SATPC0013870_Tab_4_Tech_Specs.pdf

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MSFC-SPEC-3679

National Aeronautics and REVISION A

Space Administration EFFECTIVE DATE: October 22, 2018

George C. Marshall Space Flight Center Marshall Space Flight Center, Alabama 35812

EM30

MSFC TECHNICAL STANDARD

PROCESS SPECIFICATION -

WELDING AEROSPACE

HARDWARE

Approved for Public Release; Distribution is Unlimited

MEASUREMENT SYSTEM

ENGLISH/METRIC (SI)

MSFC Technical Standard

Title: Process Specification – Welding

Aerospace Hardware

Document No.: MSFC-SPEC-3679 Revision: A

Effective Date: October 22, 2018 Page 2 of 92

DOCUMENT HISTORY LOG

Status (Baseline/

Revision/

Cancelled)

Document

Revision

Effective Date Description

Baseline - 10/11/2012

Baseline Release; document authorized through

MPDMS. [Baselined by Upper Stage Element

Control Board Directive CE4-01-0239, (PCN

CE001107, CR CLV-US-0481).]

Revision A 10/22/2018

Added section 1.3 – Units of Measurement. Moved sections 1.4 – Safety and 1.5 – Specific Process

Weld Requirements to section 3.0 – Requirements.

Added CGA specifications and removed cancelled gas specifications from section 2.0 – Applicable

Standards and Documents. Moved Acronyms and

Definitions from section 3.0 to Appendix I –

Acronyms and Definitions. Removed section 5.1.5

– Weld Equipment Requalification and added section 5.1.10 – Weld Equipment Modification.

Clarified section 7.3.2 – Weld Testing

Methodology. Moved section 9.5.2.b – Equipment

Fluctuations to Section 5.1 – Welding Equipment.

Reformatted Tables in Appendix A.

Clarified intent of Confidence Weld Requirements and moved sections within 7.3 for a logical approach.

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TABLE OF CONTENTS

PARAGRAPH PAGE

SCOPE

Purpose

Applicability

Units of Measurement

Tailoring

APPLICABLE DOCUMENTS

Applicable Standards and Documents

Reference Documents

Order of Precedence

REQUIREMENTS

Safety

Specific Process Weld Requirements

JOINT CLASSES

Inspection Criteria

Joint Classifications

EQUIPMENT

Welding Equipment

Tooling and Fixtures

Electron Beam Welding

MATERIALS

Base Metals

Filler Metals

Shielding Gas

Tungsten Electrodes

FSW Pin Tools

Anvils and Plug Weld Backing Material

Friction Plugs

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WELDER PERFORMANCE AND WELD PROCEDURE QUALIFICATION

Welder Performance Qualification

Weld Procedure Specification

Procedure Qualification Records

Records

PREWELD OPERATIONS

Weld Joint Design

Preweld Cleaning

Preweld Joint Fit-up

Weld Start and Run-Off Tabs

Laser and Electron Beam-to-Joint Alignment

PRODUCTION WELDING

Equipment Operational Readiness Check

Temperature Control

Tack Welding

Welding Techniques

Welding Procedure

POSTWELD OPERATION

The Weldment

General Workmanship Requirements

Dimensional Requirements

Weldment Straightening

Postweld Heat Treatment Requirements

Weldment Quality Requirements

Repair Welding

Material Review Board

VERIFICATION

General

Postweld Inspection

Records

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LIST OF APPENDICES

Appendix Page

Appendix A Procedure Qualification Weld Strength Requirements

Appendix B Weld Joint Dimensional Requirements

Appendix C Weld Nugget Dimensional Requirements

Appendix D Weld Quality Requirements

Appendix E Weld Procedure Specification Information

Appendix F Recommended Weld Filler Metals

Appendix G Preweld and Postweld Cleaning Methods

Appendix H Reference Documents

Appendix I Acronyms and Definitions

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LIST OF TABLES

Table Page

Table I. Minimum Inspection Requirements

Table II. WPS Allowable Qualified Thickness Range

Table III. GTAW Process Butt Weld Ultimate Tensile Strength Requirements

Table IV. VPPA Process Butt Weld Ultimate Tensile Strength Requirements

Table V. FSW Process Butt Weld Ultimate Tensile Strength Requirements

Table VI. Close-out FPW in FSW Process Ultimate Tensile Strength Requirements

Table VII. Fusion Butt Weld Ultimate Tensile Strength Requirements for Superalloys

Table VIII. Fusion Butt Weld Ultimate Tensile Strength Requirements for Titanium Alloys

Table IX. Fusion Butt Weld Ultimate Tensile Strength Requirements for Stainless Steel Alloys ... 43

Table X. Preweld Joint Fit-up Requirements

Table XI. Postweld Joint Fit-up Requirements

Table XII. Dimensional Requirements for Butt Welds – Fusion1

Table XIII. Dimensional Characteristics of Aluminum Alloy Butt Welds

Table XIV. Dimensional Requirements

Table XV. Weld Surface and Volumetric Acceptance Criteria – Aluminum Alloys

Table XVI. Surface and Volumetric Acceptance Criteria – Steels, Heat Resistant Alloys

Table XVII. Weld Surface and Volumetric Acceptance Criteria – Titanium Alloys

Table XVIII. Recommended Parameters to be Recorded in a WPS

Table XIX. Filler Alloys Recommended for Aluminum Alloys and Combinations

Table XX. Filler Alloys Recommended for Carbon and Low Alloy Steels and Combinations

