**Process Specification for Friction Stir Welding**

+-----------------------------------------------------------------------+
| **Engineering Directorate**                                           |
|                                                                       |
| **Structural Engineering Division**                                   |
|                                                                       |
| **March 2007**                                                        |
|                                                                       |
| ![](media/image1.png){width="1.3944444444444444in" height="1.15in"}   |
|                                                                       |
| National Aeronautics and                                              |
|                                                                       |
| Space Administration                                                  |
|                                                                       |
| **Lyndon B. Johnson Space Center**                                    |
|                                                                       |
| Houston, Texas                                                        |
+-----------------------------------------------------------------------+

**Process Specification for Friction Stir Welding**

+----------------+-----------------------------------+---+-------------+
| **Prepared by  | ####                              |   |             |
| :**            |                                   |   |             |
+----------------+-----------------------------------+---+-------------+
|                | Daniel J. Rybicki                 |   | Date        |
|                |                                   |   |             |
|                | Materials and Processes           |   |             |
|                | Branch/ES4                        |   |             |
+----------------+-----------------------------------+---+-------------+

+----------------+-----------------------------------+---+-------------+
| **Reviewed by  | ####                              |   |             |
| :**            |                                   |   |             |
+----------------+-----------------------------------+---+-------------+
|                | Lucie B. Johannes, PhD            |   | Date        |
|                |                                   |   |             |
|                | Materials and Processes           |   |             |
|                | Branch/ES4                        |   |             |
+----------------+-----------------------------------+---+-------------+

+----------------+-----------------------------------+---+-------------+
| **Approved     | ####                              |   |             |
| by:**          |                                   |   |             |
+----------------+-----------------------------------+---+-------------+
|                | Bradley S. Files, Chief           |   | Date        |
|                |                                   |   |             |
|                | Materials and Processes           |   |             |
|                | Branch/ES4                        |   |             |
+----------------+-----------------------------------+---+-------------+

  --------------- ------------------------------------------- -------------
  **REVISIONS**                                               

  **VERSION**     **DESCRIPTION**                             **DATE**

  Baseline        Original version                            10/23/2002

  A               Modified section 6.4 to remove "after       10/29/2002
                  completion of all welding" from the         
                  paragraph                                   

  B               Comprehensive rewrite to combine PRC-0013   1/5/2005
                  and PRC-0014 and make editorial and         
                  technical changes to accommodate non flight 
                  hardware. PRC-0013 will be cancelled with   
                  this change. Make provision for Class D     
                  welds for ground based hardware.            

  C               Comprehensive 2 year review. Added ES4      3/21/2007
                  reviewer (Johannes).                        
  --------------- ------------------------------------------- -------------

**1.0 [SCOPE]{.underline}**

This process specification provides the minimum requirements that govern
Friction Stir Welding (FSW) of flight and non flight hardware.
Procedural and quality assurance requirements are given. All work
instructions and Weld Procedure Specifications (WPS) used during welding
shall satisfy the requirements of this process specification and its
applicable documents.

# **2.0 APPLICABILITY**

This specification applies to FSW of all flight and non flight hardware
fabricated under the authority of the NASA/Johnson Space Center (JSC) by
any of the following process modes and their process derivatives whereas
the Friction Stir joining process is occurring in the solid state:

a.  **Standard** - *(force from pin tool is reacted by a stationary
    anvil beneath the part)*

b.  **Self Reacting** - *(pin tool employs opposing shoulders on either
    side of the threaded pin. Force is reacted only within the pin tool,
    between the 2 shoulders. Friction is generated at each shoulder
    interface)*

c.  **Heat Source Assisted** - *(auxiliary heat source travels
    simultaneously and in front of \[tandem arrangement\] pin tool;
    LASER, gas torch, GTAW torch, induction coil, etc.)*

The term \"flight hardware\" refers to any hardware used as part of a
spacecraft, aircraft, or payload. The term \"non flight hardware\"
refers to any hardware made for facilities (buildings and related
accessories), ground support equipment, training and mockup mission
equipment, engineering prototype and development hardware, and test
equipment. Design, fabrication and testing of pressurized hardware is
not covered by this specification.

Future builds of hardware where the existing engineering documentation
calls out NASA/JSC PRC-0013 for welding shall utilize this
specification. Existing hardware fabricated to PRC-0013 requirements
shall not be affected by this change.

# **3.0 USAGE**

This process specification shall be called out on the engineering
drawing by a drawing note with the following general format:

**WELD AND INSPECT PER NASA/JSC PRC-0014, CLASS X**

## *[Note:]{.underline} It is intended that the above welding note be used for an entire weldment drawing, however, designers should give consideration to specifying a different "Class" to individual weld joints (see 3.1).*

## **3.1 WELD CLASSES**

The specific selected weld class (see 3.2) shall be invoked by including
a note on the applicable engineering drawing with the above given
general format shown in 3.0 which specifies the PRC and weld class
nomenclature:

## To minimize fabrication costs by avoiding over-inspection and unnecessary rework/repair, individual welds, or components on a weldment shall be classified separate where possible. This can be accomplished by including a note on the engineering drawing with the general format shown below which specifies only the PRC nomenclature as shown below. The weld class shall then be indicated by either: 1) calling out the specific weld class with the welding symbol at the individual weld joints or, 2) by using specific flag notes with the welding symbol at the individual weld joints. Refer to Figure 3.0a and 3.0b below for examples of these methods.

