AWS_C3.6M_C3.6-2008

Specification forFurnace Brazing

AWS C3.6M/C3.6:2008An American National Standard

550 N.W. LeJeune Road, Miami, FL 33126

AWS C3.6M/C3.6:2008An American National Standard

Approved by theAmerican National Standards Institute

September 12, 2007

Specification for

Furnace Brazing

3rd Edition

Supersedes AWS C3.6:1999

Prepared by theAmerican Welding Society (AWS) C3 Committee on Brazing and Soldering

Under the Direction of theAWS Technical Activities Committee

Approved by theAWS Board of Directors

AbstractThis specification provides the minimum fabrication, equipment, material, process procedure requirements, as well asinspection requirements for the furnace brazing of steels, copper, copper alloys, and heat- and corrosion-resistant alloysand other materials that can be adequately furnace brazed (the furnace brazing of aluminum alloys is addressed in AWSC3.7M/C3.7, Specification for Aluminum Brazing). This specification provides criteria for classifying furnace brazedjoints based on loading and the consequences of failure and quality assurance criteria defining the limits of acceptabilityin each class. This specification defines acceptable furnace brazing equipment, materials, and procedures, as well as therequired inspection for each class of joint.

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International Standard Book Number: 978-0-87171-080-2American Welding Society

550 N.W. LeJeune Road, Miami, FL 33126© 2007 by American Welding Society

All rights reservedPrinted in the United States of America

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Authorization to photocopy items for internal, personal, or educational classroom use only or the internal, personal, oreducational classroom use only of specific clients is granted by the American Welding Society provided that the appropriatefee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, tel: (978) 750-8400; Internet:<www.copyright.com>.

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Statement on the Use of American Welding Society Standards

All standards (codes, specifications, recommended practices, methods, classifications, and guides) of the AmericanWelding Society (AWS) are voluntary consensus standards that have been developed in accordance with the rules of theAmerican National Standards Institute (ANSI). When AWS American National Standards are either incorporated in, ormade part of, documents that are included in federal or state laws and regulations, or the regulations of other govern-mental bodies, their provisions carry the full legal authority of the statute. In such cases, any changes in those AWSstandards must be approved by the governmental body having statutory jurisdiction before they can become a part ofthose laws and regulations. In all cases, these standards carry the full legal authority of the contract or other documentthat invokes the AWS standards. Where this contractual relationship exists, changes in or deviations from requirementsof an AWS standard must be by agreement between the contracting parties.

AWS American National Standards are developed through a consensus standards development process that bringstogether volunteers representing varied viewpoints and interests to achieve consensus. While the AWS administers theprocess and establishes rules to promote fairness in the development of consensus, it does not independently test, evalu-ate, or verify the accuracy of any information or the soundness of any judgments contained in its standards.

AWS disclaims liability for any injury to persons or to property, or other damages of any nature whatsoever, whetherspecial, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, or relianceon this standard. AWS also makes no guarantee or warranty as to the accuracy or completeness of any informationpublished herein.

In issuing and making this standard available, AWS is neither undertaking to render professional or other services for oron behalf of any person or entity, nor is AWS undertaking to perform any duty owed by any person or entity to someoneelse. Anyone using these documents should rely on his or her own independent judgment or, as appropriate, seek theadvice of a competent professional in determining the exercise of reasonable care in any given circumstances. It isassumed that the use of this standard and its provisions are entrusted to appropriately qualified and competent personnel.

This standard may be superseded by the issuance of new editions. Users should ensure that they have the latest edition.

Publication of this standard does not authorize infringement of any patent or trade name. Users of this standard acceptany and all liabilities for infringement of any patent or trade name items. AWS disclaims liability for the infringement ofany patent or product trade name resulting from the use of this standard.

Finally, the AWS does not monitor, police, or enforce compliance with this standard, nor does it have the power to do so.

On occasion, text, tables, or figures are printed incorrectly, constituting errata. Such errata, when discovered, are postedon the AWS web page (www.aws.org).

Official interpretations of any of the technical requirements of this standard may only be obtained by sending a request,in writing, to the appropriate technical committee. Such requests should be addressed to the American Welding Society,Attention: Managing Director, Technical Services Division, 550 N.W. LeJeune Road, Miami, FL 33126 (see Annex B).With regard to technical inquiries made concerning AWS standards, oral opinions on AWS standards may be rendered.These opinions are offered solely as a convenience to users of this standard, and they do not constitute professionaladvice. Such opinions represent only the personal opinions of the particular individuals giving them. These individualsdo not speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpretations ofAWS. In addition, oral opinions are informal and should not be used as a substitute for an official interpretation.

This standard is subject to revision at any time by the AWS C3 Committee on Brazing and Soldering. It must bereviewed every five years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommendations,additions, or deletions) and any pertinent data that may be of use in improving this standard are required and should beaddressed to AWS Headquarters. Such comments will receive careful consideration by the AWS C3 Committee onBrazing and Soldering and the author of the comments will be informed of the Committee’s response to the comments.Guests are invited to attend all meetings of the AWS C3 Committee on Brazing and Soldering to express their commentsverbally. Procedures for appeal of an adverse decision concerning all such comments are provided in the Rules ofOperation of the Technical Activities Committee. A copy of these Rules can be obtained from the American WeldingSociety, 550 N.W. LeJeune Road, Miami, FL 33126.

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Personnel

AWS C3 Committee on Brazing and SolderingP. T. Vianco, Chair Sandia National Laboratories

R. W. Smith, Vice Chair Materials Resources InternationalS. N. Borrero, Secretary American Welding Society

G. L. Alexy The Prince & Izant CompanyR. Aluru Chromalloy Gas Turbine Corporation

B. Barten Delphi Thermal & InteriorD. W. Bucholz Conforma Clad, IncorporatedD. E. Budinger General Electric Aviation

C. F. Darling Lucas-Milhaupt, IncorporatedW. J. Engeron Engineered Alloy & Systems Support

S. L. Feldbauer Abbott Furnace CompanyY. Flom NASA Goddard Space Flight Center

D. Fortuna Sulzer Metco (U.S.), IncorporatedY. Gao Pratt & Whitney Rocketdyne

R. A. Gross Gourley Curtiss-WrightS. R. Hazelbaker The Prince & Izant Company

T. P. Hirthe Kru-Mar Manufacturing ServicesF. M. Hosking Sandia National Laboratories

J. R. Jachna Modine Manufacturing CompanyD. A. Javernick Los Alamos National Laboratory

D. Kane ADB IndustriesG. F. Kayser Pratt & Whitney Rocketdyne

M. J. Kuta Lucas-Milhaupt, IncorporatedE. Liguori Scarrott Metallurgical

M. J. Lucas, Jr. General Electric AviationR. P. McKinney The Prince & Izant Company

C. R. Moyer Bodycote Thermal ProcessingT. Oyama WESGO Metals

C. A. Paponetti, Sr. Expert Brazing & Heat Treating, IncorporatedR. L. Peaslee Wall Colmonoy CorporationA. Rabinkin Metglas, Incorporated / Titanium Brazing

