What causes pin holes in mig welds?

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I bought a harbor freight bead roller and was welding a piece of angle iron to the back of it to make it more sturdy. I ground off as much of the paint as I could, held it in place and made a few tacks. Did a few mig welds with the hobart handler 140, .023 wire, max head, and about 20 cfh c25, new tip, er70s wire. Some welds came out ok looking and a good amount of them had pin holes in them. What causes these little holes? Sorry no pics.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Little to no gas or too much gas
Reply:So why would some beads have it and others not if I didn't change anything, could that be the gun angle?Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Could just be contamination if you didn't get all the paint off.  Were the holes bunched up together or just here and there?
Reply:I'd have to double check, but I think bunched together.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Poor gas coverage or contamination are usually the two big culprits with porosity. Oil, paint, rust etc is a common cause of issues. Sometimes it can even come from the base material itself, if it's say a cheap casting that has a ton of impurities in it.Spotty gas coverage can come from several things. A pinched hose, a kinked mig gun or blocked nozzle, bad angle on the gun, a draft or breeze... Might also mean you are just about out of gas as well..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:I'm going to guess cheap casting since it's harbor freight and the tank is full Thanks Doug.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Yeah I was going to say that, most of the material I have seen on the cheap tools is tough to weld......Still works OK just dirty castings  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:GMAW porosity possible causes (source with cut-n-paste is "GMAW Best Practices" from Welding Journal February 2006) (easier to cut-n-paste than typing it all out   ):PorosityPossible Causes1) Inadequate shielding gas coverage2) Gas contamination3) Electrode contamination4) Workpiece contamination5) Arc voltage too high6) Excess contact tube-to-work distanceCorrective Actions1) Increase gas flow to displace all air fromthe weld zone. Decrease excessive gas flowto avoid turbulence and entrapment of airin the weld zone. Remove spatter buildupin the nozzle. Eliminate any leaks in thegas line. Eliminate drafts (e.g. fans, opendoors) blowing into the welding arc. Eliminatefrozen (clogged) regulator in CO2welding by manifolding several cylindersor through the use of heaters. Use slowertravel speed. Reduce nozzle-to-work distance.Hold gun at end of weld untilmolten metal solidifies.2) Use welding grade shielding gas.3) Use only clean and dry electrode.4) Remove all grease, oil, moisture, rust,paint, and dirt from work surface beforewelding. Use more highly deoxidizingelectrode.5) Reduce voltage.6) Reduce electrode extension.