ISO 16338:2013

INTERNATIONAL ISO
STANDARD 16338
First edition
2013-01-15
Welding for aerospace applications —
Resistance spot and seam welding
Soudage pour applications aérospatiales — Soudage par résistance
par points et à la molette
Reference number
©
ISO 2013
© ISO 2013
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Published in Switzerland
ii © ISO 2013 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 4
5 Specific engineering requirements . 4
6 Classification of the joint . 4
7 Production requirements . 4
8 Welding personnel requirements . 5
9 Person responsible for welding procedure qualification and welding machine
qualification tests . 5
10 Material groups . 5
11 Preparation of parts to be welded . 5
11.1 General . 5
11.2 Cleaning requirements . 5
11.3 Surface coatings . 6
11.4 Assembly . 6
12 Equipment requirements . 6
12.1 Welding machines . 6
12.2 Electrodes . 6
12.3 Shear testing machines . 6
12.4 Jigs and fixtures . 6
13 Welding machines . 6
13.1 Qualification requirements . 6
13.2 Test piece configuration and examination requirements . 8
14 Welding procedure (pWPS) . 9
14.1 Qualification requirements . 9
14.2 Test piece configuration and examination requirements .11
15 Quality requirements for production .12
15.1 General .12
15.2 Production witness testing .12
15.3 Production parts .15
16 Test pieces .16
16.1 Standard test pieces.16
16.2 Test pieces for specific purposes .19
17 Examination, testing and acceptance criteria .19
17.1 General .19
17.2 Visual examination .19
17.3 Radiographic examination .21
17.4 Metallographic examination .22
17.5 Mechanical testing .26
18 Welding procedure qualification record (WPQR) .30
Annex A (informative) Machine qualification test report form .31
Annex B (informative) WPS form .33
Annex C (informative) Forms for welding procedure qualification record (WPQR) — Examples .34
Annex D (informative) Commentary on machine qualification .36
Bibliography .40
iv © ISO 2013 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16338 was prepared by Technical Committee ISO/TC 44, Welding and allied processes.
Requests for official interpretations of any aspect of this International Standard should be directed to
the Secretariat of ISO/TC 44 via your national standards body, a complete listing of which can be found
at www.iso.org.
INTERNATIONAL STANDARD ISO 16338:2013(E)
Welding for aerospace applications — Resistance spot
and seam welding
1 Scope
This International Standard specifies requirements for resistance spot and seam welding for aerospace
applications.
This International Standard does not apply if resistance welding is simply an intermediate operation and
does not affect the quality of the end product, for example when tacking basic parts prior to assembly
with another process.
Resistance welding of dissimilar material group combinations is not covered by this International Standard.
Safety and health issues and concerns are not covered by this International Standard.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 6520-2, Welding and allied processes — Classification of geometric imperfections in metallic materials —
Part 2: Welding with pressure
ISO 10447:2006, Resistance welding — Peel and chisel testing of resistance spot and projection welds
ISO 14373:2006, Resistance welding — Procedure for spot welding of uncoated and coated low carbon steels
ISO 14731, Welding coordination — Tasks and responsibilities
ISO 14732, Welding personnel — Approval testing of welding operators for fusion welding and of resistance
weld setters for fully mechanized and automatic welding of metallic materials
ISO 15609-5, Specification and qualification of welding procedures for metallic materials — Welding
procedure specification — Part 5: Resistance welding
ISO 17677-1:2009, Resistance welding — Vocabulary — Part 1: Spot, projection and seam welding
ISO/TR 25901:2007, Welding and related processes — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6520-2, ISO 14731, ISO 17677-1,
ISO/TR 25901 and the following apply.
3.1
chisel test
destructive or non-destructive test in which welds are tested by applying a predominantly tensile force
that results in stresses primarily normal to the surface of the joint interface
[SOURCE: ISO 10447:2006, 3.1]
3.2
close spaced welds
spot welds with weld pitch of less than two diameters
3.3
coring
incipient melting
melting and resolidification of material at the grain boundaries of the heat affected zone and/or in
the weld nugget
Note 1 to entry: These features appear to be cracks when examined at low magnification, but when examined at
high magnification, are seen to be completely filled. This occurs primarily in nickel alloys.