**WELD AND INSPECT PER NASA/JSC PRC-0014. WELD CLASSES SHALL BE AS
INDICATED AT WELD LOCATION CALLOUTS.**

## 

## 

## 

## **3.2 WELD CLASSIFICATION**

Welds made using this specification shall be primarily classified in
accordance with the service conditions of the weldment. The \"Class\"
governs the extent to which quality assurance provisions are applied to
the weld joint.

Alternatively, individual welds, welded connections, or entire weldments
(for simplicity, the terms weld, welded connection, and weldment will be
used interchangeably) may be classified by relating the weld to the
factor of safety used in the design. However, when classifying welds in
this manner, regardless of the factor of safety, adequate consideration
should be given to the severity of the service conditions (e.g., static
loading vs. dynamic loading, cyclic, vibration, fatigue, corrosive,
extreme temp, etc.), material characteristics (e.g., ductility,
toughness, etc.), and the potential consequences of weld failure.

Where conditions exist that make it difficult to choose between 2 weld
classes, then the more stringent of the 2 classes shall be applied.

Quality assurance provisions for all weld classes are detailed in
Section 7.0. Weld classes shall be chosen on the basis of the following
definitions:

a.  **[Class A]{.underline}** (Flight or non flight) --- Applies to
    welds in critical load bearing elements that are not fail-safe.
    Class A welds are typically used in primary load bearing
    connections. Failure of a Class A weld in service would be
    catastrophic and would result in the loss of life, system(s),
    control, or major components. Alternatively, if it is determined
    from appropriate engineering analyses that a weld has a Factor of
    Safety (FSuts) vs ultimate tensile strength of the calculated
    minimum weld throat cross section of \<2.0, it shall be designated
    as a Class A weld.

b.  **[Class B]{.underline}** (Flight or non flight) --- Applies to
    welds in load bearing elements that are fail-safe. Class B welds are
    typically used in secondary load bearing (i.e., shared load)
    connections. Failure of a Class B weld in service would reduce the
    overall efficiency of the system, but the loss of the system(s) or
    endangerment to personnel would not be expected. Alternatively, if
    it is determined from appropriate engineering analyses that a weld
    will have a FSuts of ≥2.0 and \<3.5, it may be designated as a Class
    B weld.

c.  **[Class C]{.underline}** (Flight or non flight) --- Applies to
    welds that are in minor load bearing elements that are fully
    contained where failure in service would have minor or no affect on
    the efficiency of a system and endangerment to personnel would not
    occur. Class C welds are typically used in secondary or tertiary
    load bearing (i.e., shared load) connections. Alternatively, if it
    is determined from appropriate engineering analyses that a weld will
    have a FSuts of ≥3.5 and \<5.0, it may be designated as a Class C
    weld.

d.  **[Class D]{.underline}** (Non flight hardware only) --- Applies to
    welds that are in non-critical elements and where failure would have
    no affect on the efficiency of a system and endangerment to
    personnel would not occur. Class D welds are typically used in
    connections where any expected load transfer at the weld would be
    negligible. Alternatively, if it is determined from appropriate
    engineering analyses that a weld will have a FSuts of ≥5.0, it may
    be designated as a Class D weld.

In addition to the above definitions, the following requirements shall
also apply to weld classifications:

-   If any weld intersects or overlaps another weld of a higher
    classification, then the lower classed weld shall be automatically
    upgraded to the higher of the 2 weld classes and subjected to the
    appropriate quality assurance provisions.

-   If any weld falls within ½" of any higher classed weld, then it
    shall be automatically upgraded to the higher of the 2 weld classes
    and subjected to the appropriate quality assurance provisions.

## 

## **3.3 WORK INSTRUCTIONS**

Work instructions shall be generated for implementing this process
specification. The work instructions shall contain sufficient detail to
ensure that the manufacturing process produces consistent, repeatable
results that comply with this specification. At JSC, these work
instructions are approved as Detailed Process Instructions (DPIs) that
describe in a detailed, step-by-step format the required procedures,
equipment, and materials to be used for conducting a given process.

If this manufacturing process is to be performed by an outside vendor,
work instruction development shall be the responsibility of the vendor.
The contractor shall ensure that the work instructions meet the
requirements of this process specification.

