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NO. - ----AEROSPACE WELDING STANDARDS
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FOR THE MINUTES OF THE MEETING OF AMEIUCAN ORDNANCE ASSOCfATION
I
The term "Welding Standard" is one which must be qualefied since
there are many dfjfferent classifications. There are, for example, welding
,
standards for bridge and building construction, automotive manufacturers,
machinery manufacuurers, and, of course, space vehicle manufacturers.
To
each of the functional segments of an organization, producing welds to meet
the requirements
vr
a welding standard has a different meaning:
(1) to
engineering, it is a necessary requirement to fulfill the design function;
(2) to manufacturing, it means additional operations, precise dimensional
tolerances, elaborate tooling and pre-production test sampling; (3) to
quality control, 5t is the responsibility to select inspection points within
the manufacturing operations and to apply NM: methods to insure that the
product meets engineering requirements; and (4) to top management, producing
'
welds to meet the requirements of a weld standard means much higher costs.
Fundamentally, the'basic objective of any welding application is
to obtain a weld which will perform the function for which it: was designed.
The problem then, in establishing an aerospace welding standard, is one of
determining what parameters must be controlled and the limits of acceptability
'
to meet the design function.
If perfect welds could be produced consistently with 100% reliability,
the problem would be solved. This is not possible, of course, since a
perfect weld would be one having absolutely no defects and having 100%
joint efficiency based on mechanical, metallurgical, and physical properties.
�Thds means thas realistic welding standards must be established which
require a minimum level of performance based on what engineering can
tolerate and what manufacturing can produce.
Even though the present welding
standard is based on this philosophy, the. question still arises, "Is the
high quality required by this standard really necessary?"
In reviewing
the product history, the answer is quite evident.
From the first missiles and rockets constructed, many failures which
occurred during proof testing of the components have been traced to poor
quality welds. Natueally, with each incident, engineers became educated
as to the type and magnitude of defects which can be tolerated; thus, the
standard is modified to correct the deficiences.
As an example of failures which have occurred in the past, Figure 1
shows a portion of a weld from a missile propellant tank,whichexhibits
transverse weld cracks.
Radiographic examination of the welds in this tank
revealed porosity in excess of specification requirements. Prior to this
failure, there were no requirements for 100% radiographic inspection.
quality control of these welds was based on the establishment of welding
schedules which produced welds to meet the specification requirements.
Then the operator and equipment were relied upon to produce the same weld
quality in the production part.
Upon completion of the failure analysis, it was concluded that the
failure resulted from very low ductility in the weld, with porosity being a
contributing factor.
That is, the weld could not plastically deform with
thgt base material without failure. This is an example of a defect resulting from
dissimilar mechanical properties between the base material and filler metal.
�Thus, in order to have a complete welding standard, the mechanical
properties 0f.a welded joint must be defined and controlled.
Corrective action for this failure was to modify the welding standard,
incorporating a different filler metal and, in addition,-arequirement was
imposed for 100% radiographic inspection of all subsequent welds to insure
that porosity w~uldbe within specifications.
As another example, Figure 2 shows a failure in ground support
equipment (54-in&
diameter water line flange-to-pipe weld) which occurred
during cyclic pressure proof testing. The crack shown here initiated at
the toe of the weld as a result of undercut.
The undercut was noted to
be more severe on the side of the forged flange, which happened also to be
the weaker material.
This, of course, necessitated tightening the allowable
undercut requirements for steel weldments in certain ground support equipment.
The above examples illustrate typical defects which have caused failure
and which must be controlled to insure weldment reliability. Without
attempting to define or describe in detail all of the parameters which
form a welding standard, the following may serve as a generalized description:
a.
Metallurgical Compatibility of Base Material and Filler Material
A filler metal must be selected which is metallurgically compatible
with the base material.
The filler metal should not present a
metallurgical discontinuity (i. e. , formation of brittle phases)
which could cause premature failure, nor should there be a high
electro-chemical potential.difference between the weld and base
metal which would invite corrosion. Stress corrosion characteristics
of the deposited filler metal must also be considered in the selection.
�b, Nechahical Properties of the Welded Joint
In order to have a high degree of confidence in the mechanical
properties of a weldment, a 1arge.amountof data must be obtained
and statistically analyzed. If, for example, the ductility or
tensile strength of the weld is below that of the base material,
the des$gners may compensate by increasgng the thickness of the
weld joiht.
c. Welding Brocess
~tandarazationon a particular welding process must be based
on its adaptability to the product and the quality of weld which
can be produced. Subsequently, the welding procedure must be
docum@nted, listing allowable variations for each variable in the
proce4s.
Joint preparation and fit-up tolerances must be
established to maintain good weld quality and consistent
mechanioal properties. Simultaneously, and in combination with
the det-ination
of mechanical properties, acceptance limits
for both internal and external defects must be established.