A. E. Shapiro Titanium Brazing, IncorporatedC. Walker Sandia National Laboratories

Advisors to the AWS C3 Committee on Brazing and Soldering

A. Belohlav Lucas-Milhaupt, IncorporatedS. S. Bhargava American Axle & Manufacturing Company

S. Christy Pratt and WhitneyN. C. Cole NCC Engineering

C. E. Fuerstenau Lucas-Milhaupt, IncorporatedP. K. Gupta Honeywell Aerospace

M. J. Higgins Pratt and Whitney H. Lichtenberger Williams Advanced Materials

E. Lugscheider Aachen University of TechnologyW. D. Rupert Wolverine Joining Technologies

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AWS C3D Subcommittee on Brazing SpecificationsJ. R. Jachna, Chair Modine Manufacturing Company

S. R. Hazelbaker, Vice Chair The Prince & Izant CompanyS. N. Borrero, Secretary American Welding Society

R. Aluru Chromalloy Gas Turbine CorporationD. E. Budinger General Electric AviationS. L. Feldbauer Abbott Furnace Company

Y. Flom NASA Goddard Space Flight CenterC. E. Fuerstenau Lucas-Milhaupt, Incorporated

Y. P. Gao Pratt & Whitney RocketdyneR. A. Gross Gourley Curtiss-Wright

T. P. Hirthe Kru-Mar Manufacturing ServicesF. M. Hosking Sandia National Laboratories

D. Kane ADB IndustriesG. F. Kayser Pratt & Whitney Rocketdyne

M. J. Kuta Lucas-Milhaupt, IncorporatedE. Liguori Scarrott Metallurgical

J. A. Liguori Scarrott MetallurgicalM. J. Lucas, Jr. General Electric Aviation

R. P. McKinney The Prince & Izant CompanyC. R. Moyer Bodycote Thermal Processing

J. Newman Laser Technology, IncorporatedT. Oyama WESGO Metals

C. A. Paponetti, Sr. Expert Brazing and Heat Treating, IncorporatedR. L. Peaslee Wall Colmonoy Corporation

M. J. Pohlman Honeywell AerospaceR. W. Smith Materials Resources InternationalP. T. Vianco Sandia National LaboratoriesC. M. Volpe Wolverine Joining Technologies

C. Walker Sandia National LaboratoriesC. Wohlmuth Consultant

Advisors to the AWS C3D Subcommittee on Brazing Specifications

B. Barten Delphi Thermal & InteriorN. C. Cole NCC Engineering

P. K. Gupta Honeywell AerospaceM. J. Higgins Pratt and Whitney

T. A. Kern ConsultantH. H. Lang York International Corporation

H. Mizuhara ConsultantW. D. Rupert Wolverine Joining Technologies

K. P. Thornberry Care Medical, IncorporatedR. W. Walls Walls Engineering

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Foreword

This foreword is not part of AWS C3.6M/C3.6:2008, Specification forFurnace Brazing, but is included for informational purposes only.

This specification is one of a series prepared at the request of the Aerospace Materials Division (AMD) of the Society ofAutomotive Engineers (SAE) and a number of other organizations to replace the military specification MIL-B-7883,Brazing of Steels, Copper, Copper Alloys, Nickel Alloys, Aluminum, and Aluminum Alloys, which addressed all brazingprocesses. It became both obsolete and very cumbersome as brazing technology proliferated and became more complex.

Addressing all of the diverse brazing processes in one concise, easily understood document was found to be impractical;therefore, a series of five independent specifications on brazing have been written, all in the same format. These areAWS C3.4M/C3.4, Specification for Torch Brazing; AWS C3.5M/C3.5, Specification for Induction Brazing; the presentdocument, AWS C3.6M/C3.6, Specification for Furnace Brazing; AWS C3.7M/C3.7, Specification for Aluminum Brazing,and C3.8M/C3.8, Specification for the Ultrasonic Examination of Brazed Joints.

The decision to subdivide the technology in this way was based on a survey of production brazing applications conductedby the AWS C3 Committee on Brazing and Soldering. The survey demonstrated that these five specifications would coverthe vast majority of brazing performed today.

After the completion of the fourth brazing specification, it was determined that a document providing specific criteriaand requirements for the application of ultrasonic testing to brazed joints was needed. Therefore, AWS C3.8M/C3.8,Specification for the Ultrasonic Examination of Brazed Joints, was written to complement this series.

This third edition supersedes AWS C3.6:1999, bearing the same title.

Comments and suggestions for the improvement of this standard are welcome. They should be sent to the Secretary, AWSC3 Committee on Brazing and Soldering, American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.

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Table of Contents

Page No.

Personnel ......................................................................................................................................................................vForeword ....................................................................................................................................................................vii

1. Scope .....................................................................................................................................................................1

2. Normative References .........................................................................................................................................1

3. Terms and Definitions.........................................................................................................................................2

4. Classification of Brazed Joints ...........................................................................................................................24.1 Method of Classification..............................................................................................................................24.2 Class A Joints ..............................................................................................................................................24.3 Class B Joints...............................................................................................................................................34.4 Class C Joints...............................................................................................................................................34.5 No Class Specified.......................................................................................................................................3

5. Process Requirements .........................................................................................................................................35.1 Process Description .....................................................................................................................................35.2 Equipment....................................................................................................................................................35.3 Materials ......................................................................................................................................................55.4 Procedure Requirements..............................................................................................................................55.5 Brazing Procedure Qualification .................................................................................................................65.6 Safety and Health.........................................................................................................................................6

6. Quality Assurance Provisions ............................................................................................................................76.1 Responsibility for Inspection.......................................................................................................................76.2 Requirements for Compliance .....................................................................................................................76.3 Sequence of Inspection and Manufacturing Operations..............................................................................76.4 Required Inspection of Brazed Joints ..........................................................................................................76.5 Acceptance Criteria .....................................................................................................................................9

Annex A (Informative)—Informative References .....................................................................................................11Annex B (Informative)—Guidelines for the Preparation of Technical Inquiries.......................................................13

List of AWS Documents on Brazing and Soldering ..................................................................................................15

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1. ScopeThis specification presents the minimum fabrication andquality requirements for the furnace brazing of materialssuch as steels, stainless steels, nickel, nickel alloys, copper,copper alloys, and heat- or corrosion-resistant materialsas well as other materials that can be adequately furnacebrazed. Note that the furnace brazing of aluminum alloysis addressed in AWS C3.7M/C3.7, Specification forAluminum Brazing.

The purpose of this specification is to standardize fur-nace brazing process requirements and control brazedjoint quality for all applications requiring brazed joints ofassured quality. This document establishes minimumrequirements for processes and products with a minimumof explanatory information so that sources of ambiguityare minimized. It assigns responsibility for the ultimatequality of the brazed product to a single organization andpermits that organization to modify requirements ifappropriate to the application. It requires proper docu-mentation of any such modifications.

Procedures for the protection of the safety and health ofthose performing resistance brazing and related opera-tions are of great importance. However, safety and healthissues and concerns are beyond the scope of this standardand therefore are not fully addressed herein. Safety andhealth information is available from other sources,including, but not limited to, ANSI Z49.1, Safety inWelding, Cutting, and Allied Processes.

This standard makes use of both the International Systemof Units (SI) and U.S. Customary Units. The latterare shown within brackets [ ], or in appropriate columnsin tables and figures. The measurements may not beexact equivalents; therefore, each system shall be usedindependently.

