**Process Specification for the Manual Arc Welding of Titanium Alloy
Hardware**

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| **Engineering Directorate**                                           |
|                                                                       |
| **Structural Engineering Division**                                   |
|                                                                       |
| **December 2003**                                                     |
|                                                                       |
| ![](media/image1.png){width="1.3944444444444444in" height="1.15in"}   |
|                                                                       |
| National Aeronautics and                                              |
|                                                                       |
| Space Administration                                                  |
|                                                                       |
| **Lyndon B. Johnson Space Center**                                    |
|                                                                       |
| Houston, Texas                                                        |
+-----------------------------------------------------------------------+

**Process Specification for the Manual Arc Welding of Titanium Alloy
Hardware**

+-----------------+--------------------------------+------+-----------+
| **Prepared by   | Signature on File              |      | 12/30/03  |
| :**             |                                |      |           |
+-----------------+--------------------------------+------+-----------+
|                 | Daniel J. Rybicki              |      | Date      |
|                 |                                |      |           |
|                 | Materials and Processes        |      |           |
|                 | Technology Branch/ES4          |      |           |
+-----------------+--------------------------------+------+-----------+

+-----------------+--------------------------------+------+-----------+
| **Approved      | Signature on File              |      | 12/31/03  |
| by:**           |                                |      |           |
+-----------------+--------------------------------+------+-----------+
|                 | Jose M. Hernandez,             |      | Date      |
|                 |                                |      |           |
|                 | Chief,                         |      |           |
|                 |                                |      |           |
|                 | Materials and Processes        |      |           |
|                 | Technology Branch/ES4          |      |           |
+-----------------+--------------------------------+------+-----------+

  ----------- --------------------------------------------- ---------------
  REVISIONS                                                 

  VERSION     DESCRIPTION                                   DATE

  \--         Original version                              6/1/95

  A           Formatting, changed process owner, rewrite    07/07/99
              numerous sections for clarification, deleted  
              requirement for WIR, deleted section 8.2 on   
              audits, added section 8.3 on WPQ, deleted mil 
              specs for NDE, added PRCs for NDE.            

  B           Comprehensive rewrite to combine PRC-0002 and 12/30/2003
              PRC-0004 and make editorial changes. PRC-0004 
              will be cancelled with this change. Include   
              requirements for precision cleaned hardware   
              (ref. JPG 5332.1).                            
  ----------- --------------------------------------------- ---------------

# 

# 

#  

# **1.0 SCOPE**

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

# **2.0 APPLICABILITY**

This process specification applies to manual arc welding of titanium
alloy flight and non flight hardware that is fabricated under the
authority of NASA/Johnson Space Center (JSC) by any of the following
types of welding processes:

a.  Gas tungsten arc welding (GTAW)

b.  Plasma arc welding (PAW)

The Gas Metal Arc Welding (GMAW) process is not considered an acceptable
process for welding titanium alloys under this process specification.

Future builds of hardware where the existing engineering documentation
calls out NASA/JSC PRC-0004 for welding of shall utilize this
specification. Existing hardware fabricated to PRC-0014 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 which
specifies the PRC and weld class nomenclature:

**WELD AND INSPECT PER NASA/JSC PRC-0002, CLASS X**

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. 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.

## 

## 

## **3.1 WELDING CLASSES**

Welds made using this specification shall be primarily classified in
accordance with the service conditions of the weldment. Therefore, the
\"Class\" defines the severity of service intended for the joint by
design and governs the extent to which quality assurance provisions are
applied to the weld joint as specified herein.

Alternatively, individual welds, welded connections, or entire weldments
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 condition (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, the more stringent of the 2 classes shall then 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} --- 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 is expected to be catastrophic and would likely 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} --- 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 is expected to be serious and would likely reduce
    the overall efficiency of the system, but the loss of a system(s) or
    major components or endangerment to personnel is not expected.
    Alternatively, if it is determined from appropriate engineering
    analyses that a weld will have a FSuts of ≥2.0 and \<4.0, it may be
    designated as a Class B weld.

c.  [Class C]{.underline} --- Applies to welds that are in minor load
    bearing elements that are fully contained where failure in service
    is expected to 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
    ≥4.0, it may be designated as a Class C 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.

