Saturday, November 21, 2009

Pulsed Welding Equipment

Cory G. from Norther Iowa asks:

"We use the Pulsed GMAW process with Lincoln equipment. When setting weld voltage the Trim can be adjusted between 0.5 and 1.5
What do those numbers mean and how to they relate to weld voltage?"

Pulsed welding equipment can challenge the conventional wisdom we’ve picked up over the years using a good ol’ constant voltage (CV) GMAW (Mig) welder. With typical CV equipment, the Welder will select a voltage and wire feed speed (WFS) combination, possibly a percentage of slope and/or inductance and then be ready to weld. Today’s pulsed Mig equipment changes most of that.

Most pulsed Mig welders run on pre-set programs. The Welder will select the type of wire, the wires diameter, possibly a base material and the shielding gas used. From this information the equipment will look at the WFS selected and do a calculation as to what the optimum weld voltage should be.

Of course, this optimum voltage may need some type of adjustment depending on the needs of the Welder. Example: The optimum weld voltage to weld a flat position, 3/8 inch fillet (1F) at 475 ipm may not be optimum to weld a root pass in a horizontal groove (2G) at the same WFS. Understanding that, each manufacturer of this equipment has built-in, an adjustment for voltage. Think of it as a percentage of optimum voltage.

Manufacturers may give you a 0.50 to 1.50 range, or a 0 to 50 range, or something similar. All will call this “Trim”. Using the 0.50 to 1.50 range as an example, 1.00 would be considered the optimum setting. When you reduce your Trim from 1.00 to 0.85, you have reduced arc length and, in doing so, reduced weld voltage. Similarly, when you increased Trim to, say 1.15, you’ve increased arc length and, in doing so, increased weld voltage.

This is very similar to what you were doing all along on that old CV Mig equipment. When you reduced voltage, you were reducing arc length. Even with this new fancy equipment the age-old understanding that “Weld voltage has a direct relationship to arc length” doesn’t change.
What’s different is that a Trim of 1.00 for a given electrode (type/dia.) will give you a completely different weld voltage when you change electrode, shielding gas or WFS.

Most of today’s pulsed equipment will display average weld voltage as the equipment is welding, and some will continue to display it for a short period (seconds) after welding has stopped. This feature helps the welder monitor compliance to the weld procedure (WPS).


"It's Good to be Me."

Friday, October 2, 2009

B31.3 Processes

Question: Paul, I enjoyed reading your article printed in Practical Welding this
month, thank you!
I have a question relative to ASME B31.3 the code for chemical plant piping.
The area of this code referring to the type of welding process that is
acceptable is un-clear to me. I am referring to section 328.2.2,
..."welding procedures qualified by others may be used, provided that the
following conditions are met:( f ) The welding process is SMAW or GTAW or a
combination thereof"

Does this mean that the only acceptable process for welding has to be either
SMAW or GTAW, or is GMAW acceptable as long as it follows a written and
acceptable WPS?
And if GMAW is acceptable, must it be performed by a certified welder who
has been qualified in that WPS?

With your article being written about WPS's and referencing the same code I
have questions about, I thought it wise to seek your council.

I truly appreciate any enlightenment you can provide.
Thank you and regards,
Randi Kremer

Answer: The section you are referring to (328.2.2) is specific to the use of weld procedures qualified by others (not qualified by you). When a fabricator wishes to utilize these procedures, they face many limitations. One of those, as you’ve discovered, is the process used.
There are many other allowable processes available but all would require you to produce a qualified Weld Procedure Specification (WPS).
ASME B31.3 section 328.2.1 mentions, “Qualification of the welding procedures to be used… shall conform to the requirements of… Section IX…” So ASME Section IX will layout your requirements for qualification.
The process that you are wishing to use, Gas Metal Arc Welding (GMAW), is included in Section IX as an allowable process. So, yes, you can use the GMAW process but you will need to qualify a WPS to do so.
As for your Welder being qualified to the new WPS, that is a bit of a “Chicken or the Egg” scenario.
A Welder typically wouldn’t be qualifie

d to a WPS before the WPS has been tested and developed and a WPS won’t be qualified until a competent welder completes it.
Code writers recognize this. ASME notes that a procedure qualification has a distinctly different purpose than a welder qualification.
ASME Section IX QW-100.1 makes the statement, “…the welding procedure qualification test establishes the properties of the weldment, not the skill of the welder…” Prior to that statement you’ll read, “It is presupposed that the welder… performing the welding procedure qualification test is a skilled workman.”
As for Welder Qualification, QW-100.2 notes that, “the basic criterion established for welder qualification is to determine the welder’s ability to deposit sound weld metal”.

