AMS-W-6858A

AEROSPACE
MATERIAL Issued JUL 1999
400 Commonwealth Drive, Warrendale, PA 15096-0001
SPECIFICATION Revised APR 2000

Superseding AMS-W-6858

Welding, Resistance: Spot and Seam

NOTICE

This document has been taken directly from U.S. Military Specification MIL-W-6858D, Notice 1,
Amendment 1 and contains only minor editorial and format changes required to bring it into
conformance with the publishing requirements of SAE technical standards. The initial release of this
document is intended to replace MIL-W-6858D, Notice 1, Amendment 1. Any part numbers established
by the original specification remain unchanged.

The original Military Specification was adopted as an SAE standard under the provisions of the SAE
Technical Standards Board (TSB) Rules and Regulations (TSB 001) pertaining to accelerated adoption
of government specifications and standards. TSB rules provide for (a) the publication of portions of
unrevised government specifications and standards without consensus voting at the SAE Committee
level, and (b) the use of the existing government specification or standard format.

Under Department of Defense policies and procedures, any qualification requirements and associated
qualified products lists are mandatory for DOD contracts. Any requirement relating to qualified products
lists (QPL’s) has not been adopted by SAE and is not part of this SAE technical document.

1. SCOPE:

1.1 Scope:

This specification covers requirements for resistance spot and seam welding of the following metals
and their alloys.

Group 1 - Aluminum and magnesium

Group 2 - Iron, nickel, and cobalt
Group 3 - Titanium

SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely
voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.”
SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.
Copyright 2000 Society of Automotive Engineers, Inc.
All rights reserved. Printed in U.S.A.
QUESTIONS REGARDING THIS DOCUMENT: (724) 772-7161 FAX: (724) 776-0243
TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790
SAE WEB ADDRESS: http://www.sae.org
 AMS-W-6858A SAE AMS-W-6858A

1.2 Classification:

Classification is based on function and use of the welded joint, rather than certain average levels of
strength. Therefore, reliability is the key underlying quality distinguishing the work for each class.
The criteria described herein are intended to prevent larger variations in weld strength and quality
than are compatible with the intended use.

Class A A welded joint, whose failure during any operating condition would cause loss of the
equipment or system or one or its major components, loss of control, unintentional
release or inability to release any armament score, failure of gun installation
components; or which may cause significant injury to occupants of manned systems.
Class B A welded joint whose failure would reduce the overall strength of the equipment or
system or preclude the intended functioning or use of equipment.
Class C A welded joint which is considered non-critical and for which no stress analysis is
considered.

1.2.1 The classification of welds in foil thickness is limited to Class A and Class C.

2. APPLICABLE DOCUMENTS:

The following documents of the issue in effect on date of invitation for bids, or request for proposal,
form a part of this specification.

2.1 American Welding Society (AWS) Publications:

Available from American Welding Society Inc., 2501 N.W. 7th Street, Miami, Florida 33125)

AWS A3.0 Terms and Definitions

AWS C1.1 Recommended Practices for Resistance Welding

3. REQUIREMENTS:

3.1 Design requirements:

3.1.1 Definition of terms used in this specification shall be in accordance with AWS A3.0, and as shown
in 6.2 herein.

3.1.2 The class of welding shall be designated on the item specification or drawing. The design of Class
A resistance welded joints shall require the specific approval of the procuring activity who may
approve if satisfactory resistance welded prototypes exist, or upon evidence of the adequacy of the
design and pattern of spot welding or upon the satisfactory performance of suitable static and
repeated loading testing of the design or applicable prototype.

-2-
 AMS-W-6858A SAE AMS-W-6858A

3.1.3 There shall be two methods of certification for spot welds. The Standard Certification method shall
be for a weld schedule that certifies that the requirements of Tables I through III or IV, and all other
applicable weld property requirements have been met. The Design Allowable Certification method
shall be a weld schedule that certifies a guaranteed strength value has been met.

TABLE I. Shear strength requirements for spot weld sheet specimens

-3-
AMS-W-6858A SAE AMS-W-6858A

TABLE I(SI)*. Shear strength requirements for spot weld sheet specimens

-4-
AMS-W-6858A SAE AMS-W-6858A

TABLE II. Shear strength requirements for spot weld sheet specimens

-5-
AMS-W-6858A SAE AMS-W-6858A

TABLE II(SI)*. Shear strength requirements for spot weld sheet specimens

-6-
AMS-W-6858A SAE AMS-W-6858A

TABLE III. Shear strength requirements for spot weld sheet specimens

-7-
AMS-W-6858A SAE AMS-W-6858A

TABLE III(SI)*. Shear strength requirement for spot weld sheet specimens

-8-
AMS-W-6858A SAE AMS-W-6858A

TABLE IV. Shear strength requirements for spot welds in foil

TABLE IV(SI). Shear strength requirements for spot welds in foil

-9-
 AMS-W-6858A SAE AMS-W-6858A

3.1.3.1 The Design Allowable Certification method is intended to routinely permit the design and use of
smaller welds where the design stress permits and space or equipment or material conditions
compel; or to permit the design and use of stronger welds where they are wanted and the weld
conditions are able to provide them. For a given joint a guaranteed strength value and weld
class must be specified on the drawing.

3.1.3.2 The provisions of the Design Allowable Certification method may be used to certify a weld
schedule when unusual conditions apply. For example, when welds are made through adhesives
or through protective finishes or when it is desirable to use diffusion welds as integral
reinforcements to nuggets or in lieu of nuggets.

3.1.4 When conditions are encountered which cause any of the requirements of this specification to be
inapplicable, the contractor shall submit alternate procedures and requirements for approval by the
procuring activity. The request for approval shall include a description of the conditions which
render the requirements inapplicable, such as reduced flange widths and space limitations; and
shall include data to indicate that the alternate procedures and requirements are adequate for the
given application.

3.1.4.1 Granted approvals of alternate procedures shall remain in effect as complying with this
specification until the contractor is notified otherwise by the procuring activity.

3.2 Materials and methods of preparation:

3.2.1 Material combinations:

3.2.1.1 Combinations not requiring specific approval: The metals listed below may be welded in any
combination within each lettered grouping.

a. Aluminum and its alloys

b. Magnesium and its alloys
c. Titanium and its alloys
d. Plain carbon steels of less than 0.15 percent carbon
e. Austenitic steels; precipitation hardening steels; nickel and cobalt base alloys.
3.2.1.2 Combinations requiring approval: Use of the following metals requires specific approval of the
procuring activity: Clad 7075 aluminum alloy in thicknesses less than 0.020 inch or 0.51
millimeter (mm); any aluminum alloy in the 2000 or 7000 series which is unclad; or any
magnesium alloy which will be exposed to accelerating corrosion conditions like a marine
environment.

