Temper Bead Welding - iaea.org · PDF fileWelding & Repair Technology Center - Objective How...
Transcript of Temper Bead Welding - iaea.org · PDF fileWelding & Repair Technology Center - Objective How...
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Greg Frederick WRTC Program Manager
Nick Mohr Technical Leader
IAEA-Technical Meeting on Dissimilar Metal Welding Experiences and Lessons Learned
July 11-14, 2017
Vienna, Austria
Temper Bead Welding
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Temper Bead Welding
Presentation Outline:
Electric Power Research Institute (EPRI) Background
EPRI Welding and Repair Technology Center (WRTC)
Background
Temper Bead Welding Background
Application of Temper Bead for Dissimilar Metal Weld (DMW)
Repairs
Questions
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EPRI’s Mission
Advancing safe, reliable, affordable, and environmentally
responsible electricity for society through global collaboration,
thought leadership and science & technology innovation
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Corporate Strategic Direction
Innovative solutions that enable the transformation
of power systems to be more flexible, resilient, and
connected to provide society with safe, reliable,
affordable, and environmentally responsible electricity
+
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Three Key Aspects of EPRI
Collaborative Bring together scientists, engineers,
academic researchers, and industry experts
Independent Objective, scientifically based
results address reliability,
efficiency, affordability, health,
safety, and the environment
Nonprofit Chartered to serve the
public benefit
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Born in a Blackout
Founded in 1972 as an independent, nonprofit center for
public interest energy and environmental research
New York City, The Great Northeast Blackout, 1965
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Our Members…
450+ participants in more than
30 countries
EPRI members generate approximately
90% of the electricity in the United
States
International funding – nearly 25% of
EPRI’s research, development, and
demonstrations
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EPRI Membership Funding by Type
Co
op
erative 4%
International
Fed
eral/State
Mu
nicip
al
1%
Investor-Owned
55% 28% 6% 5%
December 31, 2016 (unaudited results)
Ind
epen
den
t Po
wer P
rod
ucer
5%
Co
op
erative
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Program Overview
WRTC
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Program Overview
Mission and Objective
WRTC – Committees and Meetings
WRTC – Who We Are
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Welding & Repair Technology Center-Mission
As nuclear power producing facilities age, there is an increasing need for
technology to provide effective solutions and to support life extension
objectives
Focus on both tactical issues and strategic research
Provide a framework for identifying, prioritizing, and tracking fabrication
and repair related technology “gaps”
– Technical Advisory Committee (TAC), EPRI staff, Integration Committee
– Facilities (metallurgical lab, welding lab, materials labs, etc.)
– Collaboration–National Labs, Universities, Internal
Lead R&D activities and technology development to supplying the
necessary “TOOL” to address current and future repair, fabrication, and
mitigation issues
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Welding & Repair Technology Center - Objective
Establish technologies to address gaps in repair and
replacement technology for nuclear power generation
components and transfer that technology
– Improve material performance and component life
extension
– Develop field-usable applications of technology
focused on the repair and replacement
– Increase plant availability and reduce repair costs
and schedule
– Support implementation - technical interactions with
Code, regulators and service vendors
– Create forums for sharing operating experience
Information exchange on repair, fabrication, weld
program issues, and industry emerging issues
Provide access to materials, welding, and repair
experts/peers across the nuclear industry
Suppliers, Vendors,
National Labs,
Universities
Nuclear Utilities
Collaborative
Technology
Development,
Integration and
Implementation Solutions
Inputs
EPRI
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Welding & Repair Technology Center - Objective
How technology is transferred…..