So how does this apply to Campbell Fittings and their desire to utilize the GMAW process?
It sounds like you need to qualify the GMAW process. This can be done by any of your competent Welders. Once your Welder has successfully completed the Process Qualification testing he/she will be considered qualified. The limiting factor will be that the process will be qualified within a given range of essential variables and the performance (welder qualification) will be qualified within a different given range of essential variables.
Once the WPS is completed the welder who qualified it may need additional testing to utilize it in your specific application.

Example: Your Welder completed the Procedure Qualification test (PQR) in the Vertical (3G) position, on a Single V-Groove, with a backing strip and the progression was up. You would like to apply this same Procedure Qualification Report (PQR) to a similar joint but you intend to change the groove by eliminating the backing and weld vertical down. A new WPS could be written to reflect these changes and would not require testing, but your Welder would not be qualified to this new WPS.

Confusing? I know. When talking “Code Talk” always make sure you separate Procedure Qualification from Performance Qualification. I often see where these two consistently trip people up when talking weld qualifications. Consider contacting a competent Certified Welding Inspector who understands the ASME Codes to review your specific needs and advise you on additional testing requirements.


It's Good to be Me!

Friday, August 7, 2009

Vertical-up or -down in robotic welding?

Vertical-up or -down in robotic welding?

We have a weldment that incorporates 0.375-in.-diameter steel rods and a 0.060-in.-thick sheet metal stamping of 1018 CR material. Each weld is the same, 0.75 in. long with a 0.25- in. fillet, perhaps including weaving. The assembly is fixtured and welded robotically using GMAW with CO2 gas and repeated 100 to 300 times.

We utilize vertical welding, but which is a better progression, down or up?

Richard P.

Vertical-up and vertical-down welding are significantly different from one another in the technique used and the resulting finish weld. This is the reason welding codes consider this change in progression an essential variable and require additional testing when changing from one to the other.

From your description, I would have to conclude that of all the possible positions (flat, horizontal, vertical, and overhead), this is an ideal candidate for welding vertical-down. Your greatest concern in this application is going to be burn-through on the 0.060-in. sheet metal. Welding vertical-up will be difficult, if not impossible, in this configuration because of the low travel speed and high heat input. Welding vertical-up with GMAW typically requires a weave technique to carry the puddle and give you the proper bead profile. GMAW vertical-up is a deep-penetrating technique, and this characteristic is going to lead to consistent burn-through.

GMAW vertical-down, on the other hand, tends to lack penetration and side-wall fusion. These characteristics are undesirable in most applications, but given that you are using a fully automated system, tight control of wire feed speed (WFS), voltage, travel speed, and bead placement should allow you to counteract these characteristics and control your finish weld quality.

I’ve had a lot of success setting up similar applications in what I call the 45-degree vertical-down position. The key is using a slight drag angle (10-15 degrees) and keeping the arc on the leading edge of the puddle at all times. This is a little easier to do at a 45-degree incline than at straight 90 degrees.

If possible, consider a mix shielding gas (minimum 85 percent argon/maximum15 percent CO2) as opposed to the straight CO2 you are using today. This should reduce chances of burn-through and reduce weld spatter considerably. A 0.035-diameter solid electrode should work well in this application.
You stated the weld size was 0.25 in. Talk to the engineering team and your customer about reducing the weld size to 0.19 or even 0.125, which will help increase travel speed, ensure penetration into the root, and reduce cost. Large welds with no root penetration or side-wall fusion are of little benefit to your customers.

