Ansi-Aws Standard c3.7-2005 Specification for Aluminum Brazing (eBook, 28 Pages)

Specification forAluminum Brazing

AWS C3.7M/C3.7:2005An American National Standard

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AWS C3.7M/C3.7:2005An American National Standard

Approved byAmerican National Standards Institute

June 29 , 2005

Specification for

Aluminum Brazing

Supersedes AWS C3.7:1999

Prepared byAWS C3 Committee on Brazing and Soldering

Under the Direction ofAWS Technical Activities Committee

Approved byAWS Board of Directors

AbstractThis specification presents the minimum fabrication, equipment, material, process procedure and inspection require-ments for the brazing of aluminum by all of the processes commonly used—atmosphere furnace, vacuum furnace, andflux processes. Its purpose is to standardize aluminum brazing requirements for all applications in which brazed alumi-num joints of assured quality are required. It provides criteria for classifying aluminum brazed joints based on loadingand the consequences of failure and quality assurance criteria defining the limits of acceptability of each class. Thespecification defines acceptable brazing equipment, materials and procedures, as well as the required inspection for eachclass of joint.

Key Words—Brazing, aluminum, aluminum brazing, furnace brazing, quality control, inspection of brazed joints, brazing materials, brazing equipment, classification of brazed joints, brazed joint discontinuities, nondestructive examination, furnace brazing procedure specification

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Statement on Use of AWS American National StandardsAll 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 standards are either incorporated in, or made part of,documents that are included in federal or state laws and regulations, or the regulations of other governmental bodies,their provisions carry the full legal authority of the statute. In such cases, any changes in those AWS standards must beapproved by the governmental body having statutory jurisdiction before they can become a part of those laws andregulations. In all cases, these standards carry the full legal authority of the contract or other document that invokes theAWS standards. Where this contractual relationship exists, changes in or deviations from requirements of an AWSstandard must be by agreement between the contracting parties.

International Standard Book Number: 0-87171-022-6

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

© 2005 by American Welding Society. All rights reservedPrinted in the United States of America

AWS American National Standards are developed through a consensus standards development process that bringstogether volunteers representing varied viewpoints and interests to achieve consensus. While AWS administers the processand establishes rules to promote fairness in the development of consensus, it does not independently test, evaluate, orverify 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, whether spe-cial, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on thisstandard. AWS also makes no guaranty or warranty as to the accuracy or completeness of any information published herein.

In issuing and making this standard available, AWS is not undertaking to render professional or other services for or onbehalf 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 the adviceof a competent professional in determining the exercise of reasonable care in any given circumstances.

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, 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 writ-ing, to the Managing Director, Technical Services Division, American Welding Society, 550 N.W. LeJeune Road, Miami, FL33126 (see Annex A). With regard to technical inquiries made concerning AWS standards, oral opinions on AWS standardsmay be rendered. However, such opinions represent only the personal opinions of the particular individuals giving them. Theseindividuals do not speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpreta-tions of AWS. 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 Soldering

P. T. Vianco, Chair Sandia National LaboratoriesR. W. Smith, 1st Vice Chair Materials Resources International

C. L. Jenney, Secretary American Welding SocietyG. L. Alexy Prince & Izant Company

B. Barten Delphi Thermal and Interior*A. Belohlav Lucas-Milhaupt, Incorporated

*S. S. Bhargava General MotorsD. W. Bucholz Conforma Clad, Incorporated

*S. Christy Pratt & Whitney*N. C. Cole NCC Engineering

W. J. Engeron Engineered Alloy Systems & SupportY. Flom NASA Goddard Space Flight Center

D. Fortuna Sulzer Metco (U.S.), IncorporatedC. E. Fuerstenau Lucas-Milhaupt, Incorporated

R. A. Gross Gourley Curtiss Wright*P. K. Gupta Honeywell Aerospace

S. R. Hazelbaker Accurate Brazing, Incorporated*M. J. Higgins Advanced Systems Technologies

T. P. Hirthe Kru-Mar Manufacturing Services, IncorporatedF. M. Hosking Sandia National Laboratories

J. R. Jachna Modine Manufacturing CompanyD. Kane ADB Industries

*T. A. Kern Consultant*H. H. Lang York International Corporation

*H. Lichtenberger Williams Advanced MaterialsE. Liguori Scarrott Metallurgical

M. J. Lucas, Jr. Consultant*E. Lugscheider Aachen University of Technology

*M. Manning GE Power SystemR. P. McKinney Prince & Izant Company

*C. Moyer ConsultantT. Oyama Morgan Advanced Ceramic

C. A. Paponetti, Sr. ConsultantR. L. Peaslee Wall Colmonoy Corporation

A. Rabinkin Metglas, Incorporated*W. D. Rupert Wolverine Joining Technologies

A. Severin Bradley CorporationA. E. Shapiro Chemical Abstract ServicesJ. J. Stephens Sandia National Laboratories*R. W. Walls Walls Engineering

*Advisor

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C3D Subcommittee on Brazing Specifications

J. R. Jachna, Chair Modine Manufacturing CompanyS. R. Hazelbaker, Vice Chair Accurate Brazing, Incorporated

C. L. Jenney, Secretary American Welding Society*B. Barten Delphi Thermal and Interior

*N. C. Cole NCC EngineeringY. Flom NASA Goddard Space Flight Center

C. E. Fuerstenau Lucas-Milhaupt, IncorporatedR. A. Gross Gourley Curtiss Wright

*P. K. Gupta Honeywell AerospaceR. L. Hall, Jr. Copper Development Association, Incorporated

*M. J. Higgins Pratt & WhitneyT. P. Hirthe Kru-Mar Manufacturing Services, Incorporated

F. M. Hosking Sandia National LaboratoriesD. Kane ADB Industries

*T. A. Kern Consultant*H. H. Lang York International Corporation

E. Liguori Scarrott MetallurgicalM. J. Lucas, Jr. ConsultantR. P. McKinney Prince & Izant Company

*H. Mizuhara, P.E. H. Mizuhara Consulting Services*C. Moyer ConsultantT. Oyama Morgan Advanced Ceramic

C. A. Paponetti, Sr. ConsultantR. L. Peaslee Wall Colmonoy Corporation

*W. D. Rupert Wolverine Joining Technologies*A. Severin Bradley CorporationR. W. Smith Materials Resources International

*K. P. Thornberry J. W. Harris Company, IncorporatedP. T. Vianco Sandia National Laboratories*R. W. Walls Wall Engineering

*Advisor

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Foreword

(This Foreword is not a part of AWS C3.7M/C3.7:2005, Specification forAluminum 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 Societyof Automotive Engineers (SAE) and a number of other organizations to replace MIL-B-7883, Brazing of Steels, Copper,Copper Alloys, Nickel Alloys, Aluminum, and Aluminum Alloys, which addressed all of the brazing processes. It becameboth 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 impracti-cal; therefore, a series of four independent specifications on brazing were written, all in the same format. The first threeare AWS C3.4, Specification for Torch Brazing; AWS C3.5, Specification for Induction Brazing; and AWS C3.6, Spec-ification for Furnace Brazing. The torch, induction, and furnace brazing of aluminum alloys are addressed in the presentdocument, AWS C3.7M/C3.7, Specification for Aluminum Brazing. The decision to subdivide the technology in thisway was based upon a survey of production brazing applications conducted by the AWS C3 Committee on Brazing andSoldering. The survey demonstrated that these four specifications would cover the vast majority of brazing done in theUnited States today.

