Regulatory Guide 1.31: Difference between revisions

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{{Adams
{{Adams
| number = ML13211A485
| number = ML003739986
| issue date = 10/03/2013
| issue date = 04/30/1978
| title = Control of Ferrite Content in Stainless Steel Weld Metal
| title = Control of Ferrite Content in Statinless Steel Weld Metal
| author name =  
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/RES
Line 9: Line 9:
| docket =  
| docket =  
| license number =  
| license number =  
| contact person = Karagiannis H
| contact person =  
| case reference number = DG-1279
| document report number = RG-1.031, Rev 3
| document report number = RG-1.031, Rev. 4
| package number = ML13211A479
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 8
| page count = 5
}}
}}
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION October 2013OFFICE OF NUCLEAR REGULATORY RESEARCH
{{#Wiki_filter:U.S. NUCLEAR REGULATORY  
Revision 4 REGULATORY GUIDE
COMMISSION
  Technical Lead Michael Benson Written suggestions regarding this guide or development of new guides may be submitted through the NRC's public Web site under the Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading-rm/doc-collections/reg-guides/contactus.html.    Electronic copies of this regulatory guide, previous versions of this guide, and other recently issued guides are available through the NRC's public Web site under the Regulatory Guides document collection of the NRC Library at http://www.nrc.gov/reading-rm/doc-collections/.  The regulatory guide is also available through the NRC's Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under ADAMS Accession No. ML13211A485.  The regulatory analysis may be found in ADAMS under Accession No. ML13211A490 and the staff responses to the public comments on DG-1279 may be found under ADAMS Accession No. ML13211A483.
REGULATORY
GUIDE OFFICE OF STANDARDS
DEVELOPMENT
REGULATORY  
GUIDE 1.31 CONTROL OF FERRITE CONTENT IN STAINLESS
STEEL WELD METAL


REGULATORY GUIDE 1.31 (Draft was issued as DG-1279, dated October 2012) 
==A. INTRODUCTION==
CONTROL OF FERRITE CONTENT  
General Design Criterion
IN STAINLESS STEEL WELD METAL
1, "Quality Standards and Records," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50 requires that components- important to safety be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the
* safety function to be performed.
 
Criterion
14, "Reac tor Coolant Pressure Boundary," of Appendix A re quires that the reactor coolant pressure boundary be designed, fabricated, erected, and tested so as to have an extremely low probability of abnormal leakage, of rapidly propagating failure, and of gross rupture. Ap"pendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Processing Plants," to 10 CFR Part 50 requires that a quality assurance program be applied to the design, construction, and operation of structures, systems, and components.
 
Appendix B also requires that measures be established to ensure that special processes, including welding, are con trolled and accomplished by qualified personnel using qualified procedures and that proper process monitoring be performed.
 
This guide describes a method acceptable to the NRC staff for implementing these requirements with regard to the control of welding in fabricating and joining safety-related austenitic stainless steel com ponents and systems in light-water-cooled nuclear power plants. The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.
 
==B. DISCUSSION==
Inspection of some welds in austenitic stainless steel components of nuclear reactors has revealed the
* Lines indicate substantive changes from previous issue.presence of microfissures.
 
Further investigations re lated the presence of the microfissures to the low delta ferrite content of the deposited weld metal. Since microfissures in austenitic welds may have an adverse effect on the integrity of components, the control of weld deposits to ensure the presence of delta ferrite in these welds is advisable.


==A. INTRODUCTION==
As part of achieving this control, recommendations to test production welds were made in the original version of this guide (Safety Guide 31, "Control of Stainless Steel Welding"), and these recommenda tions were retained in Revision 1. Because licensees and other representatives of the nuclear industry be lieved that adequate control of filler metal ferrite con tent would consistently provide sound weld deposits with an absence of microfissures, a cooperative study group was formed by ASME, ANSI, and NRC to in vestigate the problem and the alternatives that would ensure adequate control of ferrite content. The study group analyzed data from welds prepared by eight different procedures.
Purpose  This guide describes a method that the staff of the U.S. Nuclear Regulatory Commission (NRC)
 
considers acceptable for controlling ferrite content in stainless steel weld metal.
About 1500 test results were analyzed, and recommendations were made to both ASME and NRC on how testing of production welds could be reduced without sacrifice of ferrite content control. Revision 2 and this Revision 3 are based on those recommendations.


Applicable Rules and Regulations Title 10 of the Code of Federal Regulations, Part 50, "Domestic Licensing of Production and Utilization Facilities" (10 CFR Part 50) (Ref. 1), Appendix A, "General Design Criteria for Nuclear Power Plants," General Design Criterion (GDC) 1, "Quality Standards and Records," requires that components important to safety be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety function to be performed.  GDC 14, "Reactor Coolant Pressure Boundary," requires that the reactor coolant pressure boundary be designed, fabricated, erected, and tested so that it has an extremely low probability of abnormal leakage, rapidly propagating failure, or gross rupture. Appendix B, "Quality Assurance Crite ria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CFR Part 50 requires that a quality assurance program be applied to the design, construction, operation, and testing of structures, systems, and components.  Appendix B also requires that measures be established to ensure that special processes, including welding, are controlled and accomplished by qualified personnel using qualified procedures and that proper process monitoring is performed.
At present, the ASME Code* provisions incorporated by reference into the NRC regulations require compliance with one of two alternative methods for control of delta ferrite in weld metal filler materials;
either a chemical analysis method or a magnetic measurement method. The NRC staff does not consider either method adequate
* Winter 1976 Addenda, Section III, "Nuclear Power Plant Components," ASME Boiler and Pressure Vessel Code. Copies may be obtained from the American Society of Mechanical En gineers, United Engineering Center, 345 East 47th Street, New York. New York 1001


Purpose of Regulatory Guides
===7. USNRC REGULATORY ===
GUIDES Comments should be sent to the Secretary of the Commission, U.S. Nuclear Regu.  latory Commission.