## **3.4 DESIGN REQUIREMENTS**

a)  All engineering drawings shall depict welded joints using the
    applicable symbols described in AWS A2.4.

b)  Groove welded joints are preferred and shall be full penetration
    where possible.

c)  Class A and B weldments, which will be subjected to unusual or
    extreme service conditions, shall be welded using a WPS qualified in
    accordance with AWS B2.1 "Special Test Weldments." This requirement
    shall be noted on the engineering drawing.

d)  Unless otherwise specified on the engineering drawing, hardware will
    be delivered in the "as welded" condition. If required, the
    engineering drawing shall include notation that will specify the
    appropriate heat treatment process, referencing NASA/JSC PRC-2001,
    PRC-2002, or PRC-2003, as applicable.

e)  Class A, B, and C welds shall be specified such that the weld
    termination point that is left with a depression is 1) removed from
    the hardware by cutting off an extension of the part (minimum 1.5
    tool diameters), 2) filled by arc fusion welding or Friction Stir
    plug welding, or 3) shown by appropriate engineering analysis that
    the presence of such a depression will not affect structural
    integrity. Where welding is selected, the specific weld procedure
    shall be qualified by test per section 6.2 to prove the structural
    integrity meets the design requirements. Where engineering analysis
    is selected and a "no fill" condition is allowed, then appropriate
    NDE shall be required to show the absence of injurious flaws in this
    area.

f)  Intermittent welding (skip welds) shall not be specified for Class A
    joints.

g)  Weld joints that are specified for intermittent welding shall have
    the ends of the parts, or departure from a straight weld line (e.g.,
    square corner, etc.), welded regardless of the interval of the weld.

h)  Intermittent welds shall not be specified for butt welds (square or
    groove design) unless the unwelded portions of the joint are
    adequately supported to prevent one member from coming out plane
    with the adjoining member.

i)  The engineering drawing shall specify any additional special testing
    or inspection requirements beyond what is required herein.

j)  Class C and D welds shall not be specified for pressure-containing
    components. Class D welds shall not be allowed on flight hardware.

# **4.0 REFERENCES**

The standards and documents listed below shall be considered a part of
this specification to the extent specified herein. Unless otherwise
indicated, the revision that is in effect on the date of invitation for
bids or the date of request for proposals shall apply.

**a. American Society of Nondestructive Testing (ASNT)**

SNT-TC-1A *Personnel Qualification and Certification in Nondestructive
Testing*

**b. American Welding Society (AWS) Standards**

ANSI/AWS A2.4 *Standard Symbols for Welding, Brazing and Nondestructive
Testing*

ANSI/AWS A3.0 *Standard Welding Terms and Definitions*

ANSI/AWS B2.1 *Standard for Welding Procedure and Performance
Qualification*

ANSI/AWS B4.0 *Standard for Mechanical Testing of Welds*

ANSIAWS QC-1 *Standard for AWS Certification of Welding Inspectors*

# **e. NASA/JSC Documents**

PRC-2001 *Process Specification for the Heat Treatment of Steel Alloys*

PRC-2002 *Process Specification for the Heat Treatment of Aluminum
Alloys*

PRC-2003 *Process Specification for the Heat Treatment of Nickel Alloys*

PRC-6503 *Process Specification for Radiographic Inspection*

PRC-6504 *Process Specification for Ultrasonic Inspection of Wrought
Metals*

PRC-6505 *Process Specification for Magnetic Particle Inspection*

PRC-6506 *Process Specification for Liquid Penetrant Inspection*

SOP-004.5 *Control of Weld and Braze Filler Materials, Electrodes, and
Fluxing Materials*

SOP-007.1 *Preparation and Revision of Process Specifications (PRCs)*

TI-0000-04 *Training For Welders and Welding Operators*

## **5.0 [MATERIAL REQUIREMENTS]{.underline}**

All base materials welded by the FSW process for flight or non flight
hardware shall meet the requirements of an applicable JSC material
specification unless otherwise specified. If a JSC material
specification is not available, then an applicable commercial
specification or a manufacturer\'s specification shall be used.

**5.1 TOOLING AND FIXTURING**

The design of fixture and tooling shall be such that the materials
selected are appropriate to ensure that contamination or degradation of
the weldment is prevented. Weldments shall be fixtured with appropriate
tooling as deemed necessary by the fabricator.

**5.2 PIN TOOLS**

FSW pin tools shall be designed such that any expected erosion of the
tool will be negligible and thus not be of concern to the final
metallurgy of the finished weld zone.

Prior to production welding, newly fabricated pin tools shall be tested
in a trial weld run in the same alloy, temper, and thickness and under
the same weld conditions (WPS) as the production hardware will be
subjected to so as to subject the tool to equivalent expected tool loads
that will be seen in the production weld runs. Prior to allowing use in
production, the pin tool shall perform as expected in the trial weld run
with no sign of detrimental wear or damage to the tool.

##### Pin tools shall be permanently marked with unique identification numbers to ensure positive traceability to the tool configuration specified by a production WPS.

Production ready pin tools shall be stored in a clean, dry, and secure
environment so as to avoid contamination and damage to the tools or
commingling of the tools with other tools in development, testing or
other non production approved operations.

# **6.0 PROCESS REQUIREMENTS**

All weldments shall be fabricated according to the requirements of this
process specification. The requirements of the applicable codes and
standards listed in Section 4.0, shall be met as specified by this PRC
based on the design and intended function of the hardware. Certain
paragraphs of this process specification are abbreviated re-statements
taken from the applicable standards and are included here for the user's
convenience. The remaining paragraphs of this process specification
represent requirements imposed in addition to the basic requirements of
the applicable codes and standards.