- 10 -
 AMS-W-6858A SAE AMS-W-6858A

3.2.1.3 Special requirements: Metal combinations not included in 3.2.1.1 shall require the following
establishment of weld ductility. The average tensile (normal to spot plane) strength of twenty spot
welded specimens shall be greater than 0.25 times the minimum average shear strength in
Tables I through IV applicable to the subject alloy or as established for the Design Allowable
Certification. This test may be conducted on specimens, as welded, or after subsequent heat
treatment. Heat treatment is a later manufacturing operation and not the post weld current
provided through welder electrodes. The production process shall specify the certified weld
schedule plus the subsequent heat treatment used to demonstrate the weld ductility required
herein.

3.2.2 Surface conditions: The surface of the parts to be welded shall be free from objectionable films
such as heavy oxides, scale, ink, grease, dirt, or other substances or surface conditions
detrimental to the welding process.

3.2.2.1 Group I materials:

3.2.2.1.1 Oxide coatings may be removed by mechanical treatment (such as sanding or wire brushing)
or by chemical treatment.

3.2.2.1.2 The ability of a cleaning procedure to effectively prepare Group I materials for welding shall be
demonstrated by ability of materials cleaned by the process to be welded in compliance with
the Certification requirements of this specification. The cleaning procedure is a necessary
component of the Certification weld schedule.

3.2.2.1.3 Conformity of test and production materials surfaces to those produced by the normal cleaning
procedure shall be checked by surface resistance readings. Maximum values for test and
production materials shall be established as indications of the conformity required for welding
in compliance with this specification.

3.2.2.1.4 The minimum and maximum time span that is permitted between parts cleaning and parts
welding shall be established by the contractor. The contractor shall demonstrate that no
deterioration of surface conditions take place during typical holding or storage conditions
during that span. Deterioration shall be excessive when high values lead to inability to meet
Certification requirements. Conditions and limitations may be applied generally as to a
standard process, or specifically as to an exceptional assembly or material combination where
warranted.

3.2.2.1.5 When a cleaning procedure is changed, if the contractor can demonstrate that the new
procedure produces the same results as the old procedure, recertification of weld schedules
shall not be required. This conformity will be shown by (1) producing the same weld results as
made during Qualification tests (with Certification quantities) with a weld heat change within
±10 percent of the established value and (2) showing a surface resistance average that is no
more than 1.05 times that achieved by the replaced procedure.

- 11 -
 AMS-W-6858A SAE AMS-W-6858A

3.2.2.1.6 Coatings which improve the corrosion resistance or sealing characteristics without affecting the
weld properties may be applied prior to welding. Such finishes must be considered as final
steps of the cleaning procedure and necessary conditions specified on the Certified weld
schedule.

3.2.3 Joint thickness: Joint thicknesses are only limited to those thicknesses or combination of
thicknesses on which Certification weld schedule can be established and production parts can be
made to meet the production requirements of this specification.

3.2.4 Fitup: Mating parts assembled for welding shall be designed and processed to fit so that before the
first and each successive weld is made the surfaces to be joined by the weld are in contact with
each other or can be made to contact each other with manual pressure.

3.3 Equipment requirements:

3.3.1 Welding machines: The welding machine shall consist of a suitable source of electrical energy,
means of adequately cooling the electrodes, and a means of reliably controlling and indicating the
relative magnitude of the current, the welding force, and the time of current flow; to fulfill the
requirements specified herein. The force and current controls shall operate so that no current can
flow until the welding force is applied by the welding electrodes. It shall not be possible to reduce
electrode force before current is terminated.

3.3.2 Electrodes: Suitable electrode material and shapes shall be used to perform welding in
conformance with this specification.

3.3.3 Shear testing machines: The contractor shall provide spot weld shear testing machines as
required. All shear testing machines shall be accurate within ±2 percent of the indicated reading.
Portable spot weld shear test machines shall be checked for accuracy at intervals not to exceed 2
months.

3.3.4 Surface resistance indicators: The contractor shall provide one or more surface resistance
indicators for checking the effectiveness of cleaning solutions and procedures engaged in
preparing Group I metals for spot welding. Surface resistance indicators shall be checked for
accuracy and recalibrated as necessary.

3.3.5 Jigs and fixtures: All tooling that is required to locate welds or assist in the assembly of welded
parts that passes through the magnetic field during the molding operation, shall be made of
nonmagnetic materials insofar as possible. Jigs and fixtures must be so designed that no welding
current can shunt through them instead of passing through the work pieces.

3.3.6 Maintenance of equipment: Unless otherwise specified, each item of equipment shall be inspected
periodically as recommended by the manufacturer. Adequate preventative maintenance shall be
furnished. Defective equipment parts affecting machine operation shall be replaced before
production welding is resumed.

- 12 -
 AMS-W-6858A SAE AMS-W-6858A

3.4 Qualification of welding machines:

3.4.1 Qualification approval: Qualification is performed on a distinctive resistance spot or seam welding
machine to determine the ability and consistency of operation of a machine type at a facility.
Qualification has as a purpose to identify and verify the range of welding that a facility may, for
contractual purposes, be considered capable. To have his equipment qualified and approved for
use the contractor shall perform the tests specified herein under the surveillance of the procuring
activity. Weld conditions shall be documented on a Machine Qualification Test Report. Typical
examples of report forms are given in AWS C1.1. Such forms may be modified or expanded as
required. Weld conditions and test results shall be submitted with an application for approval to the
procuring activity. After approval is indicated, these reports shall be posted near the machine so as
to be available to contractor operators and inspectors, and agents of the procuring activity.

3.4.1.1 Qualification by one procuring activity of the Department of Defense shall be Qualification for all
DOD procuring activities and for those other governmental agencies who elect to subscribe to
this specification.

3.4.2 Machine qualification scope: Machines shall be qualified to meet the weld requirements for the
highest classification in a metal group for which it is intended to be used in production. A machine
qualified to weld to the requirements of one weld classification in a group shall be automatically
considered qualified for lower weld classifications. When one machine of a distinctive type in a
plant site passes the Qualification tests all other machines of the same type shall be considered
qualified. Machines used for Class C foil welding are qualified just by establishing a weld schedule
Certification. Machines qualified to a class for seam welding shall be considered qualified for roll
spot welding to the same class.

