Weld Penetration Problems

Ken P...

Our problem, we get linear porosity at the furthest point of penetration (heavy plate). The size of porosity is 0.3mm dia. but occurs regularly in every weld sectioned so far. Please suggest any steps, which should be checked.
Weld Info: Semi-Automatic process, Spray Transfer, Blasted Material, Electrode: 0.045" ER70S-6, Gas: 91Ar / 5Co2 / 4O2 @ 35cfh, WFS: 485ipm, Travel Speed: 13ipm, Amps: 335A, Voltage: 29.3, Finished weld size is 12mm

Ken,
I would suspect that your weld penetration profile is showing “finger penetration” (Not sure if that is a real term but), a real deep area of penetration at the weld root. The profile is much deeper (at this location) than it is wide. This will cause this area to open up during solidification.
Grab your copy of AWS D1.1 and check out the Commentary section at C3.7.2 “Width/Depth Pass Limitations” also, Figure C-3.2 “Examples of Centerline Cracking”.
I was asked to troubleshoot a similar condition during a job interview for a former employer. To save money, they had changed a process from an 0.045 dia. electrode to an 0.052 dia. When they made the change they did not change any other parameters. The high wire feed with the larger diameter electrode created a considerable increase in current which equates to a considerable increase in root penetration. Like you, everywhere they sectioned, they had this pore, which I believe was more of a linear void. A reduction in WFS, although not popular, eliminated the problem. P.S. I got the job!
Typically, a reduction in current (WFS) will reduce this finger penetration and this should remedy your issue. One other thing; yours is a weird shielding gas mixture. Not sure why you would go with so much Oxygen but I don’t know your whole story. If you can, replace the Oxygen with more Co2. Perhaps that will change your weld profile as well.

Good Luck! PWC

"It's Good to be Me!"

Careers In Welding

Careers In Welding

That's the way we've always done it.

If someone tells me that one more time I may puke.

This story was from a fellow inspector...

One Christmas, a young girl was watching her mother prepare the ham for cooking. The mother took a sharp knife, cut off both ends of the ham,added all her other 'special' items for flavoring, put the ham in the pan and into the oven.

The girl asks, "Mother, why did you cut the ends off of the ham?" "Why, I don't know, that's the way my mother always did it."

Later, when all the family was together for the meal the mother asks "Mom,why did you cut the ends off the ham?" She says, "I can't recall, oh, Mom always did it that way." They look over to the Great Grandmother who is sitting in her seat smiling. Great Grandma says, "I had to cut the ends off because my pan was to short to fit the ham in whole."

By pure observation, a habit, a procedure, a course in history may be set for generations that has nothing to do with the finished product, science,or fact.

It's Good to be Me!
PWC

Which welds are required to be visually inspected and by who?

Ed called: “We work on Off-Road and Lifting Equipment and our welders are qualified per AWS D1.1. Which welds are required to be visually inspected and by who?”

Ed, A few documents you should consider adding to your welding library are:
• AWS D14.1- Specification for Welding Industrial & Mill Cranes & Other Material Handling Equipment,
• AWS D14.3- Specification for Welding Earthmoving, Construction & Agricultural Equipment -and-
• AWS D14.4- Specification for Welded Joints in Machinery & Equipment
These welding specifications are a little more applicable to the industry <> services.

You asked which welds are required to be visually inspected and I had to snicker… There was a time in my life when on one side of my Hard Hat was printed “AWS D1.1 Sec 6.9” I would get this question, smile, point to my Hard Hat and say, “Look it up!”

AWS D1.1 keeps it simple, Clause 6.9 – Visual Inspection, “All welds shall be visually inspected…” Section 10.6 of D14.1 is similar, “All welds shall be visually examined.” That doesn’t leave a lot of “wiggle room”. A qualified inspector needs to visually inspect all welds.

As to who the qualified inspector is, I told you over the phone that a Certified Welding Inspector (CWI) isn’t required. Welding codes and standards typically accept the qualifications of a CWI but they don’t require certification. AWS D1.1 and D14.1 require inspectors to be qualified and that the bases for qualification are documented. In addition, D1.1 requires a regular eye exam.

As long as <> writes a qualification procedure for your inspectors, the inspectors conform to Para: (1), (2) or (3) [see D1.1 Para: 6.1.4.1 or D14.1 Para: 10.1.3] and <> maintains documentation that those inspectors meet the qualification requirements, visual weld inspection can be handled internally.

A great document to use as a guide for developing your Weld Inspector Qualification Procedure is AWS B5.1 – Specification for the Qualification of Welding Inspectors (http://files.aws.org/certification/docs/b5.1-2003-errata.pdf). This is a free download made available by the American Welding Society at www.aws.org

As for what I had printed on the other side of my Hard Hat… “AWS D1.1 Sec 3.1, 2nd Sentence”. Look it up! But that’s a whole other column.

"It's Good to be Me."

PWC

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).

PWC

"It's Good to be Me."

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
Engineer

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.

PWC

It's Good to be Me!

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.