2. Normative ReferencesThe standards listed below contain provisions which,through reference in this text, constitute mandatory pro-

visions of this AWS standard. For undated references,the latest edition of the referenced standard shall apply.For dated references, subsequent amendments to, or revi-sions of, any of these publications do not apply.

American Welding Society (AWS) standards:1

AWS A2.4, Standard Symbols for Welding, Brazing,and Nondestructive Examination;

AWS A3.0, Standard Welding Terms and Definitions,Including Terms for Adhesive Bonding, Brazing, Solder-ing, Thermal Cutting, and Thermal Spraying;

AWS A5.8/A5.8M, Specification for Filler Metals forBrazing and Braze Welding;

AWS A5.31, Specification for Fluxes for Brazing andBraze Welding;

AWS B2.2, Standard for Brazing Procedure and Per-formance Qualification;

AWS C3.3, Recommended Practices for the Design,Manufacture, and Examination of Critical Brazed Com-ponents; and

AWS C3.8M/C3.8, Specification for the UltrasonicExamination of Brazed Joints.

American Society for Quality (ASQ) standard:2

ASQ Z1.4, Sampling Procedures and Tables forInspection by Attributes.

Society of Automotive Engineers (SAE)/AerospaceMaterials Division (AMD) standards:3

SAE AMS 2403, Plating, General Purpose;

1 AWS standards are published the American Welding Society,550 N.W. LeJeune Road, Miami, FL 33126.2 ASQ standards are published by the American Society forQuality, 600 North Plankinton Avenue, Milwaukee, WI 53203-3005.3 SAE standards are published the Society of AutomotiveEngineers, 400 Commonwealth Drive, Warrendale, PA 15096-0001.

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SAE AMS 2424, Plating, Nickel, Low StressedDeposit;

SAE AMS 2451/1, Plating, Brush, Nickel GeneralPurpose; and

SAE AMS 2750, Pyrometry.

American Society for Testing and Materials (ASTM)standards:4

ASTM E 230, Electromotive Force (EMF) Tables forStandardized Thermocouples;

ASTM E 1742, Standard Practice for RadiographicExamination; and

ASTM E 1417, Standard Practice for Liquid Pene-trant Examination.

National Conference of Standards Laboratories (NCSL)standard:5

NCSL Z540-1, General Requirements for CalibrationLaboratories and Measuring and Test Equipment.

3. Terms and DefinitionsAWS A3.0, Standard Welding Terms and Definitions,Including Terms for Adhesive Bonding, Brazing, Solder-ing, Thermal Cutting, and Thermal Spraying, providesthe basis for terminology used herein.

For the purposes of this document, the following termsand definitions apply:

braze joint. The total area, as defined by the engineeringdrawing, of the faying surfaces to be joined by braz-ing and the fillets that form at the edges of that area.

braze joint proper. The total area, as defined by theengineering drawing, of the faying surfaces to bejoined by brazing, excluding any fillets that form atthe edges of that area.

brazing symbol. The symbol on the engineering draw-ing designating the location, class, and configurationof the brazed joint. Such symbols shall be in accor-dance with AWS A2.4, Standard Symbols for Weld-ing, Brazing, and Nondestructive Examination.

4 ASTM standards are published by the American Society forTesting and Materials, 100 Barr Harbor Drive, West Consho-hocken, PA 19428-2959.5 NCSL standards are published by the National Conference ofStandards Laboratories, 2995 Wilderness Place, Suite 107,Boulder, CO 80301-5404.

braze wetting. Brazing filler metal should be smooth,adherent, and exhibiting no evidence of repulsion ofthe brazing filler metal by the base metal surface.

brazing procedure specification (BPS). A documentspecifying the required brazing variables for a spe-cific application.

joint dimensions. The joint length is the greater of thetwo dimensions of the joint parallel to the faying sur-faces. The joint width is the lesser of these two dimen-sions of the joint. The clearance between the fayingsurfaces is the third dimension to be considered.

lack of bond. A condition in a brazed joint wherealthough brazing filler metal is present between thefaying surfaces, the filler metal does not adhere orform a metallurgical bond with the base metal. It mostcommonly occurs when brazing filler metal is pre-placed between contaminated faying surfaces.

Organization Having Quality Responsibility. Theorganization responsible to the end user of the productfor the quality of the product and its suitability for theintended use. This organization is usually the manu-facturer and marketer of the final product in commer-cial business and the prime contractor in governmentprocurement. Although such organizations may sub-contract brazing and related operations to others, theycannot delegate the ultimate responsibility for the ser-vice suitability of the product to these subcontractors.

surface porosity. A roughened or spongy appearance oropen pores on the surface of the brazed fillet. Suchpores are not sharply linear or crack-like in shape.Surface porosity is confined to the fillet and does notprogress into the braze joint proper.

void. Any area of the braze joint proper that is not com-pletely filled with brazing filler material.

4. Classification of Brazed Joints4.1 Method of Classification. Furnace brazed joints areclassified in this specification based on two criteria: thedesign requirements and the consequences of their fail-ure. It is the responsibility of the Organization HavingQuality Responsibility to evaluate these or other factorsand assign the proper classification. This classificationcontrols which inspection methods and limits arerequired.

4.2 Class A Joints. Class A joints are those joints sub-jected to high stresses, cyclic stresses, or both, the failureof which could result in significant risk to persons or prop-erty, or could result in a significant operational failure.

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4.3 Class B Joints. Class B joints are those joints sub-jected to low or moderate stresses, cyclic stresses, orboth, the failure of which could result in significantrisk to persons or property, or in significant operationalfailure.

4.4 Class C Joints. Class C joints are those joints sub-jected to low or moderate stresses, cyclic stresses, orboth, the failure of which would have no significantdetrimental effect.

4.5 No Class Specified. When no class is specified onthe engineering drawing or other applicable documentapproved by the Organization Having Quality Responsi-bility, Class A requirements shall apply. However,because of the confusion that can result, all engineeringdrawings referencing this specification should statethe class of the brazed joint in the brazing symbol. Sym-bols shall be in accordance with AWS A2.4, StandardSymbols for Welding, Brazing, and NondestructiveExamination.

5. Process Requirements5.1 Process Description. Furnace brazing is a process inwhich assembled components, with brazing filler metalpreplaced, are loaded into a furnace. The furnace is thenpurged with a neutral or reducing atmosphere, or evacu-ated of air, and heated to a certain temperature (generallyabove the liquidus of the brazing filler metal, but lessthan the melting point of the base metals). The braze-ments are then cooled or quenched at an appropriate rateso as to minimize distortion and produce the requiredproperties in the brazing filler metal and base material.This cycle is designed to produce the melting and solidi-fication of the brazing filler metal required to join thecomponents without melting or damaging the base metals.

5.2 Equipment

5.2.1 General Furnace Requirements. All brazingfurnaces shall have automatic temperature control andrecording devices in good working order capable of con-trolling the temperature profile of the furnace to therequirements of this specification. Furnaces shall haveadequate capacity to accomplish uniform heating of theworkload at the rate required to prevent both unaccept-able thermal distortion of the assemblies and liquation ofthe brazing filler metal. The furnace and associatedequipment shall be properly maintained in good workingorder.

