CR Mo Temper Embrittlement

Challenges Meeting Temper
Embrittlement Criteria with

Welding Consumables
IPEIA 2007
14-17 February 2007
William F. Newell, Jr., PE, IWE
EUROWELD, Ltd.
Advanced Materials
When asked about his position on the reliability of

advanced materials [P91, 92, CrMoV, etc.), Dr. Martin
Prager (Exec Dir. WRC) related how he answered a
similar question when he was asked to speak at an
international conference on the same topic:
Advanced materials will be less

reliable because we will push them
harder.
-ASME II TG Creep Strength-Enhanced Ferritic Materials 25 Feb 2004
API 934 1 Edition, 2000

st
Materials and Fabrication

Requirements for 2-1/4Cr-1Mo
& 3Cr-1Mo Steel Heavy Wall
Pressure Vessels for High
Temperature, High Pressure
Hydrogen Service
API 934s
934-A, Second Edition (pending revision)
Materials and Fabrication Requirements for 2 1/4Cr-1Mo,

2 1/4Cr-1Mo-V, 3Cr-1Mo & 3Cr-1Mo-V Steel Heavy Wall Pressure
Vessels for High Temperature, High Pressure Hydrogen Service
934-B (initial draft)
Fabrication Considerations for V Steel Heavy Wall Pres Vessels for

High Temp, High Pres H2 Service
934-C (final draft)
Materials and Fabrication Requirements for 1 1/4Cr-1/2Mo Steel

Heavy Wall Pressure Vessels for High Temperature, High Pressure
Hydrogen Service
Temper Embrittlement Service
Primary Alloys
2-1/4Cr-1 Mo & 3-Cr-1 Mo

(API 934; Draft 934-A)
Enhanced Versions
2-1/4Cr-1 Mo-1/4V
3Cr-1 Mo-1/4V-Ti-B
3Cr-1Mo-1/4V-Cb-Ca
1-1/4Cr -1/2Mo (Draft 934-C)
Others ?
No techical data available that suggests or supports temper

embrittlement concerns for weld metal in elevated Cr versions
5 Cr
9 Cr
Temper Embrittlement
Phenomena typically occurs at service
temperatures between 750-1100oF (3995930C)
Segregation of P, As, Sb & Sn in the grain
boundary region
Results in an upward shift of the ductile-tobrittle transition temperature after long time
exposure
J-Factor (Watanabe)
Base Metal
J = (% Si + % Mn) (% P + Sn) x 104 (wt.%)
Cu 0.20% max; Ni 0.30% max (API 934)
Mn considered a cosegregate
Mn + Si typically < 1.1
J < 150 [initially], then J < 120
J < 100 [current]
Weld Metal
Toughness Difficulties
Possibilities
Reduce pressure at lower temperature
Use forged rings to eliminate longitudinal seams
Unacceptable.
Weld Metal
Overcoming Toughness Difficulties
Control composition
Heat treatment
Basicity of electrode coating or flux
Control grain refinement
Control Composition Weld Metal

Residual elements
P, As, Sb, Sn
Reducing these elements alone will not ensure

adequate toughness
Mn
Unlike base metal, NOT a cosegregate due to fast

quench rate
Necessary for formation of acicular ferrite (~ 0.8%

ideal)
X-Factor (Bruscato)
Weld Metal
X = (10 P + 5 Sb + 4 Sn + As) (ppm)
100
X < 20 [initial]
X < 15 [current]
Deposit will have maximum resistance to
temper embrittlement.
Heat Treatment Weld Metal

Example: -B3 (2-1/4Cr-1 Mo)
12750F (6900C) for 10 hours optimum [T1]
40 ft-lbs [54J]@ -200F [-300C]
PWHT + Step Cooling [T2]
Weld Metal Coating/Flux Basicity

Basicity of coating or flux
Goal: Lower Oxygen Content
Decrease O2, thus SiO2 & Inclusions
Maximizes Toughness
Bacisity Index (BI) = ~ 3.0

[Boniszewski]
CaF2 weighted too high
Grain Refinement Weld Metal

Temperbead Technique
~ 0.080 (2mm) max bead thickness for
SMAW
~ 0.160 (4mm) max bead thickness for
SAW
55 KJ max
Grain Refinement Weld Metal
Step Cooling Test (API 934)

48 Impact specimens
24(min.) at Minimum PWHT to Establish
Transition Curve before Step Cooling
24 (min.) at Minimum PWHT PLUS StepCooling to Establish Transition Curve
Establish 40 ft-lb (55J) Transition

Temperature
Simulate Temper Embrittlement ?