Saturday, May 16, 2009

Do I need a welding procedure specification?

Do I need a welding procedure specification (WPS) for my company when it is just me and all I do is on-site portable welding of a wide range of items?

Steven B-


Whether your company requires a WPS depends on the customers you serve. For example, if your company is hired to fabricate your neighborhood association’s new flagpole, using your skills and best judgment would most likely be acceptable. On the other hand, if you are contracted to fabricate steel supports for a new government facility in your hometown, a little more paperwork probably is involved.

Review all the documentation from your clients in detail. Ask questions if you are unsure. A common statement found in contract documents is "All welding shall meet the requirements of the latest revision of AWS D1.1, D1.2, D1.5, ASME B31.1, B31.3, API 1104 ..." This statement indicates written weld procedures and documentation are required that show your welders and welding process meet the code requirements. You need to know, before you strike an arc ... before you bid the job, if there are specific code requirements.

Does your company need (as opposed to require) written WPSs? Yes!
Without a clearly documented and followed process, it is difficult to communicate details of your welding to your customers. With a clearly defined WPS, everyone involved knows what is to take place. Should something go wrong, say that new flagpole drops on top of the neighborhood association president’s new MINI Cooper, you'll be able to show the insurance investigators that you are a professional and the failure was clearly not caused by an uncontrolled weld process.

In your company name you use the term Certified. To be a certified welder requires testing, typically to a nationally recognized standard. This is monitored by a third party, often a professional organization such as the American Welding Society (AWS) or a governing agency like the state department of transportation, and administered at an accredited test facility. These organizations would most likely require your work be completed per a qualified WPS to maintain your welder qualifications.

It's Good to be Me!

Wednesday, April 22, 2009

Good Call!

We have is a stiffener bar (continuity connection) in a column that calls for (AWS D1.1) BTC-P4 for the flanges and fillet welds both sides in the web. The stiffeners were field welded. After assembling 35 connections we discovered no fillet weld on the bottom side in the web. Problem is we can't weld the bottom side of the stiffener now because of clearance. What are our options? Could we add more than the required 1/4” fillet on top of stiffener to satisfy the inspector? He is not offering any solutions. He just wants the requirements to be met, fillet weld both sides. If you can help, it will be greatly appreciated.
Thank you,
Brian N.

Thank goodness for “on-the-ball” inspectors. The inspectors’ part in this construction project is to monitor the fabrication and erection. Should issues arise, he is to bring them to the attention of those who need to know. Speaking from past experience that can be a thankless job.
The inspector on your site is insisting the welding completed meets the requirements of the jobs documentation. When things go wrong and an inspector raises the “red flag”, it is often the case that those on the ground will look to him and ask, “What should we do?”
The inspectors’ first response should be “Contact the Engineer and come up with a documented solution”.
Often, when we start to brain-storm solutions on the job site, we don’t have all the facts or we may not understand all the requirements, to make the call. Example: Your suggestion for missing weld on one side of the joint was to increase weld size on the opposite side. There may be times when this is an acceptable solution, but if the engineers concern is the stress riser created from the missing fillet (which is often the case in today’s building construction) that oversized fillet would be of little benefit. And better to bring the issue into the light for engineering analysis now, than to find out after the concrete has set, that the fix was unacceptable.
Inspectors may or may not have the engineering back ground to make this call, but it is the engineer responsible for the project that should come up with an acceptable solution.
Brian contacted me by email to let me know that the solution to his welding issue was to backup, disassemble each connection, and add the original required ¼” fillet weld. Good call!

Monday, March 2, 2009

What are the negative effects of whipping or weaving?

“We Mig weld carbon steel materials 1/8” thick and greater. Our Welders use a whipping technique that you have described as a bad work habit. What are the negative effects of whipping or weaving?

Whipping and Weaving.
As with many welding techniques, there is a time and place for everything. Watch most robotic applications and you’ll see a constant weaving motion (side to side). Observe as a Fitter puts a 6010 root pass in a pipe and you’ll notice a distinct whipping action (fore and aft). This movement is perfectly acceptable for these applications. The robot uses the motion to find its way. The Pipe Fitter uses the “fast freeze” characteristic to burn away the land and place the root perfectly at each whip.