Table XXI. Filler Alloys Recommended for Stainless Steels and Combinations

Table XXII. Filler Alloys Recommended for Nickel- and Cobalt-Base Alloys and Combinations . 79

Table XXIII. Filler Alloys Recommended for Copper Alloys and Combinations

Table XXIV. Filler Alloys Recommended for Titanium Alloys and Combinations

Table XXV. Acceptable Preweld and Postweld Cleaning Methods

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LIST OF FIGURES

Figure Page

Figure 1. Welding Techniques

Figure 2. Mismatch and Peaking

Figure 3. Fillet Weld Throats

Figure 4. Fillet Welds

Figure 5. Aluminum Fusion Butt Weld

Figure 6. EBW Butt Weld

Figure 7. EBW Max Weld Crown and Root Widths for Penetration Depths (D) ≤ 1.6 in [41 mm] 48

Figure 8. Min EBW Root Width for Penetration Depths (D) ≤ 0.2 in [5 mm]

Figure 9. Min EBW Root Width for Penetration Depths (D) of 0.2-1.6 in [5-41 mm]

Figure 10. C-FSW Zone

Figure 11. SR-FSW Zone

Figure 12. Titanium Full-Penetration Joint Welds

Figure 13. Titanium Butt Joint Maximum Allowable Weld Width (W) versus Thickness (t)

Figure 14. Titanium Fillet Joint Maximum Allowable Weld Width versus Thickness

Figure 15. Titanium Maximum Fillet Weld Size LMIN = thickness of the thinnest member

Figure 16. Titanium Fillet Weld Dimensions for Acute Angle and Drop Through

Figure 17. Weld Size Requirements for Butt Welds

Figure 18. Class A Butt Weld Fusion Zone Weld Size Limits

Figure 19. Class B Butt Weld Fusion Zone Weld Size Limits

Figure 20. Class C Butt Weld Fusion Zone Weld Size Limits

Figure 21. Weld Size Requirements for T and Corner Welds

Figure 22. Class A, T and Corner Weld Fusion Zone Weld Size Limits

Figure 23. Class B, T and Corner Weld Fusion Zone Weld Size Limits

Figure 24. Class C, T and Corner Weld Fusion Zone Weld Size Limits

Figure 25. External Discontinuities for Aluminum Alloys

Figure 26. Internal Defects for Aluminum Alloys

Figure 27. EBW Porosity Acceptance Criteria for Steels, Heat Resistant

Figure 28. Conventional-Friction Stir Welding Process

Figure 29. Self Reacting-Friction Stir Welding Process

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SCOPE

This process specification establishes uniform requirements for the design, fabrication, and inspection of welds in flight hardware. This process specification may also be used for special test articles and ground support equipment. This specification combines the lessons learned from extensive Agency-wide welding engineering experiences and combines the requirements of project, Center, other government, and industry documents used for the manufacture of historic spaceflight hardware such as Saturn, the Space Shuttle, and the International Space Station.

When this process specification is specified on contract documents, the contractor may submit an alternative, corporate, detailed weld process specification that meets the intent of this specification.

Industry, government, and company specifications may be used for welding hardware in lieu of this specification if approved by the responsible National Aeronautics and Space Administration

(NASA) Technical Authority. The content of this process specification meets the intent of NASA-

STD-5006A.

Purpose

The purpose of this process specification is to establish the minimum process control requirements for the design, fabrication (including the qualification of welders, welding operators, and welding procedure specifications), and quality assurance of manual, semi-automatic, mechanized, and automatic welds in flight hardware, special test articles and ground support equipment used by or for Marshall Space Flight Center (MSFC). This process specification will be used for flight hardware. This process specification may be used on special test articles and ground support equipment.

Applicability

This process specification is approved for use by MSFC and may be cited in contract, program, and other documents as a technical requirement. This process specification may also apply to contractors and subcontractors to the extent specified or referenced in their contracts.

This standard applies the following convention: all mandatory actions (i.e., requirements) are denoted by statements containing the term “shall”, the term “will” denotes an expected outcome, and the terms “may” or “should” denote explanatory or guidance text indicated in italics beginning in Section 4.0.

Applicable Processes

This process specification is applicable to fusion arc, solid-state, resistance and high-energy density weld processes for joining metallic materials. These include, but are not limited to, the following and the pulsed derivate:

(1) FCAW - Flux-Cored Arc Welding

(2) GMAW - Gas Metal Arc Welding

(3) GTAW - Gas Tungsten Arc Welding

(4) PAW - Plasma Arc Welding

(5) SMAW - Shielded Metal Arc Welding

(6) SAW - Submerged Arc Welding

(7) VPPA - Variable Polarity Plasma Arc

(8) Direct Drive Friction Welding

(9) Inertia Friction Welding

(10) FRW - Friction Welding

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(11) FSW - Friction Stir Welding

(12) FPW - Friction Plug Welding

(13) EBW - Electron Beam Welding

(14) LBW - Laser Beam Welding

Applicable Materials

This process specification covers all metallic materials used in the manufacture of flight hardware.

Units of Measurement

This standard makes use of both U.S. Customary Units (US) and the International System of Units (SI).

The latter are shown within brackets ([ ]) or in appropriate columns in tables and figures. The measurements may not be exact equivalents, therefore, each system must be used independently.