Through comprehensive
documentation
Direct communication (meeting
report outs)
Rapid-response assistance
(Information Exchange)
Training and Workshops
Computer Based Training Options
Peer interaction
Welding and Repair Technology Center:
Technical Basis and Residual Stress Studies
to Support the Excavate and Weld Repair
(EWR) Methodology for Mitigation of SCC in
ASME Class 1 Butt Welds
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Welding & Repair Technology Center
11 Research Focus Areas (RFA) established to address WRTC Core and Support areas: – RFA 1: Nickel-Base Filler Metal Weldability and New Alloy development
– RFA 2: Irradiated Materials Welding Solutions
– RFA 3: Identify, Research, Develop, and Mature Advanced Welding Processes
– RFA 4: Optimize Joining, Fabrication, and Repair Processes (including Welding Residual Stress)
– RFA 5: Small Bore Piping Asset
– RFA 6: Transfer & Promote Fabrication & Joining Technologies into Codes, Standards, & Regulations
– RFA 7: Buried Pipe Asset Management / Repair Solutions
– RFA 8: Repair Solutions for Structures: Containment, Fuel Pool Asset Management, Spent Fuel Storage
– RFA 9: Tactical Implementation of Repair Methods
– RFA 10: Document & Evaluate Operating Experience for Welding & Repair Programs
– RFA 11: Thermal spray, Coatings, and Hardfacing Applications
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EPRI Welding & Repair Technology Center (WRTC)
EPRI - Charlotte, NC
• ~200 EPRI staff; 8 are WRTC staff
• WRTC staff and labs are in Buildings 1
• Building 1- welding labs, laser labs, metallurgical labs, material archives
2
1 3
1
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WRTC Meeting Strategy
WRTC Technical Advisory Meeting (TAC) and Technical Programs
Two meetings per year (June and December)
– Session: Research Focus Area Reviews (Code Issues,
Training, Alloy 52, etc.)
– Session: Operating Experience (OE) and emerging issues,
Information Exchange
– Session: Demonstrations/Training both meetings
– Breakouts sessions (Technology Gap)
Goals
– Maintain a high level of communication and peer interaction
– Increase understanding of WRTC capabilities, organization,
and staff
– Identify work scope that is important to industry
– Identify work scope that is important to
industry
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WRTC TEAM
Greg Frederick
WRTC Program Manager
Ben Sutton
Technical Leader
Dana Couch
Senior Technical Leader
Steve McCracken
Senior Technical Leader
Stacey Wells
Assistant III
Jon Tatman
Technical Leader
Nick Mohr
Technical Leader
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WRTC TEAM-Continued
David Gandy
Materials Technical Executive
Robin Dyle
Materials Technical Executive
• MK Havens
• Kendal McCord
A
B
Metallurgy Laboratories Welding Laboratories
• Mitch Hargadine
• David Hansen
• Scott Bailey
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WRTC Team–Where We Are
United States (TAC)
22 of 22 U.S. Utility Organizations participate in WRTC (all
operating BWR and PWRs)
International Participation (TAC)
CANDU Owners Group (COG) – Canada, Romania
CEZ A.S. – Czech Republic
Chubu Electric Power Co., Inc. – Japan
Chugoku Electric Power Co., Inc. - Japan
Comision Federal de Electricidad (CFE) - Mexico
Electricite de France S.A. (EDF/MAI) – France
Emirates Nuclear Energy Corporation - United Arab
Emirates
Eskom - South Africa
Horizon Nuclear – United Kingdom
Kansai Electric Power Co, Inc – Japan
Korea Hydro and Nuclear Power Co. - Korea
Kyushu - Japan
MVM Hungarian Electric (Paks) – Hungary
Nucleoelectrica Argentina S.A. – Argentina
Shikoku Electric Power Co – Japan
The Tokyo Electric Power Company, Incorporated
(TEPCO) - Japan
UNESA – A.E. Industria Electrica - Spain
Non-Utility Memberships
IHI Corporation – Japan
Fluor Enterprises
AZZ WSI LLC – Welding Services Inc.
AREVA
Westinghouse
KAPL/Bettis – Bechtel Marine Propulsion Corp.
Rolls Royce
BWXT Nuclear Operations Group (BWXT) (2017)
Doosan Heavy Industry (2018)
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Temper Bead Welding
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Temper Bead Welding
ASME Code Section IX defines temper bead (TB) welding as [1]:
“a weld bead placed at a specific location in or at the surface of a weld for the purpose of
affecting the metallurgical properties of the heat‐affected zone or previously deposited
weld metal. The bead may be above, flush with, or below the surrounding base metal
surface. If above the base metal surface, the beads may cover all or only part of the weld
deposit and may or may not be removed following welding.”
