AWS C7.1M/C7.1:2013

An American National Standard

Recommended Practices for Electron Beam Welding and Allied Processes

AWS C7.1M/C7.1:2013

An American National Standard

Approved by the American National Standards Institute

February 5, 2013

Recommended Practices for Electron Beam Welding and Allied Processes

4th Edition

Supersedes AWS C7.1M/C7.1:2004

Prepared by the American Welding Society (AWS) C7 Committee on High Energy Beam Welding and Cutting

Under the Direction of the AWS Technical Activities Committee

Approved by the AWS Board of Directors

Abstract

This document presents Recommended Practices for Electron Beam Welding and Allied Processes. It is intended to cover common applications of the process. Processes definitions, safe practices, general process requirements, and inspection criteria are provided.

International Standard Book Number: 978-0-87171-835-8

American Welding Society 8669 Doral Blvd., Suite 130, Doral, FL 33166

© 2013 by American Welding Society

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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 American Welding Society (AWS) are voluntary consensus standards that have been developed in accordance with the rules of the American National Standards Institute (ANSI). When AWS American National 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 govern- mental bodies, their provisions carry the full legal authority of the statute. In such cases, any changes in those AWS standards must be approved by the governmental body having statutory jurisdiction before they can become a part of those laws and regulations. In all cases, these standards carry the full legal authority of the contract or other document that invokes the AWS standards. Where this contractual relationship exists, changes in or deviations from requirements of an AWS standard must be by agreement between the contracting parties.

AWS American National Standards are developed through a consensus standards development process that brings together volunteers representing varied viewpoints and interests to achieve consensus. While AWS administers the process 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.

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This standard may be superseded by new editions. This standard may also be corrected through publication of amendments or errata or supplemented by publication of addenda. Information on the latest editions of AWS standards including amendments, errata, and addenda is posted on the AWS web page (www.aws.org). Users should ensure that they have the latest edition, amendments, errata, and addenda.

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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, 8669 Doral Blvd., Suite 130, Doral, FL 33166 (see Annex D). 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 professional advice. Such opinions represent only the personal opinions of the particular individuals giving them. These individuals do not speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpretations 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 C7 Committee on High Energy Beam Welding and Cutting. It must be reviewed every five years, and if not revised, it must be either reaffirmed or withdrawn. Comments (recommen- dations, additions, or deletions) and any pertinent data that may be of use in improving this standard are required and should be addressed to AWS Headquarters. Such comments will receive careful consideration by the AWS C7 Committee on High Energy Beam Welding and Cutting 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 C7 Committee on High Energy Beam Welding and Cutting to express their comments verbally. Procedures for appeal of an adverse decision concerning all such comments are provided in the Rules of Operation of the Technical Activities Committee. A copy of these Rules can be obtained from the American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166.