An additional document, AWS C3.8M/C3.8, Recommended Practices for the Ultrasonic Examination of BrazedJoints, complements this series. In the preparation of the first four brazing specifications, it was found that no suchdocument provided specific criteria and requirements for the application of this important new inspection technology tobrazed joints.

The present edition supersedes AWS C3.7:1999, bearing the same title. This edition includes new sections addressingthe molten metal bath brazing and the controlled-atmosphere brazing of aluminum.

Comments and suggestions for the improvement of this standard are welcome. They should be sent to the Secretary,AWS C3 Committee on Brazing and Soldering, American Welding Society, 550 N.W. LeJeune Road, Miami, FL 33126.

Official interpretations of any of the technical requirements of this standard may only be obtained by sending arequest, in writing, to the Managing Director, Technical Services Division, American Welding Society. A formal replywill be issued after it has been reviewed by the appropriate personnel following established procedures (see Annex A).

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AWS C3.7M/C3.7:2005


Table of Contents

Page No.

Personnel .................................................................................................................................................................... iiiForeword ......................................................................................................................................................................v

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...............................................................................................................................................24.4 Class C Joints...............................................................................................................................................24.5 No Class Specified.......................................................................................................................................2

5. Process Requirements ...........................................................................................................................................35.1 Process Description .....................................................................................................................................35.2 General Heat Source Requirements.............................................................................................................35.3 Temperature Requirements..........................................................................................................................45.4 Operating Requirements of the Furnace or Oven ........................................................................................55.5 Fixtures ........................................................................................................................................................55.6 Aluminum Brazing Materials ......................................................................................................................55.7 Product Brazing Requirements ....................................................................................................................65.8 Brazing Procedure Qualification .................................................................................................................75.9 Safety and Health.........................................................................................................................................7

6. Quality Assurance Provisions ...............................................................................................................................86.1 Responsibility for Inspection.......................................................................................................................86.2 Requirements for Compliance .....................................................................................................................86.3 Sequence of Inspection and Manufacturing Operations..............................................................................86.4 Required Examination of Brazed Joints ......................................................................................................86.5 Acceptance Criteria ...................................................................................................................................106.6 Process Completion ...................................................................................................................................11

Nonmandatory Annexes..............................................................................................................................................13Annex A—Guidelines for Preparation of Technical Inquiries for AWS Technical Committees ................................13Annex B—Bibliography ..............................................................................................................................................15

List of AWS Documents on Brazing and Soldering ....................................................................................................17

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AWS C3.7M/C3.7:2005

Specification for Aluminum Brazing


1. Scope

This specification presents the minimum fabricationand quality requirements for brazing of aluminum andaluminum alloys. Its purpose is to standardize brazingprocess requirements and control brazed joint quality forall applications for which brazed joints of assured qualityare required. This document establishes the 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 modification.

Safety and health issues and concerns are beyond thescope of this standard and therefore are not fullyaddressed herein. Safety and health information is avail-able from other sources, including, but not limited to,ANSI Z49.1, Safety in Welding, Cutting, and Allied Pro-cesses, and applicable federal and state regulations.

This standard makes use of both the InternationalSystem of Units (SI) and U.S. Customary Units. The lat-ter are shown within brackets or in appropriate columnsin tables and figures. The measurements may not beexact equivalents; therefore, each system shall be usedindependently.

2. Normative References

The following standards contain provisions which,through reference in this text, constitute provisions ofthis American Welding Society standard. For dated ref-erences, subsequent amendments to, or revisions of, anyof these publications do not apply. However, parties toagreements based on this AWS standard are encouragedto investigate the possibility of applying the most recenteditions of the documents shown below. For undatedreferences, the latest edition of the standard referred toapplies.

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The following AWS documents1 are referenced in themandatory sections of this standard:

(1) AWS A2.4, Standard Symbols for Welding, Braz-ing, and Nondestructive Examination;

(2) AWS A5.8/A5.8 M, Specification for FillerMetals for Brazing and Braze Welding;

(3) AWS A5.31, Specification for Fluxes for Brazingand Braze Welding;

(4) AWS B2.2, Standard for Brazing Procedure andPerformance Qualification;

(5) AWS C3.3, Recommended Practices for theDesign, Manufacture, and Inspection of Critical BrazedComponents;

(6) AWS C3.8M/C3.8, Recommended Practices forthe Ultrasonic Examination of Brazed Joints.

The following American National Standards Institute(ANSI) document2 is referenced in the mandatory sec-tions of this standard:

(1) ANSI Z540-1, General Requirements forCalibration Laboratories and Measuring and TestEquipment.

The following American Society for Testing andMaterials (ASTM) documents3 are referenced in themandatory sections of this standard:

(1) ASTM E 230, Standard Specification andTemperature-Electromotive Force (EMF) Tables forStandardized Thermocouples;

(2) ASTM E 1417, Standard Practice for LiquidPenetrant Inspection; and

(3) ASTM E 1742, Standard Practice for Radio-graphic Examination.

1. AWS documents are published by the American WeldingSociety, 550 N.W. LeJeune Road, Miami, FL 33126.2. ANSI standards are published by the American NationalStandards Institute, 25 West 43rd Street, Fourth Floor, NewYork, New York 10036.3. ASTM documents are published by the American Societyfor Testing and Materials, 100 Barr Harbor Drive, WestConshohocken, PA 19428-2959.

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The following American Society for Quality (ASQ)document4 is referenced in the mandatory sections of thisstandard:

(1) ASQ Z1.4 Sampling Procedures and Tables forInspection by Attributes.

The following Society of Automotive Engineers(SAE)/Aerospace Materials Specifications (AMS) docu-ment5 is referenced in the mandatory sections of thisstandard:

(1) SAE/AMS 2750, Pyrometry.