Tailoring

Tailoring of this process specification shall be formally documented as part of the program or project requirements and approved by the responsible NASA Technical Authority. These requirements may be tailored by constructing a matrix of applicable paragraphs and non-applicable paragraphs. Tailoring may include using existing or previously developed contractor processes and standards as a submittal of the various required plans. Otherwise, the tailoring of requirements may be documented in the Materials and

Processes Selection, Control, and Implementation Plan by providing the degree of conformance and the method of implementation for each requirement identified herein.

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APPLICABLE DOCUMENTS

Applicable Standards and Documents

The latest issues of the following documents form a part of this specification to the extent specified herein. In the event of a conflict between the documents referenced herein and the contents of this specification, the content of this specification will take precedence. The contractor may pursue substituting equivalent specifications and documents to the ones identified herein as long as the substitution does not compromise the intent of the specifications and documents identified herein and is approved by NASA/MSFC before implementation.

Military

MIL-HDBK-1823 Nondestructive Evaluation System Reliability Assessment

MIL-A-18455 Argon, Technical

MIL-PRF-27401 Propellant Pressurizing Agent, Nitrogen

MIL-PRF-27407 Propellant Pressurizing Agent, Helium

BB-C-101 Federal Specification Carbon Dioxide (CO2): Technical and USP

BB-H-886 Federal Specification Hydrogen

CGA G-4.3 Commodity Specification for Oxygen

CGA G-5.3 Commodity Specification for Hydrogen

CGA G-6.2 Commodity Specification for Carbon Dioxide

CGA G-9.1 Commodity Specification for Helium

CGA G-10.1 Commodity Specification for Nitrogen

CGA G-11.1 Commodity Specification for Argon

National Aeronautics and Space Administration (NASA)

NASA-STD-5006A General Fusion Requirements for Aerospace Materials Used in Flight

Hardware

NASA-STD-5009 Nondestructive Evaluation Requirements for Fracture-Critical Metallic

Component

NASA-STD-5019 Fracture Control Requirements for Spaceflight Hardware

NASA-STD- 6016 Standard Materials and Processes Requirements for Spacecraft

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NASA-STD-8739.12 Metrology and Calibration

MPCV 7016 Cross Program Fluid Procurement and Use Control Specification

NPR 8715.1 NASA Occupational Safety and Health Program

NPR 1441.1 NASA Records Management Program Requirements

Other Publications

ASTM E8/E8M Standard Test Methods for Tension Testing of Metallic Materials

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

Examination

AWS A3.0 Standard Welding Terms and Definitions

AWS A5-ALL Filler Metal Procurement Guidelines

AWS A5.01M/A5.01 Welding Consumables – Procurement of Filler Metals and Fluxes

AWS A5.12M/A5.12 Specification for Tungsten and Oxide Dispersed Tungsten Electrodes for

Arc Welding and Cutting

AWS B2.1/B2.1M Specification for Welding Procedure and Performance Qualification

AWS B4.0 Standard Methods for Mechanical Testing of Welds

AWS C6.1 Recommended Practices for Friction Welding

AWS C6.2 Specification for Friction Welding of Metals

AWS C7.4/C7.4 M Process Specification and Operator Qualification for Laser Beam

Welding

AWS D17.1 Specification for Fusion Welding for Aerospace Applications

AWS D17.2/D17.2 M Specification for Resistance Welding for Aerospace Applications

AWS D17.3 Specification for Friction Stir Welding of Aluminum Alloys for

Aerospace Applications

AWS G2.4/G2.4 M Guide for the Fusion Welding of Titanium and Titanium Alloys

AWS QC1 Standard for AWS Certification of Welding Inspectors

NAS 410 NAS Certification & Qualification of Nondestructive Test Personnel

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NAS 1514 Radiographic Standard for Classification of Fusion Weld Discontinuities

SAE AMS 2680 Electron-Beam Welding for Fatigue Critical Applications

SAE AMS 2770 Heat Treatment of Aluminum Alloy Raw Material

SAE AMS-W-6858A Welding, Resistance: Spot and Seam

Reference Documents

The documents listed in Appendix H are provided as background information for users of this specification, defining the source of the requirements in sections 4.0 through 11.0 of this specification.

The listing in this section does not levy any new or relieve any specific requirements that are imposed by this specification or other contractual documents associated with procurement of this specification end item.

Order of Precedence

When requirements in this specification conflict with those on the engineering drawing, the requirements on the engineering drawing will take precedence. Conflicts between this specification and other requirements documents will be resolved by the responsible NASA Technical Authority.

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REQUIREMENTS

Safety

Industrial Safety

Appropriate personal protective equipment shall be used in all hazardous processes.

All hazardous materials and processes that are required in compliance with provisions of this process specification and that are located or performed at sites other than MSFC are subject to applicable federal, State, and local safety codes, standards, and regulations.

All hazardous materials and processes that are required in compliance with provisions of this process specification and that are located or performed at MSFC shall be subject to NPR 8715.1.

System Safety

System safety engineering (SSE) shall identify critical and catastrophic hazards and mitigations to eliminate and/or control the hazards of the welding operations.

SSE shall participate within the various program working groups, panel reviews, and procedures and drawing reviews of welding systems and processes.

SSE shall participate in welding process reviews and decisions to ensure that safety concerns are addressed and appropriate safety requirements and design criteria are implemented in accordance with applicable program Safety, Reliability, and Quality Plan.

Specific Process Weld Requirements

Resistance Welding

Resistance welding shall be in accordance with AWS D17.2/D17.2M, or SAE AMS-W-6858A.