3.4.2.1 Types of equipment: Distinctive types of equipment must include those differing in any of the
following respects:

a. Manufacturer of machine
b. Manufacturer of control panel
c. Type of machine, or model number
d. Electrical rating or capacity
e. Type of electrical energy
f. Type of pressure application.

3.4.2.2 Test conduct: No maintenance work and no control adjustments are permitted during the welding
of a set of test specimens.

3.4.2.3 Test materials: The test materials for a Group I Qualification shall be any aluminum alloy
commonly used in resistance welded products. For Groups 2 and 3 qualification test material
shall be any steel commonly used in resistance welded products.

- 13 -
 AMS-W-6858A SAE AMS-W-6858A

3.4.2.4 Combination selection: For each group of alloys, two test sets shall be required. One at the
highest, one at the lowest end of the range for which the Qualification is desired. This normally
means that the thickest to thickest metal combination on one end and the thinnest to thinnest on
the other end.

3.4.2.4.1 Except that when a Qualification is achieved on one combination of foil thicknesses, the
equipment shall be considered qualified for all thicker foils welded to foils.

3.4.2.5 Test specimen requirements: Weld test and examination requirements are shown in Table V.

3.4.2.6 Weld machine requalification: When the equipment has once been qualified, it need not be
requalified for other contracts or production lots. A change of location within a plant, not involving
a change in power source, or maintenance, or parts replacement does not necessitate
requalification. Requalification shall be required if the machine is rebuilt or if significant
operational changes are made in it. Existing machine Qualifications made under superseded
revision of this specification shall be honored.

3.5 Weld schedule certification:

3.5.1 Certification: Tests shall he conducted to determine if a particular machine, in combination with a
specific weld schedule and other specific conditions, will produce on a given set of materials
resistance welds that conform to the requirements of specification. Documentation of these tests
will be contained in a completed Certification Test Report that will be available to agents of the
procuring activity. In addition, the weld schedule shall be posted near the machine and be
available to machine operators, inspectors, and agents of the procuring activity.

- 14 -
 AMS-W-6858A SAE AMS-W-6858A

TABLE V. Machine qualification test specimen requirements

3.5.2 Certification test reports: For each machine and each combination of relevant conditions (such as
alloy, temper, surface conditions, and thickness combinations), the contractor will determine the
effective weld machine settings for test and production parts. The schedule of conditions and
parameters shall be formally entered on a report form before the test welding. Typical examples of
report forms are given in AWS Cl.l. These shall be modified or expanded as required. After
acceptance, production setups shall be made to the schedule therein given, with the scheduled
latitude of 4.2.6 allowed.

3.5.2.1 Examination data: Part of a completed Certification test report shall be the shear strength data on
each weld, the average, the numbers of specimens with shear values outside of the set limits,
and the nugget diameters of each metallographic specimen. The examination page will have a
formal indication of the success or failure to meet the Certification criteria applicable to the
subject material combination.

- 15 -
 AMS-W-6858A SAE AMS-W-6858A

3.5.3 Test vs. production conditions: It is the purpose of Certification to show the results that can be
expected on production parts. It is necessary then to produce a correspondence between test
conditions and production conditions. The material conditions (3.5.2) must be replicated in parts
and material for weld tests. Any other production condition known to be relevant must be part of
the test. These include, for example, curvature of the parts, mandrels in lieu of electrodes, large
magnetic tools lying in the weld machine throat, narrow edge distances, offset or shaped
electrodes tips, time spans (minimum and maximum) between final preparation and welding, initial
and final surface preparations, and close spot spacing. A test of relevancy may be that the
average nugget diameters in the part will equal the average Certification nugget diameters when
produced by any machine weld heat seetings not further than 10 percent from the Certification heat
settings.

3.5.4 Certification test specimen configuration and examination requirements: Tests shall be as
specified in Tables VI Through IX and as shown in Figures 1 through 6.

- 16 -
AMS-W-6858A SAE AMS-W-6858A

TABLE VI. Certification specimen and examination requirements

- 17 -
AMS-W-6858A SAE AMS-W-6858A

TABLE VII. Certification specimen and examination requirements

- 18 -
AMS-W-6858A SAE AMS-W-6858A

TABLE VIII. Certification specimen and examination requirements

- 19 -
AMS-W-6858A SAE AMS-W-6858A

TABLE IX. Certification specimen and examination requirements

- 20 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 1. Spot welds in sheet

- 21 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 2. Close space spot welds in sheet

- 22 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 3. Spot welds in foil

FIGURE 4. Spot and seam welds in foil, peel specimen

- 23 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 5. Seam welds in sheet

- 24 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 6. Seam welds in foil, class A

- 25 -
 AMS-W-6858A SAE AMS-W-6858A

3.5.4.1 Locate all welds in all figures within ±0.060 inch or ±1.5 mm of specimen centers. Specimen
dimensions are given with a tolerance of ±0.060 inch or ±1.5 mm.

3.5.4.2 All multiple weld specimens shall be cut and dressed for testing after radiography is completed.

3.5.5 Thickness latitudes: Thickness combinations falling within the following limits shall not require
separate certified weld schedules provided that the certified nugget size average can be
reproduced with a weld heat (current) setting that lies within ±10 percent of the value established
by the original Certification schedule; all other conditions being the same.

(a) Foil - The variation in thickness (with regard to the original schedule) of outer sheet is within
±0.001 inch (±0.03 mm) and

The variation in the summed thickness of the combination is within ±0.003 inch (±0.08 mm).

(b) Sheet (outer) up to 0.040 inch (±1.02 mm), inclusive -

The variation in thickness of either outer sheet is within ±0.004 inch (±0.10 mm) and

The variation in the summed thickness of the combination is within ±0.006 inch (±0.16 mm).

(c) Sheet (Outer) Over 0.040 inch (1.02 mm) -

The variation in thickness of either outer sheet is within ±10 percent for Group 1 alloys, or ±20
percent for Groups 2 and 3 alloys and

The variation in the summed thickness of the combination is within ±10 percent.

3.5.6 Design allowable certification: A process weld schedule and conditions may be certified to produce
any strength requirement specified on a drawing by conforming to the Design Allowable
Certification requirements of this specification. This Certification method is limited to spot welds in
sheet that are not close space spot welds. Examination results shall be entered on the test report.
After acceptance, production setups shall be made to the schedule therein given, with the schedule
latitude of 4.2.6 allowed.