5.2.2 Temperature Measurement and ControlInstruments. In closed, batch-type furnaces, suitableinstrumentation and thermocouples (see 5.2.3) shall beprovided to measure and control the temperature of

assemblies being brazed. In equipment where SAE AMS2750, Pyrometry, is not used in its entirety, the provi-sions of 5.2.2 shall apply. The instrument shall be of thepotentiometer type or equivalent capable of measuring,recording, and providing a permanent record of the tem-perature through the entire brazing thermal cycle. In fur-naces with multiple heating zones (i.e., preheat zone,braze zone, postheat zone), such instrumentation shall beprovided for each zone.

All instruments used to measure the temperature ofassemblies being brazed or to control furnace tempera-ture, or both, shall have an indicated temperature accu-racy range of not more than 0.25% of the maximum forwhich the furnace is qualified over the entire operatingrange, including each furnace heat zone. The indicatedtemperature accuracy of the instrument shall be deter-mined in accordance with the equipment manufacturer’srecommendations using a known electromotive forceinput traceable to the National Institute of Standards andTechnology.6

All instruments shall be calibrated in accordance withSAE AMS 2750 and NCSL Z540-1, General Require-ments for Calibration Laboratories and Measuring andTest Equipment. Instruments shall be calibrated on a reg-ular schedule or whenever repairs or modifications aremade to them.

5.2.3 Workload Control Thermocouples. Workloadcontrol thermocouples shall be of a type listed in ASTME 230, Electromotive Force (EMF) Tables for Standard-ized Thermocouples. They shall be calibrated by compar-ison to a known calibrated test instrument traceable tothe National Institute of Standards and Technology withthe frequency specified by AMS 2750 and replaced asrequired.

5.2.4 Work-Zone Control Thermocouples. Work-zone control thermocouples (furnace control) shall be ofa type listed in ASTM E 230. They shall be calibrated bya comparison to a known calibrated instrument traceableto the National Institute of Standards and Technologywith the frequency specified by SAE AMS 2750 andreplaced as required.

5.2.5 Atmosphere-Controlling Instruments

5.2.5.1 Electronic Dew Point MeasuringDevices. Electronic dew point measuring devices shallbe calibrated in accordance with the manufacturer’s rec-ommendations against reference devices traceable to theNational Institute of Standards and Technology, or

6 National Institute of Standards and Technology (NIST),Office of Standard Reference Materials, 100 Bureau Drive,Stop 2300, Gaithersburg, MD 20899-2300.

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equivalent. Such gauges shall be calibrated before initialuse and recalibrated at a frequency not to exceed sixmonths.

5.2.5.2 Vacuum Measuring Devices. Thermocou-ple gages shall be used to measure pressure higher than0.13 Pa [10–3 torr]. Suitable electronic gauges shall beused to measure pressures of 0.13 Pa [10–3 torr] or less.These gauges shall be so mounted as to measure the pres-sure within the work zone of the furnace. Suitable instru-ments for reading and recording the pressure within thefurnace work zone shall also be provided.

These instruments and gauges shall be calibrated inaccordance with the manufacturer’s recommendationsagainst reference standards traceable to the NationalInstitute of Standards and Technology. Such gauges shallbe calibrated before initial use and recalibrated at a fre-quency not to exceed six months.

5.2.6 Furnace Qualification. In equipment for whichSAE AMS 2750 is not used in its entirety, the provisionsof 5.2.6 shall apply. All furnaces shall be qualified fortemperature uniformity and control prior to initial use forproduction brazing. Furnaces used for brazing above1093°C [2000°F] shall be requalified at least every threemonths. Furnaces used only for brazing below 1093°C[2000°F] shall be requalified every six months.

All furnaces shall be requalified after any repairs or alter-ations to the furnace that might affect furnace tempera-ture control or uniformity (e.g., new heating elements,new control thermocouple(s), burner tubes, replacementof shielding burner tubes). Requalification is notrequired when the repair or alteration has previouslybeen documented not to affect the temperature control oruniformity of the furnace.

5.2.6.1 Furnace Qualification Procedure. Tem-perature uniformity tests may be conducted with a fur-nace load representative of production parts, material,racks, or empty, and using a typical production atmo-sphere or vacuum level. The test shall be conductedusing new or recalibrated thermocouples. The potentio-metric measuring equipment or equivalent shall meet therequirements of 5.2.2.

Instruments used to control the furnace during produc-tion brazing shall not be used to monitor the qualificationthermocouples. A minimum of three thermocouples shallbe used to determine the temperature uniformity of fur-naces having a work zone volume of 0.085 m3 (cubicmeters) [3 ft3 (cubic feet)] or less. A minimum of fivethermocouples shall be used to determine the uniformityof furnaces having a work zone between 0.085m3 to0.28m3 [3 ft3 to 10 ft3]. A minimum of nine thermocou-ples or one thermocouple per 0.71m3 [25 ft3] of working

zone, whichever is greater, shall be used to determine theuniformity of furnaces having a work zone larger than0.28m3 [10 ft3]. No more than 40 thermocouples shall berequired to determine the temperature uniformity in thework zone of any furnace.

The thermocouples shall be symmetrically distributedwithin the work zone. Qualification shall be performed atthe highest and lowest brazing temperature at which thefurnace is used and at intermediate temperature such thatthe difference between qualification temperatures is notgreater than 315°C [600°F].

The temperature of all test and furnace control thermo-couples shall be recorded at intervals of no more thanfive minutes starting immediately after heating begins.Temperature measurement and recording shall continueat least 30 minutes after equilibrium has been reached todetermine the temperature pattern of the furnace. Theresults of the test shall be posted at the furnace and shallinclude the date of testing, the due date of the next test,the size of the work zone, and the results of the tests,including the location within the work zone of the hottestand coldest location.

Temperature uniformity may be run with a productionload when all requirements are met.

5.2.6.2 Temperature Uniformity Requirements.Before temperature equilibrium has been reached, notemperature reading shall exceed the temperature forwhich the furnace is being qualified by more than 14°C[25°F]. After temperature equilibrium has been reached,the temperature recorded by any test thermocouple shallnot vary from the selected furnace control temperatureby more than 14°C [25°F].

5.2.7 Atmosphere Furnace Requirements. Atmo-sphere controls shall be suitable for the intended purposeand in good working order. The gas supply and purifica-tion system shall be capable of supplying atmospheregases in accordance with the approved brazing procedurespecification (BPS) (see 5.5).

5.2.8 Vacuum Furnace Requirements. Vacuum fur-naces shall comply with the following performancerequirements: a cold and previously outgassed furnaceshall leak no more than 2.6 Pa [20 × 10–3 torr] per hourwhen the vacuum chamber is isolated from the pumpingsystem after being evacuated to 0.65 Pa [5 × 10–3 torr] orless.

Such a leak rate test shall be performed at least once aweek, or whenever there is reason to suspect that anunacceptable leak rate exists. The furnace should havethe capability of introducing argon, hydrogen, helium, ornitrogen, if required, for rapid cooling or to backfill afterevacuation to maintain a partial pressure, if required, to

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prevent sublimation of elements from the brazing fillermetal.

