH PENDANT COILS / FINISHING RH COILS / STEAM COOLED SPACERS SA 213
6. P12 ECONOMISER OUTLET HEADER / ECONOMISER JUNCTION HEADER / WATER WALL INTERMEDIATE FRONT, SA 335
RAER AND SIDE HEADER / WATER WALL UPPER FRONT AND SIDE OUTLET HEADER / WATER WAL RISER
TUBES / FURNACE LINK TO STORAGE TANK / FURANCE DOWNCOMER TO CONN SPHERE / SH FURNACE ROOF
INLET HEADER /BP EXTENDED SIDE INLET HEADER / SC FURN ARCH SUPT. INLETAND OUTLET HDR / BP
UPPER SIDE INLET HDR / SH PLATEN INLET HEADER / FINISH RH INLET HDR / SH DESUPERHEATER-1 / SC
FURN ARCH SUPT LINKS / BP EXT. SIDE CONN LINK / LINK TO SH PLATEN(BEFORE BYPASS PIPE ENTRY) /
LINK TO SH PLATEN(AFTER BYPASS PIPE ENTRY) / SH BY PASS PIPE / LEAD TO DESUPERHEATER / RH
DESUPER HEATER / LINK TO FINISH RH

7. P22 WATER WALL UPPER REAR OUTLET HEADER / BACKPASS EXTENDED SIDE OUTLET HEADER / LTRH OUTLET SA 335
HEADER
8. P91 SEPERATOR / SEPERATOR STORAGE TANK / SH FURNACE ROOF OUTLET HEADER / BP LOWER HDRS / BP SA 335
FRONT OUTLET HDR / SH PLATEN OUTELT HEADER / SH FINISH INLET HEADER / SH FINISH OUTLET HEADER
/ FINISH RH OUTLET HDR / LINK TO SH DESUPERHEATER. / SH DESUPERHEATER / LINK TO FINISH SH
9. C12A MAIN STEAM STOP VALVE-BODY ASTM A217
10. P91 MAIN STEAM LINE SA335
11 P91 HOT REHEAT LINE SA335
12. P22,GRC COLD REHEAT LINE SA335,
SA106
LIST OF ALLOY STEEL MATERIALS WITH THEIR APPLICATION

SG (L&T-MHPS- 660MW-KHARGONE)
MATERIAL AREA OF USE REFERENCE
GRADE STANDARD

1. T12 WATER WALL / ROOF PANEL / SECONDARY PASS PANELS / SECONDARY PASS DIVISIONAL WALL PANELS / SA 213
PRIMARY SH / SECONDARY SH / PRIMARY RH
2. T22 COOLING SPACER TUBE / SECONADRY RH SA 213

3. T92 SECONDARY SH OUTLET HEADER – STUB AND CONNECTING TUBE / COOLING SPACER TUBE SA 213

4. F12 WATER SEPARATOR / WATER SEPARATOR DRAIN TANK SA 336

5. P22 PRIMARY RH OUTLET HEADER / RH DE-SH INLET PIPE, RH DE-SH AND RH DE-SH OUTLET PIPE / SECONADRY SA 335
RH INLET HEADER
6. P12 FURNACE INTERMEDIATE MANIFOLDS / FURNACE INTERMEDIATE MANIFOLD OULET PIPE / FURNACE SA 335
OUTLET HEADERS / ROOF INLET PIPE / ROOF INLET HEADER / FURNACE REAR WALL HANGER INLET
MANIFOLD , INLET HEADER, SUPPLY PIPES AND OUTLET HEADER / PASSAGE SIDE INLET MANIFOLD, INLET
HEADER, SUPPLY PIPE AND OUTLET HEADER / ROOF OUTLET HEADER / SECONDARY PASS BYPASS PIPE,
INLET PIPE , INLET MANIFOLD, AND SUPPLY PIPES / SECODARY PASS DIVISIONAL WALL SUPPLY PIPE /
SECONDARY PASS INLET HEADERS / SECONDARY PASS DIVISIONAL WALL INLET HEADER / SECONDARY PASS
OUTLET HEADERS / SECONDARY PASS DIVISIONAL WALL OUTLET HEADER / SECONDARY PASS WALL
OUTLET PIPES / SECONDARY PASS DIVISIONAL WALL OUTLET PIPE / WATER SEPERATOR INLET PIPE /
WATER SEPARATOR DRAIN TANK INLET PIPE / WATER SEPARATOR DRAIN TANK STEAM PIPE / WATER
SEPARATOR DRAIN TANK OUTLET PIPE / PRIMARY SH INLET PIPE / PRIMARY SH INLET HEADER / PRIMARY
SH OUTLET HEADER / PRIMARY SH DE-SH INLET PIPE, PRIMARY SH DE-SH AND PRIMARY DE-SH OUTLET
PIPE / SECONDARY SH INLET HEADER
7. P91 SECONDARY SH OUTLET HEADER / SECONDARY SH DE-SH INLET PIPE, SECONDARY SH DE-SH AND SA 335
SECONDARY DE-SH OUTLET PIPE / TERTIARY SH INLET HEADER
8. P92 TERTIARY SH OUTLET HEADER / SECONADRY RH OUTLET HEADER SA 335
9. F92 MAIN STEAM STOP VALVE-BODY / STEM / DISC / SEAT RING A 182
10. P92 MAIN STEAM LINE SA 335
11 P92 HOT REHEAT LINE SA 335
12. P22,GrC COLD REHEAT LINE SA 335,
SA106
Steam Turbine Components Materials for On-Going 660/800MW Projects:

