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Thread: TIG filler rod

  1. #1
    jimboflying's Avatar
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    TIG filler rod

    What is the best filler rod to use on 4130 joints? What is the difference between ER70s-2 and ER70s-6?

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    Either will work. S6 is more fluid, so may be better for flat work, but not so good for out of position. Get some of both and practice to see what works best for you. If doing stuff with welding procedures, use what is called for in the procedure.


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    I've been researching this recently as although I prefer ER80S-D2, I'm having trouble finding it in diameters less than 0.035". For me, I struggle to get into the roots of acute angles with the 0.035" on 0.035" thick material. In experiments I've done I did like the flow of the 6 I was using (although I can't remember if it was ER70S) vs the ER80S-D2. And the welds were quite nice. However, after reading the following pieces from Welding Tips and Tricks, I'm a bit concerned.

    http://forum.weldingtipsandtricks.co...pic.php?t=8812

    https://www.weldingtipsandtricks.com/er70s2-er70s6.html

    From the looks of it the higher amounts of silicon and manganese in the 6 brought impurities to the surface. If my welds looked like those in the pictures I would be concerned as to their adequacy. I'm not sure if cleaning and back purging would alleviate these issues but I can't always back purge.

    It would be nice to get some clarification on this issue because I'd like to use ER70S-6 on joint clusters where necessary.

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    Quote Originally Posted by Aeronut View Post
    I've been researching this recently as although I prefer ER80S-D2,
    I would truly recommend to NOT use an 80 filler rod on 4130 unless the assembly is going to be properly post heat treated.
    The joint ends up with a high carbon content reducing ductility along the edges of the puddle. Not something you want in a flexible structure.

    ER-70S2 is the most universal filler for hand work of tube structures that will receive minimal post weld treatment.

    For very small filler rod, if you have a MIG welder run some wire out of it. This will generally be 70S6 in a .023 or .030 or near that.

    I do buy much of my tig rod in .035 for general work and .045 for mid weight welds.
    Regards, Charlie
    Super Coupe E-AB build in process
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    Quote Originally Posted by CharlieN View Post
    I would truly recommend to NOT use an 80 filler rod on 4130 unless the assembly is going to be properly post heat treated.
    The joint ends up with a high carbon content reducing ductility along the edges of the puddle. Not something you want in a flexible structure.

    ER-70S2 is the most universal filler for hand work of tube structures that will receive minimal post weld treatment.

    For very small filler rod, if you have a MIG welder run some wire out of it. This will generally be 70S6 in a .023 or .030 or near that.

    I do buy much of my tig rod in .035 for general work and .045 for mid weight welds.

    Agree 100%. I would stay away from the 80. ER70S-2 is the go to, why monkey around with anything else?
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    Aeronut's Avatar
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    Thanks for the recommendations, CharlieN and akavidflyer. To be clear, using ER70S-6 on any joint to include the entire fuselage, is OK. Is that correct? This includes the use of MIG ER70S-6 for use in TIG welding the same applications?

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    ER70s-2 is preferred over -6, But I truly doubt anything would be wrong with using the -6 for overall work.

    I use the small MIG wire when TIG welding thin steel such as .012 to .020 thick materials. I work almost exclusively with a .040 electrode, generally a 2% Thorated, I will grind this to the finest tip I can when working very thin material.
    Heck with my aging eyes I can barely see the arc now.
    Regards, Charlie
    Super Coupe E-AB build in process
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    Quote Originally Posted by CharlieN View Post
    ER70s-2 is preferred over -6, But I truly doubt anything would be wrong with using the -6 for overall work.

    I use the small MIG wire when TIG welding thin steel such as .012 to .020 thick materials. I work almost exclusively with a .040 electrode, generally a 2% Thorated, I will grind this to the finest tip I can when working very thin material.
    Heck with my aging eyes I can barely see the arc now.

    Get a pack of LAYZR tungsten. No more radioactive dust to breathe and it holds up better. It is my go to at work and home for ALL welding. CS, SS and aluminum. If you do stick the tip, it doesn't break off as easily and it will hold the arc at lower amperage amazingly well.
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  9. #9

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    I use 2% lanthinated for pretty much all my TIG, 3/32 or 1/16 for most work, but also keep .040 and .020 in the tool box in case I need it. Get some Furick cups, I use Jazzy 10 a lot, but for some of the joints a Fupa 12 or BBW will be better as you can really stick the tungsten out to get in the joint. Of course with the bigger cups, you need to flow a lot more argon. As others have stated, stay away from the ER80, your joints will be much more brittle. S6 is fine for flat work, but is much to fluid for overhead. Better to stick with S2. You will kick yourself if you don't go out and buy a TIG Button. Trying to run a pedal while climbing in and around a fuselage requires a lot of contortions. The Tig Button solves that problem and is the best accessory I have for my TIG set up. Mig wire works just fine when trying to find the real small stuff.