3.5.6.1 Design allowable Certification requires the identification of the required strength, (G), on the
applicable drawing. (See 3.1.3.) The Certification report shall state "These conditions certify a
value of ____.” The number entered shall be the value of the lowest strength specimen in 300
welds for Class A, 180 welds for Class B, and 50 welds for Class C. As reliability requirements
warrant, the denominator quantities (e.g., 300) may be changed by the part or systems designer
through drawing notes or design specifications with the approval of the procuring activity.

3.5.6.1.1 Specimen requirements are given in Figure 1a or 1b. Examination requirements are given in
3.6.1 for visible and 3.6.4.1.3 and 3.6.4.1.4 for mechanical criteria.

- 26 -
 AMS-W-6858A SAE AMS-W-6858A

3.5.7 Recertification: An existing weld schedule need not be recertified for other contracts or designs
provided all material conditions are equal. A change of location within a plant not involving a
change in power source or maintenance or parts replacement do not necessitate recertification.
Recertification shall be required if the machine is rebuilt or if significant operational changes are
made in it. Existing Certifications made under superseded revisions of this specification shall be
honored. However, recertification of a welding schedule may be required at any time if the
procuring activity doubts for any reason the ability of a machine to make welds satisfactorily with
the original Certification conditions.

3.6 Weld property requirements:

The weld acceptance criteria for Qualification and for Certification and production conducted under
the standard certification method are given under 3.6.1 for visible; 3.6.2 for radiographic; 3.6.3 for
metallographic; and 3.6.4 for mechanical. For Certification and production conducted under the
Design Allowable Certification weld acceptance criteria fall under 3.6.1 for visible, and 3.6.4.1.3 and
3.6.4.1.4 for mechanical criteria.

3.6.1 Visible criteria - spot welds and seam welds:

3.6.1.1 Sheet separation: Separation between an inner and outer member is excessive when it exceeds
a. or b., below, measured at a distance (radius) from the nugget center equal to 3 times the
radius of the minimum nugget size given in Table X for the thinner member.

a. Greater than 0.15 times the summed thickness of the outer sheet and the one adjacent to it,
or 0.006 inch (0.15 mm), whichever is greater, or

b. Greater than 0.003 inch (0.08 mm) between foil and the number adjacent to it.

- 27 -
 AMS-W-6858A SAE AMS-W-6858A

TABLE X. Nugget size (all groups)

3.6.1.1.1 Excessive separation is not acceptable on specimens.

3.6.1.1.2 Excessive separation is not acceptable on production work if it exceeds 0.03 times the Class A
or 0.10 times the Class B or C production welds sampled for examination, when the product is
raised to the next whole number.

3.6.1.2 Surface indentation: Indentations (see Figure 7) are not acceptable if their depth exceeds the
following limitations (where, t is the thickness of the indented outer member).

3.6.1.2.1 Excessive indentation is not acceptable on specimens.

3.6.1.2.2 Excessive indentation is not acceptable on production work if it exceeds 0.03 times the
samples of production welds measured in Class A welds; or in more than 0.10 times the
samples measured in Class B and C welds, when the product is raised to the next whole
number.

a. Sheet; Class A and B: 0.10 t or 0.005 inch (0.13 mm); whichever is greater.
b. Sheet; Class C: 0.20 t or 0.005 inch (0.13 mm); whichever is greater.
c. Foil; Class A and B: 0.30 t.
d. Foil; Class C: 0.40 t.
e. But when aerodynamic smoothness is a requirement, the outside indentation shall not
exceed 0.004 inch (0.10 mm) on sheet and 0.20 to on foil.

3.6.1.3 Production parts: Certain other imperfections are limited in quantity Table XI. The number of
visible imperfections shall be calculated by multiplying the factor shown in Table XI times the
number of welds inspected and raising the product to the next highest whole number. Parts or
lots with imperfections exceeding the quantity as determined from Table XI shall be rejectable.
Cracks open to the surface on seam welds shall be rejected and subject to a Material Review.

- 28 -
 AMS-W-6858A SAE AMS-W-6858A

FIGURE 7. Nomenclature for metallographic spot weld sections and seam weld transverse sections

TABLE XI. Visible external imperfections for production parts

3.6.1.4 Test specimens: Qualification, Certification, and production witness test specimens shall be
smooth, free of cracks, tip-pickup, pits and other flaws that indicate that the welds were made
with dirty electrodes, improperly prepared surfaces, or excessive heat and undue penetration.

3.6.2 Radiographic criteria - spot welds and seem welds:

- 29 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.2.1 Qualification: All Class A test welds shall be examined for compliance with the following:

a. Welds shall be free of cracks and flash.

b. No pore or instance of incomplete fusion shall have a linear dimension greater then 0.15 ST,
where ST is the nugget size as given in Table X.

c. No pore or instance of incomplete fusion shall extend into the outer 0.15 RT required clear
annulus as shown in Figure 8.

d. Porosity or incomplete fusion shall not have an aggregate area of greater than 5 percent in
Group 1 alloy, or 10 percent in Group 2 and Group 3 alloys, when seen in the nugget area of
the plane of the radiograph.

FIGURE 8. Nomenclature diagram of spot and scam weld radiographs

3.6.2.2 Standard Certification: All Class A tests welds shall be examined for compliance with the
following:

a. No crack, pore, or instance of incomplete fusion shall have a linear dimension greater than
0.15 ST.

b. No pore or instance of incomplete fusion shall extend into the outer 0.15 RT required clear
annulus as shown in Figure 8.

c. Porosity or incomplete fusion shall not have an aggregate area of greater than 5 percent in
Group 1 alloys or 10 percent in Groups 2 and 3 alloys, when seen in the nugget area of the
plane of the radiograph.

- 30 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.2.3 Production parts:

3.6.2.3.1 Class A or Class B parts: When radiography is required for Class A or Class B parts, the
following standards shall apply.

a. No class A or class B part is acceptable as it is with a no-nugget (dud) where a weld was
called for.

b. No Class A part is acceptable when any weld has a crack, pore, or instance of incomplete
fusion that either has a linear dimension greater than 0.15 ST or extends into the 0.15 RT
required clear annulus (also see 4.4.3).

c. No Class B part is acceptable when the number of welds in it that have cracks, pores, or
instances of incomplete fusion with a linear dimension greater than 0.15 ST or that extend
into the 0.15 RT required clear annulus is greater than 0.06 times the number of welds in
the part. A lot of parts may be rejected if the number of welds radiographed indicates that
0.06 of welds in the lot have imperfections above requirements (also see 4.4.3).

3.6.2.3.2 Class C parts: Radiography is not applicable to Class C parts.

3.6.3 Metallographic criteria: The metallographic examination and acceptance criteria are applicable to
Qualification, Standard Certification, and production witness specimens, and to production parts
when tested. Metallographic and visible nomenclature are shown in Figures 7 and 9.

