jimboflying
MEMBER
What is the best filler rod to use on 4130 joints? What is the difference between ER70s-2 and ER70s-6?
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.
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.
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.
With gas, just burn through all the scale.
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.
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-gb/support/welding-how-to/Pages/chrome-moly-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.
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-gb/support/welding-how-to/Pages/chrome-moly-detail.aspx
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).