Pinholes and Purging

UPDATE:

In this original posting I talked about common solutions to Pin Holes.  My apologies for not picking up on this, but in his question Marv B. stated that prior to welding he “tried cleaning them [the components] with Brake Cleaner”.  Welding and Brake Cleaners can be a deadly combination.

There are many warnings on the “everyday” chemicals we use.  Often, I will simply assume that if it’s sold over the counter surely it must be safe.  But the SDS (Safety Data Sheet) for a can of brake cleaner may read, “Do not use this product near open flames, welding operations or excessive heat.  Vapors may decompose to harmful or fatal corrosive gasses such as hydrogen chloride and possibly phosgene.”  This can be debilitating or even deadly to the Welder or those around him/her.

There are many manufacturers of cleaners, removers and degreasers used throughout our industry.  Most are safe when used as directed, so pay attention to the product labeling and review the products Safety Data Sheet (SDS).  Please use caution when determining how your weldment will be cleaned.  Only use approved cleaners to the manufacturer’s instruction.  Read the warnings and review the products SDS.  As my old boss used to say, “Somebody wants you home tonight.”

Thanks to Steve 'Brewdude' Garn who shares his experience on welding and brake cleaners at (http://www.brewracingframes.com/safety-alert-brake-cleaner--phosgene-gas.html).  I also want to give a special Thanks to the loyal readers that pointed my over-site. You come to us for good advice and I should pay attention to details when giving it.

PWC

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Hi Paul,
I was doing a search over the internet and came across your contact information.  If you don’t mind, can you help me with a problem?
I am machining a Bearing Housing made out of 1045.  I have to plug and weld some cross holes.  I am using 1018 for the plugs.  I am also using a tig welder to eliminate too large of a weld.  My problem is that I am getting pin holes in my weld.  Is it because I am not preheating the part.  or is it because I am welding 1018 to 1045?
We didn’t machine the parts dry so maybe there is a light film of coolant on the parts but I tried cleaning them and that didn’t seem to help.
If you could reply back that would be great or go ahead and give me a call.
Thanks!!!
Marv B.

Hey Marv,
The welding of the materials shouldn’t be a problem.
Let me ask, the machined port looks to be made up of 3 different drilling operations.  Are all 3 completed before the plug is welded in?
The reason I ask…
If the port to be plugged is drilled first (others drilled after welding) trying to weld a plug in the hole creates a condition I’ve dealt with most of my career.  When trying to seal weld the only opening in any cavity the air (or gases) in that cavity heat and expand. During that expansion a pin-hole will form at some location in the weld (just on solidification) to allow that expanding gas to escape.  Molten metal makes a poor seal 
Pipe-Welders see this same condition when finishing the root pass in a purged pipe.  If they don’t build an alternative location for the gas to escape the gas will blow through the final weld crater.
I also dealt with this condition on Flare Bevel Groove welds on a robotic application of a manufacturer where I served as Weld Engineer.  We were able to remedy that with a punched whole on the faying surface of the joint.
Not sure if this is your condition, but if you’re trying to seal the only opening, it sure could be.
Let me know.
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

"Put your finger on it"

Hi, Paul.
I was seeking advice from you regarding D1.1  I'm a welding instructor at a steel mill in Northwest Ind.
We were sent 12 yrs ago to Hobart welding school for train the trainer class and to certify in all positions,limited & unlimited thickness plates w/backing. All SMAW, 7018 rod. (Did not like Hobart's 7018 rod). We believed that we are Qualified to qualify welders to weld anything structural in our mill. Does this sound correct or our we missing something?
Also the big question is, does D1.1 say you have to certify to weld structural or just qualify through the testing procedure to weld structure? A new instructor is saying we have to certify I do not believe this is what D1.1 says.
Any advice would be helpfull, Thank you for time.
Thanks, Pat

