View Full Version : Welding 4130 with a carburizing flame.
09-28-2005, 10:11 PM
This weekend I was welding elevator ribs, 1018 mild steel, to the 4130 tubing. Kind of by accident I found that by using a carburizing flame, the feather 1 to 2 times the size of the cone, the welding was much easier and the beads looked much smoother. Previously when using a neutral flame I would get a little bubble at the end of the weld if I pulled back too quickly. This did not happen with the carburizing flame. "BUT" I am worried about infusing carbon into the weld and affecting the properties of the 4130. I plan on welding up some samples using both neutral and carburizing flames and doing some tensile tests on the Tinius Olsen at work but I would appreciate any feed back from other members. I also have the training DVD of them building J3's at the factory and all though it is not very clear it looks like they are using a carburizing flame to weld the fuselages.
09-28-2005, 10:34 PM
Glenn, the first thing that pops into my mind is that a carburizing flame may tend to promote superficial wetting of weld metal onto base metal. But I'm not sure. It's been too long since I've tried that, and I don't have my oxy-acetylene set here right now to go play. Since you're welding thin stuff, I think I'd try to devise a peel test. I do know that a neutral flame is considered correct, however I also know that a carburizing flame can shield the puddle from oxidation some (I use it brazing cast iron). Please let us know the results of your experiments!
09-28-2005, 10:46 PM
By superficial wetting do you mean that the filler is not penetrating the parent metal? No doubt the filler material does seem to flow much easier and I have been thinking that the heat is easier to contol as the flame is not as hot. And a peel test would be more appropriate as that would be how most of those joints are loaded.
09-29-2005, 12:25 AM
Yes, that's what I meant. But again, I'm not certain of this, just suspicious.
This weekend I was welding elevator ribs, 1018 mild steel, to the 4130 tubing. Kind of by accident I found that by using a carburizing flame, the feather 1 to 2 times the size of the cone, the welding was much easier and the beads looked much smoother.
I think that is way too much. Perfect looking welds do not always mean strong welds. Although the book says to use a neutral flame, an old aerobatic pilot told me that just a touch of carburized flame was better, but just so you can barely tell it is carburized.
Got to agree with S2D. Just a touch of neutral flame works for me.
09-29-2005, 06:26 PM
Seems to me that a slightly carburizing flame was called for in the old days. Neutral was just asking for oxidation. Nobody knows any more, because nobody (?) uses oxy acetylene. Maybe regulators are better. Mine wander all over the place.
09-29-2005, 06:57 PM
For oxy I have found the best is neutral with no more than a hint of carburizing.Did I say a hint? ( neutral is optimum but difficult to peg exactly)The cone is there , and the feather barely noticable. You do not want to add any more carbon to the steel. The only thing worse going past neutral and having to much oxy in the flame. The fizzing will make the welds crappola. The mentioned craters usually at the end of a weld is caused from pulling the heat away too suddenly with insufficiant filler metal in the puddle. Ease out of the puddle gradually and the craters will stop. Craters are a crack in the making, so make sure you get rid of them by adding more filler .
09-29-2005, 10:24 PM
And get rid of them clear to the root. Otherwise there is an internal void which is a crack waiting to grow.
09-30-2005, 12:04 PM
Thanks for all the feedback. I think I will stick to a just barely neutral flame and stay away from the carburizing flame. If anyone else has looked at the DVD training film and they've had a close look at the welding I'd like to get their opinion on what they are seeing.
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