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Up Topic American Welding Society Services / Technical Standards & Publications / GMAW-P Certification, multiple base metals
- - By BPI1 (*) Date 07-30-2007 14:44
I need a MIG pulse certification for Carbon (A36), Stainless (304) and Stainless to Carbon (304 to A36).  I was speaking with a CWI who informed me that to prequalify the process, I need to be at at least 200 amps.  Since I can only set the WFS (Millermatic 350P), how do I know when I've attained 200 amps?

Also, am I correct in saying that for a groove weld, the plates must be beveled to 22.5 degrees (45 degrees included) with a backing strip, similar to a 7018 plate test?  I am generally a TIG & stick welder, so this MIG pulse stuff is new to me.
Parent - - By Lawrence (*****) Date 07-30-2007 15:39
BP1

There are several questions lurking in the text of your post.

1.  Stainless to carbon will not be covered in pre-qualified procedures in D1.1. For this I would suggest you consult data from AWS B2.1 Specificaiton for Welding Procedure and Performance Qualification.

2. I don't know exactly what your CWI was referring to with his 200 amp minumum statement, but it has nothing to back it in the code (AWS D1.1)  What I think he may have been saying is that GMAW with Short Circuiting Transfer (GMAW-S) is not a pre-qualified process. GMAW-S is a lower amperage Mig process and requires WPS qualification per Section 4 of D1.1.

The groove angles for pre-qualified joints may be found in section 3 of D1.1.  You might want to have a look at Figure 3.3 (B-U2a-GF) if your joint has backing.  That joint provides a groove angle of 30 or 45 degrees depending on the size of the root opening.
Parent - - By BPI1 (*) Date 07-30-2007 15:53
Thanks for the reply.  I don't have a codebook available, so I can't go look up these things.  If you can give me a little more info, that'd be great.
Parent - - By Lawrence (*****) Date 07-30-2007 16:27
Welcome to the forum by the way.

Well,  If your Miller 350P is set in pulse mode you should be getting a spray transfer filler deposit no matter what the wire speed is set at....  Although I have some personal questons about GMAW-P being a prequalified process in the first place since GMAW-P is a CC or a CC/CV process and only pure CV GMAW may be prequalified per D1.1 Section 3.2.4.

As for giving you more information, and I don't want to come off like a jerk but it is really important that if someone is going to comply with a code that they are provided with a copy of it.  If you are trying to write the WPS you NEED to have a copy of the code.  If you are a welder you NEED to have a WPS available to you that complies to the code.

Anyway.... If you make your questions very specific, maybe we can help some more.
Parent - - By BPI1 (*) Date 07-30-2007 17:22
GMAW-P is a CV process.

I have been writing WPS's for several months without a codebook, although I understand the need for it.  Currently I am the WPS writer, the welder and the quality control.

Where can I get a copy of D1.1?  Do you have a link?
Parent - - By Lawrence (*****) Date 07-30-2007 17:58
GMAW-P is not a CV process... It is at best a hybred.  Have a look at the owners manual of your 350-P or any other GMAW-P power supply made in the last 15 years.

This is what Miller says at their own website:
"The AccuPulse process controls both current and voltage to stay within the optimum range for a specific wire type and diameter, wire feed speed and gas combination (other pulsed spray transfer technology only controls current). The AccuPulse control scheme starts by ramping up the current. Once the target current is reached at the beginning of each phase, the constant current (CC) control turns off and the constant voltage (CV) control loop turns on. The CV loop modulates the current within a range that maintains the target voltage. This is independent of the contact tip to work distance, which allows AccuPulse to perform with very short arc length characteristics that optimize welding performance and operator appeal. (Fig. 1)."
http://www.millerwelds.com/education/articles/story99.html

Here is a link the AWS library sales
https://www.awspubs.com/product_info.php?products_id=325&osCsid=a67660d73cb1444146d6f50a0abda793
Parent - - By 803056 (*****) Date 07-31-2007 03:18
Different companies, different models, different wave forms, different slope, still pulsing. Some may and some may not be CV.

