Spray transfer questions

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So, I just pickled up a bottle of 98/2 gas so I start working on spray with my MM252.   I did a little tonight and have a couple questions.   1.What causes it to start crackling and popping during a bead?  I would start a bead and it would be that super smooth,  quiet, hiss.  Then it would start to pop and crackle and sound more like short circuit.   Then it would go back to the quiet hiss.  I bent a couple joints in my press until the welds broke, and in the places where it was popping there was porosity.  Where it was smooth and quiet it was solid.   I got a few pictures, but I'm having trouble uploading them.  Not the greatest service here at the house. 2.Is spray not good for tacking?  Seemed every tack was very porous. Oh!  1/4" HRS plate, mill scale ground off.  .035 wire with 98/2 gas at 25 cfm24-25 volts, 400-420 wfs.Sent from my SM-G900V using TapatalkLast edited by Justme; 01-18-2016 at 11:14 PM.
Reply:Here is a butt joint.  45* bevel with about 3/32" left to butt. This is the bottom side.  On the left where you can see it had full penetration I had narrowed my slight weave so it focused into the root more.   You can also see how porous the tacks on each end were.Sent from my SM-G900V using TapatalkLast edited by Justme; 01-18-2016 at 11:15 PM.
Reply:The pictures I took of the porosity came out too blurry.  I'll make some more tomorrow and try for better pictures.Sent from my SM-G900V using Tapatalk
Reply:Ok, here's a picture of the bead where it sputtered a lot.  This one I beveled 45*, but not as deep.   Probably half way through.   Sent from my SM-G900V using Tapatalk
Reply:Dirty plate? Don't see much grinding done prior to welding.Tiger Sales:  AHP Distributor    www.tigersalesco.comAHP200x; AHP 160ST; MM350P,  Spoolmatic 30A; Everlast PowerTig 185; Thermal Dynamics 60i plasma.  For Sale:  Cobra Mig 250 w/ Push-pull gun.  Lincoln Wirematic 250
Reply:Hmm.  Well, I suppose maybe I didn't grind quite enough.   It doesn't really show in the pics,  but I did grind the mill scale off to shiny metal for about 1/2" back from the edge.  It's new plate and not oily or dirty at all.   I'll do some more tomorrow and get prep pics, bead pics, and break pics.  Maybe I'll try to get a short video.Sent from my SM-G900V using Tapatalk
Reply:Originally Posted by Justme. . . I did grind the mill scale off to shiny metal for about 1/2" back from the edge.
Reply:Well, no, I only ground the face side, but I did grind the edges.  I'll try grinding the back side too tomorrow.   Is spray more sensitive to being super clean than short circuit? And yes, CFH!  Duh!  I wouldn't get far on a tank at that rate!   Sent from my SM-G900V using Tapatalk
Reply:Originally Posted by JustmeIs spray more sensitive to being super clean than short circuit?
Reply:Originally Posted by JustmeSo, I just pickled up a bottle of 98/2 gas so I start working on spray with my MM252.   I did a little tonight and have a couple questions.   1.What causes it to start crackling and popping during a bead?  I would start a bead and it would be that super smooth,  quiet, hiss.  Then it would start to pop and crackle and sound more like short circuit.   Then it would go back to the quiet hiss.  I bent a couple joints in my press until the welds broke, and in the places where it was popping there was porosity.  Where it was smooth and quiet it was solid.   I got a few pictures, but I'm having trouble uploading them.  Not the greatest service here at the house. 2.Is spray not good for tacking?  Seemed every tack was very porous. Oh!  1/4" HRS plate, mill scale ground off.  .035 wire with 98/2 gas at 25 cfm24-25 volts, 400-420 wfs.Sent from my SM-G900V using Tapatalk
Reply:crackling while attempting to weld in spray transfer is often a sign that the wire is randomly touching the plate, creating a short circuit event.  More voltage may solve the problem.If the crackling is not present at the start of welding, but develops after welding for a while, then you may be overheating the welding gun.  What is the amperage rating for the welding gun you're using?  The OEM gun for a MM252 is rated at 250 amps.  That is 250 amps at 60% duty cycle, using 100% CO2 shielding gas.  With you high argon mix, you should de-rate the factory value by 40-50%.  So if you're running at more than 120-140 amps, you're likely overheating the gun.You mentioned 24-25 volts 400-420 IPM with 0.035" wire and 98/2 gas.  Is that 2% CO2 or 2% O2, by the way?  In any event, you're likely welding at around 200amps welding current with those setttings; per the miller welds calculator.Seems very likely to me that you're overheating the welding gun/contact tip.  This can cause wire feeding issues, and any drag on the wire will cause random drops in wire feed speed; creating random short circuit events.  This is my best guess as to why you're seeing that popping occur.Solution; Buy a MIG gun rated at 300 or 400 amps.  Your porosity issues are likely due to contamination.  High argon mixes and GMAW welding do not tolerate much rust, corrosion, etc.  Cleanliness is next to godliness, as the old saying goes...Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Originally Posted by vpd66Look at CEP's settings, 29 volts. It seems you are still in globular transfer.