## 

## 

## **3.2 WORK INSTRUCTIONS**

Work instructions shall be used 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.

## **3.3 DESIGN REQUIREMENTS**

a.  The design of welded joints (including weld sizes) shall utilize
    adequate engineering analysis methods (e.g., stress analysis,
    fracture mechanics/fracture control, FEA, FMEA, etc.) to ensure that
    the resultant connection strength is capable of successfully
    transferring the maximum load expected to pass between the
    interconnecting members and meet the required factors of safety and
    design margins.

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

c.  The engineering drawing shall specify any additional or alternate
    testing or inspection requirements. Where spot, intermittent, or
    other special inspection requirements are specified that deviate
    from those stated herein, it shall be detailed on the drawing as a
    note or by using the applicable symbology described in AWS A2.4. For
    Class A welds, alternate or reduced NDE requirements shall not be
    allowed.

d.  Class A welds are expected to be welds requiring full strength of
    the weld joint therefore, these welds shall be a groove design and
    full penetration wherever possible. The ability to successfully
    perform radiographic examination on these weld joints shall be
    considered during design.

e.  Except for titanium alloy 6Al-4V welded with 6Al-4V filler metal,
    hardware will be delivered in the "as welded" condition unless
    otherwise specified on the engineering drawing. If required, the
    engineering drawing shall include notation that will specify an
    appropriate heat treatment process, referencing SAE AMS-H-81200. For
    welds in alloy 6Al-4V welded with 6Al-4V filler metal, a stress
    relief heat treatment at 1100^o^ F for 2 hours (vacuum or inert gas
    atmosphere) shall be required.

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

g.  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.

h.  Weld filler material shall be specified on the engineering drawing
    in the parts list.

# **4.0 REFERENCES**

The standards 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 A5.12 *Specification for Tungsten Arc Welding Electrodes*

ANSI/AWS A5.16 *Specification for Titanium & Titanium Alloy Welding
Electrodes & Rods*

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

ANSI/AWS D1.6 *Structural Welding Code -- Stainless Steel*

ANSI/AWS QC-1 *Standard for AWS Certification of Welding Inspectors*

**c. Compressed Gas Association, Inc.**

G-11.1 *Argon, Commodity Specification for*

**d. Federal Documents**

BB-H-1168 *Helium Federal Specification*

**e. Military Documents**

MIL-A-18455 *Argon, Technical*

MIL-P-27407 *Propellant Pressurizing Agent, Helium*

# **f. NASA/JSC Documents**

JPG 5322.1 *Contamination Control Requirements Manual*

PRC-0008 *Process Specification for the Qualification of Manual Arc
Welders*

PRC-6503 *Process Specification for Radiographic Inspection*

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

PRC-6506 *Process Specification for Liquid Penetrant Inspection*

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

SOP-007.1 *Preparation and Revision of Process Specifications*

TI-0000-04 *Training Instruction for the Welding Processes*

**g. NASA Headquarters**

NASA-SPEC-5004 *Welding of Aerospace Ground Support Equipment and
Related Nonconventional Facilities*

NASA-STD-5006 *General Fusion Welding Requirements for Aerospace
Materials Used in Flight Hardware*

**h. SAE -- Aerospace Material Specification**

AMS-H-81200 *Heat Treatment of Titanium and Titanium Alloys*

# 

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

All base materials used in the welding of hardware per this
specification, 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.
Requirements for filler metals and electrodes are listed in 5.2. Filler
metals and electrodes purchased to alternate specifications shall be
allowed provided they meet the minimum requirements of the
specifications listed herein.