Although, Steam Turbine components materials are not

specified in technical specification, the materials offered by
QSTGM (Qualified Steam Turbine Generator Manufacturer)
are accepted based on their proven practice & supply
experiences. The following table lists the details of Steam
turbine Components offered by different QSTGM’s for their
660/800 MW NTPC on-going projects:
Steam Turbine Components Materials for On-Going 660/800MW Projects
Main BHEL(660/800) TOSHIBA(660/800) BGRE(660/800) L&T(660) ALSTOM(660)
Supplier
Item HP Outer Casing Casting
Material 1.25CrMo 1.25CrMo 1.25CrMo 1.25CrMo 1.25CrMo
Grade
Weight(T) 20/22 37/39 39/39 35/37 21/26

Item IP Outer Casing Casting

Material EN-GJS-400-18U- 1.25CrMo 1.25CrMo 1.25CrMo G20Mo5(Mo=
Grade RT(Nodular CI) 0.5,C=0.20)

Weight(T) 50/56 36/39 47/58 66/68 27/32

Item HP Inner Casing Casting

Material 9Cr-1Mo 1.25CrMo 1.25CrMo 12Cr 9Cr-1Mo
Grade
Weight(T) 20/21 20/21 18/19 35/37 21/26

Item IP Inner Casing Casting

Material 10Cr-1Mo-1W 1Cr,9Cr,1Cr 1.25CrMo 12Cr 9Cr-1Mo
Grade
Weight(T) 36/36 4/4, 7/13, 4/4 8/9,4/4 35/37 26/28
Steam Turbine Components Materials for On-Going 660/800MW Projects
Main BHEL(660/800) TOSHIBA(660/800) BGRE(660/800) L&T(660) ALSTOM(660)
Supplier
Item HP Forged Rotor
Material 10Cr-1Mo-1W 1.75Cr-0.8Mo-1.1W- 1CrMo 12Cr 0.75Cr-0.8Mo &
Grade 0.3V 10Cr-2Mo
(Welded)

Weight(T) 24 20.9 25 21 6.3/8.1

Item IP Forged Rotor

Material 10Cr-1Mo-1W 1Cr,9Cr,1Cr 10Cr 2.25 Cr, 12Cr, 0.75Cr-0.8Mo &
Grade (Welded) 2.25 Cr 10Cr-2Mo
(Welded) (Welded

Weight(T) 36 12/10/14 35 15/37/15 10/8/10

Item LP Forged Rotor

Material 3.5Ni-1.75Cr-Mo-V 3.5Ni-1.75Cr-Mo-V 3.5Ni-1.75CR-Mo- 3.5Ni-1.75Cr- 2.5Ni-2.5Cr-Mo-V
Grade V Mo-V (Welded,4 parts)

Weight(T) 60 50 57 65 50
Steam Turbine Components Materials for On-Going 660/800MW Projects
Main Supplier BHEL(660/800) TOSHIBA(660/800) BGRE(660/800) L&T(660) ALSTOM(660)

Item HP Turbine Guide Blades

Material 10Cr-1Mo-1W(1-3) ,11Cr- 10.7Cr(1-8), 12Cr(9-18) 10.7Cr(1-6), 12Cr(7- 10Cr-3Co-Mo- 17Cr-14Ni-W-Ti
Grade 1Mo(4-18) 11) W-V-N-Nb-B(1- (1st),
6), 12Cr-1Mo (Others)
12Cr-Mo-W-V-
Nb(7-16)

