GMAW vs. Pulsed GMAW

By Lawrence (*****)

Date 10-18-2007 18:33

Hey Dennis,

The easy response is to suggest you contact your Miller distributer and have them bring a 350P into your shop to demo on production mock ups.... This is a GMAW-P power supply that costs only about 3 grand and is better than anything they have produced at 3 times the cost.

GMAW-P can really help control stainless fillets (especially out of position) I suspect it would be an advantage with grooves also but it would be wise to see it proven in your own shop before throwing down the money.

No come the questons.

These are purged full pen welds?

Structural of fluid/gas service?

What code?

ASME has no limitation on GMAW-P to them its just Mig

D1.1 has language in section 3 that says pre qualified GMAW must be done with CV power supplies... Don't know about D1.6

By dschlotz (***)

Date 10-18-2007 19:04 Edited 10-19-2007 19:16

The pipe is rolled and side seamed and then butted. 75% pen. SMACNA is the governing authority and it refers to

Fig. B-P1a (Square groove butt 1/8" max thk) .035 ER308 L Si, Amp= 87-115 Volt= 16-19, gas 20-40CFH Travil 15-20 IPM

Fig. B-P1b ( Square groove butt 1/4"max thk) .045 ER308 L Si, Amp= 135-155 Volt= 16-22, gas 20-40CFH Travil 10-15 IPM

Is GMAW-P other than CV?

Thanks for the quick response.

By Kix

Date 10-18-2007 19:21

What kind of GMAW machines are you running your stainless welds on now and what wire and what gas? I know some machines with just inductance control and the right gas and wire combo will run stainless just as nice as the 350-p on pulse. Without pulse though the 350-p has a crappy arc for stainless on straight GMAW. Those 350-P's on pulse stainless however will run any wire or gas combo just ass sweet as can be. That comes with the price tag though.lol I'm just saying that you might be able to utilize what you have and save some money if you know how to do it. The salesman that comes in is going to spit some serious game at you to try and get you to buy that machine and it will look and sound like it's worth it cause it pulses that stainless in nice.

By dschlotz (***)

Date 10-18-2007 19:58 Edited 10-18-2007 20:09

Airgas tri-mix @ 90% He 7.5% Ar 2.5% CO2 with Avesta ER308lsi in .035

Miller CP302 's and a Miller Delta Weld 652. We also have a Miller XMT 304 that we can put an Optama pendant on if that is a good way to go.

We have some older Miller CV power supplies that have a high and a low inductance post for the ground cable. We were told that the high was only to be used for stainless GMAW.

I am open to anything that I can learn that will make or guys look more professional. They are willing to do nice work. We just need to get them the right stuff to work with and the proper methods.

Thanks for your input.

Dennis

By Lawrence (*****)

Date 10-18-2007 20:35 Edited 10-18-2007 20:46

High and low work cable posts

High for Spray Transfer
   This applies to stainless or plain carbon steel.
Low for Short Circuiting

I have not had fun with Miller pulse pendants... Nothing wrong with trying though. Especially if your welds are in the flat or horizontal position. I've never seen an XMT pulse worth a darn.

Another thing to think about...   When you have a situation where only one or two guys can make the nice welds. You might want to check how they prepare the joints... It may be that they are more consistant in the fitup and that is why their welds look so nice compared to others... Mig is mig most of the time... Fitup is where the craftmanship comes into play.

If better control of fitup it will take care of the issue, investing in this will be way cheaper than buying pulsed equipment only to find that a pulser won't do any better with crappy fitups.

There is much discussion and debate about GMAW-P and current output. Lincoln is unwilling to admit that their GMAW-P units produce anything but CV, I find this impossible to accept. They only sell GMAW-P with CC/CV power supplies and the behavior of the arc demonstrates quaities of both CC and CV... They say it is propriatary data... Balloney.   Miller is a bit more honest... I believe the code writers that put the limits on CC power for GMAW and FCAW were doing so in order to make sure procedures that included CC suitcase units were proven by testing before they went into production...