Best regards - Al
Parent - By Joseph P. Kane (****) Date 07-31-2007 13:13
Al,

You make a good point here.  I was discussing Pulse problems with a Lincoln Rep about six years ago at an AWS Section meeting, and I mentioned that the machine I was using was only listed as a CV machine, and was frequently used in CV mode for Short circuiting transfer, but in fact it behaved like a CC unit when using it for pulse welding.  He  told me that I had evaluated the performance correctly..I asked why the manufacturer didn't tell us that it was CC.  He said that the inner workings of the machine was a trade secret. 

I found that answer to be incredible, because these manufacturers have to file patents, and all the manufacturers buy and test out each others machines.  How can the competition not know all about the competitors machines?  However, there was a Rep from another manufacturer in the meeting, and he didn't know that!

I personally believe that the CV power supplies that revert to CC when using pulse are not permitted for prequalified D 1.1 welding operations, because of Paragraph 3.2.4.  Judging by the problems I encountered while troubleshooting during that project, there is good reason for it. 
Parent - - By BPI1 (*) Date 07-31-2007 11:45
So since the process is CC/CV, it can't be prequalified.  How does one go about getting the certification to do this process then?
Parent - - By Lawrence (*****) Date 07-31-2007 12:50
Good question.

Let me say that I have my doubts about D1.1   section 3.2.3.....   As I said before, I have *personal* quesitons about that paragraph.   My guess.. and it's only a guess, is the intent of that chapter might not intended to limit GMAW-P but rather to limit voltage sensing wire feeders slapped on the top of a CC stick/tig power supply.  It just happens that GMAW-P is also a CC process.  I think that currently, lots of people use GMAW-P pre qualified.  The Committee has been asked to clarify, but hasen't yet done so.   On the other hand if the committee did intend to keep GMAW-P from pre-qualified status the text of 3.2.4 certainly says that much, but it might do well in the future to make it a bit more clear.

So if the intent were to limit GMAW-P prequalification, the WPS would need to be qualified by testing per section 4 of the code.  
Parent - - By BPI1 (*) Date 07-31-2007 13:35
What is section 4 of the code? 
Parent - - By jwright650 (*****) Date 07-31-2007 14:26
Section 4 of D1.1 deals primarily with Qualification...of WPSs through PQRs and then also addresses the qualification of the Welding Personnel.
Parent - - By 803056 (*****) Date 08-01-2007 00:30
Since we are discussing D1.1, the subject of qualifying pulsing is a sore point with me.

The meters provided with pulsing machines are insufficient to properly document the pulsing parameters. You need an oscilloscope to see the waveform and to determine the peak parameters and the background parameters. To complicate matters more, there is no way, short of the oscilloscope to determine the duration and frequency of the pulses. Some machines have variable frequencies while welding just to add another twist.

The bottom line is that the welding procedure qualified using a machine model AAA manufacture red by XYZ can not be utilized for a different model manufacture red by XYZ or another machine manufacture red by company ZBX unless you close your eyes and click the heels of your red shoes together six times and say the magic words, "I see nothing, I hear nothing, and I say nothing!"

The same statement holds true of any welding standard used by the industrialized nations of the world. Most welding standards do not adequately addressing pulsing.

Best regards - Al
Parent - By ssbn727 (*****) Date 08-01-2007 00:42
Excellent Observation Al! :)

Respectfully,
Henry
Parent - - By BPI1 (*) Date 08-01-2007 11:35
Hey Al, glad to see you.  I really enjoyed the lo-hy discussion and used it to prove the point to my bosses (who didn't want to spend $500 on an oven).

Since there are no adequate standards to address pulsing, is there a way around the situation?