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Personnel

AWS C7 Committee on High Energy Beam Welding and Cutting

P. W. Hochanadel, Chair Los Alamos National Laboratory

T. A. Palmer, 1st Vice Chair Applied Research Laboratory, Penn State

K. W. Lachenberg, 2nd Vice Chair Sciaky, Incorporated

B. C. McGrath, Secretary American Welding Society

P. Blomquist Applied Thermal Sciences, Incorporated

P. E. Denney The Lincoln Electric Company

D. D. Kautz Los Alamos National Laboratory

G. R. LaFlamme PTR—Precision Technologies, Incorporated

E. D. Levert Lockheed Martin Missiles and Fire Control

Advisors to the AWS C7 Committee on High Energy Beam Welding and Cutting

R. D. Dixon Retired

P. W. Fuerschbach Sandia National Laboratory

R. W. Messler, Jr. Rensselaer Polytechnic Institute

J. O. Milewski Los Alamos National Laboratory

T. M. Mustaleski Retired

D. E. Powers Retired

R. C. Salo Sciaky, Incorporated

AWS C7B Subcommittee on Electron Beam Welding and Cutting

T. A. Palmer, Chair Applied Research Laboratory, Penn State

B. C. McGrath, Secretary American Welding Society

G. R. Gibbs Sandia National Laboratory

P. W. Hochanadel Los Alamos National Laboratory

D. D. Kautz Los Alamos National Laboratory

K. W. Lachenberg Sciaky, Incorporated

G. R. LaFlamme PTR—Precision Technologies, Incorporated

E. D. Levert Lockheed Martin Missiles and Fire Control

K. J. Zacharias Hamilton Sundstrand Space Systems

Advisors to the AWS C7B Subcommittee on Electron Beam Welding and Cutting

R. D. Dixon Retired

D. R. Foster Pratt & Whitney

G. S. Lawrence Retired

J. O. Milewski Los Alamos National Laboratory

J. C. Monsees Hi-Tech Welding & Forming

T. M. Mustaleski Retired

D. E. Powers Retired

R. C. Salo Sciaky, Incorporated

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Foreword

This foreword is not part of AWS C7.1M/C7.1:2013, Recommended Practices for Electron Beam Welding and Allied Processes, but is included for informational purposes only.

Electron beam processing was initiated in the early 1900s, when an electron beam was used to produce tantalum metal by melting tantalum sponge. Since then, electron beam technology for materials processing has steadily advanced and is now commonly used. While electron beam processing encompasses a wide range of metal processing activities, this doc- ument focuses on welding and joining. The commercial application of electron beam welding (EBW) was first intro- duced in the late 1950s and subsequently gained rapid and widespread acceptance by the industrial community because of its ability to produce high aspect ratio (depth-to-width) welds and join dissimilar and difficult-to-weld materials. Welding speeds on the order of 760 mm/s [1800 in/min] and single-pass autogenous welds in metals of greater than 150 mm [6 in] thickness have been achieved.

It has been estimated that there are upwards of 3000 electron beam welders presently in operation throughout the world—of which approximately 35% are involved with automotive related tasks, 15% with both aircraft and aerospace related tasks, 10% with nuclear (either commercial or military) related tasks, 20% with a variety of job shop (contract welding) related tasks, and 20% with other industries (electronic, medical bimetal, Research and Development, etc.). It is also estimated that out of this total number of operating units, approximately 40% of those that were delivered during the ’60s and ’70s time frame (i.e., units having upwards of 35 years or more of operational time) are still being used on a regular basis—if not by the original purchaser, then by the 2nd or 3rd owner of the unit, thus attesting to the fact that equipment being supplied by the EBW manufactures has a demonstrated history of performing durably and reliably.

The information contained in the Recommended Practices was compiled by the American Welding Society’s C7B Sub- committee on Electron Beam Welding and Cutting and has been carefully reviewed by a number of experts in the field, and should provide a helpful guide for use in applying the electron beam welding process. It must be noted that the oper- ating parameters specified in these recommended practices will not be the only possible parameter combinations that can be employed for successfully processing the materials and thicknesses shown. Changes in material composition, dimen- sional tolerances, and machine calibration will cause changes in the resulting welds. Therefore, the procedures contained herein are offered simply as a guide and are intended only for use in aiding the application of electron beam technology and increasing process consistency.

AWS C7.1M/C7.1:2013, Recommended Practices for Electron Beam Welding and Allied Processes, is the third revision (4th edition) of the document issued initially in 1992. This edition adds three new practical examples and adaptations of the electron beam process, including electron beam braze welding (EBBW), electron beam cutting (EBC) and drilling, the deposition of supplementary weld metal (surfacing, cladding, and hard-facing), electron beam additive manufactur- ing (EBAM), surface texturing, and heat treating of components. Previous editions of the document are as follows:

AWS C7.1-92 Recommended Practices for Electron Beam Welding AWS C7.1:1999 Recommended Practices for Electron Beam Welding AWS C7.1M/C7.1:2004 Recommended Practices for Electron Beam Welding

Comments and suggestions for the improvement of this standard are welcome. They should be sent to the Secretary, AWS C7 Committee on High Energy Beam Welding and Cutting, American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166.

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Table of Contents

Page No.