The NRC issues regulatory guides to describe to the public methods that the staff considers acceptable for use in implementing specific parts of the agency's regulations, to explain techniques that the staff uses in evaluating specific problems or postulated accidents, and to provide guidance to applicants.  Regulatory guides are not substitutes for regulations, and compliance with them is not required.  Methods and solutions that differ from those set forth in regulatory guides will be deemed acceptable if they provide a basis fo r the findings required for the issuance or continuance of a permit or license by the Commission.
Washington.


Rev. 4 of RG 1.31, Page 2 Paperwork Reduction Act This regulatory guide contains information collection requirements covered by 10 CFR Part 50 that the Office of Management and Budget (OMB) approved under OMB control number 3150-0011.  The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number.
D.C. 20555. Attention Docketing and Service Regulatory Guides are issued to describe and make available to the public methods Branch.  acceptable to the NRC staff of implementing specific parts of the Commission's regulations.


==B. DISCUSSION==
to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions or postulated accidents, or to provide guidance to applicants.
Reason for Revision


To achieve control of ferrite content in stainless steel welds, the original version of this guide, Safety Guide 31, "Control of Stainless Steel Welding," issued August 1972 (Ref. 2), provided guidance to test production welds.  This guidance was retained in Revision 1 of the Safety Guide, which was issued June 1973 as Regulatory Guide 1.31, "Control of Ferrite Content in Stainless Steel Weld Metal" (Ref. 3). Revision 2 (issued May 1977) and Revision 3 (issued April 1978) to this guide were based on recommendations from an NRC/industry study group.  Revision 2 of this guide replaced the guidance for testing production welds in Revision 1 with guidance fo r process control through testing weld test pads.  These changes considerably reduced the testing effort needed to control delta ferrite in welds.  This revision (Revision 4) references the latest consensus standards.  It supplements the American Society of Mechanical Engineers (ASME) Code requireme nts to ensure control of delta ferrite in welds in austenitic stainless steel core support structures, reactor internals, and Class 1, 2, and 3 components.  Also, the Appendix of the previous version has been removed and incorporated into the relevant specifications that are referenced in this guide.
Regulatory Guides are not substitutes for regulations.


Background Inspection of some welds in austenitic stainless steel components of nuclear reactors has revealed the presence of microfissures.  Further investigations related the presence of the microfissures to the low delta ferrite content of the deposited weld metal.  Since microfissures in austenitic welds may have an adverse effect on the integrity of components, the control of weld deposits to ensure the presence of delta ferrite in these welds is advisable.
and compliance with them is not required.


Because licensees and other representatives of the nuclear industry believed that adequate control of filler metal ferrite content would consistently provide sound weld deposits with an absence of microfissures, ASME, the American National Standards Institute (ANSI), and the NRC formed a cooperative study group to investigate the problem and the alternatives that would ensure adequate control of ferrite content. The study group analyzed data from welds prepared by eight different procedures. The group analyzed about 1,500 test results and made recommendations to both ASME and the NRC on how testing of production welds could be reduced without sacrificing control of the ferrite content. Welding Research Council (WRC) Bulletin Number 318 (Ref. 4) provides a summary of the
1. Power Reactors 6. Products Methods and solutions different from those set out in the guides will be accept. 2. Research and Test Reactors


work performed, round robin test results including statistical analysis of the reproducibility of ferrite number measurements, and the study group's recommendations.
===7. Transportation ===
3. Fuelsand Materials Facilities
8. Occupational Health able if they provide a basis for the findings requisite to the issuance or continuance
4. Environmental and Siting 9 Antitrust Review of a permit or license by the Commitsion.


The provisions of the ASME Boiler and Pressure Vessel Code (ASME Code), Section III (Ref. 5), incorporated by reference into the NRC regulations, require compliance with one of two alternative methods (either a chemical analysis method or a magnetic measurement method) to control delta ferrite in weld metal filler materials.  The NRC staff does not consider the use of the chemical analysis method for every welding process adequate by itself to ensure control of delta ferrite in production welds.  The staff Rev. 4 of RG 1.31, Page 3 positions in this guide are intended to supplement the ASME Code requirements to ensure control of delta ferrite in welds in austenitic stainless steel core support structures, reactor internals, and Class 1, 2, and 3 components.
5. Materials and Plant Protection
10. General Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides (which may be reproducedI
or for place times, and guides will be revised, as appropriate, to accommodate comments and ment on an automatic distribution list for single copies of future guides in specific to reflect new information or experience.


The staff concludes that ferrite content in the weld metal, as depicted by a ferrite number, should be between 5 and 20.  This lower limit provides sufficient ferrite to avoid microfissuring in welds, whereas the upper limit provides a ferrite content adequate to offset dilution and reduce thermal aging effects.
This guide was revised as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission.


Harmonization with International Standards
substantive comments received from the public and additional staff review. Washington.


The NRC has an interest in facilitating the harmonization of standards used domestically and internationally. This regulatory guide endorses standards from the American Welding Society (AWS) and ASME, which publish standards that are used internationally for a wide range of materials, products, systems, and services. The NRC staff  reviewed guidance from the International Atomic Energy Agency (IAEA), but did not identify any standards related to this regulatory guide that provided useful information to NRC staff, applicants, or licensees.
D.C. 20555, Attention Director.