    The biggest issue with TIG welding is cleanliness! Clean your metal, clean your filler wire. For tubing, clean all the scale, both inside and out that is in the heat affected zone. After mechanically cleaning, then use acetone to clean any oils. I think this was the hardest for me changing from Oxy-Acet welding. With gas, just burn through all the scale. With TIG, not so much!
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    RVBottomly's Avatar
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    Quote Originally Posted by CharlieN View Post

    I use the small MIG wire when TIG welding thin steel such as .012 to .020 thick materials. I work almost exclusively with a .040 electrode, generally a 2% Thorated, I will grind this to the finest tip I can when working very thin material.
    Heck with my aging eyes I can barely see the arc now.
    Wow! That's thin. Must have a steady hand.

    I have successfully torch welded .02 to .035, which is fun enough.

  11. #11
    RVBottomly's Avatar
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    Quote Originally Posted by dgapilot View Post
    With gas, just burn through all the scale.
    I've noticed that, but never wanted to admit it.
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  12. #12
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    I wanted to tie up a few loose ends on this thread and add some more information that I found in case anyone references it in the future.

    The yield strength of 4130N is 63,100 psi. The yield strength of ER80S-D2 is 68,000 psi. The yield strength of ER70S-X is 58,000 psi. The yield strength is in the ballpark for both filler materials with the weld theoretically yielding first with the ER70S-X and the tubing first with the ER80S-D2.

    The tensile strength, the strength at which ultimate material failure theoretically occurs, is 97,200 psi for 4130N. It is 80,000 psi for the ER80S-D2 and 70,000 psi for the ER70S-X.

    In the following article Lincoln Electric recommends using ER80S-D2 in that it is capable of producing welds that approximate the strength of 4130. The article acknowledges ER70S-2 and ER70S-6 as acceptable alternatives but with lower weld strength. It also states that the use of ER70S-2 and -6 will typically undermatch the 4130. However, they state that proper structural design considerations may mitigate this.

    https://www.lincolnelectric.com/en-g...ly-detail.aspx

    Double check my numbers. It appears all aforementioned weld fillers are acceptable but it's important to understand the potential impact on structural integrity of using an ER70S-2 or -6 filler.

    Thinking about the previous points of joints failing just outside of the welds, I wonder if some other culprit is at play like martensite. Note that the additional strength of the ER80S-D2 is derived from the content of Molybdenum which is greatest there (0.50% by weight) as opposed to 4130 (0.20% by weight) and ER70S-2/6 (0.15% by weight). The carbon content of all filler materials appears similar.

    The above information is only for information purposes and I'm not advocating one filler over another.

  13. #13

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    Quote Originally Posted by Aeronut View Post
    I wanted to tie up a few loose ends on this thread and add some more information that I found in case anyone references it in the future.
    You read books but you lack the decades of experience and history of material failure analysis that tells a story far different than what you are pushing for.
    Regards, Charlie
    Super Coupe E-AB build in process
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  14. #14
    Aeronut's Avatar
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    Charlie, no worries. I read a lot of older threads for information and gain value from the discourse. I just wanted to add some of what I found from the AWS and other sources. At the end of the day each one of us has to make their own decisions based on the standards and tempered by the experience of others. I appreciate your input.

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    One of the major attributes in welding are stress related properties in the heat affected zone after the weld process. To make it simple, the weld in general gets hardened during a Tig weld process, this being the reason for the lower yield filler material.
    4130 was created back in the '20s when welding was done with gas torches. The act of welding back then annealed the heat affected zone. When I was a fledgling welder my elders advised me to not use electric welders with most alloyed steels. Then we were to pre, and post heat the region with a gas torch when Tig welding. That process went away when labor rates started climbing. I do my pre heating with the Tig torch anyway.
    We can all imagine the cost of a fuselage if you more than tripled the weld time involved. I am impressed with the companies that are Mig welding frames, is there .028 wall tube in those frames? OK so their labor force is less than 1/3 my age.

    It is rare to see a crack form along a weld but that is generally caused by the heat affected zone going hard, and this has generally been due to filler material or fast quenching during the weld process. Both of these we have control over with technique and material selection.
    Regards, Charlie
    Super Coupe E-AB build in process
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  16. #16

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    Quote Originally Posted by Aeronut View Post
    I wanted to tie up a few loose ends on this thread and add some more information that I found in case anyone references it in the future.

    The yield strength of 4130N is 63,100 psi. The yield strength of ER80S-D2 is 68,000 psi. The yield strength of ER70S-X is 58,000 psi. The yield strength is in the ballpark for both filler materials with the weld theoretically yielding first with the ER70S-X and the tubing first with the ER80S-D2.

    The tensile strength, the strength at which ultimate material failure theoretically occurs, is 97,200 psi for 4130N. It is 80,000 psi for the ER80S-D2 and 70,000 psi for the ER70S-X.