Laser Beam Welding

LBW shall be in accordance with AWS C7.4/C7.4M.

Friction and Inertia Welding

Direct drive friction or inertia welding shall be in accordance with AWS C6.2.

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JOINT CLASSES

Inspection Criteria

Welds performed using this process specification shall be classified in accordance with the consequences of joint failure as described in the following sections.

Welds shall be inspected per Table I.

Table I. Minimum Inspection Requirements

Method of Inspection Weld Class

A B C

Visual X X X

Dimensional X X X

Surface X X –

Volumetric X X1

Additional Inspection When Required by Drawing X X X 1Class B welds shall be subjected to volumetric inspection if required by engineering design and specified by drawing or special instruction.

Joint Classifications

Class A Joints

A weld joint whose failure would result in loss of crew, loss of vehicle, or loss of mission shall be classified as a Class A joint.

Class A welds shall pass quantitative surface and volumetric NDE and visual inspection in accordance with Table I and Section 11.0.

Class A fillet welds shall require a Materials Usage Agreement (MUA) in accordance with

NASA-STD-6016.

Based on consequences of failure, all fracture-critical welds are, by definition, Class A joints. If the quality of the Class A joint cannot be verified as required by this specification, e.g., inaccessible volume or root surfaces, then alternative rationale for acceptance is to be presented to the responsible NASA Fracture Control Board for approval as required by NASA-STD-5019.

Class B Joints

A fail-safe weld joint shall be classified as a Class B joint.

Class B welds shall pass quantitative NDE and visual inspection in accordance with Table I and Section 11.0.

Class C Joints

A nonstructural weld joint shall be classified as a Class C joint.

Class C welds shall pass a visual inspection in accordance with Table I and Section 11.0.

Class C welds shall be fully contained so failure in service would have minor or no effect on the efficiency of a system and so endangerment to personnel would not occur.

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EQUIPMENT

Welding Equipment

All welding equipment shall be capable of producing welds that meet the quality requirements specified herein.

Welding equipment shall be procured in accordance with an approved specification.

Equipment parametric fluctuations, variations that occur in equipment without human intervention, shall be characterized by the equipment vendor and may not be cause for rejection.

Violations of tolerances related to equipment variations during the steady-state portion of the weld that occur for less than 6 seconds shall not be cause for rejection.

Variations caused by the sampling rate per second can cause the readings to be outside the certified range. As long as the number is random (hence, the 6-sec limit), it is not cause for rejection.

Weld parameters controlling the heat input for automatic and mechanized welds shall be recorded continuously using automatic recording devices during the weld operation.

Process parameter data shall be logged at a rate that sufficiently captures all essential variable data and minimizes the risk of signal artifacts.

The minimum recommended data capture rate for FSW is 5 Hz.

Process parameter log files shall be stored electronically in compliance with contractual requirements

Equipment fluctuations or natural variations that occur in equipment without human intervention and change the readings of the qualified nominal parameter settings shall not be cause for rejection.

EBW equipment shall be a high vacuum type for welding in 5x10-4 torr [6.7x10-2 Pa] (or better) vacuum.

Acceptance Testing

New or relocated welding machines shall be acceptance tested under the cognizance of the responsible organization before release to manufacturing departments for production welding.

Equipment shall meet the requirements of the applicable purchase specification or design specification.

All equipment (electrical and mechanical) shall operate reliably within the range of parameters and duty cycle to be used for welding of production parts.

Calibration

Calibration shall be in accordance with NASA-STD-8739.12. For MSFC operations, reference MPR 8730.5 in Appendix H.

Welding shall be accomplished using equipment containing calibrated data indicators within manufacturer-specified tolerance ranges that display and/or record welding parameters.

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Measuring instruments, meters, gauges, or direct reading electrical control circuits to be used for welding operations shall be calibrated.

Calibration shall be verified periodically at intervals specified by the manufacturer of the welding equipment, not to exceed 1 year, or when any maintenance or repair is performed that may have changed calibration.

Current calibration status shall be posted or made available at the equipment and verified prior to use.

Calibration record(s) shall be maintained by the responsible cognizant organization and made available upon request.

The office of record for MSFC calibration records is the MSFC Metrology and Calibration Laboratory.

Maintenance and Maintenance Records

A preventive maintenance plan shall be implemented for welding equipment.

Welding machines shall have adequate periodic preventive maintenance service.

A current record of each maintenance repair shall be maintained for each welding machine.

Maintenance records shall be maintained by the responsible cognizant organization and made available upon request.

Records shall include unique identification of equipment, date, and time of service/repair, description of work completed, and traceability to employee performing the maintenance.

Weld Equipment Modification

Weld equipment validation shall be required when the welding equipment has failed to accomplish the intended function or when any major modification is made to the equipment.

Major modifications may include any changes to relevant sensor equipment, support hardware, software, or the weld system affecting process control.

When any major modification is made to the equipment a validation plan shall be submitted to the responsible NASA Technical Authority for approval.

Equipment validation documentation shall be retained as temporary records per section 11.3.7 and made available upon request.

Tooling and Fixtures

General Requirements

Tooling and fixtures shall be identified in the Weld Procedure Specification (WPS).

Tooling and fixtures used in the welding operation shall be constructed of materials that do not adversely affect the weld process and are not detrimental to the weld quality.

Tooling and fixtures shall not be a source of contamination of the weld or of the part being welded.

