The Facts about Weld Porosity   As printed in The Welder Magazine

Don't forget to Ping that Weld

Paul, Got a question for you. I work in the mines, when we are welding something thick our boss tells us to "ping" our welds (excessive chipping /with air-chipper). I've never heard of that before. What’s your input?
Matt

Matt, Your Boss is offering some good advice.  He's actually asking you to peen your weld (I'm sure he says "ping" but this is what he means).
Peening a weld helps reduce what's called "residual stress". When you heat and cool metal it wants to move, but typically the weldment doesn't allow it to move. This builds residual stress in the part.  When residual stress exceeds "Yield Strength" you'll get distortion.  When residual stress exceeds "Tensile Strength" you'll get weldment failure.
Also, welding screws with the materials grain structure (at an atomic level). There are several ways to deal with this. You can Post Weld Heat Treat the weldment: raising it to what's called the transition temperature (Around 1600f), holding it there for some predetermined time and then allowing it to cool in some controlled manner. Or you could apply vibration (vibratory stress relief), vibrating the weldment during welding and shortly thereafter. Or you can peen, hitting the weldment with a peening hammer (or a scaler) to help reduce this stress.
So, what your Boss has you doing is stress relieving each pass to reduce distortion and /or the risk of cracking.  Listen to him.

Good question.
PWC

Radiograph and IP (off The Facebook)

James H
I recently had a friends weld get rejected by xray for a concave bead.  Repaired it, reshot it, and it came back rejected for IP.  Two times in this last year I've heard this. Both times, same example. Is it just a bad xray tech or is it a change in the rules today?

Paul W Cameron - CWI
A friend eh?
Let me preface this by saying, "I'm no RT Guy." but, a concave bead in a radiograph could easily mask Incomplete Joint Penetration (IP).
A concave bead will appear darker (because it's thinner) than the base material around it when viewed in a radiograph. Once that concave bead is repaired (adding more weld [making it thicker then base material]) the area that was once dark is now light and any IP would be clearly visible.

Great Question!
PWC
https://www.facebook.com/PaulWCameronCWI

WPS from Multiple PQRs?

Hey Paul,
How does one support a WPS from multiple PQR's?

Neil

I've used multiple PQR's on a single WPS many, many, many times.  When creating a WPS in manufacturing for GMAW I may want the WPS to cover all the electrode diameters (0.035, 0.045, 0.052) and wire feed speed (WFS) ranges that can be run.  A typical ER70S-6 WPS could take me 9 PQRs (3 dial. x 3 WFS ranges).  That was common for me as a Welding Engineer.
Equally…
When I qualify a single PQR I'll write as many WPS's from it as I can.  Example: I qualify a Bevel Groove with a PQR, I'll also write a WPS for a V-Groove, a U- or J-, all the PJP's I can and Fillets.  I try to get as much “Bang For My Buck” as I can.
PWC

Pre-Heat & Interpass Temp

Hey Paul,
From your experience, what is your preference when it comes to measuring the temperature of your PQR's?
At current I have access to 7 different rated tempilstik's, but that doesn't sound like a reasonable arsenal to do the job....or is it?
The IR Pyrometer I have is unreliable at best (as well, no calibration records).
If anything, I'm intrigued by the digital contact pyrometers out on the market. Specifically the Estik looks good, though the 2% tolerance for each displayed value is a bit concerning in the upper limits.
As always, thanks for your insight to age-old questions for us newbies!

Neil

Good questions…
The thing about the Temp Stix is that they are considered the “accepted” method (no controversy), especially when dealing w/Governmental agencies (Army Corp of Eng, DOT…).
Honestly? I use my IR gun to determine which TempilStik to use.  Sounds weird, I know.
If I can prove to myself that my IR gun is accurate (often dependent on surface condition) I’ll use its readings, but if I’m the least bit concerned, I turn to the TempilStik. 
Here’s how I’ll write a PQR:

Pass 1: Greater than 125 / Less than 175
Pass 2: Greater than 175 / Less than 225
Pass 3: Greater than 225 / Less than 300
Pass 4:  Greater than 300 / Less than 500

Kinda messy, but I don’t know a better way to do it and it’s never been questioned.  In fact, when they see the ranges they almost automatically know I used a TempStik and don’t question it.
I use to have a contact pyrometer and would spend a lot of $$$ keeping it calibrated.  After going into biz on my own I simply wrote a calibration procedure that stated “Place probe in ice water (50% crushed ice/50% water) let stand 10 min.  Insure temp reads 32 deg F +/-5%”.  That always worked (right up until I lost it).