All Friction Stir Welding shall be performed using WPSs that have been
qualified in accordance with the requirements of Section 6.2.

## **6.1 PROCESS-SPECIFIC REQUIREMENTS**

Intermittent or continuous arc fusion tack welding of weldment
assemblies to facilitate fit up or otherwise shall be allowed, with or
without filler metal. However, this allowance shall be made provided
that the weld qualification tests include the very same tacking
operation and metallurgical and mechanical test specimens that include
lengths of the weld seam which contained the specified tack weld. Tack
welding shall be considered an essential variable and shall be specified
on an approved WPS.

Wherever possible, weld run-on and run-off tabs shall be used for
starting and terminating welds. Alternatively, extra length may be
designed into the workpiece to act as starting and terminating areas.
Start and termination areas shall have a minimum length of 3 tool
diameters (measured at the O.D. of the shoulder).

## **6.2 Weld Qualification**

A Welding Procedure Specification shall be qualified for each unique
weld type (as detailed in 6.2.2) to be produced, before the production
welds are made. An existing qualified WPS for one unique weld type may
be used for a different engineering drawing provided it is demonstrated
that the essential weld variables listed in Table V and VI will be met.
Demonstration shall constitute weld trial runs detailed in Section 6.2.4
except that no additional documentation is required except, when a
WPS(s) is written for a specific item(s) of hardware, it shall be
revised/amended to show allowance for use on other than the initial
specifically stated hardware. The actual welding variables, methods,
practices, specific tooling requirements, and test results used during
WPS qualification shall be recorded on a Procedure Qualification Record
(PQR).

**6.2.1 Unique Weld Type**

A "unique weld type" includes those weld joint configurations that
differ from one another in any of the following respects:

1.  Base metal type/alloy,

2.  Base metal temper,

3.  Base material thickness,

4.  Specific type and shape of joint

5.  Addition or deletion of filler material (via a tacking pass or
    otherwise),

6.  Addition, deletion, or change in the preheat, interpass, or post
    weld heat treatment requirements.

**6.2.2 Test Requirements**

At a minimum, the following are minimum requirements for the
qualification of a welding procedure. This effort shall include the
welding of a minimum of 1 weld sample with at least 20" in length of
useable weld that represents the weld type specified. The full length of
the weld shall be made in one continuous setup and machine cycle. The
test weld shall be made in the actual production weld fixture. The
beginning and ending length of weld equal to a minimum of 3 tool
diameters, shall not be considered for examination or testing.

The sample(s) shall be visually inspected on the O.D. and I.D. to Class
A criteria, dye penetrant inspected to Class A criteria, and
radiographically inspected to Class A criteria. Prior to all
inspections, any existing weld flash shall be removed. If the weld
procedure includes a specific heat treatment (pre- or postweld heat
treatment), the dye penetrant and radiographic inspections shall, at a
minimum be performed after the final heat treat cycle.

A minimum of 5 samples from the test plate shall be mechanically tested
in tension per AWS B4.0 and the results evaluated to the strength
requirements of AWS B2.1 or evaluated to the strength requirements
specified by the drawing or contract requirements. A minimum of 2
samples shall be sectioned and metallographically examined and the
results evaluated to the requirements of AWS B2.1. Photomicrographs
shall be taken of the prepared samples and retained with the PQR. A
minimum of 2 face and 2 root bends shall be conducted to the testing
requirements of AWS B2.1. Alternatively, 2 side bend specimens may be
conducted in lieu of the face and root bend. All bend specimens shall
not exceed 3/8" in thickness.

**6.2.3 Essential Variables**

The WPS shall specify all of the essential welding variables and the
applicable allowable ranges qualified for each variable, as indicated in
Table V. In addition, the WPS shall detail all methods, practices,
specific tooling requirements that are determined necessary by the
operating facility to successfully execute the weld in production. If an
essential variable is changed beyond the allowable range listed,
requalification shall be required.