5.2.9 Fixtures. When required, furnace brazing fix-tures shall be made of suitable materials that will notcontaminate the furnace or workload either upon contactor by vaporization. Fixtures shall be designed, built, andmaintained to provide adequate support of assemblies,maintain proper braze joint clearance, and accommodatethermal expansion, all without adversely affecting massload and uniformity. Coating with stop-off, ceramic, orother protective coating of the fixtures may be requiredto prevent or minimize brazing of the assembly to thefixtures.

5.3 Materials

5.3.1 Furnace Brazing Materials Requirements. Asa minimum, the following furnace brazing materials (asrequired) shall be documented:

5.3.1.1 Brazing Filler Metals. The brazing fillermetal to be used shall be specified on the engineeringdrawing or accompanying documents and shall meet therequirements of AWS A5.8/A5.8M, Specification forFiller Metals for Brazing and Braze Welding, unless oth-erwise specified by the engineering drawing or accompa-nying documents. There are brazing filler metal/basemetal combinations that can cause severe service prob-lems under certain circumstances, e.g., nickel-basedalloys brazed with silver-bearing brazing filler metalsand iron-based alloys brazed with silver or copper-basedbrazing filler metals containing high phosphorous. Careshould be exercised to ensure that the brazing filler metalselected is metallurgically compatible with the basemetal and the furnace brazing process. Also, measuresmay need to be taken to prevent bonding of the braze-ment to the fixture material.

5.3.1.2 Fluxes. Fluxes shall be used in combina-tion with controlled atmospheres, other than in vacuum,only when specified on the approved BPS (see 5.5).Fluxes are specified in AWS A5.31/A5.31M, Specifica-tion for Fluxes for Brazing and Braze Welding. Otherfluxes may be used if permitted by the OrganizationHaving Quality Responsibility.

5.3.1.3 Cleaning Materials. Cleaning materialsshall leave no residue that will interfere with the wettingor flow of the filler metal. For example, alumina, silica,zirconia, or other nonmetallic blast cleaning media mayleave undesirable residue that could inhibit the brazewettability. Chemical cleaning solutions that are detri-mental to the base metal or brazing process shall not beused (see 5.6 for Safety Precautions).

5.3.1.4 Furnace Atmosphere. Furnace atmo-spheres shall be compatible with the brazing filler metaland base metals and suitable for the particular application.

5.3.1.5 Braze Stopoff. Braze stopoff, if used, shallbe suitable for the intended purpose and compatible withthe base metal(s), brazing filler metal, and any protectiveatmospheres used. In certain specialized applications,residues from stopoff materials can produce unaccept-able contamination of the product. If contamination issuspected, approval by the Organization Having QualityResponsibility should be obtained prior to use.

5.4 Procedure Requirements

5.4.1 Surface Preparation. The faying surfaces andadjacent areas of components to be brazed shall be freeof oil, grease, dirt, oxides, paint, scale, or other foreignsubstances that can interfere with the brazing process orcontaminate the braze joint. Burrs shall be removed asrequired prior to final cleaning to permit proper assemblyand brazing filler metal flow.

5.4.2 Nickel Plating. Nickel plating is recommendedon the braze joint areas of stainless, corrosion-, or heat-resistant steels having equal or greater percentage byweight of the following alloying elements:

(1) Titanium—0.40%,

(2) Aluminum—0.40%, and

(3) Titanium plus aluminum—0.70%.

Electrolytic nickel plate 0.01 mm to 0.02 mm [0.0004 into 0.0008 in] thick shall be applied in accordance withSAE AMS 2403, Plating, Nickel, General Purpose, SAEAMS 2424, Plating, Nickel Low-Stressed Deposit, orSAE AMS 2451/1, Plating, Brush, Nickel General Pur-pose. When the braze temperature is below 815°C[1500°F], SAE AMS 2404, Plating, Electroless Nickel,may be used. Other nickel plating methods per SAEAMS 2451/7, Plating, Brush, Nickel Low Stress, Medium-Hardness Deposit, may be used.

The plating shall extend 2.5 mm [0.10 in] minimumbeyond the brazed joint area indicated by the brazingsymbol on the engineering drawing unless the part con-figuration does not permit this allowance. In addition,nickel plate may be specified by the Organization Hav-ing Quality Responsibility to cover any area or the entiresurface of details or assemblies at its discretion. Whenthe drawing or purchase documents do not specify local-ized plating, the components may be completely plated.

CAUTION: When using nickel plating, phosphorus orsulfur—potential ingredients in the nickel plating—mayinteract with steel to form iron phosphides or sulfideswhen heated to over 815°C [1500°F]. Temperature mon-

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itoring shall be used, whenever possible, when heating toensure the nickel plating will not interact with the basemetals and form deleterious phases.

5.4.3 Joint Clearance. Joint clearance between fay-ing surfaces to be furnace brazed shall be controlled bythe assembly procedures so that proper joint clearance atthe brazing temperature is provided. When one of thefaying surfaces is cross-hatched or straight-line knurledin the direction of brazing filler metal flow into the joint,a line-to-line fit is permitted. The depth of such knurlingshall not exceed 0.13 mm [0.005 in] below the originalsurface. Suggested joint clearances for typical materialsmay be found in the AWS Brazing Handbook.

5.4.4 Tack Welding. When tack welding is requiredto maintain proper positioning of components, the tackweld size, location, and welding filler metal shall bespecified on the engineering drawing, or in writing bythe Organization Having Quality Responsibility. Tackwelds shall be applied with adequate inert gas shieldingper the approved welding procedure to assure that oxidecontamination of the braze joint surfaces does not occur.

5.4.5 Application of Brazing Filler Metal. Brazingfiller metal specified by the engineering drawing may beapplied as a paste mixture, slurry, wire, foil, transfertape, cladding (braze sheet), or preformed shapes, asdefined in the approved BPS. Brazing filler metal shallbe applied to one side of the joint only or in slotsmachined within the joint area so that it flows throughthe joint by capillary action in order to facilitate visualinspection.

Brazing filler metal placement between the joint fayingsurfaces of Class A and Class B joints shall be permittedonly when authorized by the engineering drawing, withthe prior written approval of the Organization HavingQuality Responsibility, or if ultrasonic inspection oranother approved inspection procedure per 6.4.3.4 is per-formed to assure proper metallurgical bonding betweenthe braze filler metal and base metals. After the brazingfiller metal application, assemblies shall be protectedfrom contamination by suitable means.

5.4.6 Application of Stopoff. Braze stopoff, if used,shall be applied in the quantities and locations specifiedin the approved BPS to control brazing filler metal flowas required to meet the engineering drawing. It shall beapplied so as to avoid contamination of the braze joint orthe brazing filler metal.

5.4.7 Brazing Cycle. The brazing temperature andtime shall be controlled depending on the chemical com-position of the brazing filler metal and the degree of dif-fusion brazing desired. Heating and cooling rate shall becontrolled to prevent distortion of the specific design of

the component being processed. These parameters maybe defined on the engineering drawing or in writing bythe Organization Having Quality Responsibility.

5.4.7.1 Rebrazing. Rebraze cycles shall be permit-ted only to a BPS meeting the requirements of 5.5. Whenthe original brazing filler metal application side isclosed, additional brazing filler metal may be added ifneeded to the opposite side of the joint.