Documents Discussed in Staff Regulatory Guidance This regulatory guide endorses, in part, the use of one or more codes or standards developed by external organizations, and other third party guidance documents.  These codes, standards and third party guidance documents may contain references to other codes, standards or third party guidance documents ("secondary references").  If a secondary reference has itself been incorporated by reference into NRC regulations as a requirement, then licensees and applicants must comply with that standard as set forth in the regulation. If the secondary reference has been endorsed in a regulatory guide as an acceptable approach for meeting an NRC requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that regulatory requirement as described in the specific regulatory guide.  If the secondary reference has neither been incorporated by reference into NRC regulations nor endorsed in a regulatory guide, then the secondary reference is neither a legally-binding requirement nor a "generic" NRC approval as an acceptable approach for meeting an NRC requirement.  However, licensees and applicants may consider and use the information in the secondary reference, if appropriately justified and consistent with current regulatory practice, consistent with applicable NRC requirements such as 10 CFR 50.59.  C. STAFF REGULATORY GUIDANCE
Division of Document Control.Revision 3 April 1978 by itself to ensure controlled delta ferrite in produc tion welds. The recommendations of this guide are intended to supplement the ASME Code requirements to ensure control of delta ferrite in welds in austenitic stainless steel core support structures and Class 1 and 2 components.


1. Verification of Delta Ferrite Content of Filler Materials Prior to production usage, the delta ferrite content of test weld deposits from each lot and each heat of weld filler metal procured for the welding of austenitic stainless steel core support structures, reactor internals, and Class 1, 2, and 3 components should be verified for each process to be used in production.  The definition of heat and lot of material in ASME Code, Section III, NB-2420 can be used.
The recommendations for testing of production welds in Revision 1 of this guide have been replaced by recommendations for process control by testing of weld test pads. These changes will considerably re duce the testing effort needed to control delta ferrite in welds.  The staff recommends that ferrite content in the weld filler metal as depicted by a ferrite number (FN) be between 5 and 20. This lower limit provides suffi cient ferrite to avoid microfissuring in welds, whereas the upper limit provides a ferrite content adequate to offset dilution.


For all processes, delta ferrite verification should be performed through tests using magnetic measuring devices on undiluted weld deposits.  For submerged arc welding processes, the verification tests for each wire and flux combination may be made on a production weld or simulated production weld.  All other delta ferrite weld filler verification tests should be made on weld pads that contain undiluted layers of weld metal.
C. REGULATORY
POSITION 1. Verification of Delta Ferrite Content of Filler Materials Prior to production usage, the delta ferrite content of test weld deposits from each lot and each heat of weld filler metal procured for the welding of austeni tic stainless steel core support structures and Class 1 and 2 components should be verified for each process to be used in production.


Rev. 4 of RG 1.31, Page 4 Delta ferrite determinations are not necessary for type 16-8-2 filler metal in ASME Code Section II filler metal specifications SFA-5.4, "Specification fo r Stainless Steel Electrodes for Shielded Metal Arc Welding," SFA-5.9, "Specification for Bare Stainless Steel Welding Electrodes and Rods" and SFA-5.22, "Specification for Stainless Steel Electrodes for Flux Cored Arc Welding and Stainless Steel Flux Cored Rods for Gas Tungsten Arc Welding," or for filler metal used for weld metal cladding (Ref. 6). Alternatively, delta ferrite determ inations for consumable inserts, electrodes, rod, or wire filler metal used with the gas tungsten arc welding process, and deposits made with the plasma arc welding process, may be predicted from their chemical composition of the undiluted weld deposit by using a constitutional diagram in the applicable filler metal specification (e.g., WRC-1992 diagram for stainless steel weld metal in ASME Code Section III, Figure NB-2433.1.1).  Use of the magnetic test method is also acceptable to the staff for determining delta ferrite content in welds fabricated with gas tungsten arc welding and plasma arc welding. 2. Ferrite Measurement  The NRC staff considers the procedures for pad preparation and ferrite measurement in SFA-5.4 of Section II of the ASME Code acceptable. 3. Instrumentation The weld pad should be examined for ferrite content by using a magnetic measuring instrument that has been calibrated against a Magnegage in accordance with AWS A4.2, "Standard Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic and Duplex Ferritic-Austenitic Stainless Steel Weld Metal" (Ref. 7).  Th e Magnegage should have b een previously calibrated in accordance with AWS A4.2 using primary standards as defined therein. 4. Acceptability of Test Results Weld pad test results showing an average ferrite number from 5 to 20 indicate that the filler metal is acceptable for the production welding of Class 1, 2, and 3 austenitic stainless steel components, reactor internals, and core support structures.
It is not necessary to make delta ferrite determina tions for SFA-5.4 type 16-8-2 weld metal or for filler metal used for weld metal cladding.


5. Quality Assurance  The applicable provisions of Appendix B to 10 CFR Part 50 should be used to verify compliance with requirements for delta ferrite of each lot and each heat of weld filler metal as described herein.
Delta ferrite de terminations for consumable inserts, electrodes, rod or wire filler metal used with the gas tungsten arc welding process, and deposits made with the plasma arc welding process may be predicted from their chemical composition using an applicable constitu tional diagram to demonstrate compliance.


Rev. 4 of RG 1.31, Page 5
Delta fer rite verification should be made for all other proc esses by tests using magnetic measuring devices on undiluted weld deposits.