    In the following article Lincoln Electric recommends using ER80S-D2 in that it is capable of producing welds that approximate the strength of 4130. The article acknowledges ER70S-2 and ER70S-6 as acceptable alternatives but with lower weld strength. It also states that the use of ER70S-2 and -6 will typically undermatch the 4130. However, they state that proper structural design considerations may mitigate this.

    https://www.lincolnelectric.com/en-g...ly-detail.aspx

    Double check my numbers. It appears all aforementioned weld fillers are acceptable but it's important to understand the potential impact on structural integrity of using an ER70S-2 or -6 filler.

    Thinking about the previous points of joints failing just outside of the welds, I wonder if some other culprit is at play like martensite. Note that the additional strength of the ER80S-D2 is derived from the content of Molybdenum which is greatest there (0.50% by weight) as opposed to 4130 (0.20% by weight) and ER70S-2/6 (0.15% by weight). The carbon content of all filler materials appears similar.

    The above information is only for information purposes and I'm not advocating one filler over another.
    Keep in mind that when you weld, the filler metal and the parent metal do not stay separated, they mix into a new alloy, somewhere between the parent and the filler. The majority of fuselages that were welded with gas used RG45 rod which is only 45ksi, far less that ER70. As stated by others, the welds never fail at the weld itself, but at the extent of the heat effected zone. 4130 is a heat treatable alloy, and if cooled to rapidly, will become brittle. For decades, we were cautioned against using electric welding with steel tube structures due to the suspected brittleness resulting from the rapid cooling. In A&P school even in the '70s, were were told that if you used TIG, you had to post treat by annealing (or normalizing) the joint. In recent years, that practice has gone by the wayside as everyone looks to motorsports and the success they have with chassis that aren't normalized after welding. Of course, most of them are heavier wall tubing, .058 or better while we are using .020, .032, and on rare occasions .049. If you are going to build something, use what has been tried and true, ER70 if TIG, and RG45 if gas welding. They work and provide joints that have stood the test of time.
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    Quote Originally Posted by Aeronut View Post
    I wanted to tie up a few loose ends on this thread and add some more information that I found in case anyone references it in the future.

    In the following article Lincoln Electric recommends using ER80S-D2 in that it is capable of producing welds that approximate the strength of 4130. The article acknowledges ER70S-2 and ER70S-6 as acceptable alternatives but with lower weld strength. It also states that the use of ER70S-2 and -6 will typically undermatch the 4130. However, they state that proper structural design considerations may mitigate this.

    https://www.lincolnelectric.com/en-g...ly-detail.aspx
    Slightly different take from Miller:

    "In many motorsports and aerospace applications, engineers want some degree of ductility in the weld to help absorb impacts and prevent cracking. For this reason, most NHRA fabricators intentionally dilute the strength of the parent material by selecting ER70S-2 for filler for roll cages, chassis and other applications requiring more flexibility. While actual tensile strength of the weld will vary and depend on other factors, 4130 diluted with ER70S-2 filler likely produces a weld with a tensile strength in the 80,000 to 82,000 psi range.
    For areas requiring higher strength, such as spindles and upper and lower control arms, fabricators select ER80S-D2 filler, which produces welds with a high tensile strength (as a side note, consider that S-2 fillers clean impurities better than D-2 fillers). In any event, do not use 4130 filler, as the weld will not have sufficient ductility unless it undergoes stress relief. "

    https://www.millerwelds.com/resource...e-applications
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  18. #18
    Gordon Misch's Avatar
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    I think part of the issue is the cross section of the material is typically thicker in the weld as compared to the adjacent base metal, so the lesser yield is mitigated. And maybe the lesser yield could help to reduce stress concentration at the weld boundary, where the cross section changes. Also, for very small welds, self quenching / hardening in the heat affected zone happens. I'm sorta paraphrasing what a welding engineer friend advises. And he says E70 in the absence of controlled post-weld heat treatment.
    Gordon

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  19. #19

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    I don't have anything to add to the discussion, but I have been TIG'ing 4130 a lot lately and really appreciate all of the information in this thread. Thanks to everyone taking the time to explain all of this specific to our use case (and not motorsports).
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  20. #20

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    Quote Originally Posted by Colorado-Cub View Post
    I don't have anything to add to the discussion, but I have been TIG'ing 4130 a lot lately and really appreciate all of the information in this thread. Thanks to everyone taking the time to explain all of this specific to our use case (and not motorsports).
    The goals of aircraft and motorsport frames in this case are in fact the same. They are willing to give up joint strength for desired ductility and flexibility (bottom line as CharlieN and other have recommended, use ER70).
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    So I came across some ER70-S14, what is different about it? Its not real clear on the firepower website...

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    Looking at their website here it looks like the "ER70S-14" might be their product name. The description calls it ER70S-6. Lincoln Electric calls their ER70S-6 "L-56." I doubled-checked AWS A5.18 and A5.28 and neither mentions an "ER70S-14." So my guess is that it's just ER70S-6.

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