"Bubbles" in my beads

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Hello all,I have noticed that I sometimes wind up with little pores in my welds but I'm not sure what causes this. I have a Millermatic DVI2 running on 220V, using .30 wire, the picture included is a weld between 2 pieces of 3/16" flat bar on voltage setting 4 with wire speed at about 55. See the three little holes on the right?I have also noticed on longer beads that my wire seems to bind momentarily once in a while then let go, is binds for less than a second but interrupts the weld. I was thinking maybe it is the liner but I haven't used the machine that much, maybe 1/3 of a roll of wire since I bought it new about a year ago. Attached Images
Reply:The holes are porosity in the weld. That can come from poor gas coverage. Gas off or set too low, wind blowing away the gas, or even the gas set too high and causing turbulence pulling air in. It can also be caused by contaminants in or on the steel. That would be my guess in this case since it doesn't look like the steel is clean and ground. Since it's near the start, my guess is that it wasn't hot enough to burn off the crud and you got the holes.As far as the hesitation, it could be a kinked liner. If the gun lead was bent real hard that will kink a liner. They used to do that all the time with my machine at work. They'd jam it tight in a corner and kink the liner as it came out of the machine by mashing it into the wall. if you pull the liner from the lead, you will see a definite kink if this is so. If could also be that you have just put a tight bend in the lead as you moved and the rollers are a bit loose. That can cause a momentary slip..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Thats called porosity known as a weld defect, and significantly reduces weld strength. Can be caused by a number of things, insufficient gas coverage, gun angle, dirty material, faulty wire, TOO much gas flow causing turbulence, machine set too hot. Too be honest i havent touched a mig in over 2 years and couldnt be happier all i do is tig/stick pressure work. Their are a number of variables in which you could be getting porosity just start checking/eliminating the following items and you should be good to go. I cant stress enough to anyone dosent matter what process CLEAN your material before you weld it. Take the time and use a grinder to bring the material down to clean shiney surface. If you decide to weld over rusty, oily, mill scale whatever, your drawing all these foreign contaminents into the weld thus setting yourself up for internal or external failures such as hydrogen induced cracking, cold cracking, insufficient penetration, and porosity. I can almost garuntee if you take some time to clean that mill scale off your pieces before you weld them you may have solved your prosoity problem provided everything else is set correctly.
Reply:Hummm----- need more information. What kind of wire are you using, solid with shielding gas 100% Co2, 25% Co2 / 75% Argon or self shielding flux core wire? What’s the gas flow rate, 20-25 CFM? How much is the wire sticking out from the contact tip?You say that the unit has been sitting for a year, any chance that the wire has rusted?As for the wire stop-starting, the feed roll has two groves, one for 0.30 and one for 0.35 wires, are you using the correct grove?
Reply:As far as cleanliness the welded edges in this picture are actually freshly cut, so they are clean, I could have cleaned up to the edge but this is nothing structural. Just more curious about it than anything. I have been trying to find a welding course in my area but the only thing available is a full blown college course for 13 weeks! Although I am considering taking it anyway, it's only one night a week.I am using solid wire with 25/75. I would have to check what the flow is set at, I haven't touched it since I have owned the machine. Is there a better gas to be using? My bottle has just run out and this is a good chance to switch to a different gas.I try to keep about a 1/4" of wire out.The machine hasn't really been sitting for a year, I just don't use it steady I looked at the wire today anyway and it looks normal. I seem to remember having the same issue before we moved here but it seems more pronounced now.Last edited by salem747; 10-20-2009 at 09:27 PM.
Reply:Your gas and wire type are fine, 70S-6 with 75/25.   Set your regulator/flowmeter to about 20 cfh.  Less than 15 is too little, more than 25 is wasting it and more than 35 can cause problems.Hold your gun with the nozzle near vertical and push the wire ahead of the gun rather than pulling the gun behind the wire.  Hold your stickout length to no more than 1/2".  Hold the torch vertical (side to side), pointing it right at the weld, rather than laying it to the side. This will give you best coverage.Since the problem is at the start, it is possible you are starting with a long stickout and then moving the torch closer for the rest of the weld.  If so, clip your wire to no more than 1/2" stickout before starting the weld.   To keep from having so much wire sticking out after the weld is done, don't start pulling the torch off the weld untill you've released the trigger and stopped the arc.  Your stickout length should then be at your normal length to start the next weld.Also, clean the nozzle and diffuser.  Too much spatter built up can hinder the gas flow or mess up the coverage.Check to see that your torch to machine connector is fully seated into the wire drive housing and tightened down.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Originally Posted by salem747As far as cleanliness the welded edges in this picture are actually freshly cut, so they are clean, I could have cleaned up to the edge but this is nothing structural.
Reply:Originally Posted by salem747I have been trying to find a welding course in my area but the only thing available is a full blown college course for 13 weeks! Although I am considering taking it anyway, it's only one night a week.
Reply:Originally Posted by tanglediverTake the full blown college course for 13 weeks!   I dare say, you won't regret it.
Reply:I do use splatter dip as well.I have been dragging my bead, I will try pushing it.Normally I do grind the steel before welding but I was making 24 of these things and I was lazy. They are "feet" to bolt to a 2x4 to support the ends of a firewood stand.I have been seriously considering the 13 week course, too late for this semester but maybe next. I am involved with welding a fair bit in my work (mining engineer). I am also planning to do the CWB welding engineer program but it is less about the nuts and bolts of welding and more about design.Thanks guys for the tips. Attached ImagesLast edited by salem747; 10-21-2009 at 08:44 AM.
Reply:Had a look at my regulator before I took off the bottle today to get it refilled. The flow was pinned at almost max flow!!! I think it is a size 4 bottle. How many 20# rolls of wire should a size 4 burn if the flow was set right? Just trying to loosely confirm that the flow was way high as I have never adjusted the flow.
Reply:How many 12 oz bottles did you go through?  Looks like it's almost time for a refill on the Molson!Work HARDER, not smarter! ------------------------ Miller Bobcat 250Millermatic 251Lincoln Precision TIG 185Hypertherm PM 600Hobart 135 HandlerOxweld 400 FlameMaster
Reply:Gee how many of those Molson bottles did you suck down before starting that weldCo-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:I forgot to mention one setting parameter...Set beer intake dial to 2 bottles max before performing weld.  MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:That is my "Outside Fridge" that only operates for a couple of months in the Fall and the Spring. I guess you guys would also say not to weld while sitting in the hot tub! You're just jealous that you have to drink American beer!
Reply:To paraphrase an old Don Ho song ..... Tiny bubbles  In the beer  Make me happy  Make me feel fine -- fredLincoln 180C MIG
Reply:I drink Mexican beer!MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:When I was living in California I either drank Moosehead or Pacifico.
Reply:I've never tried Moosehead, but my faves are Corona, Cerveza Sol, Dos Equis and Pacifico.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:I can't drink and weld worth a dam. I can't weld worth a dam anyway. Mexican beer also. Arizona.Vern
Reply:cranked the gas flow down, seems to be working better now.
Reply:Great! MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op