### 

### **5.1 SHIELDING GASES**

Allowable shielding gases (including purge gases) are listed in Table I.
Gases purchased to alternate specifications shall be allowed provided
they meet the minimum requirements of the specifications listed herein.
Mixtures of these gases are allowed and the nominal mixture used for the
qualification welding shall be that used for production and shall be
listed on the WPS. All shielding and purging gases and nominal gas
mixtures shall be treated as an essential procedure qualification
variable and shall be subject to the AWS B2.1 requirement for these
variables. In addition:

a.  All gases used for welding shall be delivered through clean
    low-nonvolatile residue (NVR)/particulate tubing.

b.  Nitrogen or hydrogen gas in any concentration, shall not be used for
    shielding or purging in any welding operation governed under this
    specification.

c.  All gases used for shielding or purging shall have a dewpoint of
    -60°F (-51 °C) or better and oxygen content shall not exceed 50 ppm.

**Table I. Allowable Shielding Gases**

  ------------------- --------------------------- -----------------------
  **Gas**             **Description**             **Specification**

  Argon               Gas                         MIL-A-18455

  Argon               Type II, Grade B            CGA G-11.1
                      (Liquefied)                 

  Helium              Type I, Grade A             MIL-P-27407

  Helium              Grade A                     BB-H-1168
  ------------------- --------------------------- -----------------------

# 

# **5.1.1 Weld Atmosphere**

A protective weld atmosphere shall be freely accessible to all portions
of the joint. The weld atmosphere for inert gas chambers, and gas
supplies for trailing shields shall be monitored for moisture and oxygen
content.

# 

# **5.1.2 Weld Atmosphere Purity Test**

Atmospheric purity shall be verified by making an autogenous fusion pass
on a commercially pure (CP) titanium strip, which has been properly
cleaned. A fusion zone and heat affected zone with a bright silver or
light straw color is acceptable (condition #1 or #2 below). No tacking
or welding shall be performed on production hardware until an acceptable
color has been obtained. Weld discoloration condition in increasing
order of contamination is:

1.  bright silver - acceptable

2.  light straw - acceptable

3.  dark straw - **unacceptable**

4.  purple - **unacceptable**

5.  dark blue - **unacceptable**

6.  yellow -- **unacceptable**

7.  grey - **unacceptable**

8.  white (may have loose powder) -- **unacceptable**

9.  brushed -- **unacceptable** (welds that have been brushed
    [before]{.underline} inspection are rejectable regardless of color
    before brushing)

### **5.2 FILLER METALS AND ELECTRODES**

Filler metals shall be selected based on specific base metals being
welded, service conditions, design requirements (load conditions, etc.),
and other design or service factors. The specific selection must be
approved by the NASA/JSC Materials & Processes (M&P) organization prior
to use. In addition, the following shall apply:

a)  Filler and electrode materials used shall conform to the applicable
    AWS specifications listed herein. Filler metals and electrodes
    purchased to alternate specifications shall be allowed provided they
    meet the minimum requirements of the specifications listed herein.

b)  Filler metals shall be manufactured by a high-quality (HQ) method
    involving multiple melt cycles. In addition, the final melt cycle
    shall be made under vacuum.

c)  Wherever possible, filler metals designated as extra-low
    interstitial (ELI), shall be used.

d)  Where the end product will be used in a cryogenic application, then
    ELI filler metals shall be used.

e)  Weld filler metals shall be called out on the engineering drawing in
    the parts list.

f)  Non consumable tungsten and tungsten alloy electrodes for GTAW and
    PAW shall be selected according to the process being used at the
    direction of the responsible M&P organization. The electrode type
    and size shall be specified on the WPS.

**5.2.1 [Control and Storage]{.underline}**

Welding electrodes and filler metals shall be stored in a clean, dry,
and controlled area that provides protection from contamination,
physical damage, commingling of alloys and loss of
identification/traceability. Any form of electrodes or weld filler metal
which is damaged, dirty, exhibits oxidation/corrosion or has been
contaminated with water, oil, grease or any form of hydrocarbons shall
not be used and shall be disposed of in accordance with an appropriate
disposal procedure. For JSC operations, welding electrodes and filler
materials shall be controlled in accordance with SOP-004.5. Outside
vendors shall provide control and storage according to the applicable
material specification or manufacturer\'s recommendation, whichever is
more rigid.