Step Cooling Test
Step Cooling Results

CvTr40 + 2.5DCvTr40 < 500F (100C)
CvTr40 = T1= 40 ft-lb. (55J) transition
temperature of the base metal subjected to
minimum PWHT only.
DCvTr40
= (T2- T1) = the shift of the 40 ft-lb. (55J)

transition temperature of material subjected to
minimum PWHT plus step cooling heat
treatment.
Toughness
T + 2.5(T -T )= -63+35= -28 F, OK
CvTr40 + 2.5DCvTr40 < 500F (100C)

1
Weld Metal - Step Cooling Results

Current Rules
Only PQR (same trade name, etc.)
Proposed Draft
Each lot of electrodes, heat of filler wire,
and combination of lot of flux and heat of
wire shall be tested.
X-Factor (Bruscato)
Weld Metal
X = (10 P + 5 Sb + 4 Sn + As) (ppm)
100
X < 20 [initial]
X < 15 [current]
X < 12 [proposed !!!!!]
Bare Wire = OK
SMAW & SAW = ??????????
Deposit will have maximum resistance to temper
embrittlement.
API 934, Para.7.2.1.2

Reference: 7.2.1 Welding Procedure Qualification
The welding electrodes, wire and

flux shall be of the same type and
brand as those used in production.
COMMERCIAL REALITY?
Consequences of API 7.2.2.1

Superb, if you are the vendor whose
products were used to perform the initial
welding procedure qualifications and, if
product is readily available.
Disaster, if you are a fabricator on a tight
schedule and your vendor ran out of
material and wont have any available until
after you are to have shipped the vessel !
Reality, food for thought

~ 50% require same brand as PQR, per
API 934
~ 50% only require R consumables
or those that meet X-Factor < 15 in the
deposit
Consider waiving API 7.2.1.2, If

GTAW
X < 15 of wire on actual size, OK
SMAW
X < 15 in deposit with actual size, OK
SAW
X < 15 in deposit with actual wire + flux, OK
State-of-the-Art suggests that step cooling

tests should not be requireda chemistry
check should be adequate
Summary
Control composition; X < 15
Heat treatment; 8-10hrs min
Basicity of electrode coating or flux; ~
3.0
Control grain refinement via welding
technique (temperbead)

CR Mo Temper Embrittlement

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What are the main issues related to temper embrittlement?

What are the main issues related to temper embrittlement?

What are the factors that influence temper embrittlement according to the document?

What are the factors that influence temper embrittlement according to the document?

Challenges Meeting Temper

Embrittlement Criteria with

William F. Newell, Jr., PE, IWE

When asked about his position on the reliability of

Advanced materials will be less

API 934 1 Edition, 2000

Materials and Fabrication

Materials and Fabrication Requirements for 2 1/4Cr-1Mo,

934-B (initial draft)

Fabrication Considerations for V Steel Heavy Wall Pres Vessels for

934-C (final draft)

Materials and Fabrication Requirements for 1 1/4Cr-1/2Mo Steel

Temper Embrittlement Service

2-1/4Cr-1 Mo & 3-Cr-1 Mo

1-1/4Cr -1/2Mo (Draft 934-C)

No techical data available that suggests or supports temper

J < 150 [initially], then J < 120

J < 100 [current]

Control Composition Weld Metal

Reducing these elements alone will not ensure

Unlike base metal, NOT a cosegregate due to fast

Necessary for formation of acicular ferrite (~ 0.8%

Heat Treatment Weld Metal

Weld Metal Coating/Flux Basicity

Bacisity Index (BI) = ~ 3.0

Grain Refinement Weld Metal

Grain Refinement Weld Metal

Step Cooling Test (API 934)

Establish 40 ft-lb (55J) Transition

Simulate Temper Embrittlement ?

Step Cooling Results

= (T2- T1) = the shift of the 40 ft-lb. (55J)

CvTr40 + 2.5DCvTr40 < 500F (100C)

Weld Metal - Step Cooling Results

API 934, Para.7.2.1.2

The welding electrodes, wire and

Consequences of API 7.2.2.1

Reality, food for thought

Consider waiving API 7.2.1.2, If

State-of-the-Art suggests that step cooling

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