The temper bead welding definition is broad and can be interpreted differently depending
on the industry it is being applied. However, one common purpose is the elimination of
postweld heat treatment (PWHT), but make note that stress relief does not occur.
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Temper Bead Welding
Temper Bead
Welding
Consistent Layer
Temper Bead
Technique
Controlled Deposition Technique Half-Bead
Technique
Alternate Temper Bead
Technique
• Machine GTAW or SMAW technique
• Ambient preheat (10°C)
• Grinding of layers not required
• 3 layers minimum
• Can be done remotely
• No postweld hydrogen bakeout after
welding
• Main objective tempered HAZ
• Typically SMAW technique
• Preheat typical (≈200°C)
• Grinding not required
• 2 layers minimum
• Typically, higher heat input ratio for
second layer
• Main objective eliminate coarse
grain zone (grain refinement)
• SMAW technique
• Preheat required (177°C)
• Typically, progressively larger
electrode diameters used
• Half of layer 1 is ground off before the
next layer is deposited
• Main objectives tempering and grain
refinement
• Postweld hydrogen bakeout (230°C-
290°C)
• Machine GTAW technique
• Preheat required (150°C)
• Grinding of layers not required
• 6 layers minimum
• Can be done remotely
• Main objectives tempering and
grain refinement
• Postweld hydrogen bakeout
(230°C-290°C)
There are many temper bead techniques [2]
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Temper Bead Welding
The desired metallurgical effect of temper bead welding is largely dependent on the
industry. In general, the goal for temper bead welding can be summarized as:
Nuclear: achieving a tempered heat affected zone (HAZ) (ideally tempered martensite)
with acceptable fracture toughness
Fossil: achieving grain refinement in the HAZ to avoid reheat cracking
Oil and Gas: achieving a HAZ with hardness not above a specified value
The term “temper bead” welding is used generically but the purpose and end goal can be
different depending on the industry. This discussion will focus on nuclear applications.
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Temper Bead Welding
Why is tempered martensite desired?
Answer- Very good fracture toughness
[3] Tempered Martensite + Tempered Pearlite
Tempered Martensite + Tempered Bainite
Tempered Martensite
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Temper Bead Welding
How is Temper Bead Welding done:
Precision placement of weld beads deposited using a qualified range of heat input
Precision placement of weld layers (US code cases have typically stated three temper
bead layers are required)
TB Layer 1
TB Layer 2
TB Layer 3
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Temper Bead Welding
Heat input or power ratio is required to be maintained within the qualified range of the
welding procedure specification (WPS)- ASME Code
Heat input should be documented for all temper bead weld layers. Welds should be
identified and heat input/power ratio documented on a bead log.
Heat input and power ratio equations are provided below.
𝐻𝑒𝑎𝑡 𝐼𝑛𝑝𝑢𝑡 =𝑉𝑜𝑙𝑡𝑎𝑔𝑒∗𝐴𝑚𝑝𝑒𝑟𝑎𝑔𝑒∗60
𝑇𝑟𝑎𝑣𝑒𝑙 𝑆𝑝𝑒𝑒𝑑
𝑃𝑜𝑤𝑒𝑟 𝑅𝑎𝑡𝑖𝑜 =𝑉𝑜𝑙𝑡𝑎𝑔𝑒∗𝐴𝑚𝑝𝑒𝑟𝑎𝑔𝑒
[𝑊𝐹𝑆
𝑇𝑆∗𝐴𝑓]
*wire feed speed (WFS), travel speed (TS), cross sectional area of filler metal (Af)
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Temper Bead Welding
The purpose of monitoring the heat input and power ratio is to make sure a certain range
of thermal energy is placed into the base material. This ensures that subsequent weld
layers temper the HAZ from the previous weld beads while keeping the relative size of
HAZ the same.
For gas tungsten arc welding (GTAW) the power ratio is frequently used because it
accounts for the energy required to melt the bare wire (i.e. more energy used to melt the
filler metal leaves less thermal energy for the base material)
HAZ
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Temper Bead Welding
Goals of Temper Bead Welding for Nuclear Applications:
Eliminate heat treatment
– Temper bead welding can be used without elevated preheat, post weld heat
treatment, and post weld hydrogen bakeout
Effectively temper the HAZ
Mechanical properties at least as good as the unaffected base material
– In most cases, the HAZ will actually demonstrate better mechanical properties
due to the increased proportion on tempered martensite compared to the
unaffected base material
Recall from continuous cooling transformation (CCT) diagrams. A relatively
small weld HAZ is being quenched compared to when the base material was
processed. The base material with larger mass is more difficult to obtain
optimum microstructure.
