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Thread: how strong is a weld???

  1. #1
    grinch is offline Cast Iron
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    I've always heard that a weld was stronger then the metal its self. I was wondering if anyone could tell me the facts with this?? I'm also wondering how strong brazing is as well. I'm asking cuz a guy I've I've heard of is making pistols in 2 halves and brazing them togather. I was talking to another machinist and he seemed to think a weld or a braze would be to weak to hold up. he makes the pistols in 4140 as well as aluminum.

    Thanks in advance for any insight

    GRINCH

  2. #2
    John Garner is offline Stainless
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    grinch --

    Your question is far to general to answer.

    A well-designed weld joint that is well executed (in terms of materials, weldor skill, and environmental conditions) certainly may be stronger than the parent material, but poor joint design or poor weld execution execution will probably result in a weaker-than-parent-material weld.

    Brazing? Same deal.

    In precise technical language, there have been bajillions of welded or brazed parts manufactured that will eventually quit working in ways that have nothing to do with a failure of their welded or brazed joint. I have no doubt that boatloads of those parts perform jobs that are critical to human safety or health.

    John

  3. #3
    icehd81 is offline Hot Rolled
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    I wouldn't say the weld is stronger that the parent metal. It's harder than the parent metal because of the rapid cooling, but the rapid cooling also affects the parent metal to the depth of penetration. Weld failure occures in many different forms. A fatigue failure might happen at the weld/parent metal interface where as a brittle fracture can happen right through the heart of the weld. Stress relieving can help reduce the liklyhood of most weld failures, as can design considerations. I don't think I'd trust the guys pistols if the chamber and barrel are weld construction, but it might not be a problem on the frame.

  4. #4
    Forrest Addy is online now Diamond
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    Yeah, too many factors. The key is the best joint design and a weld using the right filler metal and process.

    High quality welds such as used on boilers and submarine hulls are documented within an inch of their lives but the basic process is adaptable to most any back-yard weliding operation where the builder is concerned about reliability.

    Most welds made by people of reasonable competence rarely fail because of the weld or the process. It's bad design of the joint or structure that caused the water tower to fall on the school bus full of crippled children.

  5. #5
    gamachinist is offline Aluminum
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    Several years back,I saw a magazine write up on a 45 ACP caliber Luger Pistol built out of two frames welded together to accomadate a magazine for 45 ACP.
    The Ruger MK1 and MK 2 22 rimfire pistol frame are made of two stampings welded together(this is how they sold them for half the price of a Colt or High standard back in the fifties when they were introduced).
    It has been a somewhat common practice to weld two slides together to increase the length mostly on M1911 type pistols.
    So it is an accepted practice to weld most gun parts except barrels.There is an exception to this though,when welding small holes (from rust mostly) well forward of the chamber on shotgun barrels.
    Robert.
    Edited to add:
    I also remembered that people would cut,shorten or lengthen and weld Mauser Recievers to make short or longer actions for different cartridges.
    I don't know how I forgot all the "rewelded" M 1 Garands that were on the market in the '70's(some were good shooters and some were junk). And you have some rewelded M 14 recievers too but those get a bit sticky with the ATF's "once a machine gun always a machine gun" policy.
    Robert.

    [This message has been edited by gamachinist (edited 09-15-2003).]

  6. #6
    grinch is offline Cast Iron
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    they guy is using an "industrial brazing" and is having it professionally done so it sounds like you guys agree that it will hold up. Its on the frame its self.

    So what I'm getting is that if the material and the weld are done correctly its no problem to weld it??

    BUT it dounds like there would be some benefit gained from heat treating it after the welding is done. Is this correct read on what your saying??

    Thanks
    GRINCH

  7. #7
    icehd81 is offline Hot Rolled
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    Stress relieving will improve stability. Especially if there are subsequient machining steps after welding.