In production GMA (Mig) welding those same techniques can have negative affects on your finished product. Weaving with the Mig process is a common technique when welding vertical up. It can be difficult to carry the puddle up without the weave technique. A slight weave is common when Mig welding in other positions, but slight should be defined as 2-1/2 x the electrode (wire) diameter. With an 0.035 diameter wire that is about 1/8” of movement. Exceeding that can lead to overlap, undercut and other undesired conditions. Multiple stringer passes should be considered when additional bead width is needed.

As for whipping when Mig welding… There are times when whipping is used to bridge a gap, but often the Welder would be far better off turning the welder down to a short circuit transfer and applying that root. Again, a slight whip is common but slight in this case should be defined as 1-1/2 x the wire diameter. If the key to quality Mig welding is keeping the arc on the leading edge of the puddle, then the whip technique goes against that.

When a whip is excessive weld throats can be undersized and weld spatter is increased. Each time the Welder backs the arc up away from the leading edge the wire is driven into the molten metal and spatter increases. This will require removal and increases the cost of your product.
Good technique is important to improving weld quality. The internet is loaded with great resources for improving our welding skills. Check out this Mig Handbook for additional information. (

Tuesday, February 24, 2009

Certified Welders

My younger brother is the Service Manager for a “High-End” import car dealership on the west coast. He received a recall notice concerning Receiver Hitches on Cross-Over SUVs. Welds on the hitch could not be verified as being completed correctly therefore they would need to be removed and re-welded. The Recall Notice stated, “All welding shall be completed by an AWS Certified Welder.”
Joe’s question to me, “What does that mean? Where do I find an AWS Certified Welder?”
Not all welders are AWS Certified Welders. Certified welders are tested at an accredited test facility and their records need to be strictly maintained within AWS QC7-93 guide lines. QC7 is the AWS “Standard for AWS Certified Welders”.
So where does Joe go to find a certified welder? My first suggestion was to contact the nearest “Accredited Test Facility”. The AWS maintains a list, online, at The closest facility for Joe was in Tacoma, WA.
With a little help knowing where to look and the right questions to ask, Joe was able to get the 40 SUV’s on his lot repaired so his sales team could feel confident and start moving them.
If you want to know how you can become “Certified” log on to There are AWS certification programs for Welders, Inspectors, Supervisors and more. Certification can open doors, present opportunities (like Joe’s) and put you out front in a tough job market.

Sunday, February 15, 2009

Arc Welding 101
May/June PWT 2008
Title: A WPS lesson for beginners

Recently I was given a weld procedure specification (WPS) from a contractor to review. It’s still lying on my desk. Do you have any tips for a beginner like myself on how to review a WPS?
Habeeb Rahman
TPI Welding Inspector


It's time to pick up that WPS off your desk and give it a good, hard look. The first thing you need to arm yourself with is the correct code or standard. The WPS is going to state which code or standard it complies with. You most likely need to get familiar with ASME Section IX or AWS D1.1 Sections 3 and 4, or both.

Does it reference a procedure qualification report (PQR), or is it considered prequalified? It is important to make sure that the WPS states how it was qualified.

Review the joint design. Does the joint on the WPS match the joint referenced? Is backing required? Is the joint within the stated tolerances?
Ensure the base metal of the joint matches the base metals listed on the WPS, which may require a little homework. Your code should list materials by group or P-numbers. Also review the filler metal/flux/shielding listed and witness which is used.

Are there preheat or postweld heat-treat requirements? How will you measure them? Are the welding parameters such as current, voltage, travel speed, and number of passes being used within the range of the ones that are listed? How will you measure them?

A WPS is really a recipe for how a particular weld is going to be made. All the ingredients need to match, and when they don't, even beginners need to stand up and get the attention of someone who will get your welding back on track. Don't be intimidated by a WPS. Break it down section by section, and simply ensure that what is noted matches what is being done on your project.