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Temper Bead Welding
Example CCT: SA-508
Base Metal-
Slower Cooling Rate
Weld-
Rapid Cooling Rate
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Temper Bead Welding
Currently, the following welding processes are permitted to be used to deposit a temper
bead weldment for ASME Section III and ASME Section XI applications:
Machine/automatic GTAW (Left)
Manual shielded metal arc welding (SMAW) (Right)
Currently, gas metal arc welding (GMAW) is not permitted, but research may
demonstrate that it is acceptable.
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Temper Bead Welding
Example Code Rules (ASME)
Code rules
– ASME Section III-NB (NB-4622.9 in 2015 Code) [4]
– ASME Section XI (IWA-4600 in 2015 Code) [5]
– However, these usually require preheat and postweld hydrogen bakeout. Many heat treatments are
not possible due to fluid in the system. The latest methods, improvements, and rules are found in
the following Code Cases. The improvements will eventually filter through to the main sections.
Code Cases
– N-638-8 (Ambient temperature temper bead using machine GTAW) [6]
Reduced preheat (50°F min), qualification clarifications (coupon simulated PWHT and impact
specimens), and peening clarifications.
– N-839 (Ambient temperature temper bead using SMAW) [7]
Reduced preheat (50°F min) and no post weld hydrogen bakeout
– Unfortunately, these are not approved by the Nuclear Regulatory Commission (NRC) (N-638-4 is
conditionally accepted) and would require regulatory relief for US plants. Non-US plants may be
able to use code cases as guidance in their country.
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Temper Bead Welding
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Application of Temper Bead for Dissimilar Metal
Weld (DMW) Repairs
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Dissimilar Metal Weld Repair
Structural Weld Overlays – SCC resistant materials are deposited on the outside of pipe/nozzle such that the
deposit is considered the structural boundary. The residual stress from shrinkage can create compressive stress on the inside of the pipe/nozzle. Two types of overlays:
Full Structural Weld Overlay (FSWOL): weld overlay designed to take all loads
Optimized Weld Overlay (OWOL): weld overlay and a fraction of base material designed to take all loads.
Inlays and Onlays – SCC resistant material are applied on the inside surface of pipe/nozzle DMW creating
a resistant barrier to SCC
Excavate and Weld Repair – Partial removal of susceptible material from the outside of the pipe/nozzle that is then
replaced by resistant filler metal
Traditional Cut-Out and Replace – Remove all susceptible material and reweld using resistant materials (not practical in
many situations)-Not discussed
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Structural Weld Overlay
FSWOL assumes a full 360° circumferential through wall flaw
OWOL assumes a full 360° circumferential flaw only 75% through wall
– The thickness of the weld overlay is less because some structural credit is provided to the underlying base material
Both FSWOL and OWOL are intended to place crack tip in compression (if applicable) and use SCC resistant filler metal
Applicable ASME Code Cases: N-504-X [9], N-740-X [10], an N-754-X [11]
[8] [8]
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Structural Weld Overlay
Temper Bead Layers
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Inlay or Onlay
Inlay requires machining of small groove and then replacing SCC susceptible material with resistant material.