==D. IMPLEMENTATION==
For submerged arc welding processes, the verification tests for each wire and flux combination may be made on a production weld or simulated production weld. All other delta ferrite weld filler verification tests should be made on weld pads that contain undiluted layers of weld metal.  2. Ferrite Measurement Appendix A to this guide contains extracts from a future edition of the American Welding Society's AWS A5.4, "Specification for Corrosion-Resisting
The purpose of this section is to provide information on how applicants and licensees
* This specification has been recommended by the Subcommit tee on Welding of Stainless Steels of the High Alloys Committee of the Welding Research Council and has been approved by the American Welding Society (AWS). It is expected to be pub lished as AWS A5.4-78.Chromium and Chromium-Nickel Steel Covered Welding Electrodes,"*
1 may use this guide and information regarding the NRC's plans for using this regulatory guide.  In addition, it describes how the NRC staff complies with 10 CFR 50.109, "Backfitting," and any applicable finality provisions in 10 CFR Part 52, "Licenses, Certifications, and Approvals for Nuclear Power Plants." 
which describes a procedure for pad preparation and ferrite measurement.
Use by Applicants and Licensees Applicants and licensees may voluntarily
2 use the guidance in this document to demonstrate compliance with the underlying NRC regulations.  Methods or solutions that differ from those described in this regulatory guide may be deemed acceptable if they provide sufficient basis and information for the NRC staff to verify that the proposed alternative demonstrates compliance with the appropriate NRC regulations. Current licensees may continue to use guidance the NRC found acceptable for complying with the identified regulations as long as their current licensing basis remains unchanged.


Licensees may use the information in this regulatory guide for actions that do not require NRC
The NRC staff considers this procedure acceptable for use with covered electrodes.
review and approval, such as changes to a facility design under 10 CFR 50.59, "Changes, Tests, and Experiments."  Licensees may use the information in this regulatory guide or applicable parts to resolve regulatory or inspection issues.


Use by NRC Staff The NRC staff does not intend or approve any imposition or backfitting of the guidance in this regulatory guide. The NRC staff does not expect any existing licensee to use or commit to using the guidance in this regulatory guide, unless the licensee makes a change to its licensing basis.  The NRC staff does not expect or plan to request licensees to voluntarily adopt this regulatory guide to resolve a generic regulatory issue. The NRC staff does not expect or plan to initiate NRC regulatory action that would require the use of this regulatory guide. Examples of such unplanned NRC regulatory actions include issuance of an order requiring the use of the regulatory guide, requests for information under 10 CFR 50.54(f) as to whether a licensee intends to commit to use of this regulatory guide, generic communication, or promulgation of a rule requiring the use of this regulatory guide without further
3. Instrumentation The weld pad should be examined for ferrite con tent by a magnetic measuring instrument which has been calibrated against a Magnegage in accordance with American Welding Society Specification AWS A4.2-74, "Procedures for Calibrating Magnetic In struments to Measure the Delta Ferrite Content of Austenitic Stainless Steel Weld Metal."'**
The Mag negage should have been previously calibrated in ac cordance with AWS A4.2-74 using primary standards as defined therein.


backfit consideration.
4. Acceptability of Test Results Weld pad test results showing an average Ferrite Number from 5 to 20 indicate that the filler metal is acceptable for production welding of Class 1 and 2 austenitic stainless steel components and core support structures.


During regulatory discussions on plant specific operational issues, the staff may discuss with licensees various actions consistent with staff positions in this regulatory guide, as one acceptable means of meeting the underlying NRC regulatory requirement.  Such discussions would not ordinarily be considered backfitting even if prior versions of this regulatory guide are part of the licensing basis of the facility.  However, unless this regulatory guide is part of the licensing basis for a facility, the staff may not represent to the licensee that the licensee's failure to comply with the positions in this regulatory guide constitutes a violation.
The upper limit of 20 may be waived for (a) welds that do not receive postweld stress relief heat treat ment or welds for which such postweld stress relief treatment is conducted at temperatures less than 900'F, (b) welds that are given a solution annealing heat treatment, and (c) welds that employ consuma ble inserts.


1  In this section, "licensees" refers to licensees of nuclear power plants under 10 CFR Parts 50 and 52, and "applicants" refers to applicants for licenses and permits for (or relating to) nuclear power plants under 10 CFR Parts 50 and 52, and applicants for standard design approvals and standard design certifications under 10 CFR Part 52.
5. Quality Assurance The applicable provisions of 10 CFR Part 50, Ap pendix B, should be used in verifying compliance with requirements for delta ferrite as described herein.


2  In this section, "voluntary" and "voluntarily" mean that the licensee is seeking the action of its own accord, without the force of a legally binding requirement or an NRC representation of further licensing or enforcement action.
==D. IMPLEMENTATION==
The purpose of this section is to provide informa tion to applicants regarding the NRC staff's plans for using this regulatory guide.  Except in those cases in which the applicant pro poses an acceptable alternative method for complying with specified portions of the Commission's regula tions, the method described herein will be used in the evaluation of submittals in connection with construc tion permit applications docketed after October 1, 1978.  If an applicant wishes to use this regulatory guide in developing submittals for applications docketed on or before October 1, 1978, the pertinent portions of the application will be evaluated on the basis of this guide.  **Copies may be obtained from the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125.1.31-2 APPENDIX A The following is mainly extracted from a future edition of the American Welding Society's (AWS) "Specification for Corrosion-Resisting Chromium and Chromium-Nickel Steel Covered Welding Elec trodes," which the AWS plans to publish as AWS A5.4-78.*
This material describes a procedure for weld pad preparation and ferrite measurement of cov ered electrode**
deposits.


Rev. 4 of RG 1.31, Page 6 If an existing licensee voluntarily seeks a license amendment or change and (1) the NRC staff's consideration of the request involves a regulatory issue directly relevant to this new or revised regulatory guide and (2) the specific subject matter of this regulatory guide is an essential consideration in the staff's determination of the acceptability of the licensee's request, then the staff may request that the licensee either follow the guidance in this regulatory guide or provide an eq uivalent alternative process that demonstrates compliance with the underlying NRC regulatory requirements. This is not considered backfitting as defined in 10 CFR 50.109(a)(1) or a violation of any of the issue finality provisions in 10  
EXTRACT: A4. 10 When it is desired to measure ferrite con tent, the following procedure is recommended:
CFR Part 52.
A4.10.1 Weld pads as detailed in Figure 4 are prepared as prescribed in paragraphs A4.10.2 through A4.10.4.


