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Up Topic Welding Industry / Inspection & Qualification / Plug Weld MT Indications
- - By unclematt (***) Date 02-16-2012 12:12
Good Morning;
I was called to look at some welding this morning that involved plug welds. The MT Tech said he was getting indications at the weld metal/base metal interface where the welder ground flush. Have any of you ran into this? The Tech is saying it isn't a crack; just an indication. Could it be the boundary between the different materials of the filler metal and base metal throwing an indication? Materials are 4140 and ER80s-D2 to a 1026 insert. I appreciate any and all responses.

Have a good day;
Matt
Parent - - By fschweighardt (***) Date 02-16-2012 12:25
I had a casting welded to plate that would give a MT indication no matter what.  RT was used as the referee method, and was clean as could be.  Seems like it had to do with different microstructures having different magnetic permeability, which gave an odd sort of fuzzy indicaiton.  Wouldnt suprise me a bit if the dissimilar metals in your part could do the same thing.  May want to try UT or something
Parent - By unclematt (***) Date 02-16-2012 12:47
Thanks. I will suggest another NDE method to determine the soundness. On the part, you can clearly see the different materials after PWHT. I appreciate the response.

Matt
Parent - - By Mikeqc1 (****) Date 02-18-2012 13:22
it could be a change in permeability...i see that alot during my inspections.the indication will be visible but shouldnt hold the powder.
Parent - By unclematt (***) Date 02-18-2012 13:40
Good Morning Mikeqc1;
Thanks for the response. We haven't checked the repaired repair yet. Not sure if it matters, but I guess I should've clarified Wet Mag was the technique we are using. But powder is powder I guess. Thats what I first thought; that we were seeing where the two different materials were interfacing. It did seem to be throwing a pretty well defined indication. Have a fine Saturday morning.

Thanks;
Matt
Parent - - By ozniek (***) Date 02-20-2012 13:42
Hi unclematt

Surely DPI is the most obvious alternative NDT technique? UT'ing plug welds could be a little messy, and if there genuinely is a surface breaking crack, then DPI will pick it up.

Regards
Niekie
Parent - By unclematt (***) Date 02-20-2012 14:09
Good Morning  Niekie;
Thanks for the response. That would indeed be an easier way to tell if the indications are surface breaking.  The MT Tech is stating they are not cracks, just indications. I believe that after this last repair, they are performing Dry Particle and Dye Penetrant in the weld cell before sending to Wet Particle. I am eager to see their findings. Have a good day.

Thanks;
Matt
Parent - By unclematt (***) Date 02-22-2012 14:23
Good Morning;
After investigation, it was determined that the welder used the incorrect filler metal. Print called for E71T-1. The welder used 309 SS. The difference in magnetic properties at the weld/base metal interface was causing the indications. Drilled them out and re-welded. Passed MT with flying colors. Thanks to you all who responded. Have a good day.

Matt
- - By unclematt (***) Date 02-17-2012 13:55
Good morning;
They cut them out and re-welded them. We are getting the same indications. Going to give it one more go. Any ideas?  I will suggest an alternative NDE technique to figure out if it is indeed a crack or a difference in materials or something else. Any responses greatly appreciated.

Thanks;
Matt
Parent - - By CWI555 (*****) Date 02-17-2012 19:36
UT them and while your at it, put a mockup/reference set together. There is a PQR for this WPS your using is there not?
Parent - - By unclematt (***) Date 02-17-2012 20:14
CWI555;
Thanks for the response. There is indeed a PQR for this WPS. We will see how this next weld goes. I will suggest using UT to see if the indication is relevant or not. Appreciate it.

Have a good day;
Matt
Parent - By CWI555 (*****) Date 02-18-2012 02:59 Edited 02-18-2012 03:12
If you utilize UT, and there is a great enough transition in metallurgical conditions in the transition areas you may see a signal return coming out of the transition zone.

The technician will need to be watching his or her RF window for phase transitions to help them determine if this is a flaw or an interface signal. The probability of that can be checked by running a few transmission coefficient calcs. DM weld inspection via UT requires an experienced technician that knows what they are doing. Without having that particular set up and combination of materials and their specific velocities I can't tell you from here if it will or won't, but I did run a few calcs that suggest it is probable they will see a transition signal around 10-15 percent worth of DAC. If that is the case, knowing the constituent material velocities will be critical.

http://www.ndt.net/article/wcndt2004/pdf/materials_characterization/138_gur.pdf

Here is a study performed on 1040 and 4140 that has some application to yours. Take note on page 5 the change in velocities depending on the heat treat.

The conditions your describing have apparently been enough to create a permeability change local to the transition zone that is creating an MT indication. I believe the conditions in the linked study will be less severe than your conditions if that is the case, so keep that in mind when your performing that exam.

Overall I don't think you have another option other than UT to get any meaningful NDE results from that weld if those conditions are as stated.
Parent - - By Tyrone (***) Date 02-22-2012 18:44
Unclematt,
Can you section a sample to see what the weld looks like? or mock one up?
I ask this because I was shocked to see how little penetration I was getting on various plug welds. Lack of fusion/penetration would show up with the powder.
Definitely technique/skill involved with making acceptable plug welds.

Tyrone
Parent - By unclematt (***) Date 02-22-2012 19:00
Tyrone;
Thanks for the response. As it turns out, the welder used the wrong filler metal. The print called for E71T-1. He used 309 SS. They drilled them, used the correct filler metal and it passed.

Plug welds, in my experience, are sometimes difficult depending on the size of the hole, orientation, filler metal, etc. Sectioning of a mock-up would have been an excellent choice. Thanks for the suggestion.

Have a good day;
Matt
Up Topic Welding Industry / Inspection & Qualification / Plug Weld MT Indications

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