I don't think the code committee has any clue that every GMAW-P power supply sold in in the U.S. produces CC/CV current during synergic pulse operations. And if they did recognize the nature of GMAW-P how would they change procedures and WPS to reflect pulse settings that have as many as 18 current variables. It would be a nightmare

By dschlotz (***)

Date 10-18-2007 21:03 Edited 10-18-2007 21:08

Lawrence,

The problem is more that the welders are having trouble with the speed and heat required to wet the edges and not burn through. They turn down the heat and get humpy bumpy welds and then turn it back up and can't follow the seam with the required speed to stop burn through. From what I have seen of Pulsed at Miller's web site, Pulsed is more like what you get with 6010 when you whip it in and out of the puddle. The hot and then cooling cycle seams to be what might help to be able to slow down and see the seam better. If the process is more user friendly, to make comparison to 7024 and FCAW, then maybe they could get better looking welds and get the required 75% pen.

The welders don't fit or prep. The seams are all tight with no root opening.

Pulsed is totally new to me and I value any expertise I can get.

Thanks

Dennnis

By Kix

Date 10-19-2007 12:17

I see Airgas is really pushing that trimix for stainless mig. That stuff is getting ready to get real expensive here in the near future. So when you say 75% penn are you talking full penn to the other side of the joint or are you talking just 75% depth into the base material? If you are going for 75% full penn are you purging? Are they rolling these joints out in a turning fixture or are there some that are done kind of in postition? What type of wire are you using? What is the application for these pipes?

By dschlotz (***)

Date 10-19-2007 14:24

Kix,

The requirement is for 75% depth of pen in base material. No purge. Some of the pipe is rolled out some semi- positioned. The aplication is plant air movement. Wire is ER 308LSi .035 &.045 Avesta.

The pipe is 24" and larger. 14 ga, 12ga, 3/16"

By Kix

Date 10-19-2007 16:57

Well, for the 12 and 14 gauge you might have better results with an .030 wire and the 3/16" use .035 , but then you would have to qualify your procedure by testing. It's going to be hard not to get a good looking bead with no gap or bevel and the pieces just straight butted up. The 75% penn on the 14g should be easy with a straight but. The 12g and 3/16" thick you might have some probs with the 75% penn because of the volt and amps you posted above. I'd qualify you own WPS and bevel the 3/16" and 12g to give you weld metal some place to go and this will give you a much better bead appearance and your 75% weld penn very consistently. I'd loose that tri mix also and save yourself a buck!! Check these threads out for gas info.. http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=70344;hl=trimix%20gas#pid70344
http://www.aws.org/cgi-bin/mwf/topic_show.pl?tid=11369

By dschlotz (***)

Date 10-20-2007 16:11

Lawrence,

At your recommendation we purchased a Miller 350-P to be delivered on 10-21-07. The factory rep. will be in on the 30th. His recommendation for gas is 69% Ar, 30% He, 1% CO2. We will work out our parameters as we go. We don't have to do any production welding before the factory guy gets here.

Thanks Dennis

By Lawrence (*****)

Date 10-20-2007 17:27 Edited 10-20-2007 18:47

Dennis

My recommendation was that your Miller rep prove his machine before you bought one :) But I bet it will be an improvement.

Ed Craig at www.weldreality.com says that his recommendations for shield gas on stainless work better with the 350P than what Miller recommends... It might pay a dividend to email Ed with details about what your doing and see if he agrees with the very expensive gas selection Miller has provided for you.
http://www.weldreality.com/MIG_welding_gases.htm

By dschlotz (***)

Date 10-21-2007 23:05

Lawrence and Kix,

Thanks for sticking with me in this. My boss is the one that bought the machine. He trusts the responses that I get on this forum. You guys have been on target every time I have asked. We do a lot of aluminum and stainless. He wanted to jump right in to the twenty first century. I have been reading about pulsed for a long time and the best way for us to get our feet wet is to jump right into the cold water. I have a bottle of 98/2 on order to test the information you have provided. The rep insisted on the tri mix as the proper start-up mix for our needs. I have the ability to change gas to what is less costly.

Believe me when I say that this not just a chat room for me. I have nowhere to go but this forum to get answers that prove to be true when I put them in practice.

We will have a week to play with the two gases before the rep arrives. We will be testing with ER 308LSi in .035 & .045.
14 ga. 12 ga. 10 ga. 7 ga. All 304L square gooove butt. Figures B-P1a upto 1/8" & B-P1b for 7 ga. We will open up the roots as the testing dictates in order to get our required 75% depth of pen of base metal.

If I had some starting point parameters I would be that much farther ahead.

Thanks

Dennis

By Lawrence (*****)

Date 10-22-2007 02:23

Dennis

For Stainless. Stick with the 0.045 you will find it pulses better than the 0.035 even on thinner material Down to about 20 gague.