Additionally, an existing applicant may be required to comply with new rules, orders, or guidance if 10 CFR 50.109(a) (3) applies.   If a licensee believes that the NRC is either using this regulatory guide or requesting or requiring the licensee to implement the methods or processes in this regulatory guide in a manner inconsistent with the discussion in this Implementation section, then the licensee may file a backfit appeal with the NRC in accordance with the guidance in NUREG-1409, "Backfitting Guidelines," (Ref. 8) and the NRC Management Directive 8.4, "Management of Facility-Specific Backfitting and Information Collection" (Ref. 9).      
A4.10.2 The weld pad shall be built up between two copper bars laid parallel on the base plate by de positing single weld bead layers, one on top of the other, to a minimum height of 13 mm (1/2 in.). The spacing between the copper bars for the size of the electrode being tested shall be as specified in Figure 4. An optional welding fixture is shown in Figure 5.  If carbon steel is used as the base plate, the weld pad shall be built up to a minimum height of 16 mm (5 in.).  
Rev. 4 of RG 1.31, Page 7 REFERENCES
* When published, copies of AWS A5.4-78 may be purchased from the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125.  ** Note: The U.S. customary units in this specification are given as equivalent values to the SI units. The standard sizes and dimensions used in the two systems are not identical and for this reason conversion from a standard size of dimension in one system will not always coincide with the standard size of dimen sion in the other. Suitable conversions encompassing standard sizes of both can be made if appropriate tolerances are applied in each case. The SI values (including tolerances)  
3 1. U.S. Code of Federal Regulations (CFR) "Domestic Licensing of Production and Utilization Facilities," Part 50, Chapter 1, Title 10, "Energy"
given here for filler metal diameter, length, and package size were selected to fit the product sizes which presently are U.S. standards.
2. Safety Guide 31, "Control of Stainless Steel Welding," U.S. Nuclear Regulatory Commission, Washington, DC.


3. Regulatory Guide 1.31, "Control of Ferrite Content in Stainless Steel Weld Metal," U.S. Nuclear Regulatory Commission, Washington, DC.
Toler ances are used in some cases in this specification but not in others. In those cases where no tolerances are given, the values are those that would be obtained if the measurements were taken in SI units. In this specification, a covered electrode is defined as follows: Covered Electrode-A
composite filler-metal elec trode consisting of a core of a bare electrode or metal cored electrode to which a covering sufficient to provide a slag layer on the weld metal has been applied. The covering may contain materials providing such functions as shielding from the atmos phere, deoxidation, and arc stabilization and can serve as a source of metallic additions to the weld.A4.10.3 The welding current used for the size of the electrode being tested may be as specified in Fig ure 4 and the arc length shall be as short as practica ble. The weld bead layers may be deposited with a weave, if 'necessary, to fill the space between the copper bars. The arc shall not be allowed to impinge on the copper bars. The welding direction for each pass shall be alternated and the weld stops and starts shall be located at the ends of the weld buildup. Each pass shall be cleaned prior to depositing the next weld bead. The maximum interpass temperature shall be 95'C (200°F).**
Between passes, the weld pad may be cooled by quenching in water not sooner than 20 seconds after the completion of each pass. The last pass shall be air-cooled to below 430'C (800'F) prior to quenching in water.  A4.10.4 The completed weld pad shall be draw filed, machined, or surface ground to provide suffi cient finished surface to make the required ferrite readings.


4. Welding Research Council (WRC) Bulletin Number 318, "Factors Influencing the Measurement of Ferrite Content in Austenitic Stainless Steel Weld Metal Using Magnetic Instruments," W. W. Pickering, E. S. Robitz, and D. M. Vandergriff, September 1986 (ISBN#1-58145-317-5).
Draw filing or its equivalent filing method shall be performed with a 360 mm (14 in.)** mill bastard file held on both sides of the weld with the long axis of the file perpendicular to the long axis of the weld. The file should preferably not have been previously used on ferritic material and should be free from loosely adhering materials if previously used. Draw filing shall be accomplished by smooth forward and backward strokes along the length of the weld while applying a firm downward pressure.
4  5. American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, "Rules for Construction of Nuclear Facility Components," American Society of Mechanical Engineers (as incorporated by reference in 10 CFR 50.55a). 5
6. ASME Boiler and Pressure Vessel Code, Secti on II, Part C, "Specifications for Welding Rods, Electrodes, and Filler Metals," American Society of Mechanical Engineers, (as approved by the ASME in those Editions and Addenda of the ASME Boiler and Pressure Vessel Code, Section III, Subsection NCA-1140 which are incorporated by reference into 10 CFR 50.55a). 
7. Welding Society (AWS) A4.2, "Standard Proce dures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic and Duplex Ferritic-Austenitic Stainless Steel Weld Metal," AWS, (as approved by the ASME in those Editions and Addenda of the ASME Boiler and Pressure Vessel Code, Section III, which are incorporated by reference into 10 CFR 50.55a.). 6
8. NUREG 1409, "Backfitting Guidelines," U.S. Nuclear Regulatory Commission, Washington, DC.


3  Publicly available NRC published documents are available electronically through the NRC Library on the NRC's public Web site at http://www.nrc.gov/reading-rm/doc-collections/ and also available through the NRC's Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html  The documents can also be viewed online or printed for a fee in the NRC's Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD. For problems with ADAMS, contact the PDR staff at 301-415-4737 or (800) 397-4209; fax (301) 415-3548; or e-mail pdr.resource@nrc.gov.  4  This reference is available for purchase at the Welding Research Council (WRC) website at http://www.forengineers.org/wrc/ or by contacting WRC at P.O. Box 201547, Shaker Heights, OH 44120.
Crossfiling shall not be permitted.


