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Thread: weld bead width and slag removal questions (stick welding)

  1. #1
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    Question weld bead width and slag removal questions (stick welding)

    i'm trying to get a little better with my welding and was running a bunch of 6011 and 7018 rods today. i have 1/8" and 5/32" rods and i was running them between 130A-200A according to rod thickness.

    when you guys are laying down a bead to fill an area or build a vee up, how wide of a bead do you run? say for 1/8" rods, do you make a 1/2" bead, or can you go wider? what about the 5/32", can you go with a 3/4" bead or is that getting too wide?

    if you are laying a bead down next to another bead, not on top of it, just with a slight overlap, do you chip the slag off of the first pass before putting down the next bead, or do you wait until you've laid down all passes on that layer to chip it all off? how about when putting a bead on top of another bead, do you chip the slag off between passes (i'm guessing yes, but maybe there is a reason not to)?

    thanks,

    andy b.

  2. #2
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    Always chip and brush the slag off.. give it a second or two to cool, it usually pops right off then.

    Slag, well that is one reason you can't weld down hill with a stick, the slag runs down and contaminates the weld.

    Arc gap is critical, usually about 1/2 to 1/3rd rod diameter if my brain cells are connecting. I weld mostly by sound since I have eye troubles.

    A good dry rod is like a Cadillac.
    Excuse me, I farted.

  3. #3
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    Some types of rod can be welded over slag but it is generally a good idea to clean the slag of, less chance of getting slag inclusions and the weld will look better.

    Better to stick to stringer beads until you get good at them. If you weave the weld to wide there is a greater chance of weld flaws and the puddle will cool down and have a fish scaled appearance.

    Stringer beads are suppose to make a stronger weld and create less weld distortion than a weaved weld.

  4. #4
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    Quote Originally Posted by Dawai
    Always chip and brush the slag off.. give it a second or two to cool, it usually pops right off then.

    Slag, well that is one reason you can't weld down hill with a stick, the slag runs down and contaminates the weld.

    .
    Not entirely true, there are some down hand rods available, pipeline welders frequently use the down hand method, but most rods are not good for this use.

  5. #5
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    Quote Originally Posted by loose nut
    Better to stick to stringer beads until you get good at them. Stringer beads are suppose to make a stronger weld and create less weld distortion than a weaved weld.
    Good advice. I'm not as anal about stringers as say, Torker, but Torker convinced me to use 7018 stringers more often and I have to admit that it's easier to lay a consistent stringer bead than a consistent weave. There are exceptions, though. I still use some sort of oscillation for filling gaps, overhead, and sometimes vertical.

    As for how wide the bead, that will depend on the rod and the speed. As your speed slows, the bead widens, but if you travel too slow the slag may overtake the arc or even extinguish the arc.

    I tend to travel too fast and end up with a narrow, incomplete bead. That comes from years of maintenance welding on rusty, thin, poorly fit pieces, where the name of the game was filling the gap without burning through.

    So ....... when I have the luxury of welding in a comfortable position, I try to drag just as slow as possible without drowning the arc.

    You mentioned 200 amps ? Assuming we are talking DC+, 1/8" 7018 should be 115 - 130 amps, 5/32" around 160 amps. Less for 6011.

  6. #6
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    Rule for width is 2 1/2 times the diameter of the rod. Ei: 1/8" rod can make 5/16" wide weld. 6011 chip EVERY time you stop. 7018 you CAN weld side by side or on top of lower weld during fillet welding but it makes it difficult to accurately see the edge of last bead. You can down hand or weld verticle down with 7018. Won't make a very tall bead. " Peeling is perfect" - when your weld speed/heat/beads just right the slag peels or pops off.

    mark61

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    this is an old AC Lincoln buzzbox, no fancy DC option. maybe i am running way too high on the current?