3.6.3.1 Internal imperfections: Cracks, porosity, and instances of lack of fusion are completely
acceptable within the nugget of metallographic sections of test specimens, witness specimens,
and production parts, unless they contain:
a. An imperfection extending into the 0.15 RM required clear annulus zone.

b. An imperfection extending more than 0.25 times the thickness into that sheet (required clear
penetration zone) for Class A and Class B welds or 0.50t for Class C welds.

c. An imperfection with its largest dimension exceeding the following fraction of nugget size:
0.10 for Class A welds, 0.15 for Class B welds, and 0.25 for Class C welds.
3.6.3.1.1 For Certification and Qualification, Class A and Class B weld specimens shall not have flashes
or the imperfections of 3.6.3.1 a, b, and c, above.

3.6.3.1.2 For production witness specimens or parts sectioned for routine or postproduction tests the
work preceding the test lot shall be rejected and subjected to material review procedures, if the
imperfections of 3.6.3.1 a, b, and c, above, no-nuggets, or insufficient or excessive penetration
exceed the fraction of the test lot permitted by Table XII. The maximum number permitted in
each case shall be calculated by multiplying the factor shown in Table XII times the number of
welds in the test group and raising the product to the next highest whole number. For this
purpose, a test group shall be the instant accumulation of all metallographic sections run on a
production lot through its completion or through the end of the shift, whichever occurs first. The
provisions of 4.2.6, 4.4.3, and 4.4.4 shall continuously be applied.

- 31 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.3.1.3 Whenever a metallographic section of a production witness specimen or part reveals no-
nugget, welding shall be stopped and prior-made parts shall be rejected and subjected to
materials review procedures.

TABLE XII. Internal metallographic imperfections for production parts

3.6.3.2 Penetration: The extent of the nugget or fusion zone into the thickness of a joined member is
called penetration. Penetration shall be measured at lines located at 0.8 of the nugget size, as
shown in Figure 9.

3.6.3.2.1 Minimum penetration: Penetration shall comply with the following:

a. In two equal-thickness members, penetration shall exceed 0.2 times the thickness of each
member into each member. (See Figure 9a.)

b. In two unequal-thickness members, penetration shall exceed 0.2 times the thickness of the
thinner member, into each member. (See Figure 9b.)

c. In three or more thicknesses, penetration into the outer members shall exceed 0.2 times
the thickness of the thinner member into the thinner member and either; (1) 0.2 times the
thickness of the thicker outer member into the thicker outer member, or (2) the sum of the
center members plus 0.2 times the thickness of the thinner member into the thicker outer
member. (See Figure 9c or 9d.)

d. In three or more thicknesses, penetration into either side of an inner member shall exceed
either; (1) 0.2 times its own thickness, or (2) the measured value of penetration into its
adjacent partner; whose own minimum value is derived from c, above, it is an outer
member.

- 32 -
 AMS-W-6858A SAE AMS-W-6858A

FIGURE 9. Penetration minima

3.6.3.2.2 Maximum penetration: The upper limit of penetration for all resistance welds is the greatest
depth of the fusion zone into the thickness (t) of either outer sheet. Penetration shall not
exceed:

a. Group 1 materials. 0.8t for Class A and Class B welds,

0.9t for Class C welds.

b. Group 2 and 3 materials. 0.9t for all classes.

- 33 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.3.3 Nugget size: The minimum nugget size of Qualification, Standard Certification, and production
witness specimens shall be those specified in Table X. In welds of two members of unequal
thickness, the thinner member shall determine the required minimum nugget size at the
interface. In multiple thickness welds, the thinner of two members at any interface shall
determine the minimum nugget size from Table X, unless load carrying members are identified
for the Certification combinations, such as in Figure 10c and 10d. In this case, the lesser
thickness of the two load carrying members shall identify and be the determinant of minimum
nugget size for each interface lying between them. Each nugget shall be measured at the
subject interface plane on the metallographic section through the center of the nugget. Class A
foil weld size may be measured by the size of the fractured peel specimen instead of a
metallographic section, when the foil is an outer member.

FIGURE 10. Shear tests of three or more thicknesses

3.6.3.3.1 Qualification and Certification: The nugget size of all required metallographic sections will be
measured for each interface plane and recorded. From the values of each plane the average
size and the lowest size in the test group will be entered on the test record form. The peel test
of Class A foils, in addition to Table X, also requires that the largest weld not be more than 1.20
the size of the smallest.

3.6.3.3.2 Production specimens:

3.6.3.3.2.1 Nugget size measurement shall be the process control for close space spot welds and for
seam welds, and may be an alternate method to spot shear tests of sheet (shear tests of
production witness specimens, 3.6.4.1.2). Size shall be measured on metallographic
sections or peel specimens (3.6.3.3).

3.6.3.3.2.2 For Class A welds, the average size of welds in the test lot shall be not less than 0.9 times
the average nugget size recorded for Certification or not more than 0.020 inch (0.51 mm)
smaller than the Certification average, when the average is larger than 0.200 inch (5.08 mm).
In multi-ply welds, this applies only to the interfaces beneath outside members, while the
other interfaces must only meet the minimum requirements of Table X, determined in
accordance with 3.6.3.3.

- 34 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.3.3.2.3 Class B and Class C welds shall meet the requirements of Table X determined in accordance
with 3.6.3.3.

3.6.3.3.2.4 Welds which are examined for nugget size shall, at the same time, be visually examined for
fusion and for evidence of obvious internal defects, such as cracks, porosity, lack of fusion,
spits, and cladding inclusions. The incidence of these imperfections shall be limited by
Table XII.

3.6.4 Mechanical criteria:

3.6.4.1 Spot welds - sheet:

3.6.4.1.1 Minimum: Each and every shear text specimen (such as Figure 1a or Figure 1b) shall equal or
exceed the minimum strength required by Tables I through III. Improvement of method or
equipment shall be made after a test failure before a retest is made on a material combination.

3.6.4.1.1.2 Average: The average shear strength shall equal or exceed the applicable minimum average
strength specified in Tables I through III,

3.6.4.1.1.3 Consistency - Group 1 materials: For Class A and Class B welds, each of 90 percent of the
number of welds tested, shall have shear strength values between 0.875 and 1.125 times the
lot average. Each of the remaining 10 percent of the welds shall have shear strength values
between 0.75 and 1.25 times the lot average. For Class C welds, the spread between the
lowest and highest specimen shall be less than 0.35 times the lot average.

