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Nondestructive Evaluation Techniques : Radiography
Radiograph Interpretation - Welds
In addition to producing high quality radiographs, the radiographer
Radiographer - Any individual who performs or who, in attendance at the site where the sealed source or
sources are being used, personally supervises radiographic operations and who is responsible to the licensee
for assuring compliance with the requirements of these regulations and the conditions of the licenses.
must also be skilled in radiographic interpretation
Radiographic Interpretation - The determination of the cause and significance of subsurface discontinuities
indicated on the radiograph. The evaluation as to the acceptability or rejectibility of the materials is based
upon the judicious application of the radiographic specifications and standards governing the material.
. Interpretation
Interpretation - The determination of the source and relevancy of an ultrasonic indication.
of radiographs takes place in three basic steps: (1) detection, (2) interpretation
Interpretation - The determination of the source and relevancy of an ultrasonic indication.
, and (3) evaluation
Evaluation - The process of deciding the severity of a condition after an indication has been interpreted.
Evaluation determines if the test object should be rejected, repaired or accepted. See indication and
interpretation.
. All of these steps make use of the radiographer's visual acuity
Visual Acuity - The space visible to an eye in a given position of gaze.
. Visual acuity
Visual Acuity - The space visible to an eye in a given position of gaze.
is the ability to resolve a spatial pattern in an image. The ability of an individual to detect discontinuities
in radiography
Radiography - The process of making a radiograph
is also affected by the lighting condition in the place of viewing, and the experience level for recognizing
various features in the image. The following material was developed to help students develop an
understanding of the types of defects found in weldments
ments - Welded joints.
and how they appear in a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
.
Discontinuities
Discontinuities are interruptions in the typical structure of a material. These interruptions may occur in the
base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
, weld material or "heat affected" zones. Discontinuities, which do not meet the requirements of the codes or
specifications used to invoke and control an inspection, are referred to as defects.
General Welding Discontinuities
The following discontinuities are typical of all types of welding.
Cold lap
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ap - A surface defect, appearing as a seam, caused by folding over hot metal, fins or sharp corners
nd then rolling or forging them into the surface, but not welding them.
is a condition where the weld filler metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
does not properly fuse with the base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
or the previous weld pass material (interpass cold lap). The arc does not melt the base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
sufficiently and causes the slightly molten puddle to flow into the base material without bonding.
Porosity
Porosity - The property of being porous.
is the result of gas entrapment in the solidifying metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
. Porosity
Porosity - The property of being porous.
can take many shapes on a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
but often appears as dark round or irregular spots or specks appearing singularly, in clusters, or in rows.
Sometimes, porosity
- The property of being porous.
is elongated and may appear to have a tail. This is the result of gas attempting to escape while the metal
- An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
al, heavier than the other elemental substances.
is still in a liquid state and is called wormhole porosity
Porosity - The property of being porous.
. All porosity
Porosity - The property of being porous.
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Nondestructive Evaluation Techniques : Radiography
is a void in the material and it will have a higher radiographic density
Density - The mass of a substance per unit volume.
than the surrounding area.
Cluster porosity
osity - The property of being porous.
is caused when flux coated electrodes are contaminated with moisture. The moisture turns into a gas when
heated and becomes trapped in the weld during the welding process. Cluster porosity
Porosity - The property of being porous.
appear just like regular porosity
osity - The property of being porous.
in the radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
but the indications will be grouped close together.
Slag inclusions
Slag Inclusions - Nonmetallic solid material entrapped in weld metal or between weld metal and base
metal.
are nonmetallic solid material entrapped in weld metal
Weld Metal - That portion of a weld which has been melted during welding.
or between weld and base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electric
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, i
general, heavier than the other elemental substances.
. In a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
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, dark, jagged asymmetrical shapes within the weld or along the weld joint areas are indicative of slag
inclusions
Slag Inclusions - Nonmetallic solid material entrapped in weld metal or between weld metal and base metal.
.
Incomplete penetration
Incomplete Penetration - Welding root penetration which is less than complete or failure of a root
pass and backing pass to fuse with each other.