    NOW i see about the slag running down into the weld when you try and weld going down. i always wondered why i had trouble welding down a vertical seam.

    i will now always chip the slag off before making the next pass, as you guys mentioned. will the slag always chip off relatively easily with 6011 and 7018, or will it sometimes take a long time to harden if the metal is real hot from doing a lot of welding. by real hot i mean it melts a 315F heat crayon pretty quickly. i have an IR temp gauge and i think i'll try to get some readings next time i weld some heavier material to see just how hot the metal is staying.

    being relatively self-taught, what is a "stringer"?

    andy b.

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    A stringer is basically a straight drag very little side movement. 6010 and 6011 are about the only rods that you can whip up out of the weld puddle let the puddle solidify then lower the rod and restart the weld. Great technique when running cover passes in pipe welding, though not used much since about 1975.

    Bob

  9. #9
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    Two rods wide for width is a good average for stringers, and stringers alone are better to fill with- they will cause less shrinkage distortion, provide better grain refinement and generally penetrate more by not being crowded by puddle or slag.
    Never let the toes of weld beads meet, attempt to have the toe in the middle of prior beads, or completely cover them as when capping or filling with larger rods.
    Part of the rationale for the above is to avoid slag traps. Deep ruts with slag may even need a grinder to open up, or a hot pass technique to rip them out, if using cellulosic rod ( 10's& 11's). Slow hydrogen is not a good rod for the task as whipping will induce hydrogen.
    An experienced weldor won't do much interpass grinding or brushing- you learn to assess how much slag can be burned out, you avoid slag traps and use the bare end of the next rod to rake slag away.
    Turn up the heat when running downhill and use arc force to control the puddle- the rod should make a low angle to the joint. Yes, you can downhill 18's but I could test thirty weldors before finding one able to pass a lookout.

  10. #10
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    The 2 to 2/12 times the rod width is definitely the best and there are a couple of more tricks to add. It has already been pointed out to not let the toe ends of the welds meet so basically what you want to do is avoid stopping the bead in the same spot on each pass, this is also true for starting a new pass. Each time you start the arc (and to a lesser extent when you stop) there is going to be some porosity and thermal shock in the spot where the arc actually starts but if done properly this is very minor and usually poses no problem at all and is mostly eliminated by the next pass. However the effect is cumulative and if each succeeding pass is started in the same spot it will create a very weak area of porosity and micro-cracking that could lead to weld failure, this is easily avoided by starting/stopping the bead in a different place on each pass. On a weld where you must start and stop on an edge tack a small tab about an inch or so long at both ends of the weld, this is done so that the bead can be started on the starting tab and when the pass is finished the bead will be run off onto the other tab. This way you can start the bead in the same spot (on the tabs) at the edge, stop at the opposite edge and when finished you simply cut or grind these tabs off to eliminate the stressed portions of the weld. Another thing to consider when multi-pass welding is to PLAN AHEAD for the next bead! What I mean is, for example, don't let your next to last pass crowd the opposite edge of the weld and not leave enough room for the last bead to reach all the way to the bottom, doing this will trap slag and prevent full penetration of the last bead. Actually another good idea is to never allow the last bead to finish the weld at the edge of the fillet, if the very edge of the weld is finished with the last pass then the transition area from the weld to the base metal will be heat affected (hardened) and highly stressed. The trick is to run another bead (two is better) along the inner side of the edge bead which will tend to stress relieve the transition area, basically you want to finish with the last beads being nearer the center of the weld and never on the very edge. For even more assurance of weld integrity it is a good idea when removing those start-run-off tabs to then grind the surface of the weld, especially the area of the last passes, and then peen to remove the grinding marks which, tiny that they may be, can be stress risers. Just remember that slag inclusion and porosity, along with incomplete penetration, are the most common causes of weld failure.



    One other thing that should be covered is joint preparation, NEVER attempt to weld over torch slag or even the scale left from an otherwise clean O/A cut! Doing so is almost always an exercise in frustration especially in vertical or overhead positions. Weld base metal preparation is every bit as important as proper weld technique but is all too often improperly or poorly done or just ignored entirely, to do this is a huge mistake!


    Also for that AC machine, did you know there are 7018 rods available just for AC? These AC7018s are not a cure-all for low Hydrogen AC welding problems but they do help quite a bit compared to regular 7018s.

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