Brazed joints may be rebrazed by brazing to the originalapproved BPS without the specific written approval ofthe Organization Having Quality Responsibility, unlessotherwise specified by that organization. Additionalbrazing filler metal of the same type used in the originalprocedure may be used.

If the assembly is still not acceptable after having beenrebrazed twice, or if a brazing process or brazing fillermetal other than that approved by the qualified procedureis to be used, or if disassembly of the brazed assembly isrequired, then prior written approval of the procedures tobe used shall be obtained from the Organization HavingQuality Responsibility. If it is necessary to change thebrazing process or brazing filler metal to accomplish therebraze, then the new procedure shall be qualified asspecified in 5.5.

5.4.8 Postbrazing Operations. Assemblies shall becooled after brazing in such a manner that cracking of thebrazing filler metal or base metals does not occur andresidual stresses are minimized. Postbraze heat treat-ments, or combined brazing and heat treating cycles, ifrequired, shall be performed per the engineering draw-ing. If required, flux or stopoff residues shall be removedby suitable means.

5.5 Brazing Procedure Qualification. Brazing equip-ment, procedures, and process parameters shall be quali-fied to establish the properties that are expected to resultfrom its application to production brazements. The con-ditions used in making the test brazement (if required) orproduction assemblies, and the results of the requiredexamination, shall be documented. Qualification proce-dures may be in accordance with AWS B2.2, Standardfor Brazing Procedure and Performance Qualification,or as required by the Organization Having QualityResponsibility. If multiple brazing cycles are requiredfor product fabrication, then all cycles shall be so quali-fied, documented, and approved. Prior to use, any modi-fication of the approved procedure(s) shall be approvedin writing.

5.6 Safety and Health. Brazing fluxes and brazing fillermetals, particularly those containing cadmium, emit haz-ardous fumes during the brazing cycle. It is mandatorythat all furnace brazing operations be properly and ade-

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quately ventilated or that operators be provided with anadequate breathing apparatus, or both, as required toensure that all relevant federal, state, and local govern-ment safety and health requirements are met.

In addition, there are other hazards involved in furnacebrazing such as those relating to the use of corrosivefluxes, potentially explosive gases, and hot surfaces. Thestandard ANSI Z49.1, Safety in Welding, Cutting, andAllied Processes, provides further information on theseand other safety and health concerns that must be con-trolled during furnace brazing. Information on the hazardsassociated with materials used in the brazing processmay be found in the Material Safety Data Sheets(MSDSs) available from the manufacturer, as well asthe AWS Safety and Health Fact Sheets available viawww.aws.org.

6. Quality Assurance Provisions6.1 Responsibility for Inspection. Unless otherwisespecified in the contract or purchase order, the organiza-tion performing a brazing operation is responsible for allinspection of the brazed joints. This requirementincludes a system of quality control and documentationthat assures and can attest that all required operations andprocedures have been performed. Suppliers may usetheir own facilities or any other facility acceptable to theOrganization Having Quality Responsibility for theinspection of the final product. However, the Organiza-tion Having Quality Responsibility shall retain the rightto perform or witness the required tests or to perform anyother tests necessary to assure that the brazed assembliesconform to the requirements of this specification, and theengineering drawing.

6.2 Responsibility for Compliance. All products shallmeet all requirements of this specification except whendeviation is specifically approved in writing by the Orga-nization Having Quality Responsibility, or is part of theengineering drawing. The braze inspections requiredshall become a part of the contractor’s overall inspectionsystem or quality program. The absence of any inspec-tion requirements in this specification shall not relieve acontractor of the responsibility of assuring that all prod-ucts or supplies that the contractor produces under thisspecification meet all contractual obligations. The use ofinspection sampling systems (see 6.4.4) does not autho-rize the shipment of known defective material nor does itobligate any person or organization to accept defectivematerial.

6.3 Sequence of Inspection and Manufacturing Oper-ations. Furnace brazed joints may be inspected at theassembly or subassembly level, provided the entire joint

is accessible for inspection. Brazements requiring post-braze heat treatment at the brazing house shall beinspected after heat treatment has been completed, unlessotherwise specified on the engineering drawing. Whenbrazed joints are inspected in process prior to themachining of joint edges, reinspection shall be requiredafter machining to assure that the brazed joint has notbeen damaged in the machining operations. Inspectionshould be performed after postbraze cleaning.

6.4 Required Inspection of Brazed Joints

6.4.1 Destructive Testing. The destructive testing ofassemblies or samples shall be performed as required forprocess qualification or corrective action. The destruc-tive testing of samples or sample parts shall not be sub-stituted for any nondestructive examination required bythis specification except as part of an approved samplingin accordance with the requirements of this specificationor as part of an inspection procedure complying with6.4.3.4.

6.4.1.2 Burst Test. Burst testing shall be con-ducted when required by the Organization Having Qual-ity Responsibility.

6.4.2 Visual Examination. All brazed joints shall bevisually examined to the acceptance criteria specified in6.5.

6.4.3 Nondestructive Examination. Class A andClass B brazed joints, except as specified in 6.4.3.3 and6.4.3.4, shall be examined either radiographically orultrasonically in accordance with the requirements of6.5.2 unless otherwise specified on the engineeringdrawing. The choice of process is optional, except for thecriteria established in 6.4.3.1 and 6.4.3.2. However,ultrasonic examination is generally the preferred methodfor examining brazed joints.

6.4.3.1 Radiographic Examination. Radiographicexamination shall be performed in accordance withASTM E 1742, Standard Practice for RadiographicExamination. When the joint clearance is less than 2% ofthe total thickness of the base metals or when the brazingfiller metal is preplaced between the faying surfaces, thecapability of the radiographic technique to detect theminimum discontinuity size required by the OrganizationHaving Quality Responsibility shall be demonstrated.

NOTE: When brazing filler metal is preplaced betweenthe faying surfaces, unmelted filler metal may result inunreliable interpretations.

Ultrasonic examination shall be required when the crite-ria for radiographic examination is not met, except asspecified in 6.4.3.4.

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6.4.3.2 Ultrasonic Examination. Ultrasonicexamination shall be performed in accordance with AWSC3.8M/C3.8, Specification for the Ultrasonic Examina-tion of Brazed Joints. Ultrasonic examination shall beperformed only when the following configuration andprocess criteria are met:

(1) Surface through which the sonic pulse enters thematerial shall be parallel to the faying surfaces, and theassembly must be processed so that all brazing fillermetal runover onto this surface is removed prior to ultra-sonic inspection. Excess brazing filler metal must not beon the surfaces through which the ultrasound enters thetest specimen;

(2) A suitable ultrasonic reference standard shall beavailable. It shall be identical to the assemblies it repre-sents with respect to joint configuration, joint clearance,and brazing filler material. The reference standard shallhave defects of known size and location suitable for cali-brating the ultrasonic apparatus; and

(3) Ultrasonic apparatus shall produce a joint facsim-ile suitable for making quantitative measurements of thepercentage of the brazed joint actually bonded and fordocumenting the testing of the assembly.

Radiographic examination shall be required when any ofthese criteria are not met except as specified in 6.4.3.4.