+---+---------------------------------------------------+--------------+
| # | ####### Table V                                   |              |
| # |                                                   |              |
| # | **[ESSENTIAL WELDING VARIABLES]{.underline}**     |              |
| # |                                                   |              |
| # |                                                   |              |
| # |                                                   |              |
| # |                                                   |              |
|   |                                                   |              |
+---+---------------------------------------------------+--------------+
| # | **Variable / Weld Type**                          | **Range      |
| # |                                                   | Allowed**    |
| # |                                                   |              |
| # |                                                   |              |
| # |                                                   |              |
| # |                                                   |              |
| # |                                                   |              |
|   |                                                   |              |
| N |                                                   |              |
| o |                                                   |              |
| . |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Machine Tool Model \#                             | None         |
+---+---------------------------------------------------+--------------+
| 2 | Machine Tool Head Model \#                        | None         |
+---+---------------------------------------------------+--------------+
| 3 | Pin Tool Configuration                            | See Table VI |
+---+---------------------------------------------------+--------------+
| 4 | Joint Configuration (groove vs. lap, etc.)        | None         |
+---+---------------------------------------------------+--------------+
| 5 | Nominal Material Thickness                        | Drawing      |
|   |                                                   | tolerances   |
+---+---------------------------------------------------+--------------+
| 6 | Base Material Alloy Type(s) and Temper            | None         |
+---+---------------------------------------------------+--------------+
| 7 | Preweld Cleaning Steps                            | None         |
+---+---------------------------------------------------+--------------+
| 8 | Allowable Joint Gap                               | ≤0.015"      |
+---+---------------------------------------------------+--------------+
| 9 | Tool or Shop Aid Identification                   | None         |
+---+---------------------------------------------------+--------------+
| 1 | Tack welding filler metal                         | None         |
| 0 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Heat assistance source                            | None         |
| 1 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Heat input from heat assistance source (e.g.,     | ± 10%        |
| 2 | LASER, GTA torch, etc.)                           |              |
+---+---------------------------------------------------+--------------+
| 1 | Pin Tool Travel Angle                             | ± ½ º        |
| 3 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Pin Tool Plunge Depth (or Heel Plunge Depth)      | ± 0.010"     |
| 4 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Travel Speed                                      | ± 10%        |
| 5 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Travel Start Delay                                | ± 10%        |
| 6 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Spindle RPM                                       | ± 10%        |
| 7 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Spindle Rotation Direction                        | See Note 1   |
| 8 |                                                   |              |
+---+---------------------------------------------------+--------------+
| 1 | Heat Treat Procedure/Spec.                        | None         |
| 9 |                                                   |              |
+---+---------------------------------------------------+--------------+

+--------------+--------------------------------------+----------------+
| #######      | ####### Table VI                     |                |
|              |                                      |                |
|              | **[ESSENTIAL VARIABLES FOR PIN       |                |
|              | TOOLS]{.underline}**                 |                |
+--------------+--------------------------------------+----------------+
| ####### No.  | **Variable -- See Figure 1**         | **Range        |
|              |                                      | Allowed**      |
+--------------+--------------------------------------+----------------+
| 1            | Dimension A (dia., pitch, thread     | None           |
|              | direction; LH or RH)                 |                |
+--------------+--------------------------------------+----------------+
| 2            | Dimension B (pin end radius)         | ± 0.03"        |
+--------------+--------------------------------------+----------------+
| 3            | Dimension C (pin length from         | ± 0.002"       |
|              | shoulder edge)                       |                |
+--------------+--------------------------------------+----------------+
| 4            | Dimension D (shoulder O.D.)          | ± 0.06"        |
+--------------+--------------------------------------+----------------+
| 5            | Dimension E (draft angle on shoulder | ± ½ º          |
|              | face)                                |                |
+--------------+--------------------------------------+----------------+
| 6            | Dimension F (shoulder outer & inner  | ± 0.03"        |
|              | radius)                              |                |
|              |                                      | See Note       |
+--------------+--------------------------------------+----------------+
| 7            | Shoulder face surface configuration  | None           |
+--------------+--------------------------------------+----------------+
| 8            | LH pin thread direction & CW tool    | None (See Note |
|              | rotation                             | 1)             |
+--------------+--------------------------------------+----------------+
| 9            | RH pin thread direction & CCW tool   | None (See Note |
|              | rotation                             | 1)             |
+--------------+--------------------------------------+----------------+
| 10           | Pin tool base material               | See Note 2     |
+--------------+--------------------------------------+----------------+
| 11           | Pin tool base material temper        | See Note 2     |
+--------------+--------------------------------------+----------------+
| 12           | Pin tool wear coating                | See Note 2     |
+--------------+--------------------------------------+----------------+

> ***Note 1** -- Spindle rotation direction (CW or CCW) shall be fixed
> for a given specific pin tool thread direction (RH or LH). In
> addition, spindle rotation shall always be CW when the pin thread
> direction is LH and CCW when the pin thread direction is RH. For
> non-threaded pins, spindle rotation may be either direction.*
>
> ***Note 2** -- A change in the base material, temper, or coating (or
> the addition or deletion of a coating) of a pin tool without changing
> any of the physical configurations shall not automatically require a
> weld schedule requalification provided that the tool proves to perform
> satisfactorily as demonstrated in a preweld test run not less than 20"
> in length.*

**6.2.4 Requalification of WPS**

Requalification of the WPS shall be required when preproduction weld
samples do not meet requirements and no assignable cause for the failure
can be determined.

The samples shall, at a minimum, be subjected to visual inspection and
the same NDE as specified for the original WPS qualification and shall
meet the applicable requirements specified herein. Requalification
results shall be documented on a PQR with a specific notation made
indicating "Requalification" and an explanation as to the cause. If the
requalification activities result in any welding parameter(s) deviations
that exceed the range specified in Table V or Table VI, as applicable
for that parameter, then the level of testing in 6.2.2 shall be
required.

## **6.3 PREHEATING AND HEAT ASSISTED WELDS**

Preheat shall not exceed the temperature specified in the applicable
WPS.