3.4
design authority
engineering authority
organization having the responsibility for the structural integrity or maintenance of airworthiness of
the hardware and compliance with all relevant documents
3.5
foil
joint member with a thickness of 0,20 mm or less
3.6
metallographic section
transverse cut on the diameter of a spot weld or across
a seam weld, or a longitudinal cut down the centre of a seam weld
3.7
nugget
zone in spot, projection or seam weld where the metal has been melted
[SOURCE: ISO 17677-1:2009, 4.10, modified — “See Figure 2.” following the term has been deleted.]
3.8
nugget diameter
diameter of nugget measured at the faying surface
3.9
nugget penetration
extent of the nugget or fusion zone into the thickness of a joined member
3.10
peel test
destructive test in which a resistance-welded lap joint is tested by applying a peel force which results in
stresses mainly in the thickness direction of the weld
[SOURCE: ISO/TR 25901:2007, 2.265]
3.11
preliminary welding procedure specification
pWPS
document containing the required variables of the welding procedure which has to be qualified
[SOURCE: ISO/TR 25901:2007, 2.280]
3.12
production witness test specimen
weld of test specimen made in production setups and destructively tested to provide data on the qualities
of production welds
2 © ISO 2013 – All rights reserved

3.13
resistance seam welding
resistance welding process which produces coalescence
at the faying surfaces by the heat obtained from resistance to electric current through the work parts
held together under pressure by electrodes
Note 1 to entry: The resulting weld is a series of overlapping resistance spot welds made progressively along a
joint by turning wheel electrodes or indexing the part under fixed electrodes.
3.14
resistance spot welding
resistance welding process that produces a weld at the faying surfaces between overlapping parts by the
heat obtained from resistance to the flow of welding current through the workpieces from electrodes
that serve to concentrate the welding current and pressure at the weld area
[SOURCE: ISO 17677-1:2009, 1.12]
3.15
roll spot welding
resistance welding process variant that makes intermittent spot welds using one or more rotating
circular electrodes
Note 1 to entry: The rotation of the electrodes might or might not be stopped during the making of a weld.
[SOURCE: ISO 17677-1:2009, 3.5]
3.16
seam weld width
width of the weld metal in the plane of the faying surfaces in a direction normal to the longitudinal axis
of the linear seam weld
[SOURCE: ISO 17677-1:2009, 4.14]
3.17
sheet
joint member with a thickness of more than 0,20 mm
3.18
weld pitch
centre-to-centre distance between adjacent spot welds
[SOURCE: ISO 14373:2006, 3.5]
3.19
welding condition
provision for the manufacture of a given weld, including
material, configuration, material preparation, cooling, electrode material, electrode geometry, welding
machine number, and all weld parameters that have a direct influence on the quality of the weld
3.20
welding parameter
machine setting or adjustment
EXAMPLE Examples are electrode force, welding current, welding speed, welding time.
3.21
welding procedure specification
WPS
document that has been qualified and provides the required variables of the welding procedure to
ensure repeatability during production welding
[SOURCE: ISO/TR 25901:2007, 2.457]
4 Symbols and abbreviated terms
D minimum required nugget diameter or seam weld width (see Table 11)
s
e lower electrode indentation
l
e upper electrode indentation
u
F force
l length of test specimen
s actual nugget diameter or seam weld width, as determined by metallographic examination
M
t thickness of the thinner sheet
t thickness of outer member
o
w test specimen width/overlap
Ac test lot average
NDT non-destructive testing
pWPS preliminary welding procedure specification
QA quality assurance
SPC statistical process control
WPQR welding procedure qualification record
WPS welding procedure specification
5 Specific engineering requirements
In the event of any conflict between the requirements of this specification and those requirements
specified in the engineering definition, the engineering definition shall take precedence.
The classification of the joint (see Clause 6) shall be designated on the part specification or drawing.
6 Classification of the joint
Classification of the joint is based on the following.
— Class I: a welded joint whose failure under operating conditions causes the loss of the
aircraft/spacecraft or one of its main components, or constitutes a direct hazard to people.
