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beh188 (Mechanical) (OP)
3 Aug 11 0:02
Can anyone provide general guidelines or a good resource that describes how to interpret a weld macro etch test, specifically for a fillet weld?

I would like some examples of what the typical joint should look like, as well as what typical failures look like.

How much penetration into the parent material is typically desirable?
Kiwi2671 (Structural)
3 Aug 11 8:38
Put a ruler along one edge of your plate.
Put a ruler along the other edge of your plate at 90 degrees.
If your weld penetration doesn't encompass the meeting of the two lines then it is lack of penetration,
TVP (Materials)
3 Aug 11 11:18
Here are some links showing defects, etc.  ISO 5817 is the internationally-recognized standard regardign weld quality and defects.  I recommend you obtain this.

Weld Defects-Their Causes and How to Correct Them

A New Weld Class System

The differences between the strengths of quality levels of weld imperfections given in ISO 5817

Metallography of Welds

Weld defects / imperfections

Weld defects and quality control

Welding Defects

Duwe6 (Industrial)
7 Aug 11 15:34
Quantity of penetration is immaterial.  You are macro'ing to determine Fusion vs. Lack-of-Fusion.  Look instead for a straight line at the weldmetal-basemetal interface.  This line indicates L.F., because the basemetal has not been 'broken down'.  
beh188 (Mechanical) (OP)
7 Aug 11 19:48
Thanks for the great responses.
Kiwi2671 (Structural)
8 Aug 11 1:45
Your interpretation is correct based on ASME / AWS terminology but it differs in other countries.
Lack of penetration or incomplete penetration is the terminology used for fillet welds in Australia, New Zealand, Britain and Europe.
If there are unfused areas (straight lines)between weld metal and parent metal on the vertical or horizontal plate it is called Lack of Fusion.
If the weld metal does not envelop the junction of the vertical and horizontal plates it is called Lack of Penetration or Incomplete Penetration.
It seems even some Americans use similar terminology

 Analysis Of A Fractured Crane Frame Weldment
Report for:    Report by:
160 Bevan Drive
Mooresville, NC  28115

A fractured pipe/flange weldment from a crane frame assembly was received for analysis to determine the cause of fracturing along the circumferential fillet weld.  Results indicate the fracture occurred by cyclic fatigue crack growth that initiated at the root of the fillet weld due to incomplete penetration by the root pass and a lack of fusion to the pipe or flange at several locations around the weldment.  
Microscopic and metallographic examination revealed fatigue crack initiation sites at and between the incomplete penetration and lack of fusion sites.  The lack of penetration was noted around 60% of the circumferential fillet weld.  Lack of fusion to the pipe and flange were noted around approximately 50% of the weld.
The flange and pipe were manufactured from weldable grades of high strength, low alloy structural steels.  A compatible low alloy steel filler metal was used.  Hardness testing across the weldment revealed no unusual softening or embrittlement.  

Duwe6 (Industrial)
8 Aug 11 8:50
Typical USA usage of L.F. is as above mentioned in the Macroetch.  Lack/Incomplete Penetration -- IP -- refers to not completely consuming the basemetal on a Full-Penetration joint.  Not fully penetrated, thus IP.

LF applies to sidewall fusion conditions, vs. depth of penetration.

Both of these defects present as straight lines on X-ray [RT].  IP is easily imaged on RT film.  Fine, 'tight' LF is close to impossible to image on RT -- you are looking for a brazeline that is off-axis from the direction of radiation.

Terms do indeed vary from one country [even English-speaking ones] to another.  Thanx for the insight on terminology from other places.
stanweld (Materials)
10 Aug 11 9:00
Bridged roots (lack of penetration) in fillet welds have long been known to adversely affect peformance of fillet welds in cyclic service.  

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