Hi Pat,
Hobart is a great school and the Train the Trainer program was a great idea.
If your company accepted the Hobart documentation as your Welder Qualifications (common) and your company maintained a Welder Continuity Log (see: http://www.thefabricator.com/article/arcwelding/arc-welding-101-d1-1-welder-documentation) and as long as there is no reason to question your ability, your Welder Qualifications will continue to be current.
Although the AWS Certified Welding Educator (CWE) program would require you to maintain your Welder Qualifications, being a CWE is not a code requirement for those of us who train and qualify our Welders, so anyone your company deems competent to do so can train and qualify your Welders.
As far as qualifying Welders to weld anything structural in your mill… you would need to determine what governing documents covers the welding requirements of your mill (D1.1, D1.3, D14.1…) and insure your Welders are being qualified to those requirements.  Those Welders would need to be qualified to a (or many) test procedure(s) and the test procedures would need to encompass all of the essential variables listed in the code(s) being used.  (I know… it’s enough to make your head spin)
Bottom Line: When someone comes to me with a code requirement that I don’t believe to be accurate, my first response is to ask them to “Put your finger on it”.  Equally important, when someone asks about a code provision I would never give an answer until I had ALL the required information and I was able to “Put my finger on it” as well.

PWC

Those damn CVN requirement...

Paul,
Do you mind my asking a quick question drawing from your expertise of AWS D1.1?
Table 4.6 of AWS D1.1-2010 is a list of supplementary essential variable changes that would require WPS requalification due to CVN (Charpy V-Notch) testing requirements.  Under base metal (item 2) it indicates:

“minimum thickness qualified is T or 5/8” whichever is less except if T is less than 1/4” then the minimum thickness qualified is 1/8”

I take this to mean that to qualify a PJP groove weld of a 3/16” plate a weld procedure would have to be qualified using 3/16” thick material  (“minimum T or 5/8” whichever is less”).  Do you agree?

I had been going off of the table 4.2 where a 1” plate would qualify for a range from 1/8” to unlimited thickness.  But that table is not intended for Charpy requirements.  So I may have been wrong with using table 4.2 when Charpy requirements exist. I can see the need to qualify the thinner materials when CVN is required due to the heat input changes due to the thickness changes.  But just want a second opinion.

Thanks,
Wes

Oh those damn CVN requirement...
I currently have 2 clients that I'm working with on this issue. Your assessment of the CVN Supplement is correct.
What we advised for our client to do was to machine the test plates to a nominal of 0.230" (because I also wanted to insure I was under 6mm to eliminate any code questions). We completed PQR's on 0.230", 0.3125" and 1.0" material, that covered our range.

Other things that bite ya for CVN requirements is...
"Multi vs Single Pass": Most PQR's that are typically run are multi pass.  These multi-pass PQR's would not qualify single pass welding.
-and-
"Max. Interpass Temp": If interpass tempuratures were to be measured under 125F the Maximum qualified interpass tempuature qualified would be under 225f. This would limit Preheat Catigory A and C Steels to 1-1/2" max. and Catigory B Steels to 2-1/2" max.

Good to hear from ya Wes.
PWC

GMAW Globular Transfer

Paul,
I work at a machine shop where I am employed as a qualified welder to AWS-D.1.1. I was wondering why it is that you can certify 75% argon and 25% CO2 when you are not allowed to use a short circuit transfer on materials over 3/16". I read your article every month and in order to obtain a spray transfer you need at least 83% Argon but yet I passed on a 1 inch test piece.

Thanks K. B.

Your question insinuates that if your shielding gas mixture is not Argon rich enough to obtain a Spray Transfer mode the only alternative is Short Circuit Transfer, that's just not the case.
When using a 75% Argon and 25% Co2 mix you would not be able to achieve a Spray Transfer, but achieving a Globular Transfer would be no problem. It is quite common to complete the test you discribed (Unlimited Thickness to D1.1) in the GMAW Globular Transfer mode for all positions (3G/4G) successfully.  This is a fairly typical test commonly given in todays construction industry.  I think you will find Globular Transfer a prefered transfer mode in industries that utilize a 75/25 mix.
As for Short Circuit, when I mentioned in an earlier article, the possibility of incomplete fusion being a concern on materials greater than 3/16th inch, I prefaced that by including, "... in certain positions and progressions...".  Completing an open root limited thickness Welder Qualification in the Vertical progression (Root Down/Fill & Cover Up) is a very common transfer mode used during testing.  In fact, a test of that nature, Root Pass with Short Circuit, Fill and Cover Pass in Globular, would successfully qualify a Welder in 2 processes (GMAW-S & GMAW) in a single test.
That would be a good Welder Qualification to have in your wallet.
PWC

A Welding "Ground" doesn't ground anything!