6.4.3.3 Leak and Pressure Testing of Class Aand Class B Joints. If specified on the engineeringdrawing or approved in writing by the Organization Hav-ing Quality Responsibility, pressure and leak testing tothe following requirements may be substituted for radio-graphic and ultrasonic examination of Class A and ClassB joints:

(1) Class A joints shall be pressure tested at an inter-nal pressure and according to procedures specified inwriting by the Organization Having Quality Responsibil-ity. No measurable leakage shall be allowed. They shallthen be helium leak tested in accordance with the proce-dure outlined in AWS C3.3, Recommended Practices forthe Design, Manufacture, and Examination of CriticalBrazed Components. Leakage of not more than 3.0 ×10–5 cc3/s [2.0 × 10–6 in3/s] shall be detected with a suit-able mass spectrometer leak detector in good workingcondition calibrated as specified by its manufacturer; and

(2) Class B joints shall be air pressure tested at aninternal pressure and according to procedures specifiedin writing by the Organization Having Quality Responsi-bility. Class B joints shall be bubble leak tested using aselected procedure defined in AWS C3.3 or as specifiedin writing by the Organization Having Quality Responsi-bility. No visually detected leaks shall be allowed.

NOTE: Internal pressure test fixtures and devices shallbe suitable for the intended purpose and shall be ade-quately shielded to prevent injury to persons in case ofcatastrophic failure during pressure testing.

6.4.3.4 Alternate Examination Techniques. Cer-tain specialized brazed components may not be inspect-able using radiographic or ultrasonic techniques and maybe unsuitable for leak or pressure testing in accordancewith 6.4.3.3. In such cases, alternate examination tech-niques and acceptance limits shall be as specified in writ-ing by the Organization Having Quality Responsibility.This organization is responsible for the suitability of thefinal product for service and of the selected inspectiontechniques to verify the suitability of the brazed joints. Ifno such special inspection techniques and acceptancelimits have been specified in writing, all requirements ofthis specification shall be met.

6.4.3.5 Fluorescent or Dye Penetrant Examina-tion. Fluorescent or dye penetrant examination tech-niques performed in accordance with ASTM E 1417,Standard Practice for Liquid Penetrant Examination,shall be used only on assemblies in which the brazedjoint has been subjected to machining so as to ensure thatthe joint has not been damaged in machining or thatinternal voids or lack of bond has not been opened to thesurface. These examination techniques are not suitablefor the inspection of brazed fillets because they routinelygive false results.

6.4.3.6 Other Nondestructive Tests. Additionalnondestructive examination may be required by theOrganization Having Quality Responsibility at its discre-tion. In such cases, the acceptance criteria shall beclearly defined in writing by this organization.

6.4.4 Inspection Sampling Plans

6.4.4.1 Class A Joints. Class A Joints require theinspection of every unit. No sample plans shall be used.

6.4.4.2 Class B Joints. Class B joints shall beinspected using a sample plan in accordance with ASQZ1.4, Sampling Procedures and Tables for Inspectionby Attributes, and only with the written permission ofthe Organization Having Quality Responsibility, providedthe following criteria are met:

(1) Sampling techniques are based upon the assump-tion that all of the products in a given batch or lot areidentical; and

(2) Proof of such identical processing is therefore aprecondition for the approval of sample inspection plans.Such proof shall be documented and available to theOrganization Having Quality Responsibility. No opera-tion critical to the quality of the brazed joint shall be

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directly dependent upon the skill or care of an operator,except when a written record of the actual process variablescontrolled by the operator is automatically produced.

When allowed, a random sample shall be selected fromeach inspection lot in accordance with ASQ Z1.4 accept-able quality levels (AQL) 2.5, C = 0 (i.e., no defects) andinspected in accordance with this specification. Lot sizesfor the purposes of sampling shall consist of all brazedparts of the same design or kind manufactured using thesame process from identical details, identically preparedduring one continuous period, and submitted for accep-tance at the same time.

6.4.4.3 Class C Joints. Class C joints may beinspected using sample plans in accordance with ASQZ1.4.

When allowed, a random sample shall be selected fromeach inspection lot in accordance with ASQ Z1.4 accept-able quality levels (AQL) 2.5, C = 0 (i.e., no defects) andinspected in accordance with this specification. Lot sizesfor the purposes of sampling shall consist of all brazedparts of the same design or kind manufactured using thesame process from identical details, identically preparedduring one continuous period, and submitted for accep-tance at the same time.

NOTE: A single batch furnace run is considered onecontinuous period.

6.5 Acceptance Criteria. Unless otherwise specified bythe engineering drawing or document referenced by it,the criteria specified below are the minimum acceptancecriteria for inspection of furnace brazed joints. Anyassembly failing to meet these minimum requirementsshall be rejected.

6.5.1 External Discontinuities

6.5.1.1 Pinholes and Voids. Pinholes, voids, orbrazing filler metal skips are allowed provided they shallnot exceed the limits specified below. Discontinuities ofless than 0.38 mm [0.015 in] are uninterpretable and arenot considered as defects.

Visual inspection of the fillet provides information aboutthe wetting of the brazing filler metal to the base materi-als, adequate brazing filler metal volume, and properbrazing filler metal flow. Fillet voids, pinholes, and braz-ing filler metal skips are acceptable as long as they donot extend into the joint proper. Any fillet discontinuitythat extends into the joint proper shall not exceed thefollowing limits:

(1) Class A—Maximum size 2.3 mm [0.090 in] witha total accumulated length less than 10% of the filletlength;

(2) Class B—Maximum size 2.3 mm [0.090 in] witha total accumulated length less than 25% of the filletlength; and

(3) Class C—Maximum size 3.1 mm [0.120 in] witha total accumulated length less than 50% of the filletlength.

6.5.1.2 Cracks. Cracks are unacceptable. How-ever, discontinuities with a major dimension of less than0.38 mm [0.015 in], which are interpretable, are notconsidered defects as long as the assembly meets theapplicable leak criteria and/or pressure test acceptancecriteria.

6.5.1.3 Erosion. Any evidence of braze filler ero-sion of the exposed base metal surfaces is unacceptable ifthe erosion of either member exceeds 5% of the thick-ness for Class A and 15% for Class B or Class C of thethinnest component of the brazed joint.

6.5.1.4 Lack of Brazing Filler Metal Melting.Failure of the brazing filler metal to melt completely isunacceptable.

6.5.1.5 Edge Voids. For Class A and Class Bjoints, no through-voids (i.e., voids that extend throughthe entire brazed joint) are acceptable. For Class C,through voids are acceptable. There must be evidence ofbrazing filler metal penetration across the joint. Lack ofsuch evidence of brazing filler metal penetration is unac-ceptable. When the assembly configuration makesinspection of the edge opposite that to which brazingfiller metal was applied impossible, this requirementshall not apply.

6.5.1.6 Brazing Filler Metal Penetration. If theedge of the joint opposite that to which the brazing fillermetal is applied is visible after brazing, the brazing fillermetal shall be present at that edge of the joint. Brazingfiller metal discontinuities at this edge are acceptable, aslong as the criteria of 6.5.2 are met. This requirementshall not apply in cases where the edge of the joint oppo-site the edge to which filler material is applied is notaccessible for inspection, because of the configuration ofthe assembly.