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Fixtures within 2 in. [5 cm] of the weld joint shall be visually free from rust, oxide scale, dirt, oil, grease, paint, low melting alloys, e.g., lead, tin, cadmium, and other contaminants detrimental to weld quality.

Paint may be within 1 in. [2.5 cm] on FSW fixtures.

Clamping and Alignment

Tooling and fixtures shall maintain component alignment during welding and ensure compliance with dimensional requirements of section 10.3 of this process specification.

In FPW, there shall be contact between the component and the backing anvil.

Magnetic Materials

When used with arc or EBW, magnetic materials shall be degaussed before welding.

Degaussing of magnetic materials shall be controlled by the WPS when necessary for the successful completion of the weld.

Degaussing – Prior to welding, ferromagnetic parts or tooling which have been subjected to the influence of magnetic fields (e.g., GTAW tack welded, machined using magnetic chucks, or magnetic particle inspected) shall be degaussed prior to welding.

Degaussing is to prevent arc and electron beam deflection while welding the joint.

Chill Bars

Chill bars shall not be used in such a manner that the weld joint location surfaces pick up chill bar material.

Chrome-plated copper chill bars may be used because copper or copper alloys have resulted in liquid metal embrittlement of austenitic stainless steels and some cobalt alloys.

Electroless nickel plating introduces phosphorus, which is detrimental to the weld process.

Aluminum, aluminum alloys, or other low melting alloys shall not be used for chill bars for non-aluminum alloy weld joints.

Electron Beam Welding

EBW shall be performed in a vacuum with absolute pressure of 0.001 torr [0.133 Pa] or lower.

Back-up material used to deflect or absorb residual EBW energy shall be of the same alloy as the part being welded, except when authorized by the NASA Technical Authority.

Alternate back-up materials may be used when specified by the WPS.

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MATERIALS

Base Metals

Unless otherwise specified or approved by the procuring agency, the base metal alloy shall conform to applicable material specifications as defined on the engineering drawing.

The base metal type and condition, as well as the appropriate material specification shall be recorded as a part of the WPS.

Weld start and run-off tabs, when used, shall be of the same alloy as the material being joined and be welded with the same filler metal specified on the drawing or WPS.

Backing material may be used when authorized by the WPS.

Filler Metals

Weld filler materials shall be purchased according to AWS A5.01/A5.01M.

Unless otherwise specified or approved by the procuring agency, filler metal alloy shall conform to all AWS A5 filler metal material specifications (AWS A5-ALL).

Weld filler materials and the appropriate specifications shall be recorded on the WPS.

Weld filler materials shall be stored under conditions to maintain filler material cleanliness and quality.

Uncoated weld filler wires shall be identified with a unique identification placed at the lowest level of control, i.e., wire, package, tube, to ensure material traceability of all uncoated welding filler wires.

Recommended weld filler metals are listed in Appendix F.

Metal consumable inserts shall be certified, their material traceability maintained, and both recorded as part of the WPS.

Material traceability for friction plugs shall be ensured.

Commercially pure titanium filler metal shall not be used for joining Ti-6Al-4V weld joints.

Shielding Gas

Welding-grade gases conforming to the applicable industry or military specifications shall be used for gas shielding when required.

Argon gas shall conform to the requirements of MIL-A-18455 or CGA G-11.1.

Nitrogen gas shall conform to the requirements of MIL-PRF-27401 or CGA G10.1.

Oxygen gas shall conform to the requirements of CGA G-4.3.

Helium gas shall conform to the requirements of MIL-PRF-27407 or CGA G-9.1.

Hydrogen gas shall conform to the requirements of BB-H-886 or CGA G-5.3.

Carbon dioxide gas shall conform to the requirements of BB-C-101 or CGA G-6.2.

The shield gas type and flow rates shall be recorded as a part of the WPS.

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Inert gas back-side shielding shall be used on joints requiring full or partial penetration on alloys susceptible to heavy oxide formation on the root side, the formation of which cannot be removed by wire brushing and will interfere with surface inspection.

Only helium or argon shielding gas shall be used for welding titanium and titanium alloys.

Tungsten Electrodes

Tungsten electrodes shall conform to AWS A5.12/A5.12M.

The electrode diameter, tip shape and alloy shall be recorded as a part of the WPS.

FSW Pin Tools

FSW pin tools (shoulders and pins) and tack tools shall be made of materials that resist wear during welding.

Pin and shoulder service life shall be demonstrated to meet the intended use and the use of pins and shoulders limited to the demonstrated life.

Pins and shoulders that have reached the specified service life shall be marked and removed from service to preclude accidental future use in the FSW production process.

If used for more than one weld joint, pins and shoulders shall be cleaned and inspected as required before reuse on production hardware.

Pin tools shall be visually inspected after each production weld for unacceptable wear and damage. Cracks, pits, flakes, and missing or broken threads shall result in the rejection of the pin tool from use in production.

Findings of pin tool visual inspections shall be recorded and hardware welded with damaged pin tools dispositioned before acceptability for use.

Pin tool design and materials shall be recorded as part of the WPS.

Anvils and Plug Weld Backing Material

Unless otherwise specified or approved by the procuring agency, anvil materials shall conform to applicable government and/or industry specifications for each given alloy group.

Anvil material shall be resistant to deformation under the loads and temperatures experienced during C-FSW and FPPW.

Anvil material shall not chemically react with the components to be joined.

Anvil and plug weld backing materials shall be recorded as part of the WPS.