3. Terms and Definitions

For the purposes of this document, the terms and defi-nitions listed below 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.

getter. v. The action of absorbing or chemically bindingelements in the furnace atmosphere (i.e., oxygen) toinhibit the flow of the brazing filler metal; n., A metalor alloy added to a vacuum furnace for the purpose ofabsorbing or chemically binding elements in thefurnace atmosphere (i.e., oxygen) that may inhibit theflow of the brazing filler metal.

lack of bond or unbond. A condition in a brazed joint inwhich brazing filler metal is present between the jointfaces but does not adhere or form a metallurgicalbond with the base metal. It most commonly occurswhen brazing filler metal is preplaced betweencontaminated joint faces. In many cases, lack of bondis only nondestructively detectable by means of ultra-sonic examination.

4. ASQ documents are published by the American Society forQuality, 600 North Plankinton Avenue, Milwaukee, WI 53203.5. SAE/AMS documents are published by the Society ofAutomotive Engineers, 400 Commonwealth Drive, Warren-dale, PA 15096-0001.

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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.

pinhole porosity. Porosity consisting of numerous smallgas holes on the surface or in the subsurface of abrazed joint proper or fillet.

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

void. An area of a brazed joint proper that is notcompletely filled with brazing filler metal.

Additional terms and definitions can be found inAWS A3.0, Standard Welding Terms and Definitions,Including Terms for Brazing, Soldering, Thermal Spray-ing, and Thermal Cutting.

4. Classification of Brazed Joints4.1 Method of Classification. Brazed joints are classi-fied in this specification based on two criteria: (1) thedesign requirements and (2) the consequences of failure.It is the responsibility of the Organization Having Qual-ity Responsibility to evaluate these or other factors andassign the proper classification. This classification con-trols which inspection methods and acceptance 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 orproperty or significant operational failure.

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 significant riskto persons or property or significant operational failure.

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 significant det-rimental effect.

4.5 No Class Specified. When no class is specified onthe engineering drawing or other applicable document

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approved by the Organization Having Quality Respon-sibility, Class A requirements shall apply. However,because of the confusion that can result, all engineeringdrawings referencing this specification should state theclass of the brazed joint in the brazing symbol. Symbolsshall be in accordance with AWS A2.4, Symbols forWelding, Brazing, and Nondestructive Examination.

5. Process Requirements5.1 Process Description. Aluminum and aluminumalloys are brazed using techniques that disrupt the sur-face oxides and limit their ability to re-form during thebrazing process. These include brazing in a molten fluxbath or molten metal bath, torch brazing with fluxes,induction brazing with fluxes, brazing in a controlled-atmosphere furnace with special fluxes, and brazing invacuum or controlled-atmosphere furnaces. Fluxless pro-cesses use elemental magnesium, magnesium-containingbrazing filler metal, or magnesium-bearing base metalsto getter available oxygen in the vacuum retort and todisrupt and penetrate the oxide film present on the alumi-num surface.

The magnesium and other active elements can modifythe wetting and alloying characteristics of the standardaluminum brazing filler metals, making them signifi-cantly more effective, as well as making the base metalmore susceptible to brazing filler metal penetration.Because the melting ranges of the base metal and thebrazing filler metal are usually close together, the tem-perature control requirements are more restrictive thanthose commonly used in the brazing of other metals.

5.2 General Heat Source Requirements. All furnacesand molten baths used in the brazing of aluminum shallhave automatic temperature controlling and recordingdevices in good working order that are capable of con-trolling the temperature of the furnace or molten bath tothe requirements of this specification. Furnaces and mol-ten baths shall have adequate heating capacity to accom-plish uniform heating of the workload at the rate requiredto prevent both thermal distortion of the assemblies andliquation of the brazing filler metal. They shall be prop-erly maintained in good working order.

5.2.1 Temperature-Measurement and ControlInstruments. In closed batch-type furnaces and moltenbaths, suitable instruments and thermocouples shall beprovided to measure and control the temperature ofassemblies being brazed. The instrument shall be of thepotentiometer type or equivalent and capable of measur-ing, recording, and providing a permanent record of thetemperature throughout the entire brazing thermal cycle.In furnaces with multiple heating zones, similar instru-mentation shall be provided for each zone.



All instruments used to measure the temperature ofassemblies being brazed or to control furnace or bathtemperature shall have an indicated temperature accu-racy range of not more than ±0.5% of the maximum forwhich the furnace or bath is qualified over the entireoperating range.

The indicated temperature accuracy of the instrumentshall be determined in accordance with the equipmentmanufacturer’s recommendations using a known electro-motive force input traceable to the National Institute ofStandards and Technology (NIST). All instruments shallbe calibrated in accordance with SAE AMS 2750,Pyrometry, and ANSI Z540-1, General Requirements forCalibration Laboratories and Measuring and TestEquipment. Instruments shall be calibrated wheneverrepairs or modifications are made to them.

Instruments used exclusively to protect the furnace orbath from over-temperature accidents are not subject tothe requirements of this subclause.

5.2.1.1 Workload Thermocouples. Workloadcontrol thermocouples shall be of a type listed in ASTME 230, Standard Specification and Temperature-Electro-motive Force (EMF) Tables for Standardized Thermo-couples. They shall be calibrated by comparison to acalibrated test instrument traceable to the National Insti-tute of Standards and Technology. The frequency of cali-bration shall be in accordance with ANSI Z540-1.

5.2.1.2 Work-Zone Thermocouples. Work-zonecontrol thermocouples shall be of a type listed inASTM E 230. They shall be calibrated by comparison toa calibrated test instrument traceable to the NationalInstitute of Standards and Technology. The frequency ofcalibration shall be in accordance with ANSI Z540-1.

5.2.2 Atmosphere Control Instruments. Atmo-spheres shall be monitored in order to maintain estab-lished atmosphere limits as specified in the brazingprocedure specification. One or more of the followingdevices shall be used to assure that these limits are met.

5.2.2.1 Electronic Dew Point MeasuringDevices. Electronic dew point measurement instruments,when used, shall be calibrated in accordance with themanufacturer’s recommendations against referencedevices traceable to the National Institute of Standardsand Technology. Such gauges shall be calibrated beforeinitial use and as needed thereafter in accordance withANSI Z540-1.

5.2.2.2 Vacuum Measuring Device. Vacuummeasuring devices shall be used on all vacuum brazingfurnaces. Thermocouple gauges or the equivalent shallbe used to measure higher than 0.13 Pa [10–3 torr]. Suit-able electronic gauges shall be used to measure pressuresof 0.13 Pa [10–3 torr] or less. These gauges shall be

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mounted so as to measure the pressure within the workzone of the furnace. Suitable instruments for reading andrecording the pressure within the furnace work zone shallalso 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 as needed thereafterin accordance with ANSI Z540-1.

