aluminum welding issue

Discussion in 'Metal Boat Building' started by Brian.Lin, Jul 24, 2016.

  1. Brian.Lin
    Joined: Aug 2006
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    Brian.Lin Junior Member

    dear All,
    I got a maker's welding guideline.

    they say:
    [13.0 WELD RUNS
    Multi-pass runs maybe necessary depending on the plate and casting thickness.
    Stitch 75mm with 75mm gaps for first 2 runs to help eliminate distortion of block.
    Grind stop/starts before filling in.
    Subsequent runs may be full-length runs.]

    I didn't understand "Stitch 75mm with 75mm gaps for first 2 runs "
    is anyone can give me assistance.
     
  2. JSL
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    JSL Senior Member

    I suggest you take a welding course
     
  3. PAR
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    PAR Yacht Designer/Builder

    Yeah (a welding class), pretty much a necessity if you don't understand that simple a phrase.
     
  4. gonzo
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    gonzo Senior Member

  5. Brian.Lin
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    Brian.Lin Junior Member

    Dear JSL & PAR,

    thx for your good suggestion.
    I just can't realy understand the scentance "Stitch 75mm with 75mm gaps for first 2 runs".
    I want to make sure the Stitch 75mm with 75mm gaps is like chain intermittent welding or like the bolt tight we should tight oppisite step by step.

    thx for your patient reply
     
  6. PAR
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    PAR Yacht Designer/Builder

    If you understand the basics of welding, putting down 3" (75 mm) stitches on a 6" pitch (75 mm gap) seems pretty reasonable. Again, understanding welding basics, you'll see why they recommend stitches (butt or fillet) on the spacing suggested. This is basic welding common sense and if you're having trouble with the spec's, you need some additional instruction. The weld spec's provided tell you why:

    This seems pretty reasonable to me and very understandable on multi-pass welds, first to ease distortion and second to save material and time.
     
  7. TANSL
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    TANSL Senior Member

    Typically welding chain intermitent, zigzag, etc. is performed to decrease the heat input and hence the deformation of the material, because not always is cheaper, in hours / welder, than continuous welding.
     
  8. SamSam
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    SamSam Senior Member

    Is this what you're talking about?

    [​IMG]
    https://en.wikipedia.org/wiki/Fillet_weld

    https://www.reddit.com/r/Welding/comments/21hd6v/intermittent_welds_staggered_or_chain/

    A lot of times it is simpler and more expedient to pose a question to google rather than a forum. Google will show you multiple places where the question has been asked and answered. Although google may also pepper the page with ads for welding schools, it won't tell you that you are ******* stupid and need to go to school for a year to get the answer to your question. Google is polite in that way.
     
  9. TANSL
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    TANSL Senior Member

    This is a very interesting comment. Fortunately Google is not human and therefore is educated but has not some of the advantages, if any, of a human.
     
  10. PAR
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    PAR Yacht Designer/Builder

    I tried to be polite Sam, really, as I'm a lousy welder, but stitching is as basic as it gets, so if you have to ask here, I'll assume someone has already tried Google and still doesn't get it. My point is, even with my rudimentary welding skill set, I understand the logic behind intermittent and continuous welding. The first time you try to pull too long a bead, on too thin of stock and have to spring it back into position, because it's moved so much, you figure it out. I don't know how many inches of bead you have to pull, before you learn this valuable skill, but it's not many for most.

    Yes, it's far cheaper to make stitch welds than continuous and considerably faster as well. Welds on an industrialized level, are simply timed events per unit length, so a continuous weld would take nearly twice as much material and time, than stitched as described by the OP. Of course, the distortion issue is also an obvious reason as well.
     
  11. baeckmo
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    baeckmo Hydrodynamics

    The guideline says (in other words): "If the material thickness requires multiple weld passes, then the first two should be intermittent 75X75 mm overlapping. After that, the seam may be covered by a continous weld."

    This recommendation is aiming at tight welds, not the intermittent welding of stringers etc as shown in SamSam's Picture, and has nothing to do with "saving weld length".

    I would like to add the importance of weld sequence; if the stitches are laid down by back-stepping, there is normally less material distorsion, than if you work in one direction. That goes for the "continous" (only Machines can make it continous!) weld as well. Also, if the material thickness only requires a single weld pass for tighness and/or strength, it is important to fix the edges by tack welds, again with a separation distance around 75 mm, depending on thickness and shape.
     
  12. gonzo
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    gonzo Senior Member

    The weld should be about the same thickness as the material being welded. The amount of passes depends on the diameter of the wire and the speed of the weld. Grinding stops and starts is time consuming, but it will get rid of oxidation and other contaminants. I don't see that as common practice though. The OP has not indicated what material they are welding. Back welding is the most common practice, and it doesn't normally require any grinding of stops and starts.
     
  13. TANSL
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    TANSL Senior Member

    Gonzo, what materials do you think will use someone who titled his thread "aluminum welding issue" ?.
    What do you mean by weld thickness ?.
    What happens when the two pieces to be joined are of different thickness?
    Some other of your statements should be reviewed, imo.
    (Sorry Mr. Efficiency)
     
  14. gonzo
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    gonzo Senior Member

    I am using standard engineering terms. Go to the link I posted #4 and it will explain all the basics.
     

  15. TANSL
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    TANSL Senior Member

    In addition to reading "standard engineering terms", you must understand them, to use them properly.
     
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