Friction Plugs

Unless otherwise specified or approved by the procuring agency, friction plug materials shall conform to applicable government and/or industry specifications for each given alloy group and their material traceability be ensured.

Plugs shall be stored in an area that precludes their degradation by humidity, contamination, or chemical attack.

Plug weld design and material shall be recorded as part of the WPS.

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WELDER PERFORMANCE AND WELD PROCEDURE QUALIFICATION

Welder Performance Qualification

Operators of welding equipment shall be certified by successful completion of a qualification test for the applicable process.

Each fusion welder or fusion welding operator shall be qualified in accordance with AWS

D17.1, Section 5 and accepted to Class A requirements of this process specification.

7.1.1.1.1 All qualification groove welds shall be radiographically inspected.

7.1.1.1.2 All fillet welds with a base metal thickness more than 0.063 in [1.6 mm] shall be bend tested or examined metallographically.

Other requirements may be added but not be substituted for the requirements in AWS D17.1 Section 5.

FSW operators shall be qualified in accordance with AWS D17.3, Section 7 and accepted to

Class A requirements of this process specification.

FPW operators shall be qualified in accordance with AWS D17.3, Section 7, using a square groove test weld in sheet for making plug welds accepted to Class A requirements of this process specification.

Welder qualification testing shall be repeated at intervals not exceeding 5 years or when there is evidence to question the ability of the welder or welding operator to meet the requirements for qualification.

To maintain qualification, welders and welding operators shall have performed the weld process on the alloy groups for which they are certified within the previous 6 months.

Proficiency demonstration shall be required if a welder or welding operator has not performed the weld process on the alloy groups for which they are certified within the previous 6 months.

Records of operator certification documentation shall be maintained by the contractor’s quality assurance organization as temporary records per section 11.3.7 and be provided to the procuring agency before welding flight hardware.

Weld Procedure Specification

A WPS shall be qualified for each thickness and material combination. The allowable qualified thickness range is shown in Table II.

The WPS shall be qualified on the production equipment before welding of the first production part.

Table II. WPS Allowable Qualified Thickness Range

Process Application Thickness (t) Range, in [mm]

Automatic ±0.020 [0.51]

Semi-Automatic ±0.020 [0.51]

Mechanized ±0.020 [0.51]

Manual -0.5t / +2.0t

Orbital Tube ±0.1t

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Appendix E lists information that may be included in a WPS.

All test and evaluation data shall be recorded in the PQR.

The WPS shall contain all the information necessary to produce welds that consistently meet the strength and quality requirements.

All essential variables shall be identified on the WPS.

For weld qualification tests, base metal and consumables shall be identified by lot or heat number, type, and condition.

This base metal and consumable identification shall be maintained through all evaluation processes.

The WPS shall document all other prewelding operations, setup conditions, welding equipment, and any other pertinent information about the welding system used that affects the welding operation.

Operator trim parameter tolerances used for automatic, semi-automatic, and mechanized welding shall be listed in the qualified WPS.

Test samples representing the minimum and maximum heat input bounded in the WPS for automatic, semi-automatic, and mechanized welds shall be tested in accordance with section 7.3 of this process specification to verify acceptable welds

Procedure qualification welds shall be inspected using visual and NDE as specified in section

10.0 of this process specification, in accordance with Class A requirements.

Following visual and nondestructive inspection, the qualification welds shall be subjected to the same processes as the production parts, including reinforcement removal, mechanical deformation, stress relief, and thermal treatments associated with artificial aging or any operation affecting mechanical properties.

Rejectable surface indications may be removed using mechanical means (sanding or polishing), not rewelding. All visual and surface indications noted on the qualification welds that have been mechanically removed shall be recorded in accordance with section 7.3.1 and the records retained with the qualification weld documentation.

Operating ranges for current and voltage shall be established during the WPS qualification for the steady-state portion of manual welds.

Tapered thickness welds shall be qualified at the maximum and minimum thickness (see

Table II) and with a full-length confidence weld (specified in section 7.3.4).

In recognition of the differences in welding conditions between a test panel fixture and a major weld tool, the weld schedule developed on the test panel fixture shall be adjusted to the degree necessary when welding on the major weld tool.

The variation shall be noted on the WPS.

The adjustment shall be allowed one time only on the first part welded on the major weld tool.

An adjustment approach that allows more than one adjustment shall be approved by the responsible NASA Technical Authority.

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A confidence weld shall be completed before welding production hardware in accordance with the requirements of 7.3.4.

Procedure Qualification Records

All test results, including visual, dimensional, and NDE, shall be recorded in the PQR.

The provisions of AWS B2.1/B2.1M, may be followed for fusion welds.

Weld Testing Methodology

Welds shall be tested in accordance with AWS B4.0. Alternative methods for weld performance qualification verification shall be approved by the NASA Technical Authority.

For FSW, weld process zones should be evaluated using the qualified WPS at panel and confidence weld level.

Weld process zones may include intersections, weld overlap regions, restarts and closeout processes. This data should be evaluated to the vehicle design requirements.

Tensile Tests

7.3.2.1.1 A minimum of five specimens shall be tested to qualify a groove weld procedure.

7.3.2.1.2 Plug weld tensile test specimens gauge width shall be a minimum of 1.3 times the major diameter of the plug weld.

7.3.2.1.3 At a minimum, tensile specimens shall be tested to destruction at room temperature.

7.3.2.1.4 Percent elongation in 1.0 in. [2.5 cm] and/or 2.0 in. [5 cm] gauge lengths, 0.2% offset yield stress, and ultimate tensile strength shall be recorded.

