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  1. #1
    Join Date
    Feb 2008
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    14

    Default welding 4130 chromoly tubing

    hello,
    Can anyone give me tips on welding 4130 chromoly tubing? I.E. best tungsten material, argon flow rate, cup size etc. Also, what is the best filler rod? I used the miller calculator but would be interested in someone's real life experience. I will be welding plate up to 1/4" and tubing up to about .05" wall thickness.
    Thank you
    Last edited by swamper8; 03-01-2008 at 08:23 PM.

  2. #2
    Join Date
    Feb 2008
    Posts
    889

    Default Use ER70-S6

    A lot on this subject has been hashed out with the aircraft homebuilders. The consensus is that er70-s6 is the best filler for light tubing because it picks up enough of the 4130 alloy to do the job. You can obtain a 4130 filler, but you have to heat treat the whole assembly afterwards. Is the plate REALLY 4130?

  3. #3
    Join Date
    Mar 2006
    Location
    Queens NY
    Posts
    1,547

    Default

    1st describe what it is your trying to do. The experts here aren't going to give general info on Chromoly since it is usualy in critical applications, and the reccomendations are a little specific and complex.

    2nd do a search, this topic has been very well covered.

  4. #4
    Join Date
    Feb 2008
    Posts
    14

    Default

    Yes, the steel is definitely 4130. I am not doing anything quite 'mission critical'. I was going to build a recumbant bike frame out of 6061 aluminum but my TIG welder is flaking out in AC mode. So I have to switch my project frame to 4130 chromoly instead. I was just looking for some basics, I am a new TIG welder. I will do some searches under keywords 4130 or chromoly and read other posts............................................. .......

    OK, looks like 1/16 to 3/32 2% lanthanated or cerated tungsten. Argon flow of 10-15 CFH. #6 or #8 cup size. And either ER760S-6 or ER70S-6 filler? I saw different references and i'm not sure if they're the same.
    Last edited by swamper8; 03-02-2008 at 02:12 PM.

  5. #5
    Join Date
    Dec 2005
    Location
    wisconsin
    Posts
    836

    Default

    Right,
    The subject has been hashed out to death

    For what your working on, by the books I would suggest something along these lines.

    Filler-ER70s-2 or -6
    Tungesten-old standard is 2% thoriated....others will work though
    Argon flow and Cup size depend on your joint configuration.
    Cleaning-Clean ALLLLLLL oils from the base material and filler, use a non heavy hydrocarbon solvent of choice and be sure its all evaporated before welding.

    now the following is more technical in nature, but by the books, proven and the safest. Absolutely required for what your doing? maybe not, but why risk it, its easier to do it right the first time then re-weld and paint later.

    After welding, after the part has cooled, use use localized heating ( oa torch )to evenly bring the joint to around 1200 degrees F ( dark dull red in indoor lighting ). I suggest temp sticks to get the hang of it. Keep it there for about 1 hour per inch of metal thickness, ends up being only a minute or 2 on thin tubing. Slowly trail the torch off and let it cool in still air. Note that this is not normalizing, or true annealing...this is tempering. Places in your base material will have untempered martensite in them after TIG welding, this structure needs to be tempered to help prevent brittle fractures over time. This also helps hydrogen migrate from the material should it have been absorbed durring the welding process ( vaporizing oils on the metal and moisture in the argon are known sources of this ) and therfore helps prevent hydrogen embrittlement.

    Sounds like a fun project!! Have fun and be safe!

    -Aaron
    "Better Metalworking Through Research"

    Miller Dynasty 300DX
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  6. #6
    Join Date
    Feb 2008
    Posts
    14

    Default

    Thanks! I was going to post another question for a better description of annealing. I have a mapp gas torch and a acetylene torch. Will the mapp gas get to 1200 degrees? Also, is this process necessary for a simple recumbant bike frame? I will be gusseting each joint as well and I weigh under 200lbs.

  7. #7
    Join Date
    Dec 2005
    Location
    wisconsin
    Posts
    836

    Default

    Quote Originally Posted by swamper8 View Post
    Thanks! I was going to post another question for a better description of annealing. I have a mapp gas torch and a acetylene torch. Will the mapp gas get to 1200 degrees? Also, is this process necessary for a simple recumbant bike frame? I will be gusseting each joint as well and I weigh under 200lbs.
    I would stick to the OA torch, the chemistry of the flame of a MAPP torch may not be a good mix for base material, ill have to dig to be sure though.