**5.3 MECHANICAL PROPERTIES**

Unless otherwise specified, minimum mechanical properties that determine
an acceptable weld qualification for titanium alloys shall be that as
specified in AWS B2.1. In addition, when qualifying a WPS using a
titanium alloy not listed in AWS B2.1 the diameter of the plunger
(dimension "A" in Annex II of AWS B2.1) used for the guided bend test
shall not exceed 20T (10T radius).

**5.4 [Welding Chambers and Trailing Gas Shielding]{.underline}**

When an inert gas or vacuum chamber is used for welding or trailing
torch shields and/or a trailing or fixed gas purge assemblies are used,
the specific equipment and method shall be considered an essential
variable during qualification of the WPS and personnel qualifications.

# 

# **6.0 PROCESS REQUIREMENTS**

All weldments shall be fabricated according to the requirements of this
process specification and shall be performed using Welding Procedure
Specifications (WPS) that have been qualified in accordance with the
requirements of Section 8.0 in addition to that as detailed below. In
addition, when qualifying a WPS for titanium welding, the welding setup
shall be considered an essential variable. WPSs qualified outside of a
weld chamber using trailing shields and gas purge assemblies may also be
used for welding in a weld chamber, but not vice versa.

## **REQUIREMENTS FOR ALL PROCESSES**

### 

6.  **[Preweld Cleaning of Weld Joint Surfaces]{.underline}**

Prior to welding, all weld joint surfaces within a minimum of ½" of the
weld line shall be cleaned in a manner shown to be adequate and
repeatable in producing a surface cleanliness level conducive to
producing sound welds by a given weld process. The specific process and
procedural steps to carry out the process shall be part of the procedure
qualification activities and shall be appropriately detailed on the
qualification and procedure specification (PQR and WPS) documentation as
well in the production work instructions. Personnel shall be trained in
these same methods and process techniques.

2.  [**Intermittent Welding**]{.underline}

Applicable to all processes, unless otherwise specified, 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.

3.  **[Tooling and Fixturing]{.underline}**

Weldments shall be fixtured with appropriate tooling as deemed necessary
by the fabricator. Tools and fixtures shall be constructed of materials
that will not interefere with the welding process nor damage or
contaminate the hardware.

4.  **[Temporary or Tack Welding]{.underline}**

Temporary (includes the term "tack" welding) welding in areas of the
hardware not planned for welding or where the temporary weld will not be
totally consumed by the final weld, shall not be allowed. All temporary
welds placed at or in a weld joint shall be ground or feathered by
welding appropriately to accommodate the final welding process to
achieve the expected deposit of sound weld metal. All temporary and tack
welding shall only be performed by a welder(s) whose qualifications are
current and applicable.

5.  **[Welding Equipment]{.underline}**

Equipment (e.g., power supplies, positioners, flowmeters, etc.) used for
manual welding operations need not have calibrated instrumentation
(dials, gauges, indicators, meters, etc.). However, reference indicating
instrumentation (e.g., dials, meters, gauges, etc.) shall be fully
functional (i.e., useful output) and in good working order. The
equipment shall be capable of being used by a qualified welder, using a
qualified procedure, to produce sound and contaminant free welds. At the
discretion of the responsible M&P organization, specific equipment
instrumentation and metering devices may be calibrated to ensure
repeatability of the process.

6.  **Welding Precision Cleaned Hardware (including tube preparation for
    welding)**

Whenever precision-cleaned hardware must be maintained clean during
welding into an assembly, the welding operation shall be performed in a
dedicated Class 100,000 Clean Work Area. This may require temporary
tents over the weld area and/or local monitors located in the area of
welding to ensure the Class 100,000 environment is being met. Portable
particle counters shall be located as close as possible to the work
area, so as to monitor local contaminants during tube preparation and
welding. Tools used in weld preparation and welding (such as cutter,
weld head, files) shall be visibly cleaned per JPG 5322.1 and maintained
clean (e.g. bagged when not in use).

For hardware that cannot be subsequently precision-cleaned, a proven
method for protecting against system contamination during tube
preparation and welding shall be implemented. One such method is the use
of a physical barrier, such as plugs. The installation and removal of
plugs shall be tracked by a reliable method and independently verified.
Prior to plug removal, the exposed internal surfaces of the tube shall
be cleaned using a swab wetted with an approved solvent, and positive
backpressure shall be maintained as the plug is removed.