5.2.2.3 Oxygen-Sensing Device. Oxygen-sensingdevices, when used, shall be used to indicate the pres-ence and the quantity of oxygen within the brazing fur-nace’s interior. When a multiple-zone brazing furnace isemployed, the oxygen-sensing device shall have a pick-up point in each zone, as specified in the brazing proce-dure specification.

This device shall be calibrated in accordance with themanufacturer’s recommendations or using a samplinggas that includes a known quantity of oxygen and asneeded thereafter in accordance with ANSI Z540-1.

5.2.2.4 Residual Gas Analyzer (RGA). Residualgas analyzers, when used, shall be employed to indicatethe presence of contaminants within the braze furnaceinterior. When a multiple-zone brazing furnace is uti-lized, the RGA device shall have a pick-up point in eachzone, as specified in the brazing procedure specification.

The device shall be calibrated in accordance withmanufacturer’s recommendations and as needed there-after in accordance with ANSI Z540-1.

5.3 Temperature Requirements. All furnaces and bathsshall be qualified for temperature uniformity and controlprior to their initial use for production brazing. All fur-naces and baths used in the brazing of aluminum, includ-ing preheat ovens, shall be requalified as appropriate.They shall be requalified after any repairs or alterationsthat might affect temperature control or uniformity [e.g.,the installation of new heating elements or new controlthermocouple(s), or the replacement of shielding].

Requalification is not required when the repair oralteration has previously been documented as not affect-ing the temperature control or uniformity of the furnaceor bath.

5.3.1 Temperature Qualification Procedure. Uni-formity tests of furnaces shall be conducted using a typi-cal production atmosphere or vacuum level. All tests offurnace or baths shall be conducted using calibrated ther-mocouples. The temperature-measuring equipment shallmeet the requirements of 5.2.1. Instruments used to con-trol the furnace or bath during production brazing shallnot be used to monitor the qualification thermocouples.



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A minimum of two thermocouples shall be used to de-termine the temperature uniformity of furnaces or bathshaving a work-zone volume of 0.28 m3 [10 ft3] or less. Aminimum of nine thermocouples, or one thermocoupleper 0.70 m3 [25 ft3] of working zone, whichever yieldsthe greater number of thermocouples, shall be used todetermine the uniformity of furnaces or baths having awork zone larger than 0.28 m3 [10 ft3]. A control thermo-couple shall be located within each temperature zone ofcontrol to determine the temperature uniformity of thework zone of any furnace. The location of each tempera-ture control thermocouple shall be determined by theuser.

Qualification shall be performed at the normal braz-ing temperature or 598°C ± 5°C [1110°F ± 10°F] if thefurnace or bath is used at multiple temperatures. Thetemperature of all furnace test and control thermocouplesshall be recorded at intervals of no more than 5 minutesstarting at not less than 93°C [200°F]. Temperature mea-surement and recording shall continue at least 30 minutesafter the furnace or bath has reached thermal equilibriumto determine the recurrent temperature pattern of the fur-nace or bath.

The results of the test shall be posted at the furnace orbath. The posted results shall include the date of testing,the due date of next test, the size of the work zone, andthe results of the tests, including the location within thework zone of the hottest and coldest areas. The require-ments of 5.3.1 are considered met if the equipment iscontrolled and operated in accordance with SAE/AMS2750.

5.3.2 Temperature Uniformity Requirements. Therequirements of 5.3.2 are considered met if the equip-ment is controlled and operated in accordance withSAE/AMS 2750.

5.3.2.1 Aluminum Brazing Furnaces. Beforethermal equilibrium has been reached, no temperaturereading shall vary from the temperature for which thefurnace is being qualified by more than ±11°C [±20°F].After thermal equilibrium has been reached, the tempera-ture measured by any test thermocouple shall not varyfrom the selected furnace control temperature by morethan ±3°C [±5°F]. Within a continuous moving convey-ance-type system, the temperature set-point rate ofrecovery upon the mass load’s entering the brazingfurnace must be within established time limits of anacceptable braze profile for the subject assembly.

5.3.2.2 Flux Drying and Preheating Ovens.Before thermal equilibrium has been reached, no temper-ature reading shall vary from the temperature for whichthe oven is being qualified by more than ±11°C [±20°F].After thermal equilibrium has been reached, the tempera-ture measured by any test thermocouple shall not vary

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from the selected furnace control temperature by morethan ±6°C [±10°F]. The temperature set-point rate ofrecovery (within a continuous moving conveyance-typesystem) upon the mass load’s entering the brazing fur-nace must be within established time limits of an accept-able braze profile for the subject assembly.

5.3.2.3 Molten Metal and Flux Baths. Baths usedfor the brazing of aluminum base metals having a solidustemperature of 604°C [1120°F] or greater shall havetemperature uniformity throughout the working zonewithin ±6°C [±10°F] of the controller set point. Bathsused for the brazing of aluminum base metals having asolidus temperature of less than 604°C [1120°F] shallhave temperature uniformity throughout the workingzone within ±3°C [±5°F] of the controller set point.

5.4 Operational Requirements of the Furnace orOven

5.4.1 Atmosphere Furnaces. Atmosphere furnacesshall be suitable for the intended purpose and in goodworking order. The gas supply and purification system,if any, shall be capable of supplying atmosphere gasesin accordance with the approved brazing procedurespecification.

Atmosphere furnaces for the brazing of fluxed alumi-num assemblies shall be suitable for the intended pur-pose and in good working condition. The temperature ofthe working zone shall be controlled to within ±3°C[±5°F] of the set temperature. Suitable means shall beprovided to control the composition of the furnace atmo-sphere and dew point.

The products of combustion shall not contaminate thebrazing chamber in any way or impinge on the assem-blies being brazed. Furnace atmospheres, the means to beused to control them, and the limits to which they are tobe controlled shall be specified by the approved brazingprocedure specification.

5.4.2 Vacuum Furnaces. Vacuum furnaces used forthe fluxless brazing of aluminum shall be suitable for theintended purpose, in good working order, and complywith the following performance requirements. A coldand previously outgassed furnace shall have a total leak-age (i.e., real leakage plus virtual leakage) of no morethan 2.6 Pa [20 × 10–3 torr] per hour when the vacuumchamber is isolated from the pumping system after beingevacuated to less than 0.65 Pa [5 × 10–3 torr]. The leakrate shall be measured over a time period of no less than15 minutes. Such a leak rate test shall be performed atleast once a week or whenever there is reason to suspectan unacceptable leak rate exists.