Personnel v

Foreword vii

List of Tables xi

List of Figures xi

1. General Requirements 1

   1. Scope 1

   2. Units of Measurement 1

   3. Safety 1

2. Normative References 2

3. Terms and Definitions 2

4. Safety Considerations 6

   1. Scope 6

   2. Potential Hazards 6

5. Process Fundamentals 10

   1. Description of Process 10

   2. Areas of Application. 12

   3. Advantages and Limitations 12

   4. Allied Processes 13

6. Description of Equipment 19

   1. Introduction 19

   2. Modes of Electron Beam Welding. 19

   3. High- and Low-Voltage EBW Equipment 22

   4. Components of the EBW System 22

   5. EBW System Function and Performance Control 26

   6. EBW Equipment Specification 27

7. Metallurgical Considerations 29

   1. Introduction 29

   2. Heat-Affected Zone 29

   3. Fusion Zone 32

   4. Metallurgical and Material Considerations 33

8. General Process Considerations 40

   1. Overview 40

   2. Designing for Electron Beam Welding 41

   3. Joint Cleaning 46

   4. Welding Thin Metals 48

   5. Welding Thick Metals 49

   6. Welding Dissimilar Thicknesses 52

   7. Fixtures 54

   8. Controlling Parameters 54

   9. Calibration and Verification 55

      Page No.

9. Inspection and Testing of Welds 56

   1. Introduction 56

   2. Weld Characteristics 56

   3. Inspection Processes 56

   4. Special Inspection Techniques 58

   5. Acceptability Limits 58

   6. Inspection Plans 59

10. Equipment Maintenance Program 59

    1. Preventive Maintenance Performed Daily 59

    2. Preventive Maintenance Performed Weekly 59

    3. Preventive Maintenance Performed Monthly 60

    4. Preventive Maintenance Performed Quarterly 60

    5. Preventive Maintenance Performed Semiannually 61

    6. Preventive Maintenance Performed Yearly 61

11. Training and Qualification of Operators 61

    1. Electron Beam Welding Equipment Operation 61

    2. Welding Operator Training Program 63

12. Weld Process and Procedure Development for Electron Beam Welding 65

    1. Introduction 65

    2. Process Development Performance Requirements 65

    3. Structure/Properties Relationships 65

    4. Determination of Properties 66

    5. Procedure Development and Qualification 66

13. Practical Examples 68

    1. Example 1—Hermetic Seal on High Pressure Vessel 68

    2. Example 2—Electron Beam Welding of High Purity Niobium Superconducting RF Cavities 70

    3. Example 3—Electron Beam Deep Penetration Welding 71

    4. Example 4—Electron Beam Welding Fuel Elements for Space Reactor Test Components 72

    5. Example 5—Non-vacuum Electron Beam Welding of Torque Converters 74

    6. Example 6—Partial Vacuum Electron Beam Welding of Tangs of Planetary Gear Assemblies 75

    7. Example 7—Electron Beam Welding of Titanium Fin-to-Fuselage Brackets for the Eurofighter 76

    8. Example 8—Non-Vacuum Electron Beam Welding of Aluminum Structural Beams 80

    9. Example 9—Partial Vacuum Electron Beam Welding of Speed Gear 81

    10. Example 10—Titanium Chord Fabrication Using Electron Beam Free Form Fabrication Process 81

    11. Example 11—Electron Beam Welding of Dipole Vacuum Chamber for High Energy Accelerator 83

    12. Example 12—Knife Edge Seal Using Electron Beam Additive Manufacturing Process 87

14. Power Curves 89

Annex A (Informative)—Cross-Reference Chart for Various Pressure Units 97

Annex B (Informative)—Format for the Specification of Electron Beam Welding Equipment 99

Annex C (Informative)—Extended Glossary for Electron Beam Processing 101

Annex D (Informative)—Guidelines for the Preparation of Technical Inquiries 131

Annex E (Informative)—Informative References 133

List of AWS Documents on Electron Beam Welding and Cutting 135

List of Tables

Table Page No.

