Re-Qualifying when switching to pulsed?

By swnorris (****)

Date 08-09-2005 16:32

Pulsed is a modified form of spray transfer, but the process still allows spray transfer welding at average currents which are sometimes considerably lower than the steady state current necessary for spray transfer. Those currents are generally equal to or less than the globular to spray transition current. FYI, the following minimum spray arc current is based on 98/2 shielding gas with these electrode diameters: .030 @ 150 A, .035 @ 165 A, .045 @ 220 A, .062 @ 275 A. I didn't see anything that didn't support you switching modes, and I would think that as long as you are not operating outside the parameters set forth in your WPS, you should be ok, however, you might want to review the commentary in C4.7.1. You might also want to think about additional training on the proper adjustment of the power source. I have seen WPS that indicate the mode of transfer, so if this is your case, and your WPS shows spray transfer, you may not be following your WPS if you switched to pulsed.

By Lawrence (*****)

Date 08-09-2005 16:47

Here is the hitch

If your pulse GMAW is CC/CV or CC than C3.2.4 states that WPS for CC output on GMAW and FCAW must be qualified by testing in accordance with Section 4

By - Date 08-09-2005 22:13

D1.1 Table 4.5 at point 14) requires requalification for a change in mode of transfer. AWS seems to classify pulsed GMAW as a separate mode of transfer (it is listed as GMAW-P in AWS's Master Chart of Welding and Joining Processes, for example). It seems to fall into somewhat of a gray area, but based on the above, I think it would require requalification.
Mankenberg

By swnorris (****)

Date 08-10-2005 10:35

kipmank,

Looks like you have a valid point, however, I questioned point 13 because of the way it was worded. In the older codes, before Table 4.5, it clearly stated "A change in type of welding current (AC or DC), polarity, or mode of metal transfer across the arc". To me, there's absolutely no question about that statement, and it clearly separates polarity from mode by placing the "or" between them. In the 2004 code, Point 13 states "A change in type of current (ac or dc) or polarity and mode of transfer (GMAW only)". I literally took that as meaning that if both the polarity and the mode of transfer changed, then requalification was required, because they are not separated by an "or". They are joined by an "and", which I interpreted to mean they go hand in hand. rtrautman posted that he would not be changing the polarity, so I thought that he would still be good based on how I interpreted the wording. That's not to say that I think I'm right, but sometimes the wording in the code can be reasonably interpreted different ways. I guess when in doubt, go to the extreme. With that in mind, I would tend to agree with you, but hopefully there will be other responses as to their interpretations.

By Lawrence (*****)

Date 08-10-2005 13:25

3.2.4 FCAW and GMAW Power Sources.
FCAW and GMAW that is done with prequalified WPSs shall be performed using constant voltage (CV) power supplies.

Thats the code

Any GMAW operations other than with a constant voltage CV power supply must be qualified by section 4

So as far as rtrautman is conserned, Yes if he switches to GMAW-P he must qualify his procedures. He is not re-qualifying, it's a different process. It's not a matter of transfer modes in this case that makes the requirement, it's the type of power source

Pulsed GMAW requires Constant Current power, This includes all the old after market pulse boxes and most certainly includes newer inverters with synergic pulse capabilities. Here is a really nice explaination of the last 3 generations of pulsed GMAW technology. http://www.millerwelds.com/education/articles/articles32.html
The older GMAW-P power supplies provided CC only when doing pulsed GMAW. The newer synergic power supplies provide both CC and CV power, switching back and forth hundreds of times per second.

The next edition of D1.1 would do well to clean up section 3 to make GMAW-P and GMAW-S more similar in limitations, or else remove the limitation for gmaw-P

I think the original intent of the CC limitation was for Constant Current power supplies that did traditional GMAW and FCAW, but the quality issues involved in non CV kept these operations out of the prequaified catagory. The GMAW-P thing wasn't in mind I bet, still it fits the criteria set out in the 3.2.4 therefore must be complied with.