A cold, outgassed furnace shall be capable of reachinga vacuum of 0.0013 Pa [10–5 torr] in a time specified inthe brazing procedure specification. It shall have the

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capability of backfilling with inert gas after evacuation to0.013 Pa [10–4 torr] when required by the brazing proce-dure specification. The inert gas shall have a dew point atthe entry point to the furnace retort no higher than –68°C[–90°F]. Suitable provision shall be made for measure-ments of the dew point.

5.4.3 Flux Drying and Preheating Ovens. Preheatovens shall be in good working order and suitable for theintended purpose. Combustion-type ovens shall notexhaust combustion products onto the assembly. Thetemperature in the work zone shall be controlled towithin ±6°C [±10°F] of the set temperature.

5.4.4 Molten Metal and Flux Baths. The moltenmetal and flux baths used for the brazing of aluminumshall be in good working condition and suitable for theintended purpose.

5.4.5 Molten Metal/Flux Bath Qualification. A suit-able braze sample shall be assembled and brazed using abrazing procedure specification. The brazed joint pro-duced shall be smooth and continuous and shall exhibitadequate flow of the brazing filler-metal, as specified bythe brazing procedure specification.

Failure to meet these requirements shall require suit-able corrective action and successful retest before the useof the equipment for production brazing. The results ofthe qualification test shall be documented. Molten bathqualification procedures shall be performed on a dailybasis to assure the brazing capability of the bath. Otherbrazing processes shall be qualified on a timely basis asestablished by the user.

5.5 Fixtures. Fixtures shall be made of suitable materialsthat are stable at the brazing temperature and do not con-taminate the flux, atmosphere, base metal, or brazingfiller metal. The fixtures shall be designed to allow forthermal expansion of the components being brazed. Tothe greatest extent possible, the fixtures shall control thecomponents at points or along lines of contact. All fix-tures, racks, and baskets used in aluminum brazing withfluxes should be made of corrosion-resistant materialssuch as nickel-based alloys or stainless steels.

5.6 Aluminum Brazing Materials

5.6.1 Brazing Filler Metals. The brazing filler metalto be used should be specified on the engineering draw-ing or accompanying documents and shall meet therequirements of AWS A5.8/A5.8M, Specification forFiller Metals for Brazing and Braze Welding, unlessotherwise specified by the engineering drawing oraccompanying documents. Brazing filler metal selectionconsiderations shall be based on the base materials, pro-cess selection, and part/mass configurations.

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5.6.2 Fluxes. Fluxes shall be compatible with the basemetals and the brazing filler metals that are specified bythe engineering drawing. Fluxes shall remove oxides andprevent their re-formation during the brazing operation.They shall promote the flow of filler material and its wet-ting onto the base metal surfaces of the joint. Acceptableflux(es) shall be specified by the approved brazing pro-cedure specification.

Fluxes should conform to the requirements of AWSA5.31, Specification for Fluxes for Brazing and BrazeWelding.

5.6.3 Cleaning Materials. The components to beassembled shall be cleaned in accordance with the braz-ing procedure specification. Cleaning materials shall notleave any residues that interfere with the wetting or flowof the filler metal or contaminate the flux or filler metal.

5.6.4 Braze Stopoff. Stopoff, if used, shall be speci-fied in the brazing procedure specification. Brazing stop-off materials shall be suitable for the intended purposeand compatible with the base metal(s), brazing fillermetal(s), fluxes, and furnace atmosphere. In certainapplications, the residues from stop-off materials canproduce unacceptable contamination of the product orfurnace atmosphere.

5.7 Product Brazing Requirements. Procedures shallbe established to control the following:

5.7.1 Surface Preparation. Components to be brazedshall be sufficiently free of oil, grease, paint, dirt, scale,or other foreign substances that could interfere with thebrazing process or contaminate the braze joint. Burrsshall be removed as required to permit proper assemblyand brazing filler metal flow.

5.7.2 Joint Clearance. In assemblies for aluminumbrazing in which the brazing filler metal is in the form ofcladding on the base metals or filler metal tape or foil,the base and brazing filler metals should have a maxi-mum joint clearance of 0.08 mm [0.003 in.], but pointcontact is required to initiate capillary flow.

In assemblies in which the brazing filler metal isapplied by a molten bath or preplaced adjacent to thejoint, the clearance between the joint surfaces of the basemetals should be controlled by the assembly proceduresso that proper joint clearance is provided at the brazingtemperature unless otherwise specified by the engineer-ing drawing. Suggested joint clearances for typical mate-rials are presented in the AWS Brazing Handbook.

5.7.3 Assembly. Components shall be assembled andheld in place by suitable fixtures per 5.5. Assembly bymeans of fusion or resistance tack welding or using tabsor rivets should be specified by an approved brazingprocedure specification.



Fixturing and assembly techniques that prevent theclearance of the braze joint from closing during brazingshall not be used for fluxless brazing (i.e., vacuum braz-ing). However, such techniques are acceptable whenexternal brazing filler metal placement and flux areemployed. Vent and drain holes in components shall beas specified on the engineering drawing.

5.7.4 Application of Brazing Filler Metal. Brazingfiller metal of the type specified on the engineeringdrawing and approved brazing procedure specificationshall be applied to the joint in the form and applicationmethod specified in sufficient quantity to produce a satis-factory brazed joint. On joints having one end inaccessi-ble to visual examination, the brazing filler metal shallbe placed at the blind end of the joint or in the joint priorto assembly. Binders used in brazing filler metal slurriesshall not leave harmful residues or in any way interferewith the flow of the brazing filler metal.

5.7.5 Application of Flux. Flux shall be applied inthe form and quantity and by the method specified in anapproved brazing procedure specification. The quantityand location of placement shall be such as to produce asatisfactory brazed assembly.

5.7.6 Application of Stop Off. Braze stop-off materi-als shall be applied in quantities and locations as neces-sary to control brazing filler metal flow in order to meetthe requirements of the engineering drawing. Stopoffshall be applied in such a manner so as to prevent thesurfaces of the braze joint or the brazing filler metal frombeing contaminated.

5.7.7 Maintenance of Molten Metal and FluxBaths. Baths shall have sludge removed from the sidesand bottom of the tank by suitable means prior to anyadditions to the bath and at least once per week when inoperation. In addition, at the beginning of each day ofoperation, the bath shall be dehydrated by repeatedlyimmersing sheets or coils of clean AA 1100 or AA 3003aluminum. When this aluminum is free of visual surfacecontamination upon removal from the bath (i.e., it is lightgray in color), brazing shall commence.

This treatment shall also be performed immediatelyafter flux is added to the bath prior to the commencementof brazing. The chemical composition of the flux shall beanalyzed using suitable techniques at least once a monthand maintained within the limits recommended by themanufacturer of the flux. The pH of the flux shall bemeasured at least once a week by suitable means andshall be maintained between 6.4 and 7.0. Baths not main-tained to these requirements shall not be used to brazeassemblies to this specification, and assemblies brazed inthem shall be rejected.