Having in mind the parameters which must be controlled, the next
objective is to establish what tools will be used to insure control.
a.
Research and Development
Through research and development, the optimum filler wire for the
specific application may be determined together with the optimum
welding process, joint design, mechanical properties, defect
limitations, etc.
�b.
Measurement of Dimensional Tolerances
The component p a r t s must be dimensionally i n s p e c t e d t o i n s u r e
p r o p e r f i t - u p and proper joint p r e p a r a t i o n .
P o s t weld inspection
of dimensions i s necessary t o i n s u r e t h a t metal d i s t o r t i o n h a s
n o t renPered t h e p a r t unusable,
c.
Visual I n s p e c t i o n
V i s u a l i n s p e c t i o n , a v e r y important t o o l , i s i n continuous u s e
b e f o r e , d u r i n g , and a f t e r t h e welding operation.
d.
Sampling
Often i t i s b e n e f i c i a l , o r even necessary, t o make pre-production
and/or post-production samples which a r e s u b j e c t e d t o d e s t r u c t i v e and
n o n d e s t r u c t i v e t e s t s f o r g r e a t e r assurance of t h e q u a l i t y w i t h i n
t h e product.
e.
Radiography
Radiography i s g e n e r a l l y considered a p o s t weld i n s p e c t i o n t o o l
f o r determining i n t e r n a l q u a l i t y .
f,
Penetrants
Most s u r f a c e d e f e c t s which a r e not v i s i b l e t o t h e naked eye can
,
g.
be d e t e c t e d by p e n e t r a n t i n s p e c t i o n .
Magnetic P a r t i c l e
This i n s p e c t i o n t o o l i s used w i t h magnetic m a t e r i a l s f o r d e t e c t i n g
s u r f a c e o r s l i g h t l y subsurface d e f e c t s .
h.
Ultrasonic
U l t r a s o n i c i n s p e c t i o n may be used f o r both s u r f a c e and i n t e r n a l
defects.
�i, Eddy :Current
Eddy current inspection, also, may be used for surface and internal
defects.
It is obvious that no one of the above tools, by itself, could assure.
a high quality weldment.
In almost all instances, at least three of the
above tools are used: namely, (1) research and development, (2) measurement
of dimensional twlerances, and (3) visual inspection.
Determining a welding standard for the major structural material used
in the S-IC booster stage of the Saturn V vehicle, as discussed below,
will serve as a guide for determining a welding standard and for illustrating
the use of several of the tools.' The platerial used was aluminum alloy
2219-T87. Folluwing the selection of type 2319 filler metal as .the optimum
commercially available filler, welds were made in 1/4, 1'/2, 3/4, and 1-inch
thick plates using both the consumable and nonconsumable electrode processes in the flat, vertical,' and horizontal welding positions.
Discontinuities,such as weld undercut and joint misfit (root openings
and misalignment), were introduced purposely to establish tolerable limits.
All panels were radiographed, noting both internal and external defects in
the weld. Figure 3 shows an example of internal defects which were
tested to evaluate their effect on strength properties, This is a mild
example, for many of the weldments contained a vast amount of internal
defects.
Ultrasonic inspection was also performed for correlation to
radiographic defects and for determination of the sensitivity of ultrasonic
testing.
�T e n s i l e sgecimens and specimens f o r m e t a l l u r g i c a l examination were
s e l e c t e d from Ehe welded panels t o i n s u r e ample r e p r e s e n t a t i o n of a l l
t y p e s of d e f e c t s ,
L a t e r , t h e mechanical p r o p e r t i e s were compared t o t h e
recorded d e f e c t s , and d e f e c t l i m i t a t i o n s were e s t a b l i s h e d .
If the strength
of a specimen having a s p e c i f i c type and magnitude of d e f e v t dropped
below t h e strenggh s c a t t e r f o r sound welds, t h a t magnitude of d e f e c t was
considered unacceptable f o r s t r u c t u r a l q u a l i t y weldments.
Among t h e i n t e r e s t i n g r e s u l t s were t h e l o c a t i o n and s i z e e f f e c t of
p o r o s i t y o r i n c l u s i o n s on weld s t r e n g t h .
Very l a r g e d e f e c t s l o c a t e d i n
t h e c e n t e r of t h e weld had l e s s e f f e c t upon s t r e n g t h than small d e f e c t s
along t h e f u s i o n l i n e , which i s t h e usual path of f a i l u r e when t h e weld
reinforcement i s not removed.
For a given s i z e c a v i t y o r i n c l u s i o n , the
s t r e n g t h of a t e n s i l e specimen decreased a s t h e d e f e c t approached t h e normal
p a t h of f a i l u r e o r t h e f u s i o n l i n e .