    Is it necessary?? Thats entirely up to you to decide along with the design of the frame. The loading and fatigue applied to a portion of your frame might be the same as the engine mount for a jet turbine. Since loading is a function of both force and area, its easy to see how critical things become the lighter and smaller you make your frame. The old road racing bicycles were very light and very marginally designed, therefore every bit of joint ductility was needed. A heavily over designed joint may not have any fatigue issues, but how do you know its over designed? Its that giant "question mark" that leads me to doing all I can to improve weldment reliability. Unless I know for sure that the loading is light enough to not need every bit of the materials fatigue strength, I play it safe. Although if the part in question is that over designed....then its just wasted weight and material.

    -Aaron
    "Better Metalworking Through Research"

    Miller Dynasty 300DX
    Miller Dynasty 200DX
    Miller Spectrum 375 extreme
    Miller Millermatic Passport

    Miller Spot Welder
    Motor-Guard stud welder

    Smith, Meco, Oxweld , Cronatron, Harris, Victor, National, Prest-o-weld, Prest-o-lite, Marquette, Century Aircraft, Craftsman, Goss, Uniweld, Purox, Linde, Eutectic, and Dillon welding torches from 1909 to Present. (58 total)

  8. #8
    Join Date
    Feb 2008
    Posts
    14

    Default

    Well I like to do things right so i will probably try my hand at annealing. Do I have to anneal the joint soon after welding? Or could I fab up my frame, assemble my components and fully test my design to make sure I won't be cutting/modifying any of my joints? It'd seem like a waste of time to weld and anneal a joint then possibly have to modify it later because my design needs tweaking.
    Where can I get temp sticks? Would my local welding supply store have such a thing?
    Thanks

  9. #9
    Join Date
    Dec 2005
    Location
    wisconsin
    Posts
    836

    Default

    Quote Originally Posted by swamper8 View Post
    Well I like to do things right so i will probably try my hand at annealing. Do I have to anneal the joint soon after welding? Or could I fab up my frame, assemble my components and fully test my design to make sure I won't be cutting/modifying any of my joints? It'd seem like a waste of time to weld and anneal a joint then possibly have to modify it later because my design needs tweaking.
    Where can I get temp sticks? Would my local welding supply store have such a thing?
    Thanks
    Nope you can go through the joints after the whole frame is welded, no time limit. I buy my temp sticks from MSC ( www.mscdirect.com).

    Another little tip, if you use a jig of any kind, dont make it too ridgid. If you restrain the parts while welding you can have "hot cracking" of the material as it cools. Allow some slop in the jig for expansion and contraction. For what your doing 1/8" allowance should be fine for most of the parts. Jigs that slip ( i.e. magnetic clamps) are fine as well as they allow the parts to move upon cooling.

    Oh and be careful when using the term "annealing". Technically its tempering, but historicly its been called "Stress relieving" , " Torch annealing" , and "Normalizing". I too find myself using different names for it depending on the audience.


    -Aaron
    Last edited by Aerometalworker; 03-02-2008 at 04:14 PM.
    "Better Metalworking Through Research"

    Miller Dynasty 300DX
    Miller Dynasty 200DX
    Miller Spectrum 375 extreme
    Miller Millermatic Passport

    Miller Spot Welder
    Motor-Guard stud welder

    Smith, Meco, Oxweld , Cronatron, Harris, Victor, National, Prest-o-weld, Prest-o-lite, Marquette, Century Aircraft, Craftsman, Goss, Uniweld, Purox, Linde, Eutectic, and Dillon welding torches from 1909 to Present. (58 total)

  10. #10
    Join Date
    Feb 2008
    Posts
    14

    Default

    OK,
    So I went to my local welding store to pick up some ER70S-6. Not only did they not have it but no one thought that would be the right filler for 4130 anyway. They thought maybe ER80S-6 at first, but after asking around they think I should be using actual 4130 filler rod. So I got two lbs just to save a trip back. What does everyone think of this?

    Also, they didn't have ER70S-6, however my local harborfreight retail store has a MIG spool of ER70S6 on sale. Can I buy this spool and just use the wire like it was a straight piece of filler? It does not have a flux core or coating.

    Thanks

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