Module-6 Weldments and Castings

8/12/2019 Module-6 Weldments and Castings

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WELDMENTS AND CASTINGS

MODULE 6Birring NDE Center, IncJan 2011


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Radiograph Interpretation -

Welds In addition to producing high quality

radiographs, the radiographer must alsobe skilled in radiographic interpretation.Interpretation of radiographs takesplace in three basic steps which are(1) detection,(2) interpretation,

(3) evaluation.


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Radiograph Interpretation -Welds

The ability of an individual to detectdiscontinuities in radiography is alsoaffected by the lighting condition in the

place of viewing, and the experiencelevel for recognizing various features inthe image.


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Cold lap Cold lap is a discontinuity where the weld filler metal

does not properly fuse with the base metal or theprevious weld pass material (interpass cold lap). Thearc does not melt the base metal sufficiently andcauses the slightly molten puddle to flow into basematerial without bonding.


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Porosity Porosity is the result of gas entrapment

in the solidifying metal. Porosity can take many shapes on a

radiograph but often appears as darkround or irregular spots or specksappearing singularly, in clusters or rows.

Sometimes porosity is elongated andmay have the appearance of having a

tail. This is the result of gas attempting to

escape while the metal is still in a liquid

state and is called wormhole porosity.


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Porosity

All porosity is a void in the material it willhave a radiographic density more thanthe surrounding area.


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Cluster Porosity Cluster porosity is caused when flux

coated electrodes are contaminatedwith moisture.

The moisture turns into gases whenheated and becomes trapped in theweld during the welding process.

Cluster porosity appear just like regularporosity in the radiograph but theindications will be grouped closetogether.


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Cluster Porosity


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Slag inclusions Slag inclusions are nonmetallic solid

material entrapped in weld metal or betweenweld and base metal. In a radiograph, dark,

jagged asymmetrical shapes within the weldor along the weld joint areas are indicative ofslag inclusions


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Incomplete penetration (IP) orlack of penetration (LOP)

Incomplete penetration (IP) or lack ofpenetration (LOP) occurs when the weldmetal fails to penetrate the joint.

It is one of the most objectionable welddiscontinuities. Lack of penetration allows anatural stress riser from which a crack maypropagate.

The appearance on a radiograph is a darkarea with well-defined, straight edges thatfollows the land or root face down the centerof the weldment


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Incomplete penetration (IP) or

lack of penetration (LOP)


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Incomplete fusion Incomplete fusion is a condition where the

weld filler metal does not properly fuse withthe base metal. Appearance on radiograph:usually appears as a dark line or linesoriented in the direction of the weld seam

along the weld preparation or joining area.


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Internal Concavity or SuckBack

Internal concavity or suck back iscondition where the weld metal has

contracted as it cools and has beendrawn up into the root of the weld.

On a radiograph it looks similar to lack

of penetration but the line has irregularedges and it is often quite wide in thecenter of the weld image.


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Internal Concavity or Suck

Back


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Internal or Root Undercut

Internal or root undercut is an erosionof the base metal next to the root of theweld.

In the radiographic image it appears asa dark irregular line offset from thecenterline of the weldment.

Undercutting is not as straight edged asLOP because it does not follow aground edge.


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Internal or Root Undercut


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External or Crown Undercut External or crown undercut is an

erosion of the base metal next to thecrown of the weld. In the radiograph, itappears as a dark irregular line along

the outside edge of the weld area.


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Offset or Mismatch

Offset or mismatch are terms associatedwith a condition where two pieces being

welded together are not properly aligned. The radiographic image is a noticeable

difference in density between the two pieces.The difference in density is caused by thedifference in material thickness.

The dark, straight line is caused by failure ofthe weld metal to fuse with the land area


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Offset or Mismatch


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Inadequate Weld

Reinforcement Inadequate weld reinforcement is an area

of a weld where the thickness of weld metaldeposited is less than the thickness of thebase material.

It is very easy to determine by radiograph ifthe weld has inadequate reinforcement,because the image density in the area ofsuspected inadequacy will be more (darker)than the image density of the surroundingbase material


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Excess Weld Reinforcement

Excess weld reinforcement is an area of aweld that has weld metal added in excess of

that specified by engineering drawings andcodes. The appearance on a radiograph is a

localized, lighter area in the weld. A visual inspection will easily determine if the

weld reinforcement is in excess of thatspecified by the engineering requirements


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Cracks Cracks can be detected in a radiograph

only when they are propagating in adirection that produces a change inthickness that is parallel to the x-raybeam.

Cracks will appear as jagged and oftenvery faint irregular lines. Cracks cansometimes appear as "tails" oninclusions or porosity


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Cracks


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Evaluation of Castings

Density calculations Step Wedge ASTM Reference Radiographs


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CASTING DISCONTINUITIES

Shrinkage (sponge, centerline, micro) Cold shuts Hot tears (cracks) Inclusions Gas (porosity, voids, wormhole) Misrun Unfused chaplets


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Inclusions in Castings


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Hot Tears in CastingsJagged and Parallel lines


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EVALUATION of ASSEMBLIES

Verification of component placement Determination of Design requirements Evaluation of serviceability Determination of failure mode


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Digital Radiography of Honeycomb structure


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Digital Radiography of Printed Circuit Board


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FLUOROSCOPYOPY


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In-Motion Radiography


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Flash Radiography


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Flash Radiography


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CT Radiography of Wood


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Concrete: CT Radiography

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Module-6 Weldments and Castings