Onlay does not prohibit machining a groove, but also provides SCC resistant material barrier Both are intended to provide SCC resistant barrier (i.e. Nickel alloy with Cr 28% or greater) Temper bead welding would be likely when welding on ferritic material or within 3mm of ferritic
materials Applicable ASME Code Case: N-766-X [13]
Typical Inlay [12] Typical Onlay [12]
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Typical Inlay [10]
Inlay of Onlay
Temper Bead Layers
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Excavate and Weld Repair (EWR)
Schematic of EWR for
82/182 PWSCC Mitigation [15] Schematic of Partial Arc [15]
General approach: Replace some of the SCC susceptible material with resistant material
– In many situation repairs via inlay/onlay or WOL is not possible or practical
Four types of EWR (summarized)
– Type 1A EWR: No surface connected or subsurface defect detected AND wetted surface has tensile stresses no greater than 69MPa after
EWR
– Type 1B EWR: Surface or subsurface defect (or no pre-exam) AND wetted surface has tensile stresses no greater than 69MPa after EWR
– Type 2A EWR: No surface connected or subsurface defect detected, but wetted surface has tensile stresses greater than 69MPa after
EWR
– Type 2B EWR: Surface or subsurface defect (or no pre-exam), but wetted surface has tensile stresses greater than 69MPa after EWR
EWR can be full 360 degree, or partial arc, and can be used on similar or dissimilar metal welds
Applicable ASME Code Case: N-847 [14]
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Stainless Steel
Buffer Layer(s)
Temperbead
Layers
Stainless Steel
Safe End
Low Alloy
Steel Nozzle
82/182
Weld
Schematic of EWR for 82/182 Repair/Mitigation
Stainless Clad
182 Butter
Excavate and Weld Repair
Temper Bead Layers
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Summary
There are many temper bead techniques, each with specific objectives
Temper bead welding has been used successfully for many repairs In many cases, the use of temper bead welding is necessary for
these repairs to be done in the field – Temper bead welding can be used without preheat – Temper bead welding can be used without PWHT – Temper bead welding can be used without postweld hydrogen
bakeout – Temper bead welding can be used with machine GTAW or manual
SMAW Temper bead is frequently used in conjunction with other dissimilar
metal repairs such as weld overlays, inlay/onlay, and excavate and weld repairs
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Questions
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References 1. ASME Boiler and Pressure Vessel Code Section IX, Qualification Standard for Welding, Brazing, and Fusing Procedures; Welders;
Brazers; and Welding, Brazing, and Fusing Operators, 2015 Edition.
2. Welding and Repair Technology Center: Shielded Metal Arc Temper Bead Welding. EPRI, Palo Alto, CA: 2015. 3002005536.
3. Lundin, C.D. and Mohammed, S., “Effect of Welding Conditions on Transformation and Properties of Heat Affected Zones in LWR Vessel
Steels”, NUREG/CR-3873
4. ASME Boiler and Pressure Vessel Code Section III-NB, Rules for Construction of Nuclear Facility Components, Division 1 – Subsection
NB Class 1 Components, 2015 Edition.
5. ASME Boiler and Pressure Vessel Code Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, 2015 Edition.
6. ASME Section XI Code Case N-638-8, Similar and Dissimilar Metal Welding Using Ambient Temperature Machine GTAW Temper Bead
Technique, Approved November 5, 2014
7. ASME Section XI Code Case N-839, Similar and Dissimilar Metal Welding Using Ambient Temperature SMAW Temper Bead Technique,
Approved September 4, 2014
8. Welding and Repair Technology Center: Overlay Handbook. EPRI, Palo Alto, CA: 2013. 3002000616
9. ASME Section XI Code Case N-504-4, Alternative Rules for Repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping, Approved
July 14, 2006
10. ASME Section XI Code Case N-740-2, Full Structural Dissimilar Metal Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 Items,
Approved November 10, 2008
11. ASME Section XI Code Case N-754-1, Optimized Structural Dissimilar Metal Weld Overlay for Mitigation of PWR Class 1 Items,
Approved February 28, 2013
12. Marlette, S.E. et al., Technical Basis for Case N-766-1 Nickel Alloy Reactor Coolant Inlay and Onlay for Mitigation of PWR Full
Penetration Circumferential Nickel Alloy Welds in Class 1 Items, ASME International (2012).
13. ASME Section XI Code Case N-766-1, Nickel Alloy Reactor Coolant Inlay and Onlay for Mitigation of PWR Full Penetration
Circumferential Nickel Alloy Dissimilar Metal Welds in Class 1 Items, Approved April 7, 2013
14. ASME Section XI Code Case N-847, Partial Excavation and Deposition of Weld Metal for Mitigation of Class 1 Items, Approved October
24, 2016
15. McCracken, S., Welding and Repair Technology Center TAC Meeting, 06E-ASME Section XI Activities Presentation, December 5-8,
Palm Coast, FL
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