  8. #8
    Cass Guest

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    Weldor certification is achieved by testing the weld in bending and tension. If the weld cracks anywhere when the sample is bent in a 180 degree U bend you fail the test. If any one of about half a dozen test bars cut out of the test weld fails in tension at the weld before the base material you fail. This is a rough descripton of the weldor test for high pressure pipe line and pressure vessels. Aircraft and other important welding has similar testing. In both welding and brazing the joint is stronger than the parent metal if the joint and process are designed right and the process is done right. The way to assure quality is to test the joint in a part by cutting test articles and testing them. Doing this is very common industrial practice. Not much stress in firearms except in the chamber and bolt. Welding or brazing the frame together should be no problem. Lots of military arms are made that way where cosmetic beauty is not a factor.

  9. #9
    lunkenheimer is offline Aluminum
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    One of the suppliers of the M1 carbine in WWII was IBM (yes, the same IBM as today). Their production is easily recognized because of the many parts assembled by brazing together stampings where others machined castings or forgings.

  10. #10
    surplusjohn is offline Diamond
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    just like Remington, IBM was basically a glorified typewriter manufacturer. lots of little stampings.

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    the first 2 numbers at the beginning of them like a 7018 it has 70,000 lb per square inch and so on.

  12. #12
    CruisingRam is offline Plastic
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    Quote Originally Posted by Cass View Post
    Weldor certification is achieved by testing the weld in bending and tension. If the weld cracks anywhere when the sample is bent in a 180 degree U bend you fail the test. If any one of about half a dozen test bars cut out of the test weld fails in tension at the weld before the base material you fail. This is a rough descripton of the weldor test for high pressure pipe line and pressure vessels. Aircraft and other important welding has similar testing. In both welding and brazing the joint is stronger than the parent metal if the joint and process are designed right and the process is done right. The way to assure quality is to test the joint in a part by cutting test articles and testing them. Doing this is very common industrial practice. Not much stress in firearms except in the chamber and bolt. Welding or brazing the frame together should be no problem. Lots of military arms are made that way where cosmetic beauty is not a factor.
    Not quite true- if the welded area cracks below the rated filler metal you fail- i.e.- if your filler metal is rated to 70kpsi and it fails at <70, you fail. The weld can fail if it fails above the rating for the filler metal. Rarely happens, and it is splitting hairs, but true IIRC.

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    carl laniak is offline Aluminum
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    One point I'm amazed hasn't been clearly stated yet is that it not only depends on the weld joint design, and weldor skill, but it depends on the base materials and the filler material (if any).

    Some materials get stronger after welding due to material changes from the heat. Some get weaker. Some stay about the same.
    Some brazing materials are stronger than the things people join with them. Some are weaker. Some....about the same.

    I'm pretty sure no brazing material is stronger than 4140 steel, but as long as the joint is good, and the strength of the brazing material (some are quite strong) is high enough....obviously it will work.
    I'm quite certain there are brazing materials that are stronger than most aluminums....so that gun would seem more likely to fail in the base material....fwiw.

    I can't speak precisely to the specific example of these manufactured half-guns, but the answer in general is: IT DEPENDS!

  14. #14
    Cole2534 is offline Titanium
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    Quote Originally Posted by carl laniak View Post
    One point I'm amazed hasn't been clearly stated yet is that it not only depends on the weld joint design, and weldor skill, but it depends on the base materials and the filler material (if any).
    That was mentioned in the first reply, a decade ago.
    JMillar and Winker like this.

  15. #15
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    Metalcutter is offline Titanium
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    Example: If you have a piece of steel 1" x .25" x 20 inches long and you apply a bending force in the middle, that is the strongest the piece will ever be. If in the middle you you cut it and solder it. The solder is weak and it will break there. If in the middle you you cut and weld it with the same steel it was made with, it will still break there, because the welded material is in a stressed state. In the place it is stressed it will be either harder where it can't "give" as if it were the parent metal, or like the solder. It's a very big deal to try and make the "patch" exactly the same as when the parent material was first manufactured.

    Regards,

    Stan-

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