3.6.4.1.1.4 Consistency - Group 2 and 3 materials: For Class A and Class B welds, each of 90 percent
of the number of welds tested, shall have shear strength values between 0.9 and 1.1 times
the lot average. Each of the remaining 10 percent of the welds shall have shear strength
values between 0.8 and 1.2 times the lot average. For Class C welds, the spread between
the lowest and highest specimen shall be less than 0.33 times the lot average.

3.6.4.1.2 Production witness specimens: The spread between the lowest and highest specimen shall be
less than 0.35 times the applicable production test lot average.

3.6.4.1.2.1 Class A: The test lot average shall be not less than 0.9 times the Certification average and no
weld shall be less than the applicable minimum value shown in Tables I through III.

3.6.4.1.2.2 Class B and Class C: The test lot average shall be not less than the applicable value shown
in Tables I through III.

3.6.4.1.3 Design allowable certification:

3.6.4.1.3.1 Minimum: The value of the lowest specimen in the test lot must exceed the specified design
minimum.

3.6.4.1.3.2 Average: The test lot average (Ac) shall be recorded on the Certification report form.

- 35 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.4.1.3.3 Consistency: 95 percent of the number of specimens tested must have values greater than
0.875 time the test lot average (Ac).

3.6.4.1.4 Production witness specimens - design allowable certification:

3.6.4.1.4.1 The average strength of the production test lot shall be not less than 0.94 times Ac for Class
A welds, and not less than 0.90 for Class B and Class C welds, without consideration of the
provisions of 4.4.4.

3.6.4.1.4.2 No specimen in a group of three consecutive test lots (nine specimens) for Class A welds, or
two consecutive test lots (six specimens) for Class B and Class C welds may be less than
0.88 Ac for Class A welds, 0.83 Ac for Class B welds, and 0.80 Ac for Class C welds.

3.6.4.2 Spot welds - foil:

3.6.4.2.1 Certification and Qualification:

3.6.4.2.1.1 Class A: Each shear specimen shall equal or exceed the applicable values in Table IV. In
addition, the peel test run shall cause a button (plug) pull-out failure in 95 percent of the
welds tested. The remaining 5 percent may fail at the interface plane, but the cleavage in
each case shall be of a fused zone that is at least 0.80 times the average button size.

3.6.4.2.1.2 Class C: Peel tests shall cause a button pull-out failure in 85 percent of the welds tested. The
remaining 15 percent may fail at the interface plane, but there shall be evidence of fusion at
the interface in each case.

3.6.4.2.2 Production witness specimens: The required test lot shall be tested for compliance with the
peel requirements only of 3.6.4.2.1.1 or 3.6.4.2.1.2.

3.6.4.3 Seam welds - foil:

3.6.4.3.1 Qualification and Certification requirements:

3.6.4.3.1.1 Class A: A pressure test specimen as shown in Figure 6 shall show no evidence of leakage
through the joint while under a pressure greater than (1) 25 percent of the specimen burst
pressure for Qualification, or (2) the greatest pressure to be experienced by the weld in its
assigned service, as noted on the applicable drawing for Certification. Examination for leaks
shall begin not less than one minute after the specimen has reached its specified load. After
the leak test, the specimen shall be loaded to destruction. Failure shall occur in the metal
adjacent to the weld. Failure by cleavage fracture through the weld shall be cause for
rejection.

3.6.4.3.1.2 Class C: The weld specimen shall be tested in peel. Failure occur by tearing of the metal
adjacent to the weld nugget for more than 85 percent of the weld length. The remaining
portion of the weld length may fail by fracture across the weld in the faying plans, but
unbroken fusion shall be evident.

- 36 -
 AMS-W-6858A SAE AMS-W-6858A

3.6.4.3.2 Production witness specimen:

3.6.4.3.2.1 Class A: The weld specimen shall be tested in peel. Failure shall be by tearing of the metal
adjacent to the weld nugget for more than 95 percent of the weld length. The remaining
portion of the weld length may fail by fracture across the faying plane, but the smallest nugget
size (fusion) shall be not less than 0.80 times the average nugget size.

3.6.4.3.2.2 Class C: The weld specimen shall be tested in peel and shall meet the requirements of
3.6.4.3.1.2.

3.6.4.4 Unusual specimen configuration: Specimens of unusual configuration shall be tested so as to

stress the load carrying members, as specified on the applicable drawing or part specification.
Some examples of joints with three or more members are shown in Figure 10. The strength
requirements of such combinations shall be determined from Tables I through IV based upon the
requirement for the thinner loaded member unless otherwise specified on the applicable drawing
or part specification. Test specimen members not loaded (unshaded) may be coupons laid
crosswise or parallel to the load, may be short pieces, or may be bent out of the way of the test
fixture. The minimum width of the specimen and overlap shall be based on the thickness of the
thinnest loaded member.

4. QUALITY ASSURANCE PROVISIONS:

4.1 Responsibility for inspection:

Unless otherwise specified in the contract, the contractor is responsible for the performance of all
inspection requirements as specified herein. Except as otherwise specified in the contract, the
contractor may use his own or any other facilities suitable for the performance of the inspection
requirements specified herein, unless disapproved by the Government. The Government reserves
the right to perform any of the inspections set forth in the specification where such inspections are
deemed necessary to assure supplies and services conform to prescribed requirements.

4.2 Production quality control:

4.2.1 Production welding and inspection: Production welding shall be so accomplished as to obtain
welds of consistent strength above the prescribed minimum and of acceptable metallographic
structure, rather than welds of maximum strength without due regard to metallographic structures.
The requirement for acceptable metallographic structure is not required by this specification when
Design Allowable Certification is used. Welds shall be tested by the contractor under the
surveillance of his authorized inspector.

4.2.2 Schedules: Qualified personnel in each plant shall be responsible for the control of machine
settings and all welding schedules. Certified schedules shall be available for examination by any
authorized inspector at any time.

- 37 -
 AMS-W-6858A SAE AMS-W-6858A

4.2.3 Weld location: Welds shall be located as specified on the engineering drawing or applicable
document. The edge distance of each weld shall be such that no deformation or bulging will occur
at the edge of the sheet. Jigs shall be used whenever necessary to locate welds as specified
above.

4.2.4 Test specimens: All test specimens, except Qualification specimens, shall conform to the
production parts they represent with respect to material, thickness combination, and surface
condition or preparation.

