What filler rod do you use?

[bobthebuilder]

Hi guys,

Here in South Africa, we are not allowed to weld our airframe structures. We can tack all of the bits together, but a coded aircraft welder has to complete all of the welds and sign it off.

I am now at the stage where I have a number of parts that need to be finished off by a pro welder. I found a certified guy with 25 years experience welding aircraft structures. He came with plenty of favorable references.
From the reading I have done, an ER70S filler rod was the way to go, or so I thought. The certified guy has recommended that we use a 303 or 306 grade stainless steel filler rod on my 4130 components. He said that it would produce a better weld and that it was soft enough and wouldn't crack. The last thing I want to do is insult a man with that sort of experience.

What are your thoughts about using this type of filler rod on 4130?

 

[ncam]

Here in NZ stainless filler is widely used on steel as I believe it flows better, producing a nicer, prettier weld.
I don't know about it cracking. Obviously this will be tig or tig. Personally I would not worry.
Regards
Neville

 

[bobthebuilder]

Thanks for your input Neville.
I am going to see him later today. I'll post some pics when he has finished up with them.

 

[Des]

Hi bobthebuilder,

I am afraid you face a never ending story...
Recently, I was faced with the same question; what is (would be) the best filler rod for welding a thin walled 4130N tubular structure, which IS NOT TO BE HEAT TREATED AFTERWARDS
When asking around, I was amazed what a bunch of different answers. So I also started looking around for some literature.
After having done this, I finally settled for ER70S2.
Apparently this rod is not that much used, since not one dealer (over here in Belgium) had stock of it. I had to order mine from Aircraft spruce and specialty Co.

Best regards,
Des.

 

[EricAos]

Don't limit yourself to TIG rod. ER in the name means that the rod will work for MIG or TIG. You can sometimes find good deals on spools of MIG wire. Just cut it into lengths, and use it.

Here is the classic web document on TIG welding Chromolly.
http://www.lincolnelectric.com/en-us/support/welding-how-to/Pages/chrome-moly-detail.aspx
It talks about ER70, ER80, and 4130 rod, and the advantages/disadvantages of each. It even mentions SS filler rod. (I use it on non structural parts, because it flows out nicer, and produces a prettier weld.) The only ER80 I have ever found has been MIG wire on a spool. I have seen Chromolly tube crack, so my personal preference is ER70S-6.

Eric (not a professional welder)

 

[bobthebuilder]

I have tacked all of the smaller mechanical parts together with ER70-S6 Rods. (ER70-S2 not available here either)
We had a look at a book which compares the tensile strength and other properties of the various rods. The ER70-S6 and the 309 SS rod are similar, with the 309 rod being slightly softer. (believe it or not)

But ..... we didn't discuss heat treatment afterwards! I had better give him a call and check that out .... QUICKLY!

 

[Des]

Hi Bobthebuilder,

don't blind yourself that the strongest filler rod will be absolutely also just the best. It may, but it also may not... The total application aspect has to be taken into account, and that may yield amazing results.
In case you are dealing with an O/A gas welding procedure, I have following experience: I oxy welded my S II L in 1981, using SAFER 40 rod; (AWS eq. R45). This rod is not suitable for heat treating afterwards
Over here in Belgium, only certified welders, passing a specific practical exam, may do welding jobs on experimental ( and fully) certified aircraft. Afterwards, the welds are magnaflux checked. All my welds came out OK.
Up to now, I have flown the sonerai well over 1300 Hrs, and not any weld has shown any defect.
At the time of welding my sonerai, I did not have that much experience in O/A welding. So, I went out to the professionals, together with some reading of the tech. stuff around dealing with " O/A welding thin walled 4130N tubing"
That boiled down to selecting the "ordinary" R45 rod. So I started exercising and even succeeded the exam. (Gas welding low alloy steel)

Best regards,
Des.

 

[bobthebuilder]

Hi Des,

To get a coding qualification over here is almost impossible for the home building folks, unless you want to make welding your profession.
One would have to complete an apprenticeship, and once coded, welders are required to be re-tested every six months.

My parts are TIG welded.