— Class II: a welded joint whose failure causes malfunctions without compromising continued safe
flight until the end of the mission.
— Class III: a welded joint whose failure does not affect the safety and the transport function of the
aircraft/spacecraft.
7 Production requirements
Prior to production, the following requirements shall be met:
a) personnel qualification,
4 © ISO 2013 – All rights reserved

b) welding machine qualification,
c) welding procedure qualification.
8 Welding personnel requirements
The welding personnel shall be trained and be competent for the process. If requested by the
design/engineering authority, ISO 14732 may be invoked.
9 Person responsible for welding procedure qualification and welding machine
qualification tests
The welding coordinator (see ISO 14731) shall be designated, in writing, as responsible for welding
procedure qualification and welding machine qualification test. The welding coordinator shall have
knowledge and experience relevant to the welding process, and be acceptable to the responsible
design/engineering authority or recognized examining body.
It is recommended that the welding coordinator be qualified as International Welding Engineer (IWE)
according to IIW IAB-252-11.
The welding coordinator may authorize another person to administer the welding procedure qualification
or welding machine qualification test.
10 Material groups
Material group A: unalloyed steel, low-alloyed steels, high-alloyed ferritic steels.
Material group B: high-alloyed austenitic and martensitic steels, nickel and nickel alloys, cobalt alloys.
Material group C: titanium and titanium alloys, niobium, zirconium and other reactive metals.
Material group D: aluminium and aluminium alloys, magnesium and magnesium alloys.
Material group E: materials that do not conform to material groups A to D (e.g. molybdenum, tungsten
and copper alloys).
11 Preparation of parts to be welded
11.1 General
External and faying surfaces of the parts to be welded shall be free from contaminants, such as heavy
oxides, scale, ink, grease, dirt or other substances, or surface conditions detrimental to the welding process.
The surfaces shall be regular, this being a determining factor in ensuring good reproducibility of the weld.
11.2 Cleaning requirements
A specific cleaning procedure (e.g. pickling) shall be determined according to the materials and precisely
defined by each manufacturer in line with the design/engineering authority requirements.
The cleaning procedure used to prepare materials for welding procedure qualification shall be specified
on the pWPS. For materials in group D, surface resistance requirements shall be specified by the
design/engineering authority.
Time limits between cleaning and welding shall be specified in the pWPS or other manufacturing
documentation.
11.3 Surface coatings
Surface coatings, specified by the design/engineering authority, shall be identified in the pWPS.
11.4 Assembly
Mating parts assembled for welding shall fit so that before the first and each subsequent weld is made,
the surfaces to be joined by the weld are in contact with one another or can be made to contact one
another by manual pressure.
12 Equipment requirements
12.1 Welding machines
The welding machine shall be qualified according to Clause 13, calibrated and maintained
according to manufacturer recommendations and/or any other requirements as defined by the
design/engineering authority.
A preventative maintenance procedure shall be established and maintenance records kept.
12.2 Electrodes
All electrodes in use shall be permanently marked with the electrode material designator, as a minimum.
12.3 Shear testing machines
12.3.1 General
Shear testing machines shall be accurate to within ±2 % of the indicated reading. The shear testing
speed shall not exceed 13 mm/min.
12.3.2 Stationary shear testing machines
Stationary shear testing machines shall be calibrated for accuracy at intervals not to exceed one year.
12.3.3 Portable shear testing machines
Portable shear testing machines shall be calibrated for accuracy at intervals not to exceed two months.
12.4 Jigs and fixtures
Jigs and fixtures shall be so designed as to minimize the shunting of welding current through them
instead of passing through the workpieces. All tooling that is required to locate welds or assist in the
assembly of welded parts that passes through the magnetic field during the welding operation should be
made of nonmagnetic materials insofar as possible.
13 Welding machines
13.1 Qualification requirements
13.1.1 General
Existing machine qualifications to other standards prior to the release of this International Standard
are considered qualified, unless otherwise specified by the design/engineering authority.