In a conversation I had with a CWI yesterday, he mentioned that to pulse on stainless, the shielding gas content would have to be at least 90% Argon, and 10% other to qualify for the pulse/spray transfer.  I'm using Shieldpro 515, which is 68% Argon, 30% Helium and 2% Carbon Dioxide, which doesn't meet the prerequisites.  I'm using a Millermatic 350-P, and that is the gas recommended by the manufacturer.  Do you or anyone else have any suggestions on what to do about this?
Parent - - By Lawrence (*****) Date 08-01-2007 13:19
BP
Your CWI is giving you poor advice.

The gas you currently have might be ok... Just ok.  You still have over 80% inert gas (which is the real requirement)  The gas you are currently using is common for short circuiting transfer on stainless steels, but It will spray.

The most common Spray transfer gas for stainless steels is 98% Argon / 2% Oxygen. Some folks use 98/2 Ar/C02 in order to limit oxides.
Parent - - By BPI1 (*) Date 08-01-2007 13:50
What is the difference between "pulse" and "spray"?

I'll look into the gas setup with my supplier and see what we can come up with.
Parent - By aevald (*****) Date 08-01-2007 14:47
Hello BPI1, in a very simple description, spray is a mode of transfer where the weld metal transfers through the arc in the form of microscopic droplets, this generally occurs with gas combinations that include at least 80% argon as well as other gases and normally occurs on the upper end of the voltage scale. Pulse on the other hand, uses two basic current levels to form the weld bead(one high and one lower), these "levels" could include one that is in the spray range and a lower one that might be in the globular range or short arc range, but not necessarily. Different equipment manufacturers have different applications of this process and either have set schedules that control this on their specific machine or allow for custom modifications of these parameters. Pulse sometimes allows for a higher average energy input into the weld process while still maintaining weld control and thus could be argued allows for faster travel speeds and possibly better penetration or control of penetration in certain applications. There is really a lot of discussion that could be applied to pulse, I just included a very basic sort of description here and I'm sure others will give you much more to consider. Regards, aevald
Parent - - By BPI1 (*) Date 08-01-2007 17:07
Lawrence :

This is what the CWI said in his email when I asked specifically whether it was total inert, or total argon :

"It is argon gas specifically. Argon has a unique characteristic that when ionized at 26 volts or higher causes the "spray" transfer to occur.
No other industrial welding gas has this capability.
On stainless steels, the code says "Active gas content shall not exceed 4%".
Therefore oxygen and carbon dioxide content are limited herein but the inert gas contents are variable except when determining what transfer mode to be welded in."

What is your opinion?
Parent - By Lawrence (*****) Date 08-01-2007 17:34
Well, first off,  I guess we need to define which code is "the code" you are being advised about.

Since we are talking about stainless steel we could be talking about AWS D1.6 structural welding code for stainless steel.  Lets be sure about that first.

The limit on active gas to 4% sounds like good advice.

As far as the Tri-Mix gas being able to spray or not.. Just plug in your 350P Set for plain CV, set wire feed at 400 ipm and Voltage at 27 add your 68% Argon, 30% Helium and 2% Carbon Dioxide and watch it spray. (for 0.035 stainless filler)   Or for GMAW-P set to accupulse and 0.045 wire to 250 ipm and adjust the trim until you see spray. 
Parent - - By 803056 (*****) Date 08-02-2007 02:05
Hello BPI1;

I defer to AWS A5.32 Specificaton for Welding Shielding Gases. The following is based on that standard.

"SG-AO-2 (Argon + 2% Oxygen) This mixture is used for spray arc welding on carbon steel, low-alloy steel, and stainless steel. It provides additional wetting action over SG-AO-1 (also used for spray on stainless)."

"SG-AHeC- 10 through 40/1 through 15 (Argon with 10 to 40 Helium and 1 to 15% Carbon Dioxide. Mixtures in this range have been developed for pulse spray welding of carbon, low-alloy, and stainless steel. Used for heavy sections in positions other than flat."