(IP) or lack of penetration (LOP) occurs when the weld metal
Weld Metal - That portion of a weld which has been melted during welding.
fails to penetrate the joint. It is one of the most objectionable weld discontinuities. Lack of penetration allows
a natural stress
Stress - Force per unit area, often thought of as a force acting through a small area within a plane. It ca
divided into components, perpendicular and parallel to the plane, called normal stress and shear stress,
respectively. Usually expressed as pounds per square inch (psi), or megapascals (MPa).
riser from which a crack
long narrow discontinuity
may propagate. The appearance on a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
is a dark area with well-defined, straight edges that follows the land or root face down the center of the
weldment.
Incomplete fusion
Incomplete Fusion - Welding fusion which is less than compete. Failure of weld metal to fuse
completely with the base metal or preceding bead.
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is a condition where the weld filler metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
does not properly fuse with the base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electric
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, i
general, heavier than the other elemental substances.
. Appearance on radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
: usually appears as a dark line or lines oriented in the direction of the weld seam along the weld preparation
or joining area.
Internal concavity or suck back is a condition where the weld metal
Weld Metal - That portion of a weld which has been melted during welding.
has contracted as it cools and has been drawn up into the root of the weld. On a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
it looks similar to a lack of penetration but the line has irregular edges and it is often quite wide in the center
of the weld image.
Internal or root undercut
Undercut - In welding, a groove melted into the base metal adjacent to the toe, or edge, of a weld and
left unfilled.
is an erosion
Erosion - Destruction of metals or other materials by the abrasive action of moving fluids, usually
accelerated by the presence of solid particles of matter in suspension. When corrosion occurs simultaneously,
the term erosion-corrosion is often used.
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of the base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
next to the root of the weld. In the radiographic image it appears as a dark irregular line offset from the
centerline of the weldment. Undercutting is not as straight edged as LOP because it does not follow a ground
edge.
External or crown undercut
Undercut - In welding, a groove melted into the base metal adjacent to the toe, or edge, of a weld and
left unfilled.
is an erosion
Erosion - Destruction of metals or other materials by the abrasive action of moving fluids, usually
accelerated by the presence of solid particles of matter in suspension. When corrosion occurs simultaneously,
the term erosion-corrosion is often used.
of the base metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
next to the crown of the weld. In the radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
, it appears as a dark irregular line along the outside edge of the weld area.
Offset or mismatch are terms associated with a condition where two pieces being welded together are not
properly aligned. The radiographic image shows a noticeable difference in density
Density - The mass of a substance per unit volume.
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between the two pieces. The difference in density
The mass of a substance per unit volume.
is caused by the difference in material thickness. The dark, straight line is caused by the failure of the weld
metal
Weld Metal - That portion of a weld which has been melted during welding.
to fuse with the land area.
Inadequate weld reinforcement is an area of a weld where the thickness of weld metal
Weld Metal - That portion of a weld which has been melted during welding.
deposited is less than the thickness of the base material. It is very easy to determine by radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
if the weld has inadequate reinforcement, because the image density
Density - The mass of a substance per unit volume.
in the area of suspected inadequacy will be higher (darker) than the image density
nsity - The mass of a substance per unit volume.
of the surrounding base material.
Excess weld reinforcement is an area of a weld that has weld metal
Weld Metal - That portion of a weld which has been melted during welding.
added in excess of that specified by engineering drawings and codes. The appearance on a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
is a localized, lighter area in the weld. A visual inspection will easily determine if the weld reinforcement is in
excess of that specified by the engineering requirements.
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Cracks can be detected in a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
only when they are propagating in a direction that produces a change in thickness that is parallel to the x-ray
beam. Cracks will appear as jagged and often very faint irregular lines. Cracks can sometimes appear as "tails"
on inclusions or porosity
Porosity - The property of being porous.
.
Discontinuities in TIG welds
The following discontinuities are unique to the TIG welding process. These discontinuities occur in most
metals welded by the process, including aluminum and stainless steels. The TIG method of welding produces
a clean homogeneous weld which when radiographed is easily interpreted.