6 © ISO 2013 – All rights reserved

Prior to production, qualification shall be performed on each resistance spot or seam welding machine to
determine its ability and consistency of operation. The purpose of qualification is to identify and verify
the range of welding for which a welding machine may be considered capable. Welding conditions shall
be documented on a WPS as part of a machine qualification test report. Typical examples of report forms
are given in Annexes A and B. Such forms may be modified or expanded as required. After approval is
obtained, these reports shall be available for review.
Machines shall be qualified to meet the weld requirements for the most critical class (see Clause 6) in
each material group (see Clause 10) for which it is intended to be used in production. A welding machine
qualified to weld to the requirements of one class in a material group shall be automatically considered
qualified for less critical classes in the same material group. A spot welding machine qualified for spot
welding is also qualified for overlap spot welding. Machines used for class III foil welding may be qualified
by establishing a WPS. Machines qualified to a class for seam welding shall be considered qualified for
roll spot welding to the same class.
13.1.2 Method of welding machine qualification
13.1.2.1 General
No maintenance work or control adjustments are permitted during the welding of test specimens.
13.1.2.2 Test materials
Test materials for material groups A, B, C and D qualification may be any material from that group
commonly used in production.
Qualification with material of group A qualifies for welding material of group A only.
Qualification with material of group B qualifies for welding material of group B only.
Qualification with material of group C qualifies for welding material of group C only.
Qualification with material of group D qualifies for welding material of group D only.
Qualification with a specific material of group E qualifies for welding with the same material only.
13.1.2.3 Test requirements
Weld tests listed in 13.2 shall be performed and shall meet applicable acceptance criteria. For each material
group, two test sets shall be required: the high-end (thickest) machine qualification test and the low-end
(thinnest) machine qualification test. Typically, the high-end and low-end machine qualification tests are
each made up of two members of equal thickness. Alternatively, members of different thicknesses and/or
a weld combination of more than two members may be used. The following requirements shall be used
to determine the required machine qualification tests to cover production work:
a) The total thickness of all members in a production weld combination shall not be more than the
total thickness of all members in the high-end machine qualification test and shall not be less than
the total thickness of all members in the low-end machine qualification test.
b) The thinnest contact member (member in contact with the electrode) of any production weld
combination shall not be thicker than the thinnest member in the high-end machine qualification test
c) The thinnest contact member (member in contact with the electrode) of any production weld
combination shall not be thinner than the thinnest member in the low-end machine qualification test.
d) If a machine is used for a specific weld combination then it need only be qualified for that weld
combination according to the quantities and methods specified in 13.2.
NOTE 1 For examples of the application of rules stated in this subclause, see Annex D.
NOTE 2 If more than one welding machine of the same type is to be qualified, the extent of testing can be
reduced at the discretion of the design/engineering authority.
13.1.2.4 Welding machine requalification
Requalification shall be required if the welding machine is rebuilt or if significant operational changes
(e.g. replacement of main components, facility relocation and change of power supply) are made. The
number of test specimens for sheet welding may be reduced (see Table 2).
Unless otherwise authorized by the design/engineering authority, when welding machine requalification
is required, all WPS shall be requalified prior to production use.
Changes that do not require requalification of the welding machine are:
a) change of location within a plant, which maintains the same electrical circuit;
b) general machine maintenance;
c) replacement of parts, such as electrodes and electrode holders, which do not affect the pressure or
power characteristics.
13.2 Test piece configuration and examination requirements
Tests shall be as specified in Table 1 and as shown in Figure 1 and Figures 3 to 5.
Table 1 — Welding machine qualification test pieces and examination requirements
Examination
Class Test piece Amount per test set
Visual Radiographic Mechanical Metallographic
Spot welds — Sheet
Figure 1 a)
I 105 weld spots all all 100 shear 5 microsections
or 1 b)
Figure 1 a)
II 105 weld spots all all 100 shear 5 macrosections
or 1 b)
Figure 1 a)
III 53 weld spots all none 50 shear 3 macrosections
or 1 b)
Spot welds — Foil
l = 300 mm continuous
a
I, II, III Figure 3 all none peel none
length of weld
Seam welds — Sheet
8 microsections
l = 600 mm continuous
I Figure 5 all all none (4 transverse, 4 lon-
length of weld
gitudinal)
8 macrosections
l = 600 mm continuous
II Figure 5 all all none (4 transverse, 4 lon-
length of weld
gitudinal)
4 macrosections
l = 300 mm continuous
III Figure 5 all none none (2 transverse, 2 lon-
length of weld
gitudinal)
Seam welds — Foil
l = 300 mm continuous
a
I, II, III Figure 4 all none peel none
length of weld
a
Machines used for class III foil welding may be qualified by establishing a WPS.