Item HP Turbine Moving Blades

Material 10Cr-1Mo-1W (1-3), 10.7Cr(1-8), 12Cr(9-18) 10.7Cr(1-5), 12Cr(6- 10Cr-3Co-Mo- 17Cr-14Ni-W-Ti
Grade 11Cr-1Mo (4-18), 11) W-V-N-Nb-B(1- (1st),
6), 12Cr-1Mo (Others)
12Cr-Mo-W-V-
Nb(7-16)
Item IP Turbine Guide Blades
Material 12Cr-1Mo-V (1st, 4-10), 10.7Cr(19-24), 13.5Cr(25- 10.7Cr(1-5), 12Cr(6- 10Cr-3Co-Mo- 17Cr-14Ni-W-Ti
Grade 10Cr-1Mo-1W (2-3), 31) 8) W-V-N-Nb-B(1- (1st),
13Cr (11-15) 2), 12Cr-1Mo (Others)
12Cr(6-7),
12Cr-Mo-W-V-
Nb(3-6),
12Cr(7-12)

Item IP Turbine Moving Blades

Material 20Cr-75Ni-2Ti-1.5Al (1st), 11Cr(19-20), 10.7Cr(21-30) 10.7Cr(1-4), 12Cr(5- 37Ni-18Cr- 17Cr-14Ni-W-Ti
Grade 10Cr-1Mo-1W (2-3), 8) 3Mo(1-2), (1st),
11Cr-1Mo-V(4-7), 10Cr-3Co-Mo- 12Cr-1Mo (Others)
12Cr-1Mo-V (8-15) W-V-N-Nb-B(3- )
5),
12Cr(6-7),
12Cr-Mo-W-V-
Nb(8-12)
Steam Turbine Components Materials for On-Going 660/800MW Projects

Main BHEL(660/800) TOSHIBA(660/800) BGRE(660/800) L&T(660) ALSTOM(660)

Supplier

Item LP Turbine Guide Blades

Material X20Cr13(1-5), 13.5 Cr 12Cr 12Cr(1-5), 12Cr-1Mo-V (All
Grade GX4CrNi13-4(6) , 18Cr-8Ni(6-7) stages)
12Cr-Ni (7)

Item LP Turbine Moving Blades

Material 13Cr (1-6), 12Cr 12Cr, 12Cr(1-3), 12Cr-1Mo-V (All
Grade 12Cr-2Ni-2Mo-V (Last 11.7 Cr-1.7Mo- 12Cr-Mo-W- except last
stage) 0.3V(last stage) V-Nb(4), stage),
15Cr-4Ni- 14Cr-5.5Ni-
3.5Cu(5-7) 1.5Mo-1.7Cu
(Last Stage)

Item HP/IP Turbine Steam Admission Valves

Material 9Cr-1Mo-V (Casting) 10Cr-1Mo-0.2V-1W-Nb- 12Cr Steel 12Cr Steel 9Cr-1Mo-V
Grade N (Casting)
 Chemical Composition of Alloy Steel Material

Grade C Mn P S Si Cr Mo V W Ni
(Max.) (Max.)

P11 0.05-0.15 0.30-0.60 0.025 0.025 0.50-1.00 1.00-1.50 0.44-0.65 --------- --------- ---------

P12 0.05-0.15 0.30-0.61 0.025 0.025 0.50 max 0.80-1.25 0.44-0.65 --------- --------- ---------

P22 0.05-0.15 0.30-0.60 0.025 0.025 0.50 max 1.90-2.60 0.87-1.13 --------- --------- ---------

P23 0.04-0.10 0.10-0.60 0.030 0.010 0.50 max 1.90-2.60 0.05-0.30 0.20-0.30 1.45-1.75 0.40 max

P91 0.08-0.12 0.30-0.60 0.010 0.010 0.50 max 8.00-9.50 0.85-1.05 0.18-0.25 --------- 0.40 max

P92 0.07-0.13 0.30-0.60 0.010 0.010 0.50 max 8.00-9.50 0.30-0.60 0.15-0.25 1.50-2.00 0.40 max
 Mechanical Properties of Alloy Steel Materials

Grade Tensile Yield Elongation(%) Impact Hardness

Strength(MPa) Strength(MPa) Energy(J)