Where a heat assistance source is used simultaneously ahead of the FSW
pin tool (tandem), parameter control of the heat assistance source to
ensure absolute heat input control per linear inch of weld may be
substituted for workpiece temperature control provided there are no
conditions where the heat assistance source becomes stationary during
the weld run. The specific parameters requiring control applicable to
the selected heat assistance source shall be identified and specified by
NASA/JSC M&P organization.

**[FIGURE 1 -- FSW PIN TOOL ESSENTIAL VARIABLES]{.underline}**

**6.4 HEAT TREATMENT**

Heat treatment, when required by the engineering drawing or WPS, shall
be performed in accordance with NASA/JSC PRC-2001, PRC-2002, or
PRC-2003, as applicable. Vibratory techniques shall not be used in place
of thermal treatments.

## 

## **6.5 WELD REPAIRS AND WELDED REPAIRS TO BASE METAL**

All repairs to welds and base metal shall be performed using the WPS
used for the original weld or a specific qualified WPS for that repair
and shall meet all of the requirements of the original drawing and any
additional requirements that are documented in the WPS. Weld repair does
not include the correction of dimensional or other deficiencies of weld
joints by "buttering" or build up provided the area corrected by welding
is fully consumed in the final weld. Also, the following requirements
shall be required in the weld repair activity:

a)  [Defect Location]{.underline}. Weld repairs shall be adequately
    documented by the use of a weldment map or other manufacturing
    record with sufficient detail to ensure identification of the
    weldment, identification of repair location(s), and type of defect.
    All indicated defects shall be brought to the attention of the
    responsible manufacturing or materials engineer for consideration of
    cause, prior to repair activities.

b)  [Repair]{.underline}. No more than 1 weld repair attempt shall be
    made to successfully complete a repair. If this first attempt is
    unsuccessful, a discrepancy report shall be generated and shall
    require dispositioning by the responsible Material Review Board
    (MRB). The level of documentation of repair welds shall, at a
    minimum, be consistent with that required for the original
    production weld.

c)  [Straightening]{.underline}. Welds or adjacent base metal which have
    been deformed by the welding or heat treatment operation may be
    straightened. All straightening operations shall take place at
    temperatures not to exceed 65°C (150°F). All straightening
    operations must be validated by an appropriate method(s) to show
    that the process used for straightening does not degrade the joint
    or surrounding material below specified design requirements.

d)  [Base Metal Repairs.]{.underline} Repairs to base metal anomalies
    shall be brought to the attention of the NASA/JSC M&P organization
    for consideration of cause, prior to repair activities.

**7.0 PROCESS VERIFICATION**

Process verification shall consist of visual inspection and/or
nondestructive inspection, as described further in sections 7.1 to 7.3.
Where dye penetrant is specified, it shall be Type I, Level 3 or 4.

## **7.1 VISUAL INSPECTION REQUIREMENTS**

All visual inspections of welded joints shall be performed by an
American Welding Society (AWS) Certified Welding Inspector (CWI)
qualified in accordance with AWS QC-1. The CWI certification must be
current.

## **7.2 OTHER NON-DESTRUCTIVE EVALUATION (NDE)**

All other NDE (e.g., PT, RT, etc.) of welded joints shall be performed
by personnel qualified in accordance with the requirements of the
applicable NDE process specification. The NDE certification must be
current. All nondestructive inspections shall be performed in accordance
with the appropriate standards as referenced herein.

**7.3 INSPECTION**

**7.3.1 [Class A Inspection]{.underline}**

a)  Unless otherwise specified, Class A joints require visual, dye
    penetrant, and volumetric inspection using either the radiographic
    method or ultrasonic method to the Class A acceptance criterias in
    Appendix A and Appendix B as applicable.

b)  In cases where the Class A inspection is designated for any joint or
    component having a configuration which renders one or more NDE
    methods impractical, an alternate inspection method shall be
    utilized with approval from the responsible NASA/JSC M&P
    organization.

**7.3.2 [Class B Inspection ]{.underline}**

Unless otherwise specified in design documentation, Class B joints
require visual and dye penetrant or magnetic particle inspection to the
Class B acceptance criteria in Appendix A and Appendix B as applicable.

**7.3.3 [Class C Inspection]{.underline}**

###  

Unless otherwise specified in design documentation, Class C joints
require visual inspection to the Class C acceptance criteria in Appendix
A.

### **7.3.4 Class D Inspection** 

Unless otherwise specified in design documentation, Class D welds
require only inspection to verify the type, nominal size, length,
location, and that the welds were left in a condition exhibiting good
workmanship practices. Good workmanship shall be defined as the presence
of uniform appearance and overall clean weld zones and the absence of
flash, tool marks, and other obvious discontinuities that would likely
be questionable. Where a size is not specified, the nominal weld size
shall be per best shop practice and at the discretion of the
manufacturing organization with the intent to utilize single pass welds
wherever possible so as to avoid over-welding. A CWI is not required for
this inspection.