6.5.1.7 Flux or Flux Residue. Evidence of corro-sive flux or corrosive flux residue is unacceptable (see5.3.1.2).

6.5.1.8 Quality of Workmanship. The quality ofworkmanship shall be such that the assemblies are suit-able for the intended purpose and that surfaces are free ofexcess braze filler material that could interfere with sub-sequent operations or the function of the product.

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6.5.2 Internal Discontinuities

6.5.2.1 Class A Joints. Radiographic film or ultra-sonic facsimiles of Class A joints shall indicate that thetotal measured void, or unbonded area, of the joint doesnot exceed 15% of the total joint area. The width of thelargest void or unbonded area as measured parallel to thejoint width shall not exceed 60% of the total joint width.Any such void that is wider than 40% of the width of thejoint shall extend no closer to either edge of the joint than20% of the joint width.

6.5.2.2 Class B Joints. Radiographic film or ultra-sonic facsimiles of Class B joints shall indicate that thetotal measured void, or unbonded area, of the joint doesnot exceed 25% of the total joint area. The width of thelargest void, as measured parallel to the joint width, shallnot exceed 70% of the total joint width. Any such area thatis wider than 60% of the joint width or larger shall extendno closer to either joint edge than 15% of the joint width.

6.5.2.3 Class C Joints. Class C joints have nointernal inspection requirements.

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ANSI Z49.1:2005, Safety in Welding, Cutting, and AlliedProcesses, American Welding Society.

AWS, 1991, Brazing Handbook, 4th ed., Miami: AmericanWelding Society.

SAE AMS 2404:1997, Plating, Electroless Nickel, Societyof Automotive Engineers.

SAE AMS 2451/7:2000, Plating, Brush, Nickel LowStress, Medium-Hardness Deposit, Society of Auto-motive Engineers.

Annex A (Informative)

Informative ReferencesThis annex is not part of AWS C3.6M/C3.6:2008, Specification forFurnace Brazing, but is included for informational purposes only.

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B1. IntroductionThe American Welding Society (AWS) Board of Directorshas adopted a policy whereby all official interpretationsof AWS standards are handled in a formal manner.Under this policy, all interpretations are made by thecommittee that is responsible for the standard. Officialcommunication concerning an interpretation is directedthrough the AWS staff member who works with thatcommittee. The policy requires that all requests for aninterpretation be submitted in writing. Such requests willbe handled as expeditiously as possible, but due to thecomplexity of the work and the procedures that must befollowed, some interpretations may require considerabletime.

B2. ProcedureAll inquiries shall be directed to:

Managing DirectorTechnical Services DivisionAmerican Welding Society550 N.W. LeJeune RoadMiami, FL 33126

All inquiries shall contain the name, address, and affilia-tion of the inquirer, and they shall provide enough infor-mation for the committee to understand the point ofconcern in the inquiry. When the point is not clearlydefined, the inquiry will be returned for clarification. Forefficient handling, all inquiries should be typewritten andin the format specified below.

B2.1 Scope. Each inquiry shall address one single provi-sion of the standard unless the point of the inquiryinvolves two or more interrelated provisions. The provi-sion(s) shall be identified in the scope of the inquiry

along with the edition of the standard that contains theprovision(s) the inquirer is addressing.

B2.2 Purpose of the Inquiry. The purpose of the inquiryshall be stated in this portion of the inquiry. The purposecan be to obtain an interpretation of a standard’s require-ment or to request the revision of a particular provisionin the standard.

B2.3 Content of the Inquiry. The inquiry should beconcise, yet complete, to enable the committee to under-stand the point of the inquiry. Sketches should be usedwhenever appropriate, and all paragraphs, figures, andtables (or annex) that bear on the inquiry shall be cited. Ifthe point of the inquiry is to obtain a revision of the stan-dard, the inquiry shall provide technical justification forthat revision.

B2.4 Proposed Reply. The inquirer should, as aproposed reply, state an interpretation of the provisionthat is the point of the inquiry or provide the wording fora proposed revision, if this is what the inquirer seeks.

B3. Interpretation of Provisions of the Standard

Interpretations of provisions of the standard are made bythe relevant AWS technical committee. The secretary ofthe committee refers all inquiries to the chair of the par-ticular subcommittee that has jurisdiction over the por-tion of the standard addressed by the inquiry. Thesubcommittee reviews the inquiry and the proposed replyto determine what the response to the inquiry shouldbe. Following the subcommittee’s development of theresponse, the inquiry and the response are presented tothe entire committee for review and approval. Uponapproval by the committee, the interpretation is an official

Annex B (Informative)

Guidelines for the Preparation of Technical InquiriesThis annex is not part of AWS C3.6M/C3.6:2008, Specification forFurnace Brazing but is included for informational purposes only.

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interpretation of the Society, and the secretary transmitsthe response to the inquirer and to the Welding Journalfor publication.

B4. Publication of InterpretationsAll official interpretations will appear in the WeldingJournal and will be posted on the AWS web site.

B5. Telephone InquiriesTelephone inquiries to AWS Headquarters concerningAWS standards should be limited to questions of a gen-eral nature or to matters directly related to the use of thestandard. The AWS Board Policy Manual requires thatall AWS staff members respond to a telephone requestfor an official interpretation of any AWS standard withthe information that such an interpretation can be

obtained only through a written request. Headquartersstaff cannot provide consulting services. However, thestaff can refer a caller to any of those consultants whosenames are on file at AWS Headquarters.

B6. AWS Technical CommitteesThe activities of AWS technical committees regardinginterpretations are limited strictly to the interpretation ofprovisions of standards prepared by the committees or toconsideration of revisions to existing provisions on thebasis of new data or technology. Neither AWS staff northe committees are in a position to offer interpretive orconsulting services on (1) specific engineering problems,(2) requirements of standards applied to fabricationsoutside the scope of the document, or (3) points notspecifically covered by the standard. In such cases, theinquirer should seek assistance from a competent engi-neer experienced in the particular field of interest.

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List of AWS Documents on Brazing and Soldering

Designation Title

A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination

A3.0 Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding,Brazing, Soldering, Thermal Cutting, and Thermal Spraying

A5.8/A5.8M Specification for Filler Metals for Brazing and Braze Welding

A5.31 Specification for Fluxes for Brazing and Braze Welding

B2.2 Specification for Brazing Procedure and Performance Qualification

C3.2M/C3.2 Standard Method for Evaluating the Strength of Brazed Joints

C3.3 Recommended Practices for Design, Manufacture, and Examination of Critical BrazedComponents

C3.4M/C3.4 Specification for Torch Brazing

C3.5M/C3.5 Specification for Induction Brazing

C3.6M/C3.6 Specification for Furnace Brazing

C3.7M/C3.7 Specification for Aluminum Brazing

C3.8M/C3.8 Recommended Practices for Ultrasonic Inspection of Brazed Joints

C3.9M/C3.9 Specification for Resistance Brazing (Forthcoming)

D10.13 Recommended Practice for the Brazing of Copper Pipe and Tubing for Medical GasSystems

BRH Brazing Handbook

SHB Soldering Handbook

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