Another magnitude of p o r o s i t y which caused considerable l o s s i n
s t r e n g t h , as k l d u s t r a t e d i n Figure 4 , i s macro p o r o s i t y l o c a t e d along
t h e fusion line,
This might be d e t e c t e d by radiography, depending on t h e
f u s i o n zone geolaetry.
I n t h i s p a r t i c u l a r i n c i d e n t , it was d e t e c t e d
because of i t s o r i e n t a t i o n , b u t , i n o t h e r i n s t a n c e s where i t i s not
p a r a l l e l t o t h e beam of X-rays, it i s not detected.
I n one of t h e welded
p a n e l s , t h e s t r e n g t h of t h e specimens ranged from 40 t o 44 K s i , w i t h t h e
exception of two specimens, one being 33 and t h e o t h e r 35 K s i l o c a t e d
s i d e by s i d e .
There was no explanation f o r t h e l o s s i n s t r e n g t h ; t h e
f r a c t u r e s appeared normal t o t h e naked eye, but upon examination a t 20
�power m a g n i f i c a t i o n , very f i n e p o r o s i t y was q u i t e evident over t h e e n t i r e
f r a c t u r e surfkce.
Lack of p e n e t r a t i o n , t o t h e degree shown i n Figure 5 , was n o t d e t e c t a b l e by normal radiographic procedures.
d i d d e t e c t t h i s magnitude of d e f e c t .
U l t r a s o n i c i n s p e c t i o n , of course,
I n Figure 6 , t h e degree of incom-
p l e t e penetratzon i s very small but s e r i o u s l y lowers t h e s t r e n g t h .
In
t h i s c a s e , it was not d e t e c t e d by u l t r a s o n i c s o r , a t l e a s t , could n o t
be resolved.
TMs unpenetrated zone i s s i m i l a r t o a forge weld because
of t h e h e a t from welding and t h e pressure from shrinkage,
t h e r e was a l o s s i n s t r e n g t h .
Nevertheless,
Magnified views of t h i s zone show how
g r a i n s have a tendency t o grow a c r o s s t h e unpenetrated l i n e which i s no
l a r g e r than a g r a i n boundary,
Figure 7 shows t h e l o s s i n s t r e n g t h a s . a r e s u l t of incomplete
penetration.
It i s obvious from t h e s e d a t a t h a t incomplete p e n e t r a t i o n
cannot be t o l e r a t e d ; t h u s , methods f o r p o s i t i v e i d e n t i f i c a t i o n must be
developed.
T h i s d e f e c t i s p r e s e n t l y being c o n t r o l l e d by t h e e s t a b l i s h m e n t
of welding schedules recording t h e c u r r e n t , v o l t a g e , t r a v e l speed, and
w i r e f e e d speed necessary t o a s s u r e complete p e n e t r a t i o n ;
F u r t h e r , pre-
production test samples a r e made and checked before each production weld,
One p o s s i b l e method f o r p o s t i n s p e c t i o n c o n t r o l i s t h e use of a
modified square b u t t j o i n t wherein a shallow groove i s machined down t h e
c e n t e r of t h e a b u t t i n g p l a t e s , a s shown by t h e j o i n t c r o s s - s e c t i o n i n
F i g u r e 8.
If p e n e t r a t i o n i s n o t complete, a void i s p r e s e n t a t t h e c e n t e r
of t h e p l a t e which i s d e t e c t a b l e by radiography.
8
This i s i l l u s t r a t e d i n
�Figure 9.
(i.e.,
Id was found t h a t grooves, w h o s e . t o t a 1 width equal t o .O4O-inch,
.020-inch deep i n each p l a t e ) , would s h r i n k t i g h t and would not be
d e t e c t e d by radiography.
P r e s e n t l y , s a t i s f a c t o r y r e s u l t s 'can be obtained
w i t h a 0.030-Anch deep by 1 / 3 T width groove i n t o each a b p t t i n g edge.
R e l i a b i l i t y o r c t h e j o i n t h a s not been f u l l y e v a l u a t e d , but f u r t h e r t e s t i n g
i s being conduoced.
I n c o n s i d e r i n g radiography a s a t o o l f o r i n s p e c t i n g weldments i n
t h i c k p l a t e aluminum a l l o y s , i t was p o s s i b l e t o d e t e c t p o r o s i t y approximately 1%of t h e m a t e r i a l t h i c k n e s s and undercut of t h e same magnitude.
Defects which could not be r e l i a b l y d e t e c t e d were micro p o r o s i t y , l a c k
of p e n e t r a t i o n , l a c k of f u s i o n ( i . ' e , , t h e t i e - i n between t h e f i l l e r metal
and t h e base m e t a l ) , and t i g h t cracks o r c r a c k s which were not p a r a l l e l
t o t h e beam of X-rays.