5 Copies of American Society of Mechanical Engineers (ASME) standards may be purchased from ASME, Three Park Avenue, New York, NY 10016-5990; telephone (800) 843-2763.  Purchase information is available through the ASME
The finished machined, ground, or filed surface shall be smooth with all traces of weld ripple removed and shall be continuous in the length where measurements are to be taken. The width of the prepared surface shall not be less than 3 mm (1/8 in.).** A4.10.5 A total of six ferrite readings shall be taken on the prepared surface along the longitudinal axis of the weld pad with an instrument calibrated in accordance with the procedures specified in AWS A4.2, "Standard Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic Stainless Steel Weld Metal" (latest edition). 
Web-based store at http://www.asme.org/Codes/Publications/. 6  Publications of the American Welding Society (AWS) may be obtained through the AWS Website at http://www.aws.org/w/a or by contacting the AWS at 8669 Doral Boulevard, Suite 130 Doral, FL.
A4.10.6 The six readings 'obtained shall be aver aged to a single value for conversion to Ferrite Number.1.31-3
-H Copper bar-L L Ferrite shall be measured in this area free of arc starts and cratersI I I BASE PLATE 1 465 min All dimensions in millimetres, U.S. EQUIVALENTS*
Electrode diameter (mm)1.6 2.0 2.4 3.2 4.0 4.8 Welding current (amperes)35-45 45-55 65-75 90-100 120-140 165-185 240-260 In drawing above (approx. mm)W 6 6 8 10 13 15 18 L 30 30 40 40 40 40 40 See Editor's Note on Page 1.31-3.  Fig 4 -Details of Weld Pad for Ferrite Test 1.31-4 25x25x75 1 40 -25 min o mm 1.6 2.0 2.4 3.2 4.0 4.8 6.4 6 8 9.5 10 13 15 18 25 30 40 65 75 in.  1/16 5/64 3/32 1/8 5/32 3/16 1/4 0.25 0.3 3/8 0.4 0.5 0.6 0.7 1 1-1/4 1-1/2 2-1/2 3.I
Copper bars 85 long of cross section as shown in A-A' below.Copper bar 16 high x 9.5 thick x 70 long.Note: All dimensions are in millimetres.


Rev. 4 of RG 1.31, Page 8
U.S. EQUIVALENTS*
  9. Management Directive 8.4, "Management of Facility-Specific Backfitting and Information Collection," U.S. Nuclear Regulatory Commission, Washington, DC.}}
MM in.4.0 4.8 9.5 16 25 70 85 Copper bar same -as shown at opposite end A Type 1 For 4.0 dia. Electrodes and smaller COPPER 16 BAR T Cross Section A-A'This design allows increased visibility, making it easier to hold a short arc length.5/32 3/16 3/8 5/8 1 2-3/4 3-3/8*See Editor's Note on Page 1.31-3.COPPEIR BAR 25 square COPPER BAR Type 2 For 4.8 & larger welding electrodes and for any pads on carbon steel base plate Fig. 5 -Optional Welding Fixture for Welding Ferrite Test Pads 1.31-5 I}}


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Revision as of 02:41, 21 September 2018

Control of Ferrite Content in Statinless Steel Weld Metal
ML003739986
Person / Time
Issue date: 04/30/1978
From:
Office of Nuclear Regulatory Research
To:
References
RG-1.031, Rev 3
Download: ML003739986 (5)
v • d • e


U.S. NUCLEAR REGULATORY

COMMISSION

REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 1.31 CONTROL OF FERRITE CONTENT IN STAINLESS

STEEL WELD METAL

A. INTRODUCTION

General Design Criterion 1, "Quality Standards and Records," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50 requires that components- important to safety be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the

  • safety function to be performed.

Criterion

14, "Reac tor Coolant Pressure Boundary," of Appendix A re quires that the reactor coolant pressure boundary be designed, fabricated, erected, and tested so as to have an extremely low probability of abnormal leakage, of rapidly propagating failure, and of gross rupture. Ap"pendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Processing Plants," to 10 CFR Part 50 requires that a quality assurance program be applied to the design, construction, and operation of structures, systems, and components.

Appendix B also requires that measures be established to ensure that special processes, including welding, are con trolled and accomplished by qualified personnel using qualified procedures and that proper process monitoring be performed.

This guide describes a method acceptable to the NRC staff for implementing these requirements with regard to the control of welding in fabricating and joining safety-related austenitic stainless steel com ponents and systems in light-water-cooled nuclear power plants. The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.

B. DISCUSSION

Inspection of some welds in austenitic stainless steel components of nuclear reactors has revealed the

  • Lines indicate substantive changes from previous issue.presence of microfissures.

Further investigations re lated the presence of the microfissures to the low delta ferrite content of the deposited weld metal. Since microfissures in austenitic welds may have an adverse effect on the integrity of components, the control of weld deposits to ensure the presence of delta ferrite in these welds is advisable.

As part of achieving this control, recommendations to test production welds were made in the original version of this guide (Safety Guide 31, "Control of Stainless Steel Welding"), and these recommenda tions were retained in Revision 1. Because licensees and other representatives of the nuclear industry be lieved that adequate control of filler metal ferrite con tent would consistently provide sound weld deposits with an absence of microfissures, a cooperative study group was formed by ASME, ANSI, and NRC to in vestigate the problem and the alternatives that would ensure adequate control of ferrite content. The study group analyzed data from welds prepared by eight different procedures.

About 1500 test results were analyzed, and recommendations were made to both ASME and NRC on how testing of production welds could be reduced without sacrifice of ferrite content control. Revision 2 and this Revision 3 are based on those recommendations.