Keep us posted on how your trials go with the shiny new toy!

By dschlotz (***)

Date 10-23-2007 23:34

We began testing this morning. I called Ed Craig for parameters. He basically said to use 100 ipm for each 1/16th of thickness and fine tune from there.

With the 350-P, using Eds' rule of thumb, and 98/2 argon and CO2, I welded a square groove butt on 304L with ER304LSi @ 100 ipm with almost 100% pen @ 30ipm travel speed.

The weld profile was slightly humped up but acceptable. As far as color goes, there was a black color near the weld deposit that was easily removed with a wire brush. The weld had a little discoloration remaining that came off with the very slightest amount of buffing with a wire SS wheel.

My welder, that will be using this pulse machine, wants the rainbow of colors that one can get with stainless GTAW. Is that possible or is the fact that we can clean up the weld area without pickling more important.

His first response to the .045 and the 98/2 was, "I want color and will try anything to get it.

What is the purpose of the arc length control? Ours was set at 50 during our preliminary test.

Thanks for your time once again.

Dennis

By Lawrence (*****)

Date 10-24-2007 00:46

You could get perfect color with FCAW Stainless...

By Kix

Date 10-25-2007 17:40

The arc length control sounds like it changes the pulses per second. I know the higher you go the less spatter you will have and it really slicks the fillet welds in there. The lower the wire feed speed the lower your arc length control can be without any spatter. As you start coming up in your wire I come up a bit on the arc length control. 50 is a good starting point for the arc length control. I have noticed that on one 350-p the volts were bouncing back and forth from 19v to 20v and on another machine the volts were going back and forth from 22 to 23 with all the settings the same. Were starting out with our settings for .035 ER308L wire, 98/2 gas, run in at 100, arc length at 50, wire at somewhere around 250ipm, an inductance at 90, but I don't know if inductance even comes into play when this thing is pulsing. All this is on 2.5mm stainless. Are you using .045 for all your work? I can't see using .045 on that thin gauge stuff. You'll get a rope in your joint every time when you try to cool it down enough not to burn through.. Just keep playing with it and you'll find the sweet spot! It's there somewhere.....

By dschlotz (***)

Date 10-29-2007 19:27

To all interestesd,

The welder won and switched back to .035 with 98/2 gas. His welds are superior to those he was able to make with .045. I don't know if it was all size wire or personal prefrence. The long and the short of it is we are pulsing and loving it. Thanks Lawrence and Kix & DaveBoyer for your help. The reason I joined the forum was to be able to get information that I don't have another source for, and to help where my experience is useful.

Thanks

Dennis

By Lawrence (*****)

Date 10-29-2007 19:49

Success is hard to argue with.

Well done!

By DaveBoyer (*****)

Date 10-22-2007 03:49

Dennis: I don't know if You have seen WWW.WeldReality.com, there might be some information that is usefull to You there. Ed Craig seems to be pretty well respected by people who's opinions I value.

By dschlotz (***)

Date 10-22-2007 19:21

Dave,

I have been there and am in the process of testing. If we can make good looking welds as well as meet the requirements of the job, as far as penatration is concerned, I will see if our welders can be weened off tri-mix. I'm very interested in what I have seen at Ed Craigs site.

Thanks

Dennis

By Kix

Date 10-20-2007 17:51

Thats the gas Miller used when setting up the 350-p's pulse program or writing the software or something. We probably have over 20 350-p's in our plant and they kept having probs with the circuit boards going bad in them so we had the 350-p specialist come in from miller right down the road. He put a new board in one of our machines and set it up for pulse with a bottle of 98/2 argon/co2 and ran some samples. I was impressed no spatter, excellent wetting and good color!!! Make sure you ask him about those circuit boards. I think if you have probs they will come out and replace the board for free. Anyway I've seen with my own eyes that the 350-p does not need helium to produce excellent quality welds. Just maybe something to think about although 30% helium is a lot cheaper then what Airgas is pushing. I'm going to miller next weekend to work with our U.S. representative for the World Skills Welding Competition and the guy that developed all of the goodies for the 350-p is suppose to come hang out with us. I will try to get some info out of him on those board probs and I'll relay it back to ya. Well, good luck and hope everything works out for ya.

By dschlotz (***)

Date 10-22-2007 15:16

Kix,

See the response above addressed to Lawrence and you.

Thanks

Dennis