For welding machine requalification, the number of test specimens for sheet welding may be reduced
according to Table 2.
8 © ISO 2013 – All rights reserved

Table 2 — Machine requalification test pieces and examination requirements
Examination
Class Test piece Amount per test set
Visual Radiographic Mechanical Metallographic
Spot welds — Sheet
Figure 1 a)
I 53 weld spots all all 50 shear 3 microsections
or 1 b)
Figure 1 a)
II 53 weld spots all none 50 shear 3 macrosections
or 1 b)
Figure 1 a)
III 28 weld spots all none 25 shear 3 macrosections
or 1 b)
Seam welds —Sheet
4 microsections
l = 300 mm continuous
I Figure 5 all all none (2 transverse, 2 lon-
length of weld
gitudinal)
4 macrosections
l = 300 mm continuous
II Figure 5 all all none (2 transverse, 2 lon-
length of weld
gitudinal)
2 macrosections
l = 150 mm continuous
III Figure 5 all none none (1 transverse, 1 lon-
length of weld
gitudinal)
14 Welding procedure (pWPS)
14.1 Qualification requirements
14.1.1 General
Existing WPS qualifications to other standards prior to the release of this International Standard are
considered qualified, unless otherwise specified by the design/engineering authority.
Prior to production, a WPS shall be established to produce the minimum strength, nugget diameter or
seam weld width or quality requirement specified in this International Standard or as defined by the
design/engineering authority. Qualification results shall be entered on the test report, which includes
the settings used to weld the test specimens. Weld settings shall not be adjusted during the welding of
the qualification test specimens. After qualification acceptance, production setups shall be allowed to
deviate from the WPS as allowed by 15.2.4.
NOTE If production parts are used for qualification, design/engineering authority approval can be required.
14.1.2 Determination of weld settings
For each welding machine and each combination of relevant material conditions (such as alloy, heat
treatment, surface conditions, geometry, material stack-up and thickness combinations), effective
welding machine settings for test and production parts shall be determined. The conditions and
parameters shall be defined on a pWPS before welding the qualification test pieces. Typical examples
of report forms are given in Annexes A and B. These shall be modified or expanded as required. After
acceptance, production setups shall be made to the qualified pWPS, with the variation of 15.2.4 allowed.
14.1.3 Methods of welding procedure qualification
A welding procedure shall be qualified by one of the following methods.
14.1.3.1 Standard welding procedure qualification
Tests shall be conducted to demonstrate that on a given set of materials and a particular welding machine,
the welding procedure produces resistance welds that conform to the requirements of Tables 12 to 14
(sheet), 14.2 and Clause 17.
14.1.3.2 Design allowable qualification
The design allowable qualification method shall be used when specific requirements are defined by the
design/engineering authority. Tests shall be conducted to demonstrate that on a given set of materials
and a particular welding machine, the welding procedure produces resistance welds that conform to
these requirements.
The pWPS shall state that the design allowable qualification method was used and shall give reference
to the specific requirements.
14.1.4 Thickness combination limits
Thickness combinations falling within the following limits shall not require a separate qualified welding
procedure, provided the qualified average nugget diameter or seam weld width can be reproduced with
a weld heat (current) setting that lies within ±10 % of the value established by the original WPS; all
other conditions being the same.
a) Foil. The variation in thickness (with regard to the original procedure) of either outer sheet is within
±0,03 mm and the variation in the sum of the thicknesses (with regard to the original procedure) of
the combination is within ±0,08 mm.
b) Outer sheet ≤ 1,02 mm, inclusive:
1) the variation in thickness of either outer sheet is within ±0,10 mm;
2) the variation in the sum of the thicknesses of the combination is within ±0,15 mm.
c) Outer sheet >1,02 mm:
1) the variation in thickness of either outer sheet is within ±10 % for material groups D and E
alloys, or ±20 % for material groups A, B and C alloys;
2) the variation in the sum of the thicknesses of the combination is within ±10 %.