Hope that helps.

PWC

What Goes In a Visual Inspection Report?

Hi, Paul,

Could you let me know what information you think should be included in a visual welding inspection report?

I’m seeing a lot about what the inspector should be verifying, but not the actual items that should be in the report.

 I appreciate your help.

  

Best Regards,

 Anthony N.

Good question.  For NDE (nondestructive evaluation) we typically go to our code books to find the correct forms required.  Although using those specific forms isn’t a requirement, they are a great guide to determine what information we need to capture. 

Visual Inspection (VT [visual testing]) is a form of NDE, but I’m not aware of a code supplied form for recording it.  There is no simple form to download and fill out when it comes to VT.

In my day-to-day, I may use a spread sheet, a Word doc, or the old reliable composition note book.  It all depends on my situation.

As for what information to capture? My guidelines are; keep it simple... Let’s assume AWS D1.1 is our code. Sub-Clause 6.9 states, “All welds shall be visually inspected...”  That doesn’t leave a lot of “wiggle-room”.  We know we have to look at all welds.  It also states, “...and shall be acceptable if the criteria of Table 6.1 are satisfied.”  So now we know our acceptance criteria.

At a minimum your visual inspection (VT) report should state:

What was the date of fabrication?

What was the part/print number?

What was the welds location?

What was the acceptance criteria? (i.e.: AWS D1.1:2010 Table 6.1, Statically Loaded)

Did it meet the requirement?

Did anything restrict your inspection? (i.e.: Part was galvanized, Root was lot accessible, Roof decking covered weld face...)

Was it acceptable?

What is the date of inspection?

...and always add your name (legibly), signature and CWI# (if applicable).
Remember, listen to your customer to gage the level of detail requested, but always make the report clear enough so you understand what was written long after the project is complete.

Good Luck,

PWC

Weld Inspection After Coating

Hi Paul,
I see your references on The Fabricator.com website and am wondering; how I can inspect/verify welds on painted product without being destructive?

Best regards,
Eric D.

Hey Eric,
On fabricated products coatings come in many types. galvanizing, paint, even the oxidizing of a weathering steel will have negative effects on the inspection of welded products.  For visual inspection (a form of nondestructive evaluation) any coating on the finished weld has the potential to mask or cover rejectable discontinuities such as size, cracks, undercut, overlap, porosity, etc…  Keep in mind, when we list defects by criticality, those that come to the surface generally top the list.  So there is risk in completing a visual inspection on any coated product.
That being said, as a CWI I’m often asked to do visual inspection on coated product.  I do, but I will ALWAYS note that the weldment viewed was coated and that coating limited the inspection.
As for other forms of NDE…
• Die penetrant (PT) would not be affective.  With die penetrants the discontinuity needs to come to the surface and the penetrent needs to enter the discontinuity through capillary action.  Any coatings would not allow that to happen.
• Magnetic particle testing (MT) does have the potential to reveal sub-surface discontinuities but that ability is limited and any coating will certainly affect its dependability.  MT will not work on your aluminum products, the material tested needs to be ferromagnetic.
• It’s not uncommon to do Ultrasonic testing (UT) on coated weldments.  I’ve performed UT on thousands of galvanized and painted products successfully.  Calibrations need to be adapted to allow for loss due to the coating, but those types of inspections are performed every day (at least in my world).
• Radiograph (RT) is another nondestructive method that would not be affected by most coatings.  In fact, RT would probably be the least affected.
So there ya’ go.  There are several nondestructive methods of NDE that can be performed on coated products, there are simply some adjustments that may be required due to the coating.  But your most affective form of nondestructive testing is visual inspection performed before, during and after welding and prior to any coating.

Ask me the time and I build you a watch.
PWC