7.3.2.1.5 Percent elongation for round samples shall be measured across a length of 4 times the diameter.

7.3.2.1.6 Weld strength shall meet or exceed the values in Appendix A.

7.3.2.1.7 Qualification welds for aluminum alloys used in cryogenic applications shall be tensile tested at the intended use cryogenic temperature and at room temperature.

A minimum of four test specimens shall be tested to destruction.

Shear Tests

7.3.2.2.1 A minimum of five specimens shall be shear tested for fillet welds in corner, T, lap, or edge joint configuration to qualify the weld procedure.

When it is not feasible to fabricate shear test specimens from qualification welds, shear tests may be implemented in accordance with AWS B4.0.

7.3.2.2.2 The shear ultimate strength shall meet 60% of the weld ultimate tensile strength requirement shown in Appendix A, unless otherwise approved by the responsible NASA Technical Authority.

Metallographic Examination

7.3.2.3.1 The welded joint shall be sectioned transverse to the direction of welding and the surface adequately prepared for visual examination in an unetched condition at a magnification of 10X for weld characteristics and defects.

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7.3.2.3.2 The section shall be lightly etched to reveal microstructure and reexamined at a higher magnification (a minimum of 50X and not greater than 200X) for dimensional requirements and the following weld quality requirements:

Overall fusion or consolidation of the weld, root penetration, burn-through, and blowholes.

Convexity, concavity, and size of bead, nugget or fillet.

Undercutting, underthickness, and overlapping.

Inclusions or voids.

Cracks.

Titanium Chemistry

7.3.2.4.1 Titanium weld qualification samples shall be analyzed for hydrogen, oxygen, and nitrogen content, in accordance with the requirements of the base metal specification, to assure conformance to the purity requirements.

7.3.2.4.2 The level of interstitial gases in the completed weld shall not exceed the worst-case maximum level permissible in the procurement specification for the base materials being welded.

7.3.2.4.3 The weld cross section in titanium welds shall contain no titanium hydrides (TiH2) or alpha case.

These two detrimental phenomena are indications of the hydrogen content exceeding the solubility limit and an oxygen-enriched alpha-stabilized surface resulting from air contamination at elevated temperatures, respectively.

Specimens described in section 7.3.2 of this process specification shall be produced and tested at a minimum interval of 5 years for Class A and Class B welds to verify PQR data.

Failed qualification welds that have anomalies with a clear definable cause may be repeated with a 2-for-1 replacement.

Additional testing (fatigue, simulated service, hardness, impact, etc.) may be performed in support of meeting the design requirements.

Confidence Weld Requirements

A confidence weld for each of the following different weld configurations shall be made and tested in accordance with section 7.3.2 of this process specification to validate the WPS. Class C welds are not required to have a confidence weld performed for qualification.

7.3.4.1.1 Tapered thickness welds made with automatic, semi-automatic, or mechanized weld processes.

7.3.4.1.2 Pressure vessel or pressurized structure welds; excluding pressurized component welds.

7.3.4.1.3 All SR-FSW.

7.3.4.1.4 All C-FSW.

7.3.4.1.5 Cases in which the procedure qualification weld does not provide an appropriate representation of the product form, e.g., forging, casting, extrusion, or geometry of the components being welded, e.g., tubing, rolled shape.

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7.3.4.1.6 Class A weld without root side access to verify full penetration.

7.3.4.1.7 Primary structural vehicle or payload welds. This may include payload attachment hardware or similar structures that constitute the primary load path within or between the vehicle and payload.

The confidence weld shall replicate the production part with respect to section thickness, alloy, heat treat condition, joint preparation, preweld cleaning, and fit-up and be made in the actual production weld fixture, using the actual production welding equipment.

The confidence weld shall replicate the production weld with respect to length, startup, and tailout or closeout.

7.3.4.3.1 A minimum of 15 total specimens shall be tested from the confidence weld(s).

Five specimens shall be taken from the beginning, five specimens from the middle, and five specimens from the end of the confidence weld. Specimen removal locations shall be approved by the NASA Technical Authority.

a) Beginning – As near the weld start as part geometry allows but outside of any overlap region

b) Middle – As near the weld midpoint as part geometry allows

c) End – As near the weld end as part geometry allows but prior to any overlap region

In FSW, the closeout process shall be tested at the service temperature.

For weldments of insufficient size or configuration, the NASA Technical Authority shall approve the test approach.

The pathfinder article may be used for the confidence weld if the above criteria are met.

Qualification shall be required if any of the essential variables on the WPS are modified.

Records

Records of test specimens that meet the acceptance requirements of this process specification shall be signed and dated by a Safety Mission Assurance (SMA) representative as an accurate record of the welding and testing of the procedure test weldment.

The WPS and PQR shall be prepared and retained as temporary records in accordance with section 11.3.7, with the current WPS being accessible at the welding station to the welder or welding operator.

All WPSs and PQRs shall be maintained and made available for review by the responsible

NASA Technical Authority before production.

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PREWELD OPERATIONS

Weld Joint Design

Joint configurations shall be documented in the WPS and on the design drawing.

Acceptable joint designs are butt, lap, corner, T, and edge. Corner and T joint designs should be designed to minimize susceptibility to lamellar tearing.