4.2.4.1 Witness specimens: Production witness specimens shall be run with production weld conditions
and either Certification specimens or a simulation of the production part. When production
conditions exist that were not applied during Certification, but cause machine settings to differ
from Certification settings so as to exceed the permitted latitude (4.2.6), the Certification shall be
run again with the subject critical production conditions included. Examples of such production
conditions are, but are not limited to, magnetic material in the machine throat, curvature of the
part, spot spacing, and part width.

4.2.5 Surface resistance: A daily check of the surface resistance in michohoms shall be made for Class
A, Group 1 welds. A minimum of five readings shall be made 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 Certification of welding
schedules or cleaning procedures, and the values of the surface resistance shall not exceed the
limits of consistency and maximum values established at that time.

4.2.6 Control adjustments: When adjustment of the control settings is desirable, the settings may be
varied by ±5 percent from the established certification values, or by ±10 percent when only one
setting is adjusted. Rounded to the nearest unit this shall be called the permitted schedule latitude
adjustment. Production welds must be made within ±5 percent of the settings used on witness
specimens. If satisfactory welding cannot be maintained within these limits of adjustment, welding
shall be stopped and the machine shall be checked for faulty operation. It can be shown that
conditions other than certified welding schedule conditions were the cause of faulty welding and
with the correction of these conditions the original certified welding schedule is capable of
producing acceptable welds, the establishment of a new certified welding schedule will not be
required. For Class A welds, also see 4.4.4.

4.3 Production witness welds:

The following welding shall accompany the welding of production parts to represent properties, such
as material, thickness combinations, and surface conditions, of production parts not themselves
tested. Results of these tests shall be maintained in a register by the welding machine. The
witnessing of welding test lots by contractor quality control personnel may or may not be required by
the contractor at his discretion.

- 38 -
 AMS-W-6858A SAE AMS-W-6858A

4.3.1 Test lots: Test lots of witness specimens for production parts shall be as noted below. Each test lot
shall consist of the number and configuration of test specimens and method of evaluation as
specified in Table XIII. Any of the quantities specified my be made an a simulation of the
production joint or a production part.

a. Preproduction lot: 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. Routine lot: At specified points or intervals in production welding and after an electrode
change, or other minor welding equipment change.

c. Postproduction lot: At the end of each production work day or after the completion of a
production lot. The last routine test lot may be entered as the postproduction test lot if the
production work lot is finished before half of the required routine time interval has elapsed.

TABLE XIII. Production witness welds, test lots

- 39 -
 AMS-W-6858A SAE AMS-W-6858A

4.3.2 Testing requirements:

4.3.2.1 Class A welds shall be accompanied by the following test lots:

a. Preproduction lot
b. Routine lot at each 1 hour interval or minor equipment change
c. Postproduction lot.

4.3.2.2 Class B welds shall be accompanied by the following test lots:

a. Preproduction lot
b. Routine lot at each 2 hour interval or minor equipment change
c. Postproduction lot

4.3.2.3 Class C welds shall be accompanied by the following test lots:

a. Preproduction lot
b. Postproduction lot

4.3.3 Table XIII identifies the kind and quantity of specimens required for each lot whose frequency is
specified in 4.3.2. Each line of Table XIII identifies the kind and amount of welding in the test lot for
each material group and kind of weld. The lengths of seam welds or specimens that the
referenced figures give may be reduced to the values given in this table for these production tests.

4.3.3.1 Single spot welds established by the Standard Certification procedure may be controlled either
by mechanical strength (3.6.4.1.2) or by nugget size with soundness examination (3.6.3.3). Spot
welds established by the Design Allowable Certification are only required by this specification to
meet the requirements for visible criteria of 3.6.1 and strength criteria of 3.6.4.1.4.

4.3.3.1.1 When mechanical tests are used to witness production weld compliance of spot welds
established by the Standard Certification procedure, three welds will be added for
metallographic examination (3.6.3.3) to the preproduction lot for Class A and Class B welding,
and three welds for metallographic examination will be added to every fourth routine lot for
Class A welds.

4.3.3.2 All specimens shall be visually examined in accordance with 3.5.1. Radiographic examinations of
specimens shall not be required, unless otherwise specified in the applicable drawing or part
specification.

4.3.3.3 The contractor may substitute nondestructive evaluation for routine lot tests upon approval of the
procuring activity, provided he can demonstrate that the evaluation system will identify welds
complying with strength or size requirements with a 99.5 percent reliability.

- 40 -
 AMS-W-6858A SAE AMS-W-6858A

4.4 Inspection of production parts:

4.4.1 External imperfections: Welds shall be examined for compliance with the visible criteria (3.6.1) by
determining the presence and number of imperfections on the following basis.

a. Class A parts - All welds.

b. Class B and Class C parts - On sampling plans established by the contractor and approved by
the procuring activity.

4.4.2 Internal imperfections: Inspection for internal imperfections in production parts is not normally
required. When specified on the applicable drawing or part specification, the inspections shall be
made on randomly selected production parts. At the option of the contractor, inspection may be
accomplished by:

a. Nondestructive radiographic examination (3.6.2.3.1)

b. Destructive metallographic examination (3.6.3).

4.4.3 Distribution of imperfections: Imperfections are instances of external or internal discontinuities or

departures from specified dimensions. They begin to affect the weld and welded assemblies when
they achieve the dimensions of:

a. 3.6.1.1.2, 3.6.1.2.2, and 3.6.1.3 for visible

b. 3.6.2.3.1 for radiographic
c. 3.6.3.1.2 for metallographic sizes.

4.4.3.1 Production parts and lots are acceptable as welded with imperfections of the sizes stipulated,
provided the quantity does not exceed:

a. 3.6.1.1.2, 3.6.1.2.2, and 3.6.1.3 for visible

b. 3.6.2.3.1 for radiographic
c. 3.6.3.1.2 for metallographic kinds.

4.4.3.1.1 The sum of all these imperfections shall not exceed 0.10 of the sample in Class A parts, 0.15 in
Class B parts, and 0.20 in Class C parts. Spot welding work is acceptable without repair, when
the quantities of imperfections are less than those permitted by a, b, and c, above, and the
imperfections are randomly distributed and not clustered in one area, in one part, or in a group
of parts.

4.4.3.2 When imperfections (of the size stipulated by 4.4.3) exceed the quantity limited by the
paragraphs referenced in 4.4.3.1, but do not exceed twice that quantity limit, the manufacturer
may use standard repair procedures to make repairs without recourse to salvage or materials
review action. Such procedures shall be approved by the procuring activity prior to their use.