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5.7.8 Procedure for Dip Brazing. The process of dipbrazing is divided into two basic techniques: (1) dippingthe assemblies to be brazed into molten brazing fillermetal bath or (2) dipping the assemblies to be brazed intoa molten salt bath. Components that have been cleanedand assembled to the requirements of this specificationshall be preheated in a suitable furnace to a temperature14°C to 60°C [25°F to 100°F] below the solidus temper-ature of the brazing filler metal until the entire assemblyhas reached this temperature.

The assembly shall then be removed from the preheatfurnace and immediately lowered into the molten bath ata uniform rate such that the positioning of the assembliesand any preplaced brazing filler metal is not disturbed.The temperature of the bath shall not exceed the solidusof the base metals.

Assemblies shall remain in the bath until the flow ofthe brazing filler metal is complete. Removal shall be ata uniform rate such that neither the components nor thebrazing filler metal is disturbed before solidification iscomplete. Assemblies shall be hung over the bath untilall draining has ceased. Assemblies shall be cooled in asuitable manner to prevent cracking, reduce residualstresses, and accomplish any postbraze heat treatmentrequired by the engineering drawing.

Procedures shall be qualified and documented per 5.8.

5.7.9 Procedure for Flux Drying and Preheating.Clean components and/or assemblies that have had fluxapplied must then have all moisture removed from theapplied flux prior to their entering the inert gas atmo-sphere brazing furnace. The flux drying oven mustremove the moisture from the flux without removing asignificant amount of flux from the intended braze jointlocations of the component and/or assembly.

Once the flux moisture has been removed, the second-ary purpose of the flux drying oven is to preheat the com-ponent and/or assembly prior to its entering the inert gasatmosphere brazing furnace. The preheating function ofthe flux oven must not allow part temperature to reachthe temperature that would induce the formation of anydetrimental oxides on the surfaces of the aluminum com-ponent and/or assembly or activate the flux.

The reasons for preheating the component and/orassembly are to aid in reducing the thermal inertianeeded to overcome the mass load as product enters thecontinuous conveyance brazing furnace and to enhancethe component or assembly’s temperature uniformitylevel necessary to achieve acceptable braze results.

5.7.10 Procedure for Controlled-AtmosphereBrazing. Components cleaned, fluxed (when required),and assembled or flux dried/preheated to the require-ments of this specification shall be placed in the furnacein such a manner that the atmosphere can readily reach

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all surfaces. They shall be heated to the required temper-ature in the shortest possible time after temperature sta-bilization, if stabilization is required, by the approvedbrazing procedure specification.

Assemblies shall be cooled in a suitable manner toprevent cracking, reduce residual stresses, and accom-plish any heat treatment required by the engineeringdrawing.

Procedures shall be qualified and documented per 5.8.

5.7.11 Flux Removal. All residual corrosive fluxesshall be removed by suitable means after brazing untilthe requirements of 6.4.3.5 are met.

5.7.12 Procedure for Aluminum Fluxless Brazing.Assemblies cleaned and assembled to the requirementsof this specification shall be brazed to a cycle as requiredby the engineering drawing or documents referenced byit or to a procedure qualified and documented in accor-dance with 5.8.

5.7.13 Torch Brazing. Torch brazing is normallycontrolled by visual indicators related to process vari-ables. Since these indicators are developed through expe-rience related to outcome as opposed to specificmeasured values, torch brazing has been excluded fromthe sections of this specification on process descriptionand control. The balance of the torch brazing require-ments, as applicable to torch brazing, beginning with 5.6shall be applied.

5.7.14 Induction Brazing Induction brazing isaddressed in AWS C3.5, Specification for InductionBrazing. Brazing procedures shall be qualified in accor-dance with C3.5 or used with the approval of the Organi-zation Having Quality Responsibility.

5.8 Brazing Procedure Qualification. Brazing proce-dure specifications, equipment, and operators shall bequalified in accordance with AWS B2.2, Standard forBrazing Procedure and Performance Qualification, inaccordance with 5.2, 5.3, 5.4, and 6.4.1 of this document,or as specified by the Organization Having QualityResponsibility.

Such qualifications shall be documented andapproved in writing. The modification of proceduresrequires the written approval of the Organization HavingQuality Responsibility before use.

5.9 Safety and Health. Brazing fluxes and filler materi-als may emit hazardous fumes during the brazing cycle.It is mandatory that brazing operations be properly andadequately ventilated or that operators be provided withadequate breathing apparatus, or both, as required toassure that all relevant federal, state, and local govern-ment safety and health requirements are met. In addition,there are other hazards involved in brazing, such as those

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relating to the use of corrosive fluxes, potentially explo-sive gases, and hot surfaces.

For information on these and other safety and healthhazards that must be controlled during brazing, refer toANSI Z49.1, Safety in Welding, Cutting, and Allied Pro-cesses. Information on the hazards associated with mate-rials used in the brazing process can be found in theMaterial Safety Data Sheets (MSDSs), available fromthe manufacturer.

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 theperformance of all inspections of the brazed joints. Thisrequirement includes a system of quality control anddocumentation that assures and can prove that allrequired operations and procedures were performed.Suppliers may use their own facilities or any other facil-ity acceptable to the Organization Having QualityResponsibility for the inspection of the final product.

The Organization Having Quality Responsibility shallretain the right to perform or witness the required tests,or to perform any other tests necessary to ensure that thebrazed assemblies conform to the requirements of thisspecification and of the engineering drawing.

6.2 Requirements for Compliance. All products mustmeet all the requirements of this specification except incases in which deviation is specifically approved in writ-ing by the Organization Having Quality Responsibilityor is part of the engineering drawing.

The braze inspections required shall become a part ofthe contractor’s overall inspection system or quality pro-gram. The absence of any inspection requirements in thisspecification shall not relieve a contractor of the respon-sibility of ensuring that all products or supplies producedunder this specification meet all contractual obligations.The use of inspection sampling systems (see 6.4.4) doesnot authorize the shipment of known defective material,nor does it obligate any person or organization to acceptdefective material.

6.3 Sequence of Inspection and Manufacturing Oper-ations. Brazed joints may be inspected at the subassem-bly or assembly level, provided the entire joint isaccessible for inspection. Brazements requiring post-braze heat treatment shall be inspected after the heattreatment has been completed unless otherwise specifiedon the engineering drawing.

When brazed joints are inspected in process prior tomachining of joint edges, reinspection shall be requiredafter machining to ensure that the brazed joint has not



been damaged in the machining operations. Final fluxresidue testing shall be performed per 6.4.3.5 after allmachining operations of the brazed joint have beencompleted.

