Any ideas what this could be?

Date 01-18-2010 17:37

looks like porosity, not being able to touch the piece, those areas have depth to them right? It's almost as if the passivation process ate away at some certain element in the weld filler metal. I am not familier w/ S/S welds and filler metals so I can't help there sorry.

By pataterchip (**)

Date 01-18-2010 17:44

You are correct in that they have a small amount of "depth" but it is not porosity as that would have not passed PT, and there is no open pores to speak of.

By jwright650 (*****)

Date 01-18-2010 17:56

I know you stated it was SS done with GTAW, but it reminds me of mild steel done with GMAW(silicon islands). Will it chip off?

By MMyers

Date 01-18-2010 18:27

That's close to what I was thinking. Maybe localized pitting/etching during that pickling due to localized oxide formations.

By joe pirie (***)

Date 01-18-2010 18:42

were welds wire brushed before pickling ? looks like a surface contamination of some sort
welds look a little lumpy

By pataterchip (**)

Date 01-18-2010 19:44

Yes the welds were brushed in preparation for PT. I was looking into the filler metal chem anly. to see were we could have picked up excess silicon as that was my first thought. These black spots adhere tightly similar to silicon inlands I have the guys trying to chip a few of them and see if they can get a sample of it off the weld.

By Metarinka (****)

Date 01-18-2010 20:59

looks like silica or a similar type of flux scale to me? perhaps some type of surface contaminant prior to welding that is light and has a low melting point, acting much like silica and floating to the surface.

It seems the pickling just increased the contrast. IF it's purely a a surface issue can it not be removed? or is this a root cause type situation?

By pgoswami (*)

Date 01-18-2010 18:40 Edited 01-18-2010 18:55

This could be due to improper pickling and passivation.Pickling pastes or solutions are highly corrosive.If the composition or concentration,cleaning methods ,time of appliaction etc are not under controll, pits or crevices may get formed as shown in the attached photographs.

Avesta has detailed guidelines on pickling and passivation of S.S.See the following link:-
http://www.bohler-uddeholm.cz/czech/files/Prirucka_Avesta_AJ.pdf.

The damaged areas shall be GTAW rapair welded, Cleaned and repickled. It may be a good idea to get the pickling procedure approved and a sample weld pickeld before pickling rthe entire weld.

Thanks

Pradip Goswami

Attachment: AvestaWeldingManual.pdf (31k)

By ssbn727 (*****)

Date 01-19-2010 09:36 Edited 01-20-2010 07:39

That could also be some sort of Ti oxide or Ti carbide scale that wasn't able to be removed by the pickling and passivation as pgoswami mentioned because it wasn't performed properly, and like Kix mentioned, there pre weld surface prep - if nonexistent, could have introduced some contaminants that coalesced with what looks like some sort of oxide layer or carbide layer... Remember, that it's only a guess on my part since I do not have all of the variables available to give a proper analysis here so, if you don't like what I wrote - Too friggin BAD!!! :) :) :)

Respectfully of course,
Henry

By Kix

Date 01-19-2010 02:06

It's contamination coming to the surface while welding. This will brush over to a nice appearance, but will passivate differently then where the boils didn't occur. I'd try looking into your pre prep before welding and maybe even your technique. Give us some before brushing pictures so we can see what kind of color you're getting. Those boils usually come with pretty decent color, but dirty material from flapper wheels or a power brush smearing contaminants into the base material. What's the thickness? Is it butted straight up for a square groove and no? Some before brushing pictures would let you have some really good advice from the experts.

Kix

By jsdwelder (***)

Date 01-19-2010 23:51

We would get this same thing on 304 material welded with 308 filler, automated GTAW. We sandblasted all of our weldments afterwards and if you spent enough time you could get it off. One of the guys that had been there a long time seemed to think it was contamination from the belt sander they were using to prep the material.

By pataterchip (**)

Date 01-20-2010 00:15

I am leaning to the same conclusion these parts are stamped and the it appears that the welders are not following the pre weld cleaning procedure as that slipped out today during a discussion about the parts. I think that this is contaminates left by the stamp house. I will let everyone know when we get to the bottom of it.
Thanks everyone for your input it was helpful.

By ssbn727 (*****)

Date 01-20-2010 07:52 Edited 01-20-2010 08:09

Hi Pataterchip!

After looking at the photos again, I noticed that in your OP, you mention that your photo's show that the "blotches' as well as the visually colored HAZ were still present even after the components were sent out for pickling & passivation!!! That really struck me after I read that again, because usually one can get rid of the visually colored HAZ after pickling and passivation very easily and that was not the case in the photo's!!!

This leads me to believe ever so strongly that the pickling and passivation process was NOT properly performed otherwise why would the visually colored HAZ which wasn't a wide HAZ, still present even after pickling and passivation??? If the proper procedures were used, at the very least, the visually colored HAZ would no longer be there especially if it was a HAZ of that width!

I would ask the provider of the pickling and passivation why would there still be a visually colored HAZ present afterwards since it's supposed to be removed as part of the process???

Btw, I owe you an apology for stating what I did in the previous post now that I've re-read it again... When I said: "if you don't like what I wrote - Too friggin BAD!!!" I did not mean it towards you personally... I meant it towards anyone else that may disagree with me, and it was sort of a "knee-jerk" reaction as a result of some previous confrontations I had experienced a few times before in recent times with certain individuals who would twist whatever I wrote, or expressed as an opinion and turn it against me in order to discredit me...

Thank goodness, that one of the persons I have alluded to has been banned so once again, My sincerest apology for being so defensive when it really wasn't directed at you personally but nonetheless, I felt the need to clarify what I meant when I wrote that statement in my previous post. ;)

Respectfully,
Henry

By Stephan (***)

Date 01-20-2010 10:36

Henry,

(quote):

"...why would the visually colored HAZ which wasn't a wide HAZ, still present even after pickling and passivation???"

(unquote)

Excellent view!

Stephan

By Milton Gravitt (***)

Date 01-20-2010 21:58 Edited 01-21-2010 10:46

you might need to passivate before you welded it up. Thats what we do where I work because it gets a lot of the carbon out of the material. Thats what I was told.

M.G.