Tube cutters shall use a sharp blade, changed frequently. Cutting shall
be performed with minimal cutter pressure to aid in preventing particle
generation. Vacuum shall be used during tube facing operations to remove
particulate. Whenever possible, facing operations shall be performed
away from the weld assembly area, to reduce particulate contamination of
the welding work area. Tube facing shall be performed without the use of
cutting oils, other fluids, lubricants or coolants. Abrasives, including
sandpaper or abrasive pads, shall not be used inside tubes or when
unprotected internal surfaces are exposed. After each tube preparation,
and prior to welding, a high-velocity gas purge shall be performed. The
purge gas velocity shall be the maximum attainable using a 90-psig
source. The purge gas used during facing and welding shall meet the
hydrocarbon and particulate requirements for the system under assembly.
The purge gas shall be supplied in accordance with Section 5.1.

**6.2 PROCESS SPECIFIC REQUIREMENTS**

### 

### **6.2.1 Gas Tungsten Arc Welding**

Additional filler metal shall be used with the GTAW process unless it
can be demonstrated by weld qualification that weld cracking and other
undesirable metallurgical conditions will not exist in the finished weld
made without filler metal (autogenous weld). This method of welding
shall be specified on an approved WPS.

## 

### **6.2.2 Plasma Arc Welding**

Additional filler metal shall be used with the PAW process unless it can
be demonstrated by weld qualification that weld cracking and other
undesirable metallurgical conditions will not exist in the finished weld
made without filler metal (autogenous weld). This method of welding
shall be specified on an approved WPS.

## 

## **6.2 PREHEATING**

Preheat shall not exceed the temperature specified in the applicable
WPS. Actual welding shall begin immediately after preheating has reached
the temperature specified on the WPS.

## **6.3 INTERPASS TEMPERATURE**

a.  In weld joints between different base metal types and thickness, the
    higher of the preheat requirements of the joint members shall apply.

b.  Minimum interpass temperature during welding shall be the same as
    the preheat temperature specified in the welding procedure
    specification and shall be maintained by the application of
    concurrent heat if necessary.

**6.4 POST-WELD HEAT TREATMENT (PWHT)**

Postweld heat treatment shall be applied only when specified by the
engineering drawing and/or WPS and shall be performed after completion
of welding. All PWHT shall be performed according to SAE AMS-H-81200.
Vibratory techniques shall not be used in place of thermal treatment.
All weld inspections shall be applied immediately following all post
weld heat treatment activities.

##  

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

All weld rework and welded repairs shall be documented on an appropriate
non conformance report (NCR), discrepancy report (DR), or weld repair
record (WRR) form and shall be performed using the WPS used for the
original weld or a specific qualified WPS for that repair. Rework and
repairs shall meet all of the requirements of the original drawing and
any additional requirements documented in the WPS. Weld rework and
repair does not include the correction of dimensional or other
deficiencies of the groove/bevel preparation 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 apply
in the weld repair activity:

a.  [Defect Removal]{.underline}. Defect removal shall be by means of
    grinding, chipping, machining, or a combination of these methods.
    Thermal gouging and cutting [shall]{.underline} [not]{.underline} be
    used. The final repair cavity shall be of a configuration suitable
    for welding. The excavation shall be subjected to visual and/or
    other NDE examinations to ensure defect removal prior to welding.
    Weld repairs shall be adequately documented by the use of a weldment
    map or other record with sufficient detail to ensure identification
    of the weldment, identification of repair location(s), and type of
    defect.

b.  [Repair]{.underline}. No more than two weld attempts shall be made
    to successfully repair a rejected flaw. If a second attempt is
    unsuccessful, a discrepancy report requiring review and
    dispositioning by the responsible Material Review Board (MRB) shall
    be generated.

c.  [Straightening]{.underline}. Welds or adjacent base metal which have
    been deformed by the welding operation may be straightened. All
    straightening operations shall take place at temperatures not to
    exceed the determined critical temperature for that alloy.
    Straightening operations determined to be severe in nature shall be
    reviewed and approved by the responsible M&P engineering authority
    prior to the operation(s) taking place. All straightening operations
    shall be performed prior to any final inspection.