P11 >= 415 >= 205 >= 22 >= 35 <= 163HB

P12 >= 415 >= 220 >= 22 >= 35 <= 163HB

P22 >= 415 >= 205 >= 22 >= 35 <= 163HB

P23 >= 510 >= 400 >= 20 >= 35 <= 250HB

P91 585-760 >= 415 >= 20 >= 35 190-250 HB

P92 >= 620 >= 440 >= 20 >= 35 <= 250HB

Turbine Steel Casting for Service Temp.upto
540 Deg.
Type of Castings Material Typical
Specifications Components
Low alloy Creep EN-10213 HP/IP Outer
Resistant (European Std.) Casings,
Castings(For High G17CrMo5-5 HP/IP Inner Casing,
Temp. & High G17CrMo9-10 Guide Blade
Pressure Services) Carriers,
G17CrMoV5-10
G20M05 Turbine Valves
Casings,Covers,Diff
users,Inserts,Exhau
st Housing etc.
 DESIGNATION OF LOW ALLOYED STEEL
LOW ALLOY STEEL: WHERE CONTENT OF ALL ALLOYS IS
=< 5%.
CARBON INDEX
Express the carbon content multiplied by the factor 100.
In order to arrive at carbon percentage, it should be
divided by 100.
The letter C can be dropped for the sake of briefness.
the carbon index is always the leading symbol.

INDICIES FOR ALLOYING CONSTITUENTS AND

MULTIPLIERS.
These are intended to produce easy to handle alloying
indices (avoiding decimals) which can be easily arranged
by decreasing percentages.
 INDICIES FOR LOW ALLOYING CONSTITUENTS

ALLOYING CONTITUENTS MULTIPLIER

Cr, Co, Mn, Ni, Si, W 4

Al, Be, Pb, Cu, Mo, Nb, Ta, Ti, V, Zr 10

P, S, N, Ce, C 100

B 1000

ROUND OFF INDICIES TO NEAREST 1

ALLOYING INDICIES ARE ARRIVED AT BY
MULTIPLYING THE SPECIFIED MEAN PERCENTAGE
 LOW ALLOYING CONSTITUENTS, EXAMPLE

Example 13 CrMo 4-5

0.08 to 0.18, 0.13(Average) x 100 = 13

CrMo = Chrome and Molybdenum are the alloys

used to specify the steel.

Cr = 0.7 to 1.15, 0.925(Average) x 4 = 4

Mo = 0.4 to 0.6, 0.5(Average) x 10 = 5

 Material Grade G17CrMo9-10
• Identification of chemical composition by material
grade
• G : Stands for Casting Material
• 17: Carbon ~0.17%(Avg.value)
• Cr: 9/4 ~2.25%(Avg.value)
• Mo:10/10 ~1% (Avg.value)
C Cr Mo Mn Ni Si Cu Ti

0.13 2.00 0.90 0.50 < < < <

- - - - 0.50 0.60 0.30 0.025
0.20 2.50 1.20 0.90
INDICIES FOR HIGH ALLOYING CONSTITUENTS

HIGH ALLOY STEEL IS WHEN AT LEAST ONE ELEMENT IS

ABOVE 5%

CARBON RETAINS ITS MULTIPLIER OF 100. THE MULTIPLIER

OF ALL OTHER CONSTITUENTS IS 1.

TO DISTINGUISH HIGH ALLOY STEEL FROM LOW ALLOY

STEEL, THE DESIGNATION OF THESE GRADES IS PRECEDED
BY CAPITAL LETTER X.

X 10 Cr Ni 18 8 (TP 304) OR X 20 Cr 13 (TP410, HW10786)

 DESIGNATION OF CAST STEEL GRADES

FOR ALLOY CAST STEEL GRADES, THE LETTER ,”G” IS BEING

EMPLOYED.
Example G X 7 Cr Ni Nb 18 9 ( High Alloy)
G STANDS FOR CASTING
C 7/100 0.07 AVERAGE
Cr 18 18 AVERAGE
Ni 9 9 AVERAGE
Nb Stabilized, Minimum 5XC

Example G17CrMoV 5-10 (Low Alloy)

G STANDS FOR CASTING
C 17/100 0.17 AVERAGE(0.15-0.20)
Cr5/4 1.25 AVERAGE(1.20-1.50)
Mo 10/10 1.00 AVERAGE(0.90-1.10)
 Steel Casting for Service Temp.>
540 Deg.
Type of Castings Material Typical
Specifications Components