Class A and Class B full-penetration weld joint configurations that will be inaccessible for root side inspection are subject to the requirements of section 7.3.4 and shall be identified on engineering drawings and require approval for use as a weld joint design by the responsible NASA Technical

Authority.

For Class A welds, faying surfaces of joints shall have a surface roughness of 32 to 125 µin

[0.81 to 3.2 µm] per ASME B46.1.

LBW and EBW weld joint edges shall be machined parallel to ensure proper fit-up and meet the preweld joint fit-up requirements in Appendix B.

FSW joint design shall be butt joint configuration only.

Plug weld joint preparation shall be performed per the WPS or Engineering Drawing. This may include deburring.

Preweld Cleaning

Preweld cleaning of contaminants detrimental to weld quality or filler materials and surfaces to be welded shall be in accordance with Appendix G.

Preweld cleaning shall be accomplished in a controlled environment that does not degrade weld quality and that is maintained until the weld operation is complete.

After surface preparation, parts shall be covered or otherwise protected to prevent contamination until welding is completed.

Personnel performing the cleaning operation or any subsequent operation shall wear powder-free, non-vinyl, moisture barrier gloves.

Before use, tooling (including hold-down clamps, anvils, and parts of welding fixtures that contact or are placed in close proximity to the weld joint) shall be free of oil, moisture, and foreign materials.

Tools and instruments used for measurements or other devices that contact the surfaces to be welded shall be free of oil, grease, moisture, or other foreign materials before use.

Tools shall be cleaned initially and intermittently as necessary.

Preweld and interpass cleaning requirements shall be included in the WPS.

Stainless steel wire brushes shall be used in all instances where wire brushing is performed.

Low-current (10 ampere maximum), reverse–polarity, high-frequency arc cleaning (using manual, automatic, semi-automatic, or mechanized welding equipment) may be used to remove oxides from iron-, nickel-, and cobalt-base alloys.

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Fusion welding shall be started within 24 hrs. of initiating preweld cleaning, unless otherwise permitted by the responsible NASA Technical Authority.

Time between initiation of preweld cleaning and welding shall be documented in production build records.

In aluminum alloys, C-FSW joints will subsequently be intersected by fusion welds shall be cleaned by draw filing or scraping the abutting edges and scraping or wire brushing the crown and root surfaces of the weld land 0.5 in [12.7 mm] beyond the shoulder diameter.

All SR-FSW joints in aluminum alloys shall be cleaned by draw filing or scraping the abutting edges and mechanically abrading the crown and root surfaces of the weld land 0.5 in [12.7 mm] beyond the shoulder diameter.

Following the mechanical cleaning operations described in sections 8.2.11 and 8.2.12 above, solvent cleaning by wiping with lint-free clean cloth may be permitted.

The FSW full-penetration pass shall be started within 48 hrs. of initiating preweld joint cleaning unless otherwise permitted by the responsible NASA Technical Authority.

Tack welding is not considered a full-penetration weld.

EBW shall start within 40 hrs. after surface preparation has been completed, unless otherwise permitted by the responsible NASA Technical Authority, with the following exceptions:

EBW of aluminum alloys shall be performed within 8 hrs. after being cleaning.

If parts have been vacuum dried and stored in a sealed plastic film (other than polyethylene or nylon) bag purged with dry argon or gaseous nitrogen, the parts shall be welded together within 100 hrs. of cleaning.

Weld joints adjacent to brazed surfaces shall be cleaned in accordance with Appendix G to remove contamination from brazing operations.

All brazing alloy deposits shall be removed from the weld joint region that includes the joint and the area within 0.25 in [6.4 mm] of the joint, unless otherwise specified on the engineering drawing.

When welding precision-cleaned hardware, all welding of assemblies for precision-cleaned systems (including tube preparation) shall meet the requirements of MPCV 7016.

Plugs used for friction plug welding and the material to be plug welded shall be cleaned by abrasion to remove the oxide layer, followed by solvent cleaning within 8 hrs. of plug welding.

Preweld Joint Fit-up

After the parts have been mated, positioned and tacked for the welding operation, the joint shall be verified for compliance with the preweld and postweld dimensional requirements of Appendix B of this process specification.

Preweld joint gap requirements for specific materials and processes shall meet the requirements listed in Appendix B.

The interrelationship of mismatch, joint gap, peaking, and pin tool offset shall be shown by engineering analysis or test to assure that positive margins of safety exist for FSW.

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Weld Start and Run-Off Tabs

Weld start and run-off tabs (when used) shall be of the same alloy as the detail parts being welded.

Weld start and run-off tabs shall be cleaned in the same manner as the parts.

Tabs shall be integral with the part, being either machined in, welded with the same filler metal, or rigidly attached to the part pieces before assembly.

Length of weld start and run-off tabs shall be established, based on the confidence panel test results.

Use of weld start and run-off tabs shall be included in the WPS.

Laser and Electron Beam-to-Joint Alignment

Flat and Circular Welds

Before welding every weld joint of every production run, the entire length of the joint shall be leveled to within ±0.005 in [±0.127 mm] using a calibrated dial indicator.

The assumed centerline of the beam shall be aligned within 30 min of the gun angle defined in the approved weld parameter, as determined using a calibrated inclinometer in conjunction with a surface at a known reference angle to the joint faces.

Circumferential Welds

Before welding every weld joint of every production run, the axis of the assembly shall be leveled, using a calibrated dial indicator to within ±0.005 in [±0.127 mm] in relation to reference surfaces for weld joint faces…