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.

**6.6 SURFACE DEGRADATION FROM CONTAMINANTS**

To prevent surface contaminants that can induce stress corrosion,
hydrogen embrittlement, or reduce fracture toughness from coming in
contact with the base material, the use of these substances on or with
titanium is prohibited:

1.  Hydrochloric Acid

2.  Cadmium

3.  Silver

4.  Chlorinated Cutting Oils and Solvents

5.  Methyl Alcohol

6.  Fluorinated Hydrocarbons

7.  Components Containing Mercury

8.  Metholyne Chloride

# **7.0 PROCESS VERIFICATION**

Process verification shall consist of nondestructive examination(s)
(NDE), as described in sections 7.1 to 7.3. In addition, the
manufacturer shall assure that the fabrication activities are carried
out in a manner that meets the requirements of this process
specification.

## 

## **7.1 INSPECTION**

Unless otherwise specified in design documentation, all inspections
(examinations) detailed herein are required to include all welds in a
structure.

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

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a)  Class A welds require visual (VT), surface, and subsurface NDE.
    Surface inspections shall be accomplished using the liquid penetrant
    (PT) inspection process. Surface inspections shall be accomplished
    using the PT, Type I, Level 3 or 4 process and shall be performed
    per AWS D1.6. Results of all surface inspections for Class A joints
    shall utilize the Class A acceptance criteria in Appendix A.
    Subsurface inspections shall be accomplished using the radiographic
    (RT) inspection process and shall be performed per AWS D1.6.

b)  In cases where the Class A inspection is designated for any weld
    having a configuration which renders adequate RT methods
    impractical, an alternate examination method shall be utilized as
    approved by the responsible NASA/JSC M&P engineering organization.

c)  When the PT method is selected and approved as a complete alternate
    to RT for multipass welds, inspections shall be performed on the
    root pass, each 1/4" thick layer of weld metal, and the final or
    cover pass.

d)  When the ultrasonic (UT) inspection method is selected as an
    alternate to RT, it shall be performed per AWS D1.6.

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

Unless otherwise specified in design documentation, Class B welds
require VT and surface NDE only. Surface inspections shall be
accomplished using the PT, Type I, Level 3 or 4 process and shall be
performed per AWS D1.6. Results of all surface inspections for Class B
joints shall utilize the Class B acceptance criteria in Appendix A.

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

Unless otherwise specified in design documentation, Class C welds
require VT only. Results of all VT inspections for Class C joints shall
utilize the Class C acceptance criteria in Appendix A.

## **7.2 VISUAL EXAMINATION REQUIREMENTS**

All visual inspections (VT) of all welds shall be performed by an
American Welding Society (AWS) Certified Welding Inspector (CWI). The
CWI certification must be current.

## **7.3 NON-DESTRUCTIVE EVALUATION (NDE)**

The NDE 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.

# **8.0 PROCESS DOCUMENTATION REQUIREMENTS**

The WPS, PQR, and WPQ shall be prepared and retained as a permanent
record and made available upon request to the NASA/JSC M&P engineering
organization for review**.** These procedures must contain, at a
minimum, all of the essential welding parameters (procedure
qualification variables, etc.), an identification of the welding
equipment, 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 welders, inspectors, supervision, and
engineering.

## 

1.  **PROCEDURE QUALIFICATION VARIABLES**

Applicable to all processes, the process variables considered
"essential" and applicable to qualification of a welding
procees/procedure shall be all those as required by AWS B2.1 and to
include the following:

a.  A change from vertical downhill welding to vertical uphill or vice
    versa,

b.  A change from a stringer to a weave bead and vice versa,

c.  A change from multiple passes per side to a single pass per side,
    and vice versa,

d.  As deemed necessary by the NASA/JSC M&P engineering organization, an
    increase or decrease in any one or more of the variables considered
    integral to the calculated heat input (i.e., current, voltage, and
    travel speed) beyond that which was qualified. Where necessary, the
    procedure shall include weld tests that define the tolerance ranges
    of specifically identified parameters,

e.  For keyhole welding techniques, a change from keyhole to non-keyhole
    and vice versa,

f.  WPSs qualified outside of a weld chamber using trailing shields and
    gas purge assemblies may also be used for welding in a weld chamber,
    but not vice versa.