Radiography, of course, i s only one t o o l f o r
i n s u r i n g a high q u a l i t y weld, and i t s l i m i t a t i o n must be defined Eor each
application.
This c e r t a i n l y i n d i c a t e s t h a t more than one i n s p e c t i o n t o o l
i s necessary t o p r o p e r l y e v a l u a t e weld q u a l i t y .
Similar definition,of
l i m i t a t i o n s can, and should, be obtained f o r each of t h e i n s p e c t i o n t o o l s
f o r a given a p p l i c a t i o n .
I n summary, an a e r o s p a c e welding standard must encompass (1) m e t a l l u r g i c a l c o m p a t i b i l i t y of base metal and f i l l e r m e t a l , (2) mechanical
proper-
ties of t h e welded j o i n t , and (3) t h e welding process ( d e f e c t l i m i t a t i o n s ,
s t a n d a r d i z a t i o n of equipment, e t c , ) .
The t o o l s a v a i l a b l e f o r i n s u r i n g
h i g h q u a l i t y have been reviewed, and i t h a s been shown why t h e h i g h q u a l i t y
welds a r e necessary.
�Although welding i s not the only i t e m which can cause the f a i l u r e
of a v e h i c l e , i t i s a f a c t that poor welds'can be a s o l e cause.
The
succeae of agaoa vekLcle structures dependslargely upon the quality af
welding and tihe completeness of the welding standards.
�FIGURE 1
Transverse Weld Cracks i n Aluminum Alloy Weldrnen't
FIGURE 2
Longitudinal Crack A t The Toe O f The Weld In A
S t e e l Weldrnent
�FIGURE 3
Radiographic Reproduction Of Weld Test panel
FIGURE 4
Macro-Porosity In Aluminum Alloy Weld Test Panel
�FIGURE 5
Incomplete Penetration Not Detected By Normal
Radiographic Procedures
�(c)
FIGURE 6
200X
Incomplete Penetration Having Overlap Of Heat Affected Zone
�-
50
-
45
-
40
-
35
-
30
-
-
25
-
-
20
-
I
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WELDED 2219.787 ALUMINUM ALLOY
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SOUND WELDS
X-
WELDS WITH LACK OF PENETRATION
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THICKNESS, INCHES
FIGURE 7
Loss In Weld Strength Resulting From Incomplete
Penetration
�FIGURE 8
Cross-Section Of Modified Square Butt Joint Design
�(b)
FIGURE 9
Weld In Modified Square Butt
Joint Design
50X
�
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
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Saturn V Collection
Relation
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<a href="http://libarchstor.uah.edu:8081/repositories/2/resources/60" target="_blank" rel="noreferrer noopener">View the Saturn V Collection finding aid in ArchivesSpace</a>
Identifier
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Saturn V Collection
Description
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<p>The Saturn V was a three-stage launch vehicle and the rocket that put man on the moon. (Detailed information about the Saturn V's three stages may be found<span> </span><a href="https://www.nasa.gov/centers/johnson/rocketpark/saturn_v_first_stage.html">here,<span> </span></a><a href="https://www.nasa.gov/centers/johnson/rocketpark/saturn_v_second_stage.html">here,<span> </span></a>and<span> </span><a href="https://www.nasa.gov/centers/johnson/rocketpark/saturn_v_third_stage.html">here.</a>) Wernher von Braun led the Saturn V team, serving as chief architect for the rocket.</p>
<p>Perhaps the Saturn V’s greatest claim to fame is the Apollo Program, specifically Apollo 11. Several manned and unmanned missions that tested the rocket preceded the Apollo 11 launch. Apollo 11 was the United States’ ultimate victory in the space race with the Soviet Union; the spacecraft successfully landed on the moon, and its crew members were the first men in history to set foot on Earth’s rocky satellite.</p>
<p>A Saturn V rocket also put Skylab into orbit in 1973. A total of 15 Saturn Vs were built, but only 13 of those were used.</p>
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Identifier
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spc_stnv_000052
Title
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"Aerospace Welding Standards for the Minutes of the Meeting of American Ordnance Association."
Creator
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American Ordnance Association
Date
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1963-01-01
Temporal Coverage
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1960-1969
Subject
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Saturn Project (U.S.)
Aerospace industries
Space vehicles
Welding
Type
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Minutes (administrative records)
Text
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Saturn V Collection
Box 8, Folder 2
University of Alabama in Huntsville Archives, Special Collections, and Digital Initiatives, Huntsville, Alabama
Is Part Of
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Aerospace Welding Standards for the Minutes of the Meeting of American Ordnance Association
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en
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spc_stnv_000051_000074