14.1.5 Welding procedure specification (WPS)
After qualification, the WPS shall be available to machine operators and quality assurance (QA). The
following parameters shall be included in the WPS and any changes of these critical parameters outside
the allowable limits of 15.2.4 shall require requalification:
a) force;
b) electrode (geometry and material group);
c) weld settings (time, current, number of cycles);
d) surface preparation;
e) weld overlap (number of spots in seam weld unit length) on seam welds;
f) travel speed on roller seam welds.
The purpose of qualification is to replicate the results expected on production components; therefore,
test conditions for qualification shall correspond with expected production conditions.
A suggested form for a WPS is given in Annex B. Further information on WPS guidelines is given in ISO 15609-5.
10 © ISO 2013 – All rights reserved

14.1.6 Welding procedure requalification
Requalification of the WPS shall be required if the welding machine was requalified (see 13.1.2.4) or if
significant operational changes are made to the WPS as specified in 14.1.5.
Requalification of the WPS shall also be required if a change in the cleaning procedure produces different
results (nugget and strength ranges) than the former method.
NOTE An existing WPS need not be requalified for another contract or design, provided all material conditions
(such as alloy, heat treatment, surface conditions, geometry, material stack-up and thickness combinations) are
equivalent as defined by the existing WPS.
Requalification of a welding procedure shall be required at any time if there is any reason to doubt the
ability of a welding machine to produce satisfactory welds using the existing WPS.
14.2 Test piece configuration and examination requirements
Tests shall be as specified in Tables 3 to 6 and as shown in Figures 1 to 5. Welds shall be located within
±1,5 mm of the centre of the overlap. Test piece size tolerance shall be ±1,5 mm.
Table 3 — pWPS test pieces and examination requirements — Spot welds — Sheet
Number Examination
Material
Type Class Test piece of weld
group
a
Visual RadiographicMechanical Metallographic
a
spots
Figure 1 a)
I 13 all all 10 shear 3 microsections
or 1 b)
Figure 1 a)
A, B, C II 8 all all 5 shear 3 macrosections
or 1 b)
Figure 1 a)
Isolated
III 5 all none 3 shear 2 macrosections
or 1 b)
or roll
spot
Figure 1 a)
I 25 all all 20 shear 5 microsections
weld
or 1 b)
Figure 1 a)
D, E II 15 all all 10 shear 5 macrosections
or 1 b)
Figure 1 a)
III 5 all none 3 shear 2 macrosections
or 1 b)
I Figure 2 20 all all none 10 microsections
Close
A, B, C,
spaced II Figure 2 10 all all none 5 macrosections
D, E
welds
III Figure 2 3 all none none 3 macrosections
a
If more than two sheets are assembled, the mechanical tests are to be repeated for separate examina-
tion of each assembly joint face in the final configuration (two series of tests for assembly of three sheets, three
series for four sheets, etc.; see 17.5.4).
Table 4 — pWPS qualification test pieces and examination requirements — Spot welds — Foil
Examination
Material
Class Test piece
group
Visual Radiographic Mechanical Metallographic
4 microsections: ran-
peel test
domly select four spot
I Figure 3 all none min. 10 consecutive
welds from a minimum
spot welds
of 10 welded
A, B, C, D, E
peel test
II, III Figure 3 all none min. 10 consecutive none
spot welds
Table 5 — pWPS qualification test pieces and examination requirements — Seam welds — Sheet
Examination
Material
Class Test piece Length of weld
group
Visual Radiographic Metallographic
l = 300 mm con- 4 transverse microsections (Tr)
I, Figure 5 tinuous all all 4 longitudinal microsections
length of weld (Lo)
l = 300 mm con- 4 transverse macrosections (Tr)
A, B, C,
II Figure 5 tinuous all all 4 longitudinal macrosections
D, E
length of weld (Lo)
l = 300 mm con- 1 transverse macrosections (Tr)
III Figure 5 tinuous all none 2 longitudinal macrosections
length of weld (Lo)
Table 6 — pWPS qualification test pieces and examination requirements — Seam welds — Foil
Examination
Material Length of
Class Test piece
group weld
Visual Radiographic Mechanical Metallographic
Figure 4, 2 l = 300 mm 1 longitudinal
I specimens continuous all none peel 17.5.3 a) microsection:
required length of weld 25 mm
A, B, C, D, E
Figure 4, l = 100 mm peel 17.5.3 b) 1 longitudinal
II, III 2 specimens continuous all none (75 mm mini- macrosection:
required length of weld mum length) 25 mm
15 Quality requirements for production
15.1 General
A WPS shall be available and used for each production joint.