6.4 Required Examination of Brazed Joints

6.4.1 Destructive Tests. Metallurgical analysis andinspection for excessive silicon diffusion into base met-als and for undercutting and erosion of the base metalsshall be performed as part of the brazing qualificationprocedure per AWS B2.2 for all brazed aluminum joints.A microsection through the joint shall be prepared andetched by suitable means and examined at a magnifica-tion of 100X.

Evidence of intergranular attack and excessive braz-ing filler metal penetration further than 20% into thebase metal shall be unacceptable unless qualified by theOrganization Having Quality Responsibility. The braz-ing procedure specification shall be modified, asrequired, to eliminate the undesirable or unwanted reac-tions. Assemblies brazed in accordance with the modi-fied procedure shall be inspected to and shall meet therequirements of this paragraph. This test shall berepeated periodically if so specified by the OrganizationHaving Quality Responsibility.

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

6.4.1.3 Other Destructive Tests. The destructivetesting of assemblies or samples shall be performed asrequired for process qualification or corrective action.The destructive testing of samples or sample parts shallnot be substituted for any nondestructive examinationrequired by this specification except as part of anapproved sampling plan in accordance with the require-ments of this specification or as part of an inspection pro-cedure complying with 6.4.3.2.

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 shall be examined either radio-graphically or ultrasonically to determine the area of thejoint surfaces actually brazed and detect internal discon-tinuities unless the requirements of 6.4.3.3 are met. Thechoice of process is optional, except for the criteriaestablished in 6.4.3.1 and 6.4.3.3. However, ultrasonicexamination is generally the preferred method forinspecting brazed joints. Ultrasonic examination shall berequired when the criteria for radiographic examinationis not met, except as specified in 6.4.3.4.

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6.4.3.1 Radiographic Examination. Radiographicexamination shall be performed in accordance withASTM E 1742, Standard Practice for RadiographicInspection. When the joint clearance is less than 4% ofthe total thickness of the base metals or when the brazingfiller metal is preplaced between the joint faces, 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 be-tween the joint faces, unmelted filler metal may result inunreliable interpretations.

Ultrasonic examination shall be required when theabove criterion is not met, except as specified in 6.4.3.4.

6.4.3.2 Ultrasonic Examination. Ultrasonicexamination shall be performed in accordance with AWSC3.8, Recommended Practices for 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 joint faces, and theassembly must be processed so that all brazing fillermetal run over is removed prior to ultrasonic inspection;

(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 filler material. The reference standard shall havedefects of known size and location suitable for calibrat-ing 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 anyof these 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 air pressure tested at an in-ternal 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 Inspection of CriticalBrazed Components. Leakage of not more than 3.0 ×10–5 standard cubic centimeters (cc3) per second [2.0 ×

10–6 in3/s] shall be detected with a suitable mass spec-trometer leak detector in good working condition cali-brated as specified by its manufacturer;

(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. The procedureshall be specified in writing by the Organization HavingQuality Responsibility. No visually detected bubblesshall be allowed; and

(3) Internal pressure test fixtures and devices shall besuitable for the intended purpose and shall be adequatelyshielded to prevent injury to persons in case of cata-strophic 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 the suitability of the brazedjoints.

6.4.3.5 Flux Removal Test. All aluminum compo-nents brazed using corrosive chloride-based flux shall betested for flux and flux residues after flux removal. Thistest shall consist of rinsing the assembly with deionizedor distilled water such that all areas of the component areflushed, and a representative sample of this rinse water iscollected. Five percent by weight aqueous solution of sil-ver nitrate equal to 1% of the total volume of the sampleshall then be added to it in a suitable, clean glass con-tainer. Any evidence of a precipitate shall be cause forrejection.

Other test methods may be used as alternates with thewritten approval of the Organization Having QualityResponsibility if they are shown to be capable of depend-ably detecting chloride ion concentrations five parts permillion, or less. Any assemblies so tested and rejectedshall (1) be recleaned by suitable means to remove theflux and flux residues, (2) undergo retesting, and (3) meetthe requirements of this paragraph prior to acceptance.

6.4.3.6 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 Inspection, maybe used only on assemblies but are not suitable for theinspection of brazed fillets because they may result inunreliable interpretations.



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6.4.3.7 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 Sample Inspection Plans

6.4.4.1 Class A Joints. Class A joints requireinspection of every unit. No sampling plans shall beused.

6.4.4.2 Class B Joints. Class B joints shall beinspected using a sample plan in accordance with ASQZ1.4 provided the 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. In most cases, each lot will be a single furnaceload or a single shift’s or less production of a molten fluxbath made from identical detail parts identically pro-cessed; 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.

When allowed, a random sample shall be selectedfrom each inspection lot in accordance with ASQ Z1.4,Sampling Procedures and Tables for Inspection byAttributes, acceptable quality levels (AQL) 2.5, C = 0(i.e., no defects) and inspected in accordance with thisspecification. Lot sizes for the purposes of samplingshall consist of all brazed parts of the same design orkind manufactured using the same process from identicaldetails, identically prepared during one continuousperiod, and submitted for acceptance at the same time.

6.4.4.3 Class C Joints. Class C joints may beinspected using sample plans in accordance with ASQZ1.4, Sampling Procedures and Tables for Inspection byAttributes.

When allowed, a random sample shall be selectedfrom each inspection lot in accordance with ASQ Z1.4,Sampling Procedures and Tables for Inspection byAttributes, acceptable quality levels (AQL) 2.5, C = 0(i.e., no defects) and inspected in accordance with thisspecification. Lot sizes for the purposes of samplingshall consist of all brazed parts of the same design orkind manufactured using the same process from identicaldetails, identically prepared during one continuousperiod, and submitted for acceptance at the same time.

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



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6.5.1 External Discontinuities

6.5.1.1 Pinhole Porosity and Voids. Pinholeporosity and voids are allowed provided they do notexceed the following limits:

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

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

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

6.5.1.2 Cracks. Cracks are unacceptable.Imperfections of less than 0.38 mm [0.015 in.] are

uninterpretable and are not considered defects.

6.5.1.3 Erosion. Any evidence of braze filler ero-sion of the exposed surfaces of the base metal is un-acceptable if the erosion of either member exceeds 5% ofthe thickness of the thinnest component of the brazedjoint for Class A and 15% for Class B or Class C.

6.5.1.4 Lack of Brazing Filler Metal Melting.Failure of the brazing filler metal to melt completely isunacceptable. However, filler residue is acceptable onassemblies brazed using a fluxless process as long asevidence of brazing filler metal flow is visible.

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 un-acceptable. 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 Flux Residue. Evidence of corrosive fluxor corrosive flux residue is unacceptable (see 5.4.3.5).