1. Radiation Exposure Standards 7

2. Preweld Cleaning Materials 47

3. Welding Variables Example 1—Hermetic Seal on High Pressure Vessel 69

4. Welding Variables Example 2—Electron Beam Welding of High Purity Niobium Superconducting

   RF Cavity 71

5. Welding Variables Example 3—Electron Beam Deep Penetration Welding 73

6. Welding Variables Example 4—Electron Beam Welding Fuel Elements for Space Reactor Test Components 74

7. Welding Variables Example 5—Non-Vacuum Electron Beam Welding of Torque Converters 75

8. Welding Variables Example 6—Partial Vacuum Electron Beam Welded Tangs of Planetary

   Gear Assemblies 76

9. Welding Variables Example —Electron Beam Welding of Titanium Fin-to-Fuselage Brackets

   for the Eurofighter 79

10. Welding Variables Example 8—Non-Vacuum Electron Beam Welding of Aluminum Structural Beams 81

11. Welding Variables Example 9—Partial Vacuum Electron Beam Welding of Speed Gear 82

12. Weld Process Variables used to Produce the Chord Perform 84

13. Nominal Parameters—Dipole Chamber Assembly 86

14. Weld Process Variables used to Produce Knife Edge Air Seal 88

E.1 Cross-Reference Chart for Electron Beam Welding Standards 134

List of Figures

Figure Page No.

1. Sample Form for Radiation Survey 7

2. Simplified Representation of an Electron Beam Gun Column 10

3. Schematic Representation of a Keyhole Weld 12

4. (A) Impeller Blade and Cover Assembly, (B) Placement of Braze Foil, and (C) Cross Section

   of Completed Braze-Welded Joint 14

5. Finished T-Joint of Thin Impeller Blade and Thick Cover Joined with a Combination of

   Electron Beam Welding and Brazing 15

6. Sequence of Electron Beam Drilling with Speed of Beam Travel, Expulsion of Metal, and

   Completed Hole 15

7. Spinner with 25,600 Holes 0.55 mm [0.022 in] Diameter Drilled by the Electron Beam Process 16

8. Repair Welds on Titanium Drum Rotor Part of an Aircraft Engine, As-Welded (Upper Left

   Section) and Finished Product After Machining (Upper Right Section) 17

9. Schematic Representation of EBAM Process 17

10. Example of EB Textured Surface. 18

11. Example of EB Simultaneous Heat Treatment 19

12. Electron Beam Modes of Operation 20

13. Mobile Gun Configuration 20

    Figure Page No.