# 

# 

# **8.0 PROCESS DOCUMENTATION REQUIREMENTS**

The WPS, PQR, and WOPQ shall be prepared and retained as a permanent
record and made available upon request to the NASA/JSC M&P organization
for review**.** These procedures must contain, at a minimum, all of the
essential welding parameters, an identification of the welding equipment
(machine tool or specific machine), and include any pertinent tooling
information. One copy of the WPS shall be maintained in the vicinity of
the welding station and shall be readily accessible by the welding
operators, inspectors, supervision, and engineering.

## 

**8.1 WELDING PROCEDURE SPECIFICATION**

A Welding Procedure Specification (WPS) is a qualified written working
procedure that must be developed before beginning production for each
unique weld type to be produced. Qualification support documentation in
the form of a Procedure Qualification Record (PQR) shall be maintained
on file to show proof of process/procedure capability using the WPS. The
WPS shall be traceable by means of serialized nomenclature and shall
show traceability to the applicable PQR(s). The WPS used for production
welding shall meet the requirements stated herein and shall be certified
by the responsible M&P organization at the operating facility, prior to
use in production.

**8.2 PROCEDURE QUALIFICATION RECORD**

A Procedure Qualification Record (PQR) is documentation to support the
welding procedure specification to show proof of process/procedure
capability. A PQR shall be unique and traceable, by means of serialized
nomenclature. The PQR shall be process-specific and specific to a unique
weld type. Data required in the PQR shall include detailed descriptions
of the test coupon configurations and joint designs, all pertinent
material specifications, all pertinent essential process variables used,
all destructive and nondestructive test results from the qualification
sample set, and all required certifications from the approving
organization. The PQR shall be approved by the responsible M&P
organization at the operating facility.

## **8.3 WELDING OPERATOR PERFORMANCE QUALIFICATION RECORD**

A Welding Operator Performance Qualification (WOPQ) is certified
documentation that a welding operator has been tested in accordance with
the requirements stated herein and shown competent to produce a sound
weld for a specific welding process/base material/base metal thickness
combination. WOPQ records shall show the limits of the operator's
qualification.

# 

# 

# **9.0 TRAINING AND QUALIFICATION OF PERSONNEL**

## **9.1 TRAINING**

At JSC, if welding operator training is considered necessary prior to
qualification/requalification of existing JSC welding personnel or the
initial qualification of new hires, it shall be conducted in accordance
with TI-0000-04. For an outside JSC vendor, welding operator training
(when necessary) should consist of practice using the facility welding
equipment and a specific WPS to demonstrate proficiency, under the
supervision of a qualified/certified welding operator. Specific
development of an appropriate training program shall be the
responsibility of the vendor.

## 

## **9.2 WELDING OPERATOR QUALIFICATION**

Welding shall be performed by a welding operator qualified and certified
in accordance with AMS-STD-1595 . Sufficiently detailed records shall be
maintained to demonstrate continuity of operator performance on the
welding system (machine tool) or system(s) on a semi-annual (6 month)
basis. These records shall be made available to the NASA/JSC M&P
organization upon request.

## **10.0 [DEVIATIONS AND WAIVERS]{.underline}**

Any deviations or waivers regarding the use of this process
specification shall be requested in writing by the outside vendor. This
request shall be directed to the NASA/JSC M&P organization with the
appropriate justification and rationale. A written response will be
provided upon such a request.

**Appendix A**

**[WELD INSPECTION CRITERIA]{.underline}**

**[GENERAL]{.underline}** . Unless otherwise stated, the criteria in
this Appendix shall apply to all weld classes except class D welds.
Acceptance criteria for Class D welds is detailed only in Section 7.3 of
this specification. Alternate and/or additional acceptance criteria may
be used for any weld class however, it shall be specified in the design
documentation. If any of the inspection conditions listed herein
conflict with the requirements of the engineering drawing, then the more
strict criteria shall govern. Pertinent to this Appendix, the
designation 'T' shall mean the nominal base metal thickness of the
thinnest component in the welded connection. In addition, the term "weld
length" shall be the distance from end to end of the weld deposit or to
a sharp change in direction of the weld where the angle of change in any
direction is greater than 30 degrees at a radius of \<1/2".

**A1.0 [SIZE AND APPEARANCE]{.underline}**

**[All Classes]{.underline} -** The minimum weld size shall be the size
(i.e., size = effective weld throat) specified on the drawing. If
profile requirements are not specified, the weld shall be flat or
concave within the limits specified in A2.0. Where a weld size is not
specified, the penetration requirement shall be 100%.

**A2.0 [WELD CONCAVITY]{.underline}**

Weld concavity depth (face and root) shall not exceed that specified in
Table A2.0. This requirement shall not apply where the weld is specified
to be machined to the extent of being indistinguishable from the
adjacent base metal.

**TABLE A2.0 -- Weld Concavity Depth Limits**

  ----------------- -----------------------------------------------------
  **Weld Class**    **Concavity Depth (apply whichever value is lesser)**

  Class A           0.02" or 10% of T

  Class B           0.03" or 15% of T

  Class C           0.045" or 20% of T
  ----------------- -----------------------------------------------------

**A3.0 [MISALIGNMENT]{.underline}**

Weld joint misalignment shall not exceed that specified in Table A3.0.