**8.2 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 of AWS B2.1 and shall be certified
by the responsible M&P organization at the operating facility, prior to
use in production. If a qualified WPS does not exist prior to welding of
production parts, one shall be qualified according to AWS B2.1 "Standard
Test Weldments" at a minimum. "Prequalified" or "Standard Welding
Procedure Specifications" shall not be permitted for production use on
Class A or B welds made on flight hardware.

**8.3 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.

## **8.4 WELDER PERFORMANCE QUALIFICATION**

A Welder Performance Qualification (WPQ) is documentation that shows
that a welder has been tested in accordance with PRC-0008 and shown
competent to produce a sound weld for a specific welding process/base
material/filler metal/position combination.

## 

## **8.5 DEVIATIONS AND WAIVERS**

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.

# **9.0 TRAINING AND CERTIFICATION OF PERSONNEL**

## **9.1 TRAINING**

At JSC, if welder training is considered necessary prior to
qualification/requalification of existing JSC welding personnel or for
the initial qualification of new hires, it shall be conducted in
accordance with TI-0000-04. For an outside JSC vendor, welder 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 welder. Specific development of an
appropriate training program shall be the responsibility of the vendor.

## **9.2 WELDER QUALIFICATION**

Welding shall be performed by a welder qualified and certified in
accordance with NASA/JSC PRC-0008. Sufficiently detailed records shall
be maintained to demonstrate continuity of performance qualification on
a semi-annual (6 month) basis.

**9.2.1 [Additional Qualification Variables]{.underline}**

When qualifying personnel for titanium welding, the welding setup shall
be considered an essential variable. Personnel qualifying outside of a
weld chamber using trailing shields and gas purge assemblies shall also
be qualified for welding in a weld chamber but not vice versa. When
qualifying personnel for titanium welding by the guided bend test
method, titanium alloys not listed in AWS B2.1, Appendix C1 or C2, the
plunger diameter (dimension "A" in Annex II of AWS B2.1) shall not
exceed 20T (10T radius).

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

Any deviations or waivers regarding the use of this process
specification shall be requested in writing. 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}** Pertinent to this Appendix, the designation
'T' shall mean the nominal base metal thickness of the thinnest
component in the welded connection. Alternate and/or additional
acceptance criteria may be used for B or C class welds however, it shall
be specified in the design documentation.

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

**A1.1 GROOVE WELDS**

**[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 convex. Where
a size is not specified, the penetration requirement shall be 100%.
Reinforcement requirements shall be as specified below in A2.0.

**[Class A]{.underline} --** Groove welds shall be 100% penetration of
the joint section thickness.

**A1.2 FILLET WELDS**

**[All Classes]{.underline} -** The minimum weld size shall be the size
specified on the drawing (i.e., size = leg size). If profile
requirements are not specified, the weld may be slightly concave, flat,
or slightly convex. However, concave profiles shall have at least the
minimum throat for the size of weld specified. For intermittent welding,
the ends shall be exempt from these profile requirements but shall be
outside the specified effective weld length. Where a size is not
specified, the weld size shall be a minimum of 75% of the thickness of
the thinner component. Reinforcement requirements shall be as specified
below.

**[Class A and B]{.underline} -** The weld size may fall below the size
specified by up to 1/16" or T/4, whichever is less, for 10% of the total
weld length ^(1)^.

**[Class C]{.underline} -** The weld size may fall below the size
specified by up to 1/16" or T/3, whichever is less, for 30% of the total
weld length ^(1)^.

(1) The 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".

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

**A2.1 GROOVE AND FILLET WELDS**

**[All Classes]{.underline} -** Weld reinforcement (face and root) shall
not exceed that specified in Table A2.1a. However, in all cases, the
reinforcement shall transition into the base metal smoothly within the
limits of the allowable undercut.