14. Weld Penetration Versus Vacuum Level Chart 21

15. A Large Chamber, High Vacuum and EBW Production Units 23

16. Overview of EB Seam Tracking Basics Using Secondary Emissions 24

17. Electron Beam Welder CNC Pendant and Console 25

18. Graphic Representation of the Energy Density Changes an EB Experiences When Being Focused 27

19. Examples of EB Deflection Patterns and the Effect Use of such Patterns has on Workpiece 28

20. Illustration of Simulated Multi-Beam EB Processing 28

21. Comparison of Electron Beam Weld and Gas Tungsten Arc Weld Profiles 30

22. Longitudinal Cross Section of TZM Welded with Electron Beam Process showing Grain

    Growth in Weld Metal Zone and Epitaxial Solidification from Base Metal 31

23. Cross Section of Stainless Steel showing the Solutioning of Carbides in the Fusion Zone 31

24. Various Butt Joint Configurations used in Electron Beam Welding 42

25. T-Joint Configurations 42

26. Various Corner Joint Configurations 43

27. Various Lap Joint Configurations 44

28. Various Edge Joint Configurations 44

29. Circular Joints 45

30. Thin-Section Weld Joints 48

31. Large Chamber Electron Beam Welding Machine 50

32. Photomicrograph of Thick Section EB Weld 50

33. Electron Beam Welding Record 64

34. Electron Beam Welded Hermetic Seal on a High Pressure Vessel 69

35. EB Welded Niobium Cavity Part shown within the Weld Chamber 70

36. A Cross Section of the Cavity Girth Weld in High Purity Niobium 71

37. Proposed Double Wall High-Level Waste Container Section after Welding 72

38. Cross Section of Copper Lid to Wall Weld Displaying 44.5 mm [1.75 in] Single Pass Joint

    Penetration 73

39. Cross Section of an EB Weld in Nb1Zr Material 74

40. Non-Vacuum Electron Beam Welded Torque Converter 75

41. PVEBW Welding of Planetary Carriers 76

42. Fin-to-Fuselage Half Section Weld Path and Photos 77

43. EB Weld of Rudder to First Section Assembly 78

44. Completely Welded Fin-to-Fuselage Bracket Assembly 79

45. Aluminum Dashboard Beam 80

46. Partial Vacuum Electron Beam (PVEBW) Welded Speed Gear 82

47. CAD Model of Target “Chord” Preform 83

48. Deposited Chord Preform and Final Part 84

49. Cooling Bar Welding Illustration—Two Positions for Movable Gun 85

50. DIP Screen Welding Illustration—Two Positions for Moveable Gun 85

51. Dipole Chamber Sample Section after Cooling Bar & Dip Screen Welding 86

52. Jet Engine Knife Seal with EB Additive Process 87

53. Knife Edge Air Seal in EBW Chamber 88

54. Power Curves for Electron Beam Welding of Aluminum Alloys 89

55. Power Curves for Electron Beam Welding of Copper Alloys 90

56. Power Curves for Electron Beam Welding of Molybdenum Alloys 91

57. Power Curves for Electron Beam Welding of Niobium Alloys 92

58. Power Curves for Electron Beam Welding of Stainless Steel Alloys 92

59. Power Curves for Electron Beam Welding of Steel Alloys 93

60. Power Curves for Electron Beam Welding of Tantalum Alloys 93

61. Power Curves for Electron Beam Welding of Titanium Alloys 94

62. Power Curves for Electron Beam Welding of Tungsten Alloys 95

63. Power Curves for Electron Beam Welding of Zirconium Alloys 95

64. Power Curves for Electron Beam Welding of Zircaloy Alloys 95

Figure Page No.

1. Ideal Focusing 119

2. Simple Diode 120

3. Current Density Distribution 121

4. Focusing Action 122

5. Focused Electron Beam 123

6. Focus Position and Current Densities 124

7. Crossover of a Light Source 125

8. Elements of a Typical Electron Beam Gun 126

9. Types of Focusing 127

10. Plot of  vs. r 128

11. Quantitative Characterization of an Electron Beam 129

12. Numerical Values for the Radiance of Various Beam Systems 129

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xiv

Recommended Practices for Electron Beam Welding and Allied Processes

1. General Requirements

   1. Scope. These recommended practices present descriptions of electron beam welding equipment and procedures for welding a wide range of metals and thicknesses; allied processes, to include electron beam braze welding (EBBW), cut- ting, drilling, surfacing, additive manufacturing, surface texturing, and heat treating, are also discussed. The appropriate terms, definitions, and safety considerations are presented. Information is included on designing for electron beam weld- ing (EBW), welding dissimilar metals and thicknesses, fixturing, specifications, and operator training and qualification. Information regarding the safe practice of electron beam welding and allied processes can be found in Clause 4 of this standard.

      
      

      Highly technical and detailed descriptions of metallurgy and the physics of the EBW process, though important to the engineer and scientist, were considered beyond the scope of this publication.

      
      

   2. Units of Measurement. This standard makes use of both the International System of Units (SI) and U.S. Customary Units. The latter are shown within brackets ([ ]) or in appropriate columns in tables and figures. The measurements may not be exact equivalents; therefore, each system shall be used independently.

      
      

   3. Safety. Safety issues and concerns are addressed in this standard, although health issues and concerns are beyond the scope of this standard. Some safety considerations are addressed in Clause 4.

      
      

      Safety and health information is available from the following sources: American Welding Society:

      1. ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes

         
         

      2. AWS Safety and Health Fact Sheets

         
         

      3. Other safety and health information on the AWS website Material or Equipment Manufacturers:

1. Material Safety and Data Sheets supplied by materials manufacturers

   
   

2. Operating Manuals supplied by equipment manufacturers Applicable Regulatory Agencies

Work performed in accordance with this standard may involve the use of materials that have been deemed hazardous, and may involve operations or equipment that may cause injury or death. This standard does not purport to address all safety and health risks that may be encountered. The user of this standard should establish an appropriate safety program to address such risks as well as to meet applicable regulatory requirements. ANSI Z49.1 should be considered when developing the safety program.