6.5.1.7 Quality of Workmanship. The quality ofworkmanship shall be such that the assemblies are suit-able for the intended purpose and at surfaces are free ofexcess brazing filler metal, which could interfere withsubsequent operations or the function of the product.

6.5.2 Internal Discontinuities

6.5.2.1 Class A. Radiographic film or ultrasonicfacsimiles of Class A joints shall show that the total mea-sured unbrazed or unbonded area of the joint does notexceed 15% of the total joint area. The width of the larg-est 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 the

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joint in width or larger shall extend no closer to eitheredge of the joint than 20% of the joint width.

6.5.2.2 Class B. Radiographic film or ultrasonicfacsimiles of Class B joints shall show that the total mea-sured unbrazed or unbonded area of the joint does notexceed 25% of the total joint area. The width of the larg-est void or unbonded area as measured parallel to thejoint width shall not exceed 70% of the total joint width.Any such area that is wider than 60% of the joint widthor larger shall extend no closer to the joint edge than15% of the joint width.

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

6.6 Process Completion

6.6.1 Process Completion—Flux Processes. Jointsbrazed with flux may be reworked by brazing to the orig-inal qualified brazing procedure specification (see 5.8)twice without the specific written approval of the Orga-nization Having Quality Responsibility, unless otherwise



specified by that organization. Additional brazing fillermetal of the same type used in the original proceduremay be used.

Written prior approval of the procedures to be usedshall be obtained from the Organization Having QualityResponsibility if (1) the assembly is still not acceptableafter having been rebrazed twice and inspected to therequirements of 6.4 and 6.5, (2) a brazing process orbrazing filler metal other than that specified by the quali-fied brazing procedure specification is to be used, or (3)the disassembly of the brazed assembly is required.

If it is necessary to change the brazing procedurespecification or the brazing filler metal in order toaccomplish this rework, the procedure shall be qualifiedas specified in 5.8.

6.6.2 Process Completion—Fluxless Processes. Therebrazing of rejected joints brazed by fluxless processesshall only be performed with the prior written approvalof the Organization Having Quality Responsibility andwith a rebrazing procedure specification qualified to therequirements of 5.8.

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AWS C3.7M/C3.7:2005

Annex A

Guidelines for Preparation of Technical Inquiriesfor AWS Technical Committees

(This Annex is not a part of AWS C3.7M/C3.7:2005, Specification forAluminum Brazing, but is included for informational purposes only.)

Nonmandatory Annex


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A1. IntroductionThe American Welding Society (AWS) Board of

Directors has adopted a policy whereby all official inter-pretations of AWS standards are handled in a formalmanner. Under this policy, all interpretations are madeby the committee that is responsible for the standard.Official communication concerning an interpretation isdirected through the AWS staff member who works withthat committee. The policy requires that all requests foran interpretation be submitted in writing. Such requestswill be handled as expeditiously as possible, but due tothe complexity of the work and the procedures that mustbe followed, some interpretations may require consider-able time.

A2. ProcedureAll inquiries must be directed to:

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

All inquiries must contain the name, address, andaffiliation of the inquirer, and they must provide enoughinformation 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.

A2.1 Scope. Each inquiry must address one single provi-sion of the standard unless the point of the inquiry



involves two or more interrelated provisions. That provi-sion must be identified in the scope of the inquiry alongwith the edition of the standard that contains the provi-sions of that the inquirer is addressing.

A2.2 Purpose of the Inquiry. The purpose of theinquiry must be stated in this portion of the inquiry. Thepurpose can be to obtain an interpretation of a standard’srequirement or to request the revision of a particular pro-vision in the standard.

A2.3 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 must be cited. Ifthe point of the inquiry is to obtain a revision of the stan-dard, the inquiry must provide technical justification forthat revision.

A2.4 Proposed Reply. The inquirer should, as a pro-posed reply, state an interpretation of the provision thatis the point of the inquiry or provide the wording for aproposed revision, if this is what the inquirer seeks.

A3. Interpretation of Provisions of the Standard

Interpretations of provisions of the standard are madeby the relevant AWS technical committee. The secretaryof the committee refers all inquiries to the chair of theparticular subcommittee that has jurisdiction over theportion of the standard addressed by the inquiry. Thesubcommittee reviews the inquiry and the proposed replyto determine what the response to the inquiry should be.Following the subcommittee’s development of the

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response, the inquiry and the response are presented tothe entire committee for review and approval. Uponapproval by the committee, the interpretation is an offi-cial interpretation of the Society, and the secretary trans-mits the response to the inquirer and to the WeldingJournal for publication.

A4. Publication of InterpretationsAll official interpretations will appear in the Welding

Journal.

A5. Telephone InquiriesTelephone inquiries to AWS Headquarters concerning

AWS standards should be limited to questions of a gen-eral nature or to matters directly related to the use of thestandard. The AWS Board of Directors’ policy requiresthat all AWS staff members respond to a telephonerequest for an official interpretation of any AWS stan-



dard with the information that such an interpretation canbe 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.

A6. AWS Technical Committees

The 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 the committeesnor the staff is in a position to offer interpretive or con-sulting services on (1) specific engineering problems, (2)requirements of standards applied to fabrications outsidethe scope of the document or (3) points not specificallycovered by the standard. In such cases, the inquirershould seek assistance from a competent engineer experi-enced in the particular field of interest.

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Annex B

Bibliography(This Annex is not a part of AWS C3.7M/C3.7:2005, Specification forAluminum Brazing, but is included for informational purposes only.)


(1) Accredited Standards Committee Z49, Safety inWelding and Cutting. Safety in Welding, Cutting, and AlliedProcesses. ANSI Z49.1. Miami: American Welding Society.



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(2) American Welding Society Committee on Braz-ing and Soldering. Brazing Handbook. Miami: AmericanWelding Society.

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AWS C3.7M/C3.7:2005

17

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 Welding, Brazing, and NondestructiveExamination, Including Terms for Adhesive Bonding, Brazing, Soldering, Thermal Cutting, andThermal 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 Brazed Components

C3.4 Specification for Torch Brazing

C3.5 Specification for Induction Brazing

C3.6 Specification for Furnace Brazing

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

C3.8M/C3.8 Specification for the Ultrasonic Examination of Brazed Joints

C3.9 Specification for Resistance Brazing (Forthcoming)

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

BRH Brazing Handbook

SHB Soldering Handbook



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Ansi-Aws Standard c3.7-2005 Specification for Aluminum Brazing (eBook, 28 Pages)

Documents

Transcript of Ansi-Aws Standard c3.7-2005 Specification for Aluminum Brazing (eBook, 28 Pages)