By - Date 08-12-2005 12:58

Mr. Norris,
Your point about the use of "and" and "or" is excellent. It is always tempting to try and guess the intent of those who write and approve code verbage. This is one reason the Commentary is so useful. However, the Commentary does not address this specific issue, so we are left to interpret the code exactly as written. I would tend to agree with your interpretation of point 14) then.
To me however, the idea of being able to switch from spray to globular, for instance, without requalification does not make sense.
Mankenberg

By ssbn727 (*****)

Date 08-15-2005 19:52

Excellent thread so far!

I just wanted to get some clarity on this issue as it pertains to GTAW-P... In other words, is requalification required if one changes to pulse mode if the original WPS did not include it for let's say - ASME Section IX B31.1? I personally believe that it does require requalification. An old friend believes different so, who is correct in their belief?

Respectfully,
SSBN727
Run Silent... Run Deep!!!

By - Date 08-16-2005 13:45

This seems to be a bit more straightforward than the D1.1 discussion. B31.1 sends you to ASME IX of course for WPS qualification.

Table QW-255 lists transfer mode as an essential variable (an essential variable being defined at paragraph QW-251.2 as a variable for which a change requires requalification of the procedure). Table QW-255 references paragraph QW-409.2 for the definition of transfer mode as an essential variable, and it states "a change from spray arc, globular arc, or pulsating arc to short circuiting arc, or vice versa".

To me this wording is clear - a change from spray to pulsed does not require requalification. A change from short arc to pulsed does.
Mankenberg

By ssbn727 (*****)

Date 08-20-2005 23:30

Hi Kipmank!

I've never seen GTAW in the short circuit, globular or spray transfer mode... Then again, I have'nt seen enough in my lifetime to claim that I have... Anywho, my original question referred to Gas Tungsten Arc Welding as opposed to Gas Metal Arc Welding.

I apologize for not having immediate access to ASME Section IX. The problem is that I do not have immediate access to QW-250 through QW-280 or Article IV, Welding Data.

So, would it become a requirement to qualify a new WPS if one decides that they are going to add pulsing to the original non-pulsing GTAW process they had listed in the original WPS, provided that nothing else has been changed in the procedure they are welding to?

The reason I'm seeking clarification on this is because, I was previously informed that pulsing with GTAW was considered a supplementary essential variable, and had to be listed in the WPS. If it is'nt listed in the original WPS, then a new WPS has to be requalified if pulsing is to be included in the production process.
Am I incorrect? Thanks in advance.

Respectfully,
SSBN727
Run Silent... Run Deep!!!

By - Date 08-21-2005 01:12

SSBN727,
There is no short circuit, globular, or spray mode in GTAW, only GMAW.
QW-256 lists pulsing as a nonessential variable for GTAW process. Also see QW-409.3. QW-251.3 says, "Nonessential variables are those in which a change, as described in the specific variables, may be made in the WPS without requalification."

Chuck

By ssbn727 (*****)

Date 08-23-2005 04:01

Hi Chuck!

Thanks for the reply...it seems that this person who does have access to ASME section IX did'nt really bother to look it up like you did and, to think that I believed he was correct - oh well...

So, the only thing we would have to do is amend the WPS/PQR? What about the WOPQR?

Btw, I known for years that there are'nt short circuit, globular or spray transfer modes in GTAW... I was just trying to be polite.

Respectfully,
SSBN727
Run Silent... Run Deep!!!

By - Date 08-30-2005 15:23

Just back from vacation. Sorry, but I have to admit that I did not read your post as closely as I should have. The thread up until then had been talking about GMAW and that is how I read it. Sorry again for the mistake.
Mankenberg

By ssbn727 (*****)

Date 09-01-2005 06:57

Hi Kipmank!

No need to apologize! A wise man once told me that: "The closest one achieves perfection is two mniutes before they throw the dirt over you after you're dead and buried!" So of course I had to ask him: "What about if you're cremated or buried at sea?" He replied: "I ca'nt answer that question yet because, I'm still alive!!!"

Btw, Chuck from Avesta helped me out on my ASME Section IX GTAW query as per QW-256, QW-409.3, then referring to QW-251.3... Thanks anyway!!!

Respectfully,
SSBN727
Run Silent... Run Deep!!!