GMAW Mil-Std 278?

By Lawrence (*****)

Date 07-28-2009 22:25

I've asked this question many times as it applies to D1.1

GMAWP is an open arc spray type transfer... The only limitation I can see is that D1.1 requires that GMAW be performed by CV power for pre qualified procedures.. if a CC power supply is used than a PQR is required..

The argument is that GMAWP is a hybred with both CC and CV charicteristics so where does it fall?

If your Mil Standard has similar language regarding power supplies this could be a consern.

GMAWP is being used more and more with mild steel appications... I wish some clear direction from the codes would clear these kinds of issues up.

By kipman

Date 07-29-2009 12:09

Tater,
Are you working to MIL-STD-248 or the NAVSEA Tech Pub 248 (S9074-AQ-GIB-010-248)? If it is the Tech Pub, look at paragraph 4.7.4 (c). One of the things I found in working with this document is that as you go up the supply chain and have to deal with people from the various naval contractors and people from the navy there can be some pretty wild interpretations. I recommend that if there is any question whatsoever as to how to interpret something from this document (278 also) that you engage your customer and get their opinion and buy in.
Mankenberg

By pataterchip (**)

Date 07-29-2009 13:47 Edited 07-29-2009 13:52

Thank you for your response,
The procedure in question was qualified to Mil-Std-278 we do work to the tech pub's but only on a few of the newest procedures (makeing the switch to tech pub's was a pain in the AS*). I will take your advise and get our customer involved. Just not looking forward to it.

By 803056

Date 07-29-2009 21:51 Edited 07-29-2009 21:55

Most of the welders recently purchased new have precanned programs for pulsed spray transfer (and other modes of transfer). In actuality, there is no way for the inspector or welder to record the variables used while welding. The meters provided by the manufacture simply are not sophisticated enough to provide that type of information. Better yet, or worst yet for the fabricator, is the fact that using the information garnered from the welding machine simple does not provide sufficient information to use the same "set-up" with a machine that is a different model or different manufacturer.

I record the program number and the machine reading for the paperwork and to satisfy the person that has to review and approve the welding documentation. The truth of the matter is that the inspector needs to use an oscilloscope to record what is actually happening while the welder is depositing weld.

Based on the fact that you mentioned the procedures were qualified to the MIL-STD, I would put money on the fact that the machines used for pulsing back then have been replaced with newer machines. That being the case, there is little likelihood you can replicate the parameters used with the original machines because you don't know what they were then and most likely don't know what they are now.

The ammeter and voltmeter on the machine may show the average values, but they don't tell you the back ground current, the peak current, the pulse frequency, slope, or pulse duration. Clause 4.8(g) of TP248 requires requalification (level II) when either the amperage or voltage vary by 25%. How do you know? To make matters more interesting, some machines even vary the slope as the welding conditions change.

I tell my clients the procedure is qualified for the one model produced by that manufacturer. A change in the model or the manufacture requires a new procedure. End of story, end of never ending discussions no one can win without the oscilloscope. Even then, it is unusual for any of the major shipyards to agree to accept a procedure that was qualified and approved by a different shipyard.

Point of information; when you do submit your WPS/PQR, include all your material test reports, supporting laboratory test reports, and radiograph.

Good luck.

Best regards - Al

By petty4345 (**)

Date 08-05-2009 11:01

The procedure/welder qual. for 278 is 248 and in table V of 248 "machine model or type" is an essential element, so you cannot switch macines without requalification.
Switching to pulse is not an essential variable, but a new WPS must be written and approved.
Switching to "short circuit" transfer is another whole new PQR.
The foot notes of table V in 248 say to give specific information of the pulse parameters that can be changed by the operator.(in short, you just need to read all of the notes that apply)

There is new software that has been developed by NAVSEA to aid in writting PQRs and WPSs. It's called NAVWeld. It's free.
You can go through and pick process,base metals and such and it will tell you what the required tests are for your application.
It may stop you from missing a required destructive test.