High alloy 9-10% Cr Turbine Inner

Enhanced Creep Ferritic-Martensitic Casing
Resistant Steel Turbine Valves
Castings(For High GX12CrMoVNbN9-1, MSCV,CRV
Pressure & Super Casings etc.
Critical Temp. GX12CrMoWVNbN10
Services) -1-1
 Material Grade GX12CrMoWVNbN10-1-1
• Identification of chemical composition by material
grade
• G : Stands for Casting Material
• X : Stands for High Alloy
• 12 Carbon ~0.12%(Avg.value)
• Cr ~10.0%(Avg.value)
• Mo ~1.0% (Avg.value)
• W ~ 1.0% (Avg. value)
C Cr Mo Mn Ni W Nb N

0.11 10.2 1.00 0.40 - 0.70 - 0.95 0.04 0.045-

- 0.13 - 10.6 -1.10 0.50 0.80 -1.05 -0.06 0.060
Precautions during Alloy Steel
Welding
 Welding of CrMoV-steels
22V/ T24/ T23
Decisive factors:

Less numbers of skilled

- Preheating Temp.
- Interpass Temp
- Welding Processes
- Welding Consumable

fabricators
- Heat Input
- Weld Build Up
- Weld Bead Thickness
- PWHT
- Equipment T/P22
- QA
- Welders

Welding of Creep resistant steels

Why Preheat?

Preheat reduces the temperature differential between the

weld region and the base metal
– Reduces the cooling rate, which reduces the
chance of forming martensite in steels
– Reduces distortion and shrinkage stress
– Reduces the danger of weld cracking
– Allows hydrogen to escape
Welding of creep resistant steels
Measuring of preheat temperature acc. to EN ISO 13916

t≤50mm: A ≤ 4 x t (max. 50mm)

t>50mm: A ≥ 75mm

The preheat temperature is the temperature in the area of the weld

before the start of welding.
Why Post-Weld Heat Treat?

• The fast cooling rates associated with welding often

produce martensite
• During postweld heat treatment, martensite is
tempered (transforms to ferrite and carbides)
– Reduces hardness
– Reduces strength
– Increases ductility
– Increases toughness
• Residual stress is also reduced by the post weld heat
treatment
 l
Postweld Heat Treatment and Hydrogen
Cracking
• Postweld heat treatment (~ 1200°F) tempers any
martensite that may have formed

– Increase in ductility and toughness

– Reduction in strength and hardness

• Residual stress is decreased by postweld heat

treatment
• Rule of thumb: Hold at temperature for 1 hour per inch
of plate thickness; minimum hold of 30 minutes
Welding of creep resistant steels
Measuring of Interpass temperature acc. to EN ISO 13916

Measuring of the ITP

The Interpass temperature is the temperature for multilayer welding

on the surface of the weld right before starting the next layer.
 Welding of CrMo-steels
Quality Thermocouples for PWHT

record by thermocouple in the furnace: 705°

actual: 740 – 760°C
770

765 Kanal 1
Kanal 2
-low cost for equipment
Kanal 3
Kanal 4

760 Kanal 5
Kanal 6
Kanal 7
-far cheaper than repeat test
Kanal 8
Temperatur in °C

Kanal 9
755 Kanal 10
Kanal 11
-online control on PC possible
Kanal 12
Kanal 13
750 Kanal 14
Kanal 15
Kanal 16
LESS RISKS
Kanal 17
Kanal 18
745 Kanal 19
Kanal 20
Kanal 21
Kanal 22
740 Kanal 23
Kanal 24
Kanal 25
Kanal 27
735

730
14,0 14,2 14,4 14,6 14,8 15,0 15,2 15,4 15,6 15,8 16,0
Zeit in Stunden
GRADE 91 PIPE BUTT JOINT WELDING – TYPICAL WELDING CYCLE
SIZE OF PIPE : 323.9 OD X 30 MM THICKNESS
IMPORTANCE OF
Electrode : ER90S-B9 and E9015-B9
MICROSTRUCTURAL
Shielding Gas : 15L/min ; Purging Gas : 10L/min (Root + 2 Hot Pass)
STUDY

KEY
QUESTIONS
TO BE
ANSWERED
 Welding of CrMo-steels
Influences on the hardness
Welding without preheating and without PWHT

Welding with 300°C preheating and without PWHT

Welding with 300°C preheating and a PWHT at 680°C

Base HAZ HAZ Base

material Weld metal material
Hardness HV 10
Thank U