Best welding rod (tig) for welding 4130 chromoly tubing

[zkoobs1978]

Does anyone know the best (strongest) rod for welding 4130 Chromoly tubing. I am building mini sprint chassis.


Thanks,

Zeb

[ASKANDY]

ER80S-D2

Lots of stuff here on that subject.

Andy

[Aerometalworker]

Er80S-D2 is used in aircraft weldments that are heat treated, ER70S-2 is used for non heat treated. Of course standard practice involves post weld tempering or oven treating.
-Aaron

[FM117]

Zeb,
You will not get agreement on the answer to your question.
Some use ER70 others use ER80. On the frame itself I doubt
you'll be able to do post weld heat treating.
I use ER80 and don't believe in the practice of torch annealing
the welded joints. I do use lowest heat needed an don't "hurry"
the weld along.
Opinions vary....do lots of reading and make your choice.
Will also mention that the Lincoln motorsports welding program
falls in the ER80 camp.
Dave P.

[Showdog75]

Murf McKinney who builds most of the NHRA Top Fuel chassis uses ER80S D2 and doesn't stress relieve all the welds . If it's good enough for 8000-10000 horsepower I'd say it would work for you .

[ASKANDY]

ER80S-D2 is a higher strength steel filler that contains 1/2% of Molybdenum and more closely matches the strength of the 4130 than the ER70. You can stress relieve the weld joint if you wish but even some of the top drag chassis builders don't do it. Heat treating is only somewhat useful and relies on how much base metal is diluted with the filler. Normally, heat treating is done with 4130 filler and on thicker weldments. Keep your arc lengths as close to the joint as you can and do not overheat by using too much amperage but make sure the toes of the weld are tied in properly. With a mini-sprint chassis and the amount of triangulation that is used in the tube layout, you should be fine.

Like Dave said.
You will get many answers here....

Andy

[Aerometalworker]

Murf McKinney who builds most of the NHRA Top Fuel chassis uses ER80S D2 and doesn't stress relieve all the welds . If it's good enough for 8000-10000 horsepower I'd say it would work for you .

Funny, notice where that got them? Ever see the failed welds on the Force teams cars? Hmmmm.
-Aaron

[steven_oharra]

When we did our AWS cert in 4130, our first run failed using ER70.
The as-welded strength of ER70 is 70ksi.
The normalized state of 4130 is 90-95ksi.
Our welds had excellent fusion, penetration, and inter-pass cleaning.
The visuals looked great, then came the 20 ton bend test.
The 4130 coupons tried to remain straight while all the bending-stretching was being done by the filler on the 2" ram (2" used due to higher ksi of 4130).
The effect was almost a T-Pee or V bend instead of a U-bend and ultimately, the filler was stretched to the point of breaking into two coupon fragments.

A second run was made using ER80 (still weaker as-welded than the normalized 4130) and you could see more stretch of the weldment but in the end, the 4130 coupons were forced to follow the 2" ram shape and create a perfect U-bend that passed AWS criteria. Not that you'll be bending your welds into U-bends but as always, you try to make sure your filler is as close a match to the base as possible for a more homogenous weld.
(closer match of 80ksi/ER80 to normalized 4130's tensile of 90-95ksi)
-Steven L. O'Harra

[steven_oharra]

When we did our AWS cert in 4130, our first run failed using ER70.
The as-welded strength of ER70 is 70ksi.
The normalized state of 4130 is 90-95ksi.
Our welds had excellent fusion, penetration, and inter-pass cleaning.
The visuals looked great, then came the 20 ton bend test.
The 4130 coupons tried to remain straight while all the bending-stretching was being done by the filler on the 2" ram (2" used due to higher ksi of 4130).
The effect was almost a T-Pee or V bend instead of a U-bend and ultimately, the filler was stretched to the point of breaking into two coupon fragments.

A second run was made using ER80 (still weaker as-welded than the normalized 4130) and you could see more stretch of the weldment but in the end, the 4130 coupons were forced to follow the 2" ram shape and create a perfect U-bend that passed AWS criteria. Not that you'll be bending your welds into U-bends but as always, you try to make sure your filler is as close a match to the base as possible for a more homogenous weld.
-Steven L. O'Harra

[Aerometalworker]

Steven,
What you were testing sounds like guided bend tests on heavy plate, butt welds im guessing? Thats a completely different set of criteria than a welded tubular structure, and has little value. We have fillets, and a much lager weld area to CSA ratio. We also have more relative movement and fatigue issues. SO nothing against your comments, just realize that not everything translates from one application to another.