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  1. #1
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    Default How do you know if a weld has good penetration??

    Referencing the failed trailer hitch that was posted. It's an important topic.

    How do you know if a weld has good penetration or is cold?
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  2. #2
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    Destructive testing.

    When not possible, you base it on lots of experience that was verified with destructive testing.

    Or are you looking to hear about X-ray testing, and other industrial methods?

  3. #3
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    Default

    Quote Originally Posted by Laiky View Post
    Referencing the failed trailer hitch that was posted. It's an important topic.

    How do you know if a weld has good penetration or is cold?
    THe first clue is the line of rust on the right side of the weld the is in between the toe of the weld and the parent metal.
    The second is the visible lack of fusion at the right toe of the weld that led to the formation of rust.
    Third form experience it looks small and cold for the mass of the parent metal.
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  4. #4
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    a cold weld bead with no penitration tends to be tall and skiny. the shape of the bead can help but to realy know you need to do distructive or X-ray.
    tall and skiny is what i watch out for. look at the outer edge of the bead to see if its curels up under, thats another bad sign.
    what kind of bead and on what are you looking for??
    thanks for the help
    ......or..........
    hope i helped

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  5. #5
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    I just figured this is a good topic for the really experienced guys to comment on. I have a clue as to when a weld is cold but i'm not really 100% sure.

    I have picked few out in the past, one time about 10 years ago my company had some 1" D rings installed on a truck to hold down a skid steer. I was annoyed at my boss since he didn't ask me what we needed (forged eye bolts worked better in this case). So i started installing the eye bolts. he came out yelling at me. I took a close look at the straps holding the Ds in and realized that they didn't look right. After the first trip with the loader they started popping clean off!! I then finished the eye bolts.

    One of the things i have trouble "comprehending" is just how deep the weld pool must melt into the base metal to reach full strength. Some people will say you need 100% penetration but thats not true in most cases. When welding thicker stuff you rarely get 100% penetration, then there is the "multiple pass" contingent who will swear you can weld 3' sections with a 110 mig. I know multiple pass works since stick welders weld huge steel every day, but again what constitutes enough penetration? Without the option of x-ray or destructive testing (regular hobby guy stuff) what are the charicteristics of a good weld and a cold one??

    I think this is a good place for the Experts to chime in, and give us the benefit of there experience.
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  6. #6
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    Jun 2007
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    Too much emphasis is put on the word penetration. Fusion is always more important. You will not achieve large amounts of "penetration" with any typical manual welding process. Look what it takes to do what they call a full penetration pipe root pass. It takes a small land and a gap. If you just lay a bead on some stock you will find that you actually melt very shallow into the parent metal. Look at any cross section T joints. Fusion is what's important. If you fuse into the root and all the way out to the toes with adequate fill at the same time then you're creating a strong weld. The trailer shown in this thread suffered from bad fusion not penetration as defined in the welding world.

    Full penetration can normally only be done with heavy prep. You won't find it very achievable to butt two pieces of 3/16'' plate together and find melted and fused metal on the backside of your weld. It just doesn't happen. "Full penetration", imo, should be a term that is discarded all together. For pipe and the like it should just be called full weld or something.

    You know when you likely have a proper weld by analyzing the toes, bead profile, bead size, bead consistency, and taking into account the material, process, and joint used. That's the best you can do shy of destructive testing.

  7. #7
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    Default

    Quote Originally Posted by Billet Benny View Post
    Too much emphasis is put on the word penetration. Fusion is always more important. You will not achieve large amounts of "penetration" with any typical manual welding process. Look what it takes to do what they call a full penetration pipe root pass. It takes a small land and a gap. If you just lay a bead on some stock you will find that you actually melt very shallow into the parent metal. Look at any cross section T joints. Fusion is what's important. If you fuse into the root and all the way out to the toes with adequate fill at the same time then you're creating a strong weld. The trailer shown in this thread suffered from bad fusion not penetration as defined in the welding world.

    Full penetration can normally only be done with heavy prep. You won't find it very achievable to butt two pieces of 3/16'' plate together and find melted and fused metal on the backside of your weld. It just doesn't happen. "Full penetration", imo, should be a term that is discarded all together. For pipe and the like it should just be called full weld or something.

    You know when you likely have a proper weld by analyzing the toes, bead profile, bead size, bead consistency, and taking into account the material, process, and joint used. That's the best you can do shy of destructive testing.
    I knew what i wanted to say but didn't know how to word it properly. After reading this post I have to agree for sure. To achieve full penetration in that 3/16 metal it would warp like crazy & probably undercut at the same time. I believe FUSION is definitley the key word here.,This is my opinion but I still want to here from other's on this subject.
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  8. #8
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    I also think what Benny said makes a lot of sense. The only thing I would add is that to have proper fusion combined with sound design elements is the best possible combination.
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  9. #9
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    Jul 2007
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    campbellsville ky
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    the old pro here in our down who is now deceased once told me the best welders are the best fabricators.kinda what kb is saying i believe.

    with good fabricating skills,the weld has less stress.kinda just holding it in its proper place.but im in no way saying you dont still need good penetration

  10. #10
    Join Date
    Feb 2006
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    what I do is take some pieces of metal that are the same as what I am welding and do some practice welds on them. then weld a coupon cut the test piece in-half ( you can use a torch or a bandsaw ), smooth out with the grinder then sand with the grinder using a piece of sand paper over a grinding disk, then us some scotch Britte, then take some nitric acid and a Q-tip apply nitric acid to the weld and you can see where you get penetration into the base metal and fusion. as the images appear, mark the penetration with a pencil because after the nitric acid dries sometime the images go away. after you do this you can clearly see if you have penetration or fusion . and yes their is a big difference between penetration and fusion. yes you can see the difference between base metal and filler metal. you may have to adjust the settings on your machine,wire feed speed . amps also gun angle, travel-speed, and work angel will also have a big factor in all the results you get when doing a acid etch test. you will be surprised what you find when doing a test. you can see impurities in the weld, lack of fusion, lack of penetration, lack of penetration at the root ,incorrect gun angle- one leg bigger than the other. and much more . .this helps to achieve the best parameters and welding techniques to get the best weld for that application. also I suggest you try this because you can see where you may need to change your own welding techniques . . make note of what you find and apply them to future welds.
    if a weld could have someone's life on the line (and most of the time somewhere down the line it does ) its good to test and know that you are welding correctly
    that is how I know I get proper penetration in welds ,tests .plus appearance and experience


    ....................
    Richard

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