At present, the ASME Code* provisions incorporated by reference into the NRC regulations require compliance with one of two alternative methods for control of delta ferrite in weld metal filler materials;

either a chemical analysis method or a magnetic measurement method. The NRC staff does not consider either method adequate

  • Winter 1976 Addenda,Section III, "Nuclear Power Plant Components," ASME Boiler and Pressure Vessel Code. Copies may be obtained from the American Society of Mechanical En gineers, United Engineering Center, 345 East 47th Street, New York. New York 1001

7. USNRC REGULATORY

GUIDES Comments should be sent to the Secretary of the Commission, U.S. Nuclear Regu. latory Commission.

Washington.

D.C. 20555. Attention Docketing and Service Regulatory Guides are issued to describe and make available to the public methods Branch. acceptable to the NRC staff of implementing specific parts of the Commission's regulations.

to delineate techniques used by the staff in evaluating specific problems The guides are issued in the following ten broad divisions or postulated accidents, or to provide guidance to applicants.

Regulatory Guides are not substitutes for regulations.

and compliance with them is not required.

1. Power Reactors 6. Products Methods and solutions different from those set out in the guides will be accept. 2. Research and Test Reactors

7. Transportation

3. Fuelsand Materials Facilities

8. Occupational Health able if they provide a basis for the findings requisite to the issuance or continuance

4. Environmental and Siting 9 Antitrust Review of a permit or license by the Commitsion.

5. Materials and Plant Protection

10. General Comments and suggestions for improvements in these guides are encouraged at all Requests for single copies of issued guides (which may be reproducedI

or for place times, and guides will be revised, as appropriate, to accommodate comments and ment on an automatic distribution list for single copies of future guides in specific to reflect new information or experience.

This guide was revised as a result of divisions should be made in writing to the US. Nuclear Regulatory Commission.

substantive comments received from the public and additional staff review. Washington.

D.C. 20555, Attention Director.

Division of Document Control.Revision 3 April 1978 by itself to ensure controlled delta ferrite in produc tion welds. The recommendations of this guide are intended to supplement the ASME Code requirements to ensure control of delta ferrite in welds in austenitic stainless steel core support structures and Class 1 and 2 components.

The recommendations for testing of production welds in Revision 1 of this guide have been replaced by recommendations for process control by testing of weld test pads. These changes will considerably re duce the testing effort needed to control delta ferrite in welds. The staff recommends that ferrite content in the weld filler metal as depicted by a ferrite number (FN) be between 5 and 20. This lower limit provides suffi cient ferrite to avoid microfissuring in welds, whereas the upper limit provides a ferrite content adequate to offset dilution.

C. REGULATORY

POSITION 1. Verification of Delta Ferrite Content of Filler Materials Prior to production usage, the delta ferrite content of test weld deposits from each lot and each heat of weld filler metal procured for the welding of austeni tic stainless steel core support structures and Class 1 and 2 components should be verified for each process to be used in production.

It is not necessary to make delta ferrite determina tions for SFA-5.4 type 16-8-2 weld metal or for filler metal used for weld metal cladding.

Delta ferrite de terminations for consumable inserts, electrodes, rod or wire filler metal used with the gas tungsten arc welding process, and deposits made with the plasma arc welding process may be predicted from their chemical composition using an applicable constitu tional diagram to demonstrate compliance.

Delta fer rite verification should be made for all other proc esses by tests using magnetic measuring devices on undiluted weld deposits.

For submerged arc welding processes, the verification tests for each wire and flux combination may be made on a production weld or simulated production weld. All other delta ferrite weld filler verification tests should be made on weld pads that contain undiluted layers of weld metal. 2. Ferrite Measurement Appendix A to this guide contains extracts from a future edition of the American Welding Society's AWS A5.4, "Specification for Corrosion-Resisting

  • This specification has been recommended by the Subcommit tee on Welding of Stainless Steels of the High Alloys Committee of the Welding Research Council and has been approved by the American Welding Society (AWS). It is expected to be pub lished as AWS A5.4-78.Chromium and Chromium-Nickel Steel Covered Welding Electrodes,"*

which describes a procedure for pad preparation and ferrite measurement.

The NRC staff considers this procedure acceptable for use with covered electrodes.

3. Instrumentation The weld pad should be examined for ferrite con tent by a magnetic measuring instrument which has been calibrated against a Magnegage in accordance with American Welding Society Specification AWS A4.2-74, "Procedures for Calibrating Magnetic In struments to Measure the Delta Ferrite Content of Austenitic Stainless Steel Weld Metal."'**

The Mag negage should have been previously calibrated in ac cordance with AWS A4.2-74 using primary standards as defined therein.

4. Acceptability of Test Results Weld pad test results showing an average Ferrite Number from 5 to 20 indicate that the filler metal is acceptable for production welding of Class 1 and 2 austenitic stainless steel components and core support structures.

The upper limit of 20 may be waived for (a) welds that do not receive postweld stress relief heat treat ment or welds for which such postweld stress relief treatment is conducted at temperatures less than 900'F, (b) welds that are given a solution annealing heat treatment, and (c) welds that employ consuma ble inserts.

5. Quality Assurance The applicable provisions of 10 CFR Part 50, Ap pendix B, should be used in verifying compliance with requirements for delta ferrite as described herein.