- 41 -
 AMS-W-6858A SAE AMS-W-6858A

4.4.4 Deterioration of welding: If investigation of imperfections in welding indicates that welding quality
has deteriorated due to clear causes, (for example, swaged or improperly cleaned tips) and those
causes are corrected so that acceptable welds (compared to Certification requirements) are made,
then a new Certification weld schedule will not be required. Under conditions where the
Certification weld schedule does not produce acceptable welds within the weld schedule latitude
(4.2.6), then the Certification shall be voided and the machine shall be requalified. All Class A weld
schedule Certifications for that machine shall be discarded and new Certifications shall be
established.

4.4.5 Tack welds: Tack welds shall not be used on Class A parts unless they are allowed on engineering
drawings or applicable documents and are finally removed, or completely covered by subsequent
production welding. Tack welds require no tests and need be only of sufficient strength to fulfill
their temporary function. They are not subject to this specification except insofar as residual
imperfections may be detrimental to the production part. The imperfections shall not exceed limits
established for production parts.

5. PACKAGING:

This section is not applicable to this specification.

6. NOTES:

6.1 Intended use:

This specification in intended to establish the basic controlling factors in the resistance welding
process through Qualification of equipment and Certification of weld schedules, designation of
material combinations, methods of preparing materials, and for methods of process control in the
resistance welding.

6.2 Definitions:

6.2.1 Resistance spot welding: A resistance welding process which produces coalescence at the faying
surfaces in one spot by heat obtained from the resistance to electric current through the work parts
held together under pressure by electrodes. The size and shape of the individually formed welds
are limited primarily by the size and contour of the electrodes.

6.2.2 Resistance seam welding: A 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. The resulting weld is a series of overlapping resistance
spot welds made progressively along a joint by turning wheel electrodes.

6.2.3 Close space welds: Close space welds art spot welds on sheet placed less than two diameters
apart, center to center. Such proximity requires more power than other spot welds.

6.2.4 Weld parameters: Weld parameters are machine settings or adjustments, such as, but not limited
to, weld current, weld time, and electrode force.

- 42 -
 AMS-W-6858A SAE AMS-W-6858A

6.2.5 Weld conditions: Weld conditions are all circumstances surrounding the making of a given weld,
including material configuration and kind, material preparation, electrode shape, machine number
and all weld parameters. Weld conditions that are relevant require documentation on the
suggested forms.

6.2.6 Production witness specimens: Welds of specimens made in production setups and destructively
tested to provide data on the qualities of production welds which cannot be tested.

6.2.7 Sheet: A thickness, for the purpose of this specification, of more than 0.008 through 0.250 inch
(0.02 through 6.35 mm).

6.2.8 Foil: A thickness of 0.008 inch (0.02 mm) or less.

6.2.9 Nugget: The weld metal (cast) joining the parts in spot, seam, or projection welds.

6.2.10 Nugget size: The diameter of a spot weld nugget or the width of a seam weld nugget measured at
the plane of the faying surfaces.

6.2.11 Metallographic section: A metallographic section is a transverse cut on the diameter of a spot weld
or across a seam weld, or a longitudinal cut down the center of a seam weld, polished down to the
near center of the weld and often etched to accentuate the metallographic structure. Microsections
are prepared for examination at magnifications between 25 and 40X. Macrosections are prepared
for examination at magnifications up to 10X.

6.2.12 Peel test: A mechanical test in which the corners (or sides) of seam or spot welded foil or sheet
members are gripped and pulled apart to determine if the joint fails by delamination, by fracture of
a cleaved surface, or by tearing of a button (plug) out of the parent material. Delamination, in
contrast to fracture, is a sign of no fusion between the two adjacent members. A button or plug,
which is pulled out of the removed member, is not necessarily equal in size to the cast nugget
underlying it.

6.3 Solid state corona or diffusion weld effects:

6.3.1 The relation between weld strength and nugget size should be kept clear. Weld strength, normally
a regular consequence of weld area, varies often from strict proportion because of the possible
existence of a variable solid state weld around the cast nugget. Because this solid state weld
varies widely with subtle surface conditions, the melted nugget diameter size itself is a superior
index of the welding process consistency. The solid state corona, or diffusion weld confuses
results by adding strength to the nugget strength. When it is occasional and strong, it causes a
wide spread of specimen strengths. When it occurs regularly, Certification weld strengths may be
considerably higher than the nugget strengths alone.

6.3.2 Certifications must be run in such a manner as to be free of the corona strength additions that may
not occur in production parts (Group 1 in particular). On the other hand, when a diffusion weld can
be produced so reliably as to be an integral and counted quality of Certification, then the production
parts should be handled so that they will have the same diffusion weld in them.

- 43 -
 AMS-W-6858A SAE AMS-W-6858A

6.4 Design consideration:

The designer's ultimate interest lies in the strength of his assembly; this may be dependent either on
average strength of the welds in a group or on a guaranteed minimum strength of each weld. The
difference may be illustrated by the examples in 6.4.1 and 6.4.2.

6.4.1 A given weld schedule produces 300 welds that have an average strength of 1100 pounds and the
lowest spot is 600 pounds. The guaranteed strength (G) in this case is 600 pounds. The
guaranteed strength is usually the basis for design calculations, not the average strength of the
welds. Thus, two members that must withstand a 33,000 pound load will be designed for 55 welds,
(for example, 33,000 divided by 600). If the average spot strength was used, then only 30 welds,
(for example, 33,000 divided by 1100), would be required.

6.4.2 Consider then, the affect of a weld schedule that raises the average, while lowering the guarantee.
For example, an average of 1200 pounds with a guarantee of 500 pounds. Then, in spite of the
average strength rise, the number of welds required would rise in this case to 66 welds, (for
example, 33,000 divided by 500).

6.4.3 For economy’s sake, the designer should establish when an entire joint depends on each weld
meeting the guarantee (G) and when the weld array operates as a gang. In the latter, the strength
of the joint can indeed be calculated to be the number of the welds times the weld average
strength. With gang shear strength, the numerical example in 6.4.2 has the joint strength well
satisfied by 28 welds, (for example, 33,000 divided by 1200 equals 27.5).

6.5 Certification and Production comparisons:

A graphical method of showing the comparison of Certification and Production requirements is

shown in two versions in Figures 11a and 11b.

- 44 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 11a. Graphical summary of standard certification and

production strength requirements
(Example given for Class A, Group 1)

- 45 -
AMS-W-6858A SAE AMS-W-6858A

FIGURE 11b. Graphical summary of design allowable certification

and production strength requirements
(Example given for Class A, all groups)

PREPARED UNDER THE JURISDICTION OF AMS COMMITTEE “E”

- 46 -