Tungsten
Tungsten - A metal commonly used to make the plugs used for connecting metal wires to one anothe
or to the devices in integrated circuits.
inclusions. Tungsten
Tungsten - A metal commonly used to make the plugs used for connecting metal wires to one another or to
the devices in integrated circuits.
is a brittle and inherently dense material used in the electrode
Electrode - An electrical conductor, usually of metal or graphite, that leads current into or out of a solution
(electrolyte).
in tungsten
Tungsten - A metal commonly used to make the plugs used for connecting metal wires to one another or
the devices in integrated circuits.
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inert gas welding. If improper welding procedures are used, tungsten
Tungsten - A metal commonly used to make the plugs used for connecting metal wires to one another or to
the devices in integrated circuits.
may be entrapped in the weld. Radiographically, tungsten
Tungsten - A metal commonly used to make the plugs used for connecting metal wires to one another or to
the devices in integrated circuits.
is more dense than aluminum or steel, therefore it shows up as a lighter area with a distinct outline on
the radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
.
Oxide inclusions are usually visible on the surface of material being welded (especially aluminum). Oxide
inclusions are less dense than the surrounding material and, therefore, appear as dark irregularly shaped
discontinuities in the radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
.
Discontinuities in Gas Metal Arc Welds (GMAW)
The following discontinuities are most commonly found in GMAW welds.
Whiskers are short lengths of weld electrode
Electrode - An electrical conductor, usually of metal or graphite, that leads current into or out of a solution
(electrolyte).
wire, visible on the top or bottom surface of the weld or contained within the weld. On a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
they appear as light, "wire like" indications.
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Burn-Through results when too much heat causes excessive weld metal
Weld Metal - That portion of a weld which has been melted during welding.
to penetrate the weld zone. Often lumps of metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
sag through the weld, creating a thick globular condition on the back of the weld. These globs of metal
Metal - An opaque, lustrous elemental chemical substance that is a good conductor of heat and electricity
and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in
general, heavier than the other elemental substances.
are referred to as icicles. On a radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
, burn-through appears as dark spots, which are often surrounded by light globular areas (icicles).
Nondestructive Evaluation Techniques > Radiography Testing > Radiograph Interpretation - Castings
Radiograph Interpretation - Castings
The major objective of radiographic testing of castings is the disclosure of defects that adversely affect the
strength of the product. Castings are a product form that often receive radiographic inspection since many of
the defects produced by the casting process are volumetric in nature, and are thus relatively easy to detect
with this method. These discontinuities of course, are related to casting process deficiencies, which, if
properly understood, can lead to accurate accept-reject decisions as well as to suitable corrective measures.
Since different types and sizes of defects have different effects of the performance of the casting, it is
important that the radiographer
Radiographer - Any individual who performs or who, in attendance at the site where the sealed source or
sources are being used, personally supervises radiographic operations and who is responsible to the licensee
for assuring compliance with the requirements of these regulations and the conditions of the licenses.
is able to identify the type and size of the defects. ASTM E155, Standard
Standard - A reference object used as a basis for comparison or calibration. - A concept established by
authority, custom or agreement to serve as a model or rule in the measurement of quantity or the
establishment of a practice or procedure.
for Radiographs of castings has been produced to help the radiographer
Radiographer - Any individual who performs or who, in attendance at the site where the sealed source or
sources are being used, personally supervises radiographic operations and who is responsible to the licensee
for assuring compliance with the requirements of these regulations and the conditions of the licenses.
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make a better assessment of the defects found in components. The castings used to produce the standard
Standard - A reference object used as a basis for comparison or calibration. - A concept established by
authority, custom or agreement to serve as a model or rule in the measurement of quantity or the
establishment of a practice or procedure.
radiographs have been destructively analyzed to confirm the size and type of discontinuities present. The
following is a brief description of the most common discontinuity
Discontinuity - a break in the continuity of a medium or material.
types included in existing reference radiograph
Radiograph - a photographic recording produced by the passage of radiation through a subject onto a film.
documents (in graded types or as single illustrations).
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