Help me become a better welder - critique this

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Practice butt joint on a couple of pieces of scrap 1/8" mild steel.  Photos show topside (weld bead) and bottom side (penetration).  Equipment: Millermatic 175 CO2Ar mixture.  ER70 .030 wireLaid flat.  Seemed like good penetration on the last half, I slowed down a little. Attached Images
Reply:I'd hoped to get better penetration and less bead height.
Reply:it is cold
Reply:Is what cold?  In my shop it's about 60 degrees.  The metal itself was cool when i took the photo.
Reply:The weld looks cold...... what settings where you using?
Reply:Actually the weld was hot.  The Miller cheat sheet call for a setting of 4.5 volts/60ipm, I wante to get deeper penetration and my Welding books says to increase current.  I did - to 5.5 volts (one the machine).
Reply:too much pen on the end of your weld. You want to penetrate, but you don't want it to suck through like that. You shouldn't distort the back side of the steel.You could have went from the thin part to the thicker part and it would've helped with such a change in heat.When you look on the backside of your plate all you want to see is the color change like how it did about 1.5" into your weld. Your penetration is way overkill and will cause a lot of problems if you decide to back-gouge or even just weld the back side. are you pushing or pulling your puddle?
Reply:Thanks - I wan't sure of what the 'appropriate' penetration should look like.  This was actually the second practice of the night.  On the first the weld only penetrated half way - viewed from the end.  I was pushing (forehand?)Last edited by reefera4m; 11-12-2008 at 08:58 PM.
Reply:Originally Posted by reefera4mActually the weld was hot.  The Miller cheat sheet call for a setting of 4.5 volts/60ipm, I wante to get deeper penetration and my Welding books says to increase current.  I did - to 5.5 volts (one the machine).
Reply:Thanks
Reply:Are you sure that picture didn't come from a secret military base in the desert?  It looks like a ufo.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:Your weld bead looks very good and consistant.The plates you were welding need to be tacked on each end first.You will see in the photo how on one end there is a gap and on the other end no gap.I would use rectangular plates if possible in the future to give yourself a fair trial.Last edited by Donald Branscom; 11-13-2008 at 02:55 PM.AWS certified welding inspectorAWS certified welder
Reply:Not bad, but could be better.  Your travel speed was pretty consistent, but you didn't melt into the base material enough (aka the weld was cold) and your voltage (for the wire speed in use) was a little too high and thus you have a bit more spatter than you could/should have had.And your settings were 4.5 up to 5.5 on the voltage dial.  Which is obviously (or maybe not obviously) NOT the actual voltage.  It is just a reference number on the voltage dial.Same thing with your wire speed.  The numbers go from 0 to 100 as a reference scale, but that is not the actual wirespeed in inches per minute.Some bigger industrial machines have dials or meters that show the actual voltage and amperage or wire speed in ipm, which is what I think David was thinking of.And what David was correctly pointing out to you was that in general, the wire speed is the amperage adjustment.  The voltage needs to be adjusted to get the right 'balance' for the diameter of wire being used and the wire speed being used and the shielding gas being used, etc, etc, which is why Lincoln/Miller/etc usually give you 'starting' parameters in a table form to get you in the ballpark of where to set the machine.  Then you can make small adjustments if needed.If you look in your manual, you will see some graphs that show different voltage and amperage settings that the machine is capable of.What Donald said about the gap is that because you didn't tack (or otherwise clamp firmly) the two ends of your practice plates, as you were welding from one end and the metal started to get hot it got bigger (due to thermal expansion).  But because one end was already welded by that point, the two plates 'pivoted' apart from one another and the gap between the plate grew bigger and bigger.  And -that- is part of why/how your weld is showing though the back by the time you got to the end of the weld.Yes the metal was hot!  Hot enough to burn you if you touched it.  But what the previous posters meant by "cold" was that there actually wasn't enough heat/energy in the weld to properly melt the base material AND the wire and get it all to melt and flow together and become one continuous piece at the weld bead.  Although you melted the wire just fine, the base metal didn't melt enough to get everything to get into 'one'.  The metal was hot to you, but the amount of heat in the welding zone wasn't properly enough to melt the original steel enough.  It looks like you pretty much have most of the weld bead just sitting on top of the plates.  Often refered to as a "cold" weld, or incomplete fusion, or cold lap.  A common 'drawback' with GMAW aka MIG welding, especially for beginners because the wire melts just fine and they think that the weld is good when the melted bead of wire/filler is mostly just sitting on top of the base metal.Here are some troubleshooting hints (right out of the Miller manuals IIRC):Low arc voltage : wire stubs into workHigh arc voltage :arc is unstable (spatter)  Set voltage midway between high/low voltageWire speed (amperage) controls penetrationVoltage controls height and width of weld beadPractice some more, read your manual a bit and looks at the illustrations in the back about good versus not-so-good welds, and also look at the websites of Miller and Lincoln and ESAB for info and pictures about welding.  Practice some more and take some more pictures.    The best laid schemes ... Gang oft agley ...
Reply:Originally Posted by reefera4mThanks - I wan't sure of what the 'appropriate' penetration should look like.  This was actually the second practice of the night.  On the first the weld only penetrated half way - viewed from the end.  I was pushing (forehand?)