"SG-HeAC-7.5/2.5 (90% Helium + 7.5% Argon + 2.5% Carbon Dioxide) This mixture is widely use for short circuit GMAW of stainless steel in all positions"

I hope this helps. I would also refer to the AWS Reommended Practice for GMAW. They provide some useful gudelines for which gas mixes to use for different metals and modes of metal transfer. I have a copy around here. somewhere.

Best regards - Al
Parent - - By BPI1 (*) Date 08-02-2007 12:00
Al -

Thanks for that clarification.  I've purchased some codebooks, D1.1 & D1.6, that I have to read in full today, provided I can get the PDF files open.  Some serious DRM on those files...

Thanks for your help!
Joshua
Parent - - By jwright650 (*****) Date 08-02-2007 12:24
"D1.1 & D1.6, that I have to read in full today"-quote

Whoa, you better get a large pot of coffee started, that is some really dry reading to get through in one sitting.....LOL D1.1:2006 is 504 pages, by itself.
Parent - - By BPI1 (*) Date 08-02-2007 13:53
I know, it'll be almost as good as Harry Potter   /end sarcasm
Parent - By ssbn727 (*****) Date 08-02-2007 16:20 Edited 08-03-2007 17:23
Hi BPI1!

If you want to know about the AWS structural welding codes for steel and stainless steels, then go ahead and read away but, I seriously do not think you're going to find anything enlightening with respect to applying the optimal welding parameters, shielding gas parameters or anything else that will guide you in depositing the best welds possible using the aforementioned forms of GMAW methods of metal transfer.
deposits

If you want to find information about how to achieve the best GMAW deposits with various methods of metal transfer through process control without all of the sales hype, then I strongly suggest that you visit Ed Craig's:  http://www.weldreality.com  

Take a journey around his site and you'll see why most of us here have such respect for the experience and, knowledge this man has to offer when it comes to just about everything one wants to find out about how to deposit optimal welds through process control knowledge!!! :)

I'm not going to give you any other suggestions because, I really do'nt need to anymore!!! Especially since I've pointed you in the direction where you need to be so, enjoy your journey into Ed's world!!! :) :) :)

Respectfully,
Henry
Parent - - By js55 (*****) Date 08-02-2007 16:54
john,
LMAO!!!  I was going to say myself, D1.1 and D1.6 in one day without your head hittin the table.
Much greater motivation than I could ever muster. I salute you.
Parent - - By BPI1 (*) Date 08-03-2007 11:19
Alright, reading the codes in a day was a little extreme, seeing as how I got through D1.6 section 2 and was more confused than when I started reading.  I think if this was a book on tape, it would have to be read by Ben Stein!

Thanks for the link, I will take a look at it.  Can you suggest any other literature that I should read along with the code that will help it make a little more sense?
Parent - - By Lawrence (*****) Date 08-03-2007 12:28
Well Ed Craig's website is prolly more wordy than those code books.... (but more exciting)

Ed also sells parameter handbooks (I have both on my desk) that are worth spending the money on.
Parent - - By js55 (*****) Date 08-03-2007 13:44
Ed's Mig Welding book is excellent. I highly recommend.
Parent - By js55 (*****) Date 08-03-2007 13:44
By the way, my name ain't Ed.
Parent - - By 803056 (*****) Date 08-06-2007 04:50 Edited 08-06-2007 04:55
I keep them (D1.X and ASME Section ZZZ) close to my night stand just for those nights when its hard to go to sleeeeep.

Sorry, no disrespect intended to the men (and ladies) that spend their own money and time to write the codes we depend on. I wonder if people realise the people that sit on committees for AWS and ASME are volunteers and do so without any compensation from AWS or ASME. I guess that is the definition of "volunteer".

Al
Parent - By BPI1 (*) Date 08-06-2007 11:07
It's a very hard read, especially when I have very very little experience on the engineering side of things.  I can read the pictures!
Up Topic American Welding Society Services / Technical Standards & Publications / GMAW-P Certification, multiple base metals

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