15.2 Production witness testing
15.2.1 General
Periodic tests shall be conducted to determine if a particular welding machine, in combination with a
specific welding procedure and other specific conditions used during production, produces resistance
welds that conform to the requirements of this International Standard. Documentation of these tests
shall be contained in an individual register (logbook) for each resistance welding machine and shall be
available for review.
15.2.2 Witness test specimens
Qualification and production witness test specimens shall conform to the production parts they represent
with respect to material, thickness, overlap, configuration, and surface condition or preparation.
Production witness specimens shall be run with production weld conditions using either qualification
specimens or a simulation of the production part.
When production conditions exist that were not applied during qualification, but cause machine settings
to differ from qualification settings so as to exceed the permitted parameter adjustments (see 15.2.4),
the qualification shall be run again with the subject critical production conditions included. Examples
of such production conditions include, but are not limited to, magnetic material in the machine throat,
curvature of the part, spot spacing and part (overlap) width.
12 © ISO 2013 – All rights reserved

15.2.3 Surface resistance
A daily check shall be made of the surface resistance, in microohms, for material group D welds when
running production parts. A minimum of five readings shall be made on the production parts or on
samples typical of the material being welded and its surface condition and preparation. The details of
the method of obtaining the surface resistance measurement shall be the same as those used for the
pWPS qualification or cleaning procedures and the values of the surface resistance shall not exceed the
limits of consistency and maximum values established at that time.
Use of existing material cleaning and etching process control/monitoring may be substituted for the
surface resistance checks as deemed appropriate by the design/engineering authority.
Use of in-process weld control monitoring capable of detecting when a surface resistance shift outside
of the specification range occurs may be substituted for the surface resistance checks as deemed
appropriate by the design/engineering authority.
15.2.4 Parameter adjustments
Welding parameters (see 14.1.5) may be varied by ±5 % from the established WPS values, or by ±10 %
when only one setting is adjusted. When adjustments are made during production, welding parameters
shall stay within this range, and within ±5 % of the parameters used for the witness test specimens.
If satisfactory welding cannot be maintained within these limits of adjustment, welding shall be stopped
and the welding machine shall be checked for faulty operation. If it can be shown that conditions other
than those controlled by the qualified welding procedure were the cause of the faulty welding and that
after their correction the original qualified welding procedure is capable of producing acceptable welds,
the establishment of a new qualified welding procedure shall not be required (see 15.3.2).
NOTE For roller seam weld electrode diameter, variations >5 % can be permissible with the agreement of the
responsible design/engineering authority.
15.2.5 Production witness test specimen configuration and examination
15.2.5.1 General
The following witness tests shall accompany the welding of production parts. The witness test
specimens duplicate the production parts in all conditions controlled by the qualified welding
procedure and the drawing. Results of these tests shall be maintained in an individual register
(logbook) by each welding machine.
15.2.5.2 Witness test
Production witness test specimens shall be as follows:
a) preproduction witness test: witness test specimens taken at the start of each work day or before a
new production lot is welded or before welding is resumed after a machine shutdown;
b) intermediate witness test: witness test specimens taken during production welding or before or
after minor welding equipment change;
EXAMPLE Examples of minor equipment changes are electrode change or fixture change.
c) postproduction witness test: witness test specimens taken at the end of each production work day
or after the completion of a production lot.
Depending on the weld class, production parts shall be accompanied by witness tests according to Table 7.
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