D. IMPLEMENTATION

The purpose of this section is to provide informa tion to applicants regarding the NRC staff's plans for using this regulatory guide. Except in those cases in which the applicant pro poses an acceptable alternative method for complying with specified portions of the Commission's regula tions, the method described herein will be used in the evaluation of submittals in connection with construc tion permit applications docketed after October 1, 1978. If an applicant wishes to use this regulatory guide in developing submittals for applications docketed on or before October 1, 1978, the pertinent portions of the application will be evaluated on the basis of this guide. **Copies may be obtained from the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125.1.31-2 APPENDIX A The following is mainly extracted from a future edition of the American Welding Society's (AWS) "Specification for Corrosion-Resisting Chromium and Chromium-Nickel Steel Covered Welding Elec trodes," which the AWS plans to publish as AWS A5.4-78.*

This material describes a procedure for weld pad preparation and ferrite measurement of cov ered electrode**

deposits.

EXTRACT: A4. 10 When it is desired to measure ferrite con tent, the following procedure is recommended:

A4.10.1 Weld pads as detailed in Figure 4 are prepared as prescribed in paragraphs A4.10.2 through A4.10.4.

A4.10.2 The weld pad shall be built up between two copper bars laid parallel on the base plate by de positing single weld bead layers, one on top of the other, to a minimum height of 13 mm (1/2 in.). The spacing between the copper bars for the size of the electrode being tested shall be as specified in Figure 4. An optional welding fixture is shown in Figure 5. If carbon steel is used as the base plate, the weld pad shall be built up to a minimum height of 16 mm (5 in.).

  • When published, copies of AWS A5.4-78 may be purchased from the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125. ** Note: The U.S. customary units in this specification are given as equivalent values to the SI units. The standard sizes and dimensions used in the two systems are not identical and for this reason conversion from a standard size of dimension in one system will not always coincide with the standard size of dimen sion in the other. Suitable conversions encompassing standard sizes of both can be made if appropriate tolerances are applied in each case. The SI values (including tolerances)

given here for filler metal diameter, length, and package size were selected to fit the product sizes which presently are U.S. standards.

Toler ances are used in some cases in this specification but not in others. In those cases where no tolerances are given, the values are those that would be obtained if the measurements were taken in SI units. In this specification, a covered electrode is defined as follows: Covered Electrode-A

composite filler-metal elec trode consisting of a core of a bare electrode or metal cored electrode to which a covering sufficient to provide a slag layer on the weld metal has been applied. The covering may contain materials providing such functions as shielding from the atmos phere, deoxidation, and arc stabilization and can serve as a source of metallic additions to the weld.A4.10.3 The welding current used for the size of the electrode being tested may be as specified in Fig ure 4 and the arc length shall be as short as practica ble. The weld bead layers may be deposited with a weave, if 'necessary, to fill the space between the copper bars. The arc shall not be allowed to impinge on the copper bars. The welding direction for each pass shall be alternated and the weld stops and starts shall be located at the ends of the weld buildup. Each pass shall be cleaned prior to depositing the next weld bead. The maximum interpass temperature shall be 95'C (200°F).**

Between passes, the weld pad may be cooled by quenching in water not sooner than 20 seconds after the completion of each pass. The last pass shall be air-cooled to below 430'C (800'F) prior to quenching in water. A4.10.4 The completed weld pad shall be draw filed, machined, or surface ground to provide suffi cient finished surface to make the required ferrite readings.

Draw filing or its equivalent filing method shall be performed with a 360 mm (14 in.)** mill bastard file held on both sides of the weld with the long axis of the file perpendicular to the long axis of the weld. The file should preferably not have been previously used on ferritic material and should be free from loosely adhering materials if previously used. Draw filing shall be accomplished by smooth forward and backward strokes along the length of the weld while applying a firm downward pressure.

Crossfiling shall not be permitted.

The finished machined, ground, or filed surface shall be smooth with all traces of weld ripple removed and shall be continuous in the length where measurements are to be taken. The width of the prepared surface shall not be less than 3 mm (1/8 in.).** A4.10.5 A total of six ferrite readings shall be taken on the prepared surface along the longitudinal axis of the weld pad with an instrument calibrated in accordance with the procedures specified in AWS A4.2, "Standard Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic Stainless Steel Weld Metal" (latest edition).

A4.10.6 The six readings 'obtained shall be aver aged to a single value for conversion to Ferrite Number.1.31-3

-H Copper bar-L L Ferrite shall be measured in this area free of arc starts and cratersI I I BASE PLATE 1 465 min All dimensions in millimetres, U.S. EQUIVALENTS*

Electrode diameter (mm)1.6 2.0 2.4 3.2 4.0 4.8 Welding current (amperes)35-45 45-55 65-75 90-100 120-140 165-185 240-260 In drawing above (approx. mm)W 6 6 8 10 13 15 18 L 30 30 40 40 40 40 40 See Editor's Note on Page 1.31-3. Fig 4 -Details of Weld Pad for Ferrite Test 1.31-4 25x25x75 1 40 -25 min o mm 1.6 2.0 2.4 3.2 4.0 4.8 6.4 6 8 9.5 10 13 15 18 25 30 40 65 75 in. 1/16 5/64 3/32 1/8 5/32 3/16 1/4 0.25 0.3 3/8 0.4 0.5 0.6 0.7 1 1-1/4 1-1/2 2-1/2 3.I

Copper bars 85 long of cross section as shown in A-A' below.Copper bar 16 high x 9.5 thick x 70 long.Note: All dimensions are in millimetres.

U.S. EQUIVALENTS*

MM in.4.0 4.8 9.5 16 25 70 85 Copper bar same -as shown at opposite end A Type 1 For 4.0 dia. Electrodes and smaller COPPER 16 BAR T Cross Section A-A'This design allows increased visibility, making it easier to hold a short arc length.5/32 3/16 3/8 5/8 1 2-3/4 3-3/8*See Editor's Note on Page 1.31-3.COPPEIR BAR 25 square COPPER BAR Type 2 For 4.8 & larger welding electrodes and for any pads on carbon steel base plate Fig. 5 -Optional Welding Fixture for Welding Ferrite Test Pads 1.31-5 I


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