**TABLE A2.1a -- Weld Reinforcement Height Limits**

  ----------------------------------- -----------------------------------
  **Weld Width**                      **Reinforcement Height**

  **≤ ¼"**                            **1/16"**

  **¼" \< and ≤ ¾"**                  **1/8"**

  **¾"\< and ≤ 1-3/4"**               **3/16"**

  **\> 1-3/4"**                       **¼"**
  ----------------------------------- -----------------------------------

**A3.0 [MISALIGNMENT AND ANGULAR DISTORTION (Peaking)]{.underline}**

**[Class A]{.underline} -** Misalignment shall not exceed T/10 or 1/16",
whichever is less. Angular distortion (AD) shall not exceed 5 degrees.
If both misalignment and AD are present then the maximum allowable limit
of misalignment allowed shall be reduced accordingly by an amount equal
to the proportion that exists of the maximum allowable limit of AD, and
vice versa.

**[Class B and C]{.underline} -** Misalignment shall not exceed T/5 or
1/8", whichever is less. Combined misalignment and AD shall be subject
to the rules given above for Class A welds.

**A4.0 [SURFACE DISCOLORATION AND OXIDATION]{.underline}**

**[All Classes]{.underline} --** Weld zones shall exhibit a bright
silver or light straw appearance. In addition, welds that have been
brushed [before]{.underline} inspection are rejectable regardless of
color before brushing.

**A5.0 [SURFACE ROUGHNESS]{.underline}**

**[All Classes]{.underline} --** On mechanically dressed (e.g., ground,
sanded, etc.) weld and adjacent surfaces within ½" of the weld toe,
surface roughness shall not exceed 125 μin.

**A6.0 [DISCONTINUITIES]{.underline}**

**[All Classes]{.underline} -** Weld discontinuities exceeding the
maximum allowable sizes for the applicable Class in Table A6.0 shall not
be allowed. Elongated 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.

For base metal thicknesses (T) ≥ 1/8", the following shall apply to
Table A6.0a:

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

**TABLE A6.0 - 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 (e.g.,                                        
                 longitudinal,                                       
                 transverse,                                         
                 crater, toe,                                        
                 etc.) ^(1)^**                                       

  **2**          **Undercut Depth  0.01" or 0.1T,   1/32" or 0.33T,  1/16" or 0.33T,
                 ^(1)^**           whichever is     whichever is     whichever is
                                   less             less ^(3)^       less ^(3)^

  **3**          **Arc Strike**    None allowed     None allowed     None allowed

  **4**          **Spatter**       None allowed     None allowed     None allowed

  **5**          **Elongated       None allowed     0.032" or 0.3T   0.062" or 0.6T
                 ^(1)^**                            in length,       in length,
                                                    whichever is     whichever is
                                                    less ^(4)^ Sum   less ^(4)^ Sum
                                                    of all visible   of all visible
                                                    indications      indications
                                                    shall be ≤1/4"   shall be ≤3/8"
                                                    or T in length,  in length, in
                                                    whichever is     any 1" of weld
                                                    less, in any 1"  length and
                                                    of weld length   ≤0.75" in any
                                                    and ≤1/2" in any 12" of weld
                                                    12" of weld      length ^(5)^
                                                    length ^(5)^     

  **6**          **Rounded ^(1)^** Surface: 1/16"   0.045" or 0.4T   0.062" 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 ^(5)^
                                                    and ≤3/4" in any 
                                                    12" of weld      
                                                    length ^(5)^     
  -------------- ----------------- ---------------- ---------------- ----------------

(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 longer discontinuity shall be considered a single
    discontinuity.*

(3) *Undercut may be 2X the value permitted, but never to exceed 1/16",
    for a continuous or accumulated length of 2" in any 12" weld length
    or 15% of the total weld length where the weld length is less than
    12".*

(4) Adjacent elongated discontinuities separated by ≤ 3X the diameter of
    the larger discontinuity, shall be considered a single
    discontinuity.

(5) 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

**FIGURE A6.0 -- [DISCONTINUITY APPROACHING FREE EDGE]{.underline}**