Reply:All great info!   Thank you guys.   The settings I listed, 24-25 volts and 400-420 ipm were Miller's recommended settings.  But I have found I usually use a little hotter setting for short circuit than the recommended.  In fact for 1/4" I'll often use the 3/8" recommended settings.   The gas is 98% argon and 2% O2.  That was the Miller recommended mix for spray. My gun is a Bernard 300 amp gun.  I didn't do any really long beads, or rapid succession of them.   It didn't "feel" like it was over heating,  but maybe.    Know I've felt it get way hotter when doing a lot of welding short circuit before without any issues. Sent from my SM-G900V using Tapatalk
Reply:I like to use 90/10 gas mixture. Might be worth trying. I use a pulser, so settings may be a little different but I'm usually around 28V and ~375 IPM for 1/4". And actually now that I think about it, I think that's using 0.045 wire.John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Originally Posted by vpd66Try raising the voltage. 24-25 volts seems to be on the low end for spray transfer with .035 wire. I have a Millermatic 250 (I know not the same machine) and with 98/2-95/5 gas ( I have a gas mixer and its hard to tell the exact  mix}. I need to set it to 28 volts to get into spray transfer. Look at CEP's settings, 29 volts. It seems you are still in globular transfer.
Reply:Originally Posted by Justme Is spray more sensitive to being super clean than short circuit? Sent from my SM-G900V using Tapatalk
Reply:Well, as life would have it I wasn't able to get in the shop today to try some more, and my work week starts tomorrow.   So I'll try it again next week and report back.   Thank you all for all the information and suggestions! Sent from my SM-G900V using Tapatalk
Reply:Originally Posted by soutthpawInteresting, with my mixer and 90/10 I can get into spray @24 volts on my 350p
Reply:Originally Posted by Stick-manSorry to hijack, but CEP, if I get 90/10 can I still short circuit at lower settings?
Reply:Originally Posted by vpd66I never tried 90/10. Next time I have some thick scrap laying around I'll have to try it.
Reply:Originally Posted by Mark's WeldingWhat are you using for gas? argon/co2? I get spray out of 75/25. unless of course I'd need a special gas mix for some kind of stainless
Reply:Originally Posted by vpd66Try raising the voltage. 24-25 volts seems to be on the low end for spray transfer with .035 wire. I have a Millermatic 250 (I know not the same machine) and with 98/2-95/5 gas ( I have a gas mixer and its hard to tell the exact  mix}. I need to set it to 28 volts to get into spray transfer. Look at CEP's settings, 29 volts. It seems you are still in globular transfer.
Reply:Originally Posted by Stick-manThank you. I was going to try spray for the pusher shoes I'm welding, but I am NOT going to worry that much about cleanliness.Sorry to hijack, but CEP, if I get 90/10 can I still short circuit at lower settings?
Reply:Originally Posted by DanThe numbers around the voltage dial on the Millermatic 250 are the open circuit voltage for that dial setting. Even then it's only roughly accurate. The load voltage for a 28 volt dial setting is going to be roughly some we're in the 26 volt range. The old Millermatic 250 isn't/wasn't a very good spray arc unit with .035 wire. The spray arc with .030 is noticeably better. The 250 always seemed to require a little more voltage then other units I ran too.With 98/2 oxy and an .035 wire, my Millermatic 251, Millermatic 210, and Migmaster 250 all produce (d) a very solid spray arc in the 24 -25 load volt range with 400 -420 IPM of wire being fed.
Reply:Stick, If you have 150CF cyls and cannot get 85/15,90/10,95/5 get some argon based tri mix. I welded the front mount for my loader with .035 and tri mix and it works pretty good just takes higher voltage(27 I think) and more WFS.I was taught that 75/25 does not have enough argon and will only take you to globular transfer......takes 80% or more(the more the better)argon.Originally Posted by vpd66I'm using argon and CO2 with a Smith 2 gas mixer. I can't get my Millermatic 250 to weld in spray transfer with 75/25. It can just barely get into spray transfer with 80/20 gas, .035 wire, and around 30 volts. With 95/5 it will go into spray at 28 volts. Just a tick under 28 volts and nope it starts sputtering.
Reply:Not to raise an old thread, but thought I would throw a little update on this.   I was down with pneumonia for two months, and have been out of the shop for quite awhile, but did some welding yesterday, and may have found my issue. I was running Hobart wire, and my son's finished off the roll in the machine while I was sick.   So I loaded up a roll of HTP wire I got to try.  Both are er70s-6.  This HTP wire runs smooth as silk, even through the mill scale with no grinding or prep.  I had looked to see if there was some rust or something on the Hobart wire, but couldn't see anything,  but there is a marked difference with this HTP wire.  The problem seems to be gone. Sent from my SM-G900V using Tapatalk