**TABLE A3.0 -- Weld Misalignment Limits**

  ----------------- -----------------------------------------------------
  **Weld Class**    **Misalignment (apply whichever value is lesser)**

  Class A           0.01" or 10% of T

  Class B           0.02" or 15% of T

  Class C           0.025" or 20% of T
  ----------------- -----------------------------------------------------

**A4.0 [SURFACE ROUGHNESS]{.underline}**

Weld surface finish shall not exceed that specified in Table A4.0. This
requirement shall not apply where the weld is specified to be machined
to the extent of being indistinguishable from the adjacent base metal.

**TABLE A4.0 -- Weld Surface Finish Limits**

  --------------------------------- -------------------------------------
  **Weld Class**                    **Surface Finish**

  Class A                           250 µ-inch

  Class B                           250 µ-inch

  Class C                           250 µ-inch
  --------------------------------- -------------------------------------

**A5.0 [DISCONTINUITIES]{.underline}**

**[All Classes]{.underline} -** Weld discontinuities exceeding the
maximum allowable sizes for the applicable Class in Table A5.0 shall not
be allowed. Linear discontinuities shall be defined as having a length
to width ratio of ≥ 3:1. Rounded discontinuities shall be defined as
having a length to width ratio \< 3:1. A crack shall be defined as a
fracture type discontinuity characterized by a sharp tip and a high
ratio of length to width.

For base metal thicknesses (T) ≥ 1/8", the following shall apply to
Table A5.0:

> **[Class A]{.underline} -** Any discontinuity, except cracks and
> linear discontinuities, \<0.01" at its greatest dimension, shall not
> be considered.
>
> **[Class B]{.underline} -** Any discontinuity, except cracks and
> linear discontinuities, \<1/32" at its greatest dimension, shall not
> be considered.
>
> **[Class C]{.underline} -** Any discontinuity, except cracks and
> linear discontinuities, \<1/16" at its greatest dimension, shall not
> be considered.

**TABLE A5.0 - Maximum Allowable Discontinuity Sizes**

  -------------- ----------------- ---------------- ---------------- ----------------
  **LINEITEM**   **DISCONTINUITY   **Class A**      **Class B**      **Class C**
                 TYPE**                                              

  **1**          **Cracks in the   None allowed     None allowed     None allowed
                 weld or base                                        
                 metal ^(1)^**                                       

  **2**          **Inadequate      None allowed     1/16" or 0.3T,   3/32" or 0.6T,
                 Penetration and                    whichever is the whichever is the
                 Incomplete Fusion                  lesser           lesser
                 ^(1)^**                                             

  **3**          **Linear ^(1)^**  None allowed     1/32" or 0.4T in 1/16" or 0.6T in
                                                    length,          length,
                                                    whichever is     whichever is
                                                    less ^(3)^ Sum   less ^(3)^ Sum
                                                    of all visible   of all visible
                                                    indications      indications
                                                    shall be ≤3/8"   shall be ≤1/2"
                                                    or T in length,  in length, in
                                                    whichever is     any 1" of weld
                                                    less, in any 1"  length and
                                                    of weld length   ≤1.75" in any
                                                    and ≤3/4" in any 12" of weld
                                                    12" of weld      length ^(4)^
                                                    length ^(4)^     

  **4**          **Rounded ^(1)^** Surface: 1/16"   3/32" or 0.4T    1/8" or 0.6T
                                   or 0.3T          diameter         diameter,
                                   diameter,        whichever is     whichever is
                                   whichever is     less ^(2)^ Sum   less ^(2)^ Sum
                                   less ^(2)^       of all visible   of all visible
                                                    indications      indications
                                                    shall be ≤3/8"   shall be ≤1/2"
                                                    or 1.5T in       in any 1" of
                                                    length,          weld length and
                                                    whichever is     ≤1.75" in any
                                                    less, in any 1"  12" of weld
                                                    of weld length   length ^(4)^
                                                    and ≤3/4" in any 
                                                    12" of weld      
                                                    length ^(4)^     
  -------------- ----------------- ---------------- ---------------- ----------------

*TABLE A5.0 Footnotes:*

(1) For all discontinuities approaching a free edge (See Figure A6.0
    below) that are being considered, the closest edge of the
    discontinuity shall have clearance from the free edge ≥ 3X the
    largest of its dimensions or, ≥ 2X the nominal weld throat,
    whichever is greater.

(2) *Adjacent rounded discontinuities separated by ≤ 1X the length of
    the longest dimension of the larger discontinuity shall be
    considered a single discontinuity.*

(3) Adjacent linear discontinuities separated by ≤ 3X the length of the
    longest dimension of the smaller discontinuity, shall be considered
    a single discontinuity.

(4) For weld lengths less than 12", the total sum of indications shall
    be an equivalent proportion of the weld length, to that given.

![](media/image2.png){width="2.4590277777777776in"
height="1.9916666666666667in"}

C = Clearance spacing between closest edge of discontinuity and free
edge