What makes a good ground (Work Lead) connection and why is it important?

In a welding circuit, current needs to pass through as few connections as possible and the circuit it self needs to be as short as is practical.
On the positive (+) side current passes through the (+) stud connection, the feeder connection, the Gun connection and the contact tip (to the wire) connection. With the exception of the wire, all of those connections are typically, copper or brass.
On the negative (-) side current should passes through the (-) stud connection, the cable to the Work Lead (ground) clamp, possibly across a rotating surface and then to the work piece.
When any of these connections are anything less than clean copper or brass to clean copper or brass the possibility of a poor connection and a current and/or voltage loss exists. These losses can be great enough to run outside the parameters of the weld procedure causing spatter or a lack of fusion. That can get a welder into trouble.
Some good examples of poor connections would be:

• A Work Lead (ground) connected to a building column. 
• Using a steel building column and a steel bolt, this connection will oxidize (rust) and create resistance.
• A Work Lead (ground) connected to a steel plate run across the floor. 
• Of course the initial connection is the same as the building column. 
• When that steel plate isn't of a sufficient size (area) and that plate is joined by one or several welds (extra reduction in area) the condition are ripe for a drop in current and/or voltage.

The 2 conditions mentioned above also create a safety issue. Once a Work Lead (ground) contacts a building it gives current alternate routes. One of the most popular is through a jib or bridge crane.

Aside from creating havoc with the cranes electrical system, current passes through the lifting devices (cables, hooks and chains), heating them over and over and thus weakening them and making them susceptible to failure.
One last good example of a poor connection would be an unlubricated rotary clamp, or a rotary clamp lubricated with a lubricant that is not made for electrical connections.

A key to quality welding starts with a good quality circuit and a key component of that circuit is the condition of the Work Lead (ground).

Side Note: Notice I’ve replaced the word “ground” with “Work Lead”.  You should too.  Keep in mind, a welding “ground’ doesn’t ground anything.
PWC

"All Welding Shall Comply with AWS-D1.1"

Paul,
I am a welding instructor/inspector. I have a business client that builds control panels and a potential client of theirs is requesting that they conform to AWS D1.1 standards on a control panel. Seems odd to me what the customer is wanting? Does or can a company become AWS D1.1 certified? Is there a certain process they have to go through to become a D1.1 facility? I tested some of their welders over a year ago to the sheet metal code. Looks like they would want them to conform to D1.6-Structural welding Code - Stainless Steel? Thanks for any help. I got your name from practical welding.
John

Hi John,
Let’s dispel a few myths: Companies are not AWS-D1.1 “Certified” or “AWS-D1.1 facilities”. They simply comply, or they do not, and they call on folks like you and I to insure that. It’s not uncommon for contract documents to call for compliance to AWS D1.1 when the work being requested falls outside the limitations of AWS D1.1. The code is so accepted throughout industry that often those calling it out are unaware of its requirements. It has become some-what of a “Boiler Plate”.
The D1.1 committee recognizes this. If you look to the Limitations of D1.1 noted in Cause 1 at 1.2 it states, “The code may be suitable to govern structural fabrications outside the scope of the intended purpose.” It then goes on to state that the user may be better off looking into the requirements of other D1 documents that are more practical for your application (I used a little creative liberty in that last line).
In your case, AWS D1.3 and AWS D1.6 are far more applicable. Focusing your procedure and welder qualification on these codes will (a.) comply with AWS D1.1 and (b.) save your company, or the company you are working with, boat loads of money.
You could certainly review the job requirements and develop the requirements to AWS D1.1, but you would find yourself doing PQR’s and Welder Qualifications that may not have been required if you had used the Pre-Qualified procedures laid out in AWS-D1.3 and AWS-D1.6.
Using documents like AWS-D1.2, D1.3, D1.4, D1.5 and D1.6 when your welding doesn’t quite fit in a D1.1 box is certainly considered acceptable when your contract documents read, “All welding shall comply with AWS-D1.1”.
PWC