Lap joints with O/A question

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My buddy and I were practicing with my little O/A setup last night.  We've been running lap, butt, T / inside corner joints with 1/8" scraps.  I decided to try some lap joints with 1/4" and ran into some problems.  I did the first weld and he did the second.  We were using the largest tip I have at the moment and running that tip pretty hot.  All welds were done in the flat position using 1/16" filler rods. In the third weld things went ok as you can see.  The bottom plate was a single piece of steel while the top plate was the joined piece.  I focused most of the heat on the base and it traveled up to melt the top plate.  I was getting a nice inverted C shape (traveling right to left) of molten metal and a adding a dab of filler would get that C to fill in nicely.In the fourth weld things went, well, not so good.  I was putting a ton of heat onto the base (now the joined piece) and the top plate would melt away before I could even get a puddle going in the base.  I couldn't get near the previous travel speed as I'd keep loosing whatever puddle I got.  In spots I marked "A" in the picture you can see where the top edge just melted away.  In the spots "B" you can see where I gouged the base but couldn't get a puddle.  It was like I was melting it to molasses but not liquid.  I couldn't get the base metal to flow with the top plate.What could I have done different?  To me it seems like my problem was that in the 4th weld the base became a much bigger heatsink than the top.  How would you normally weld a thinner piece of steel to a larger/thicker piece like in this case?  Was I trying to do too much with the tool I had?  In the class I'm taking I was able to weld together 1/4" to 1/2" using MIG in transfer mode with no problem.  Any tips for me? Attached Images
Reply:Clean the scale... makes a world of difference on heat control and everything.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:3rd weld was getting too hot, 4th weld it was too hot.  Looks like you were dipping your flame into the weld puddle too.To adjust your heat, back off a bit on the flame when it looks like one side is getting too hot (puddle just runs).  You can also work your tip in an overlapping 'OOOOO' pattern, maybe slowing a bit on the lower side to increase the heat on the built up sections.  Your correct in thinking the previously welded areas are acting like a huge heat sink.Others may have better answers than this, but it looks like it's too hot to me.MarkI haven't always been a nurse........Craftsman 12"x36" LatheEnco G-30B MillHobart Handler 175Lincoln WeldandPower 225 AC/DC G-7 CV/CCAdd a Foot Pedal to a Harbor Freight Chicago Electric 165A DC TIG PapaLion's Gate Build
Reply:I think the tip was too small for the 1/4" stuff. I also think 1/4" thick is stretching O/A without overheating everything. IMHO1/8" filler would be more suited the the thickness, although it has nothing to do with the question.Last edited by Craig in Denver; 12-04-2008 at 05:25 PM.9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:First and third weld looks good to me.  I think you just have much heat in the metal from previous welds and it got difficult to control.  On the fourth weld did you increase the pressures.  That is the way my welds look when I attempt weld with pressures that are too high.Looks like you know what your are doing.  Good job.
Reply:check your torch angles, if the top plate is melting away to fast direct the flame more towards the bottom plate.Have we all gone mad?
Reply:Originally Posted by tapwelderFirst and third weld looks good to me.  I think you just have much heat in the metal from previous welds and it got difficult to control.  On the fourth weld did you increase the pressures.  That is the way my welds look when I attempt weld with pressures that are too high.Looks like you know what your are doing.  Good job.
Reply:Originally Posted by Craig in DenverI think the tip was too small for the 1/4" stuff. I also think 1/4" thick is stretching O/A without overheating everything. IMHO1/8" filler would be more suited the the thickness, although it has nothing to do with the question.
Reply:I've said before 220v MIG, TIG and stick are all better choices for 1/4" than O/A. Yes it can be done and if that's all that's available, drill holes and use bolts.   1" plate with O/A no problem These guys are trying to learn O/A in the home garage. If Zap said something like this, you'd let it go?? 9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:Thanks for the tips!You were right that I didn't remove the mill scale.  I'll try that next time.  May I'll remove it for one weld and not for another and see the difference for myself.The tip I was using was the largest one I have out of 3.  It's true that I had alot of flow going into it (that's what I meant by running the tip hot).  I had the acetylene flaming way past the sooty flame point (not quite leaping off the tip).  Then I added the oxygen for a neutral flame so the overall flow out of the tip was high.  My pressures were about 4 acetylene, 10 oxygen.I didn't let it cool at all between the 3rd and 4th weld.  I got to the end of the "L", flipped it over and kept going.  It makes sense to me that I probably had alot of heat in one of the plates compared to the other.  That would explain why one was melting away so fast.I had my torch angle aimed not quite into the corner, more at the base with a 50-60 degree downward angle.  I also had it tipped about 20 degrees to the right to push my puddle along towards the left.  When it was "working" when the base would melt enough heat would travel up to also melt the top.  Also on the 4th weld I was trying hard to get heat into the base so I tried getting the tip of the blue flame right on the base, thinking that's the hottest part.  I think that's when I gouged it.Again thanks for the help!
Reply:Originally Posted by Craig in DenverI've said before 220v MIG, TIG and stick are all better choices for 1/4" than O/A. Yes it can be done and if that's all that's available, drill holes and use bolts.   1" plate with O/A no problem These guys are trying to learn O/A in the home garage. If Zap said something like this, you'd let it go??
Reply:Yeah OA is an art.  But it is also a decent substitute for tig when it isn't available. It also can keep you warm on a cold day, if you got the time to putz around.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:gibbertipfiggerbillergibbertipfiggerbillergibberti  pfiggerbillerthanks fatbastard gotta go get dry pants..
Reply:i have 13 inch foamfilled wheels o n my o/a cart.. it can go offroad and where the electric dont shine...