Welding A-286 and 17-4 PH 3

[SirCallipygous]

Hi everyone.

I could use some input on fusion welding A-286 thin-walled tube (.054-.065") to 17-4 PH. From what I read, the A-286 should be welded in the solution annealed condition with no post-welding heat treatment. I'm worried this won't be strong enough for my purposes (how much strength is really lost in this state?). If I weld it in the aged condition, I get the strength I want, but then I'm worried about the weld. It's not in a high pressure location, but I still worry about cracking. Also, in the past we've used 316L instead and it welded great to 17-4 PH with the fusion weld process.

Any input on either scenario is greatly appreciated.

 

[EdStainless]

17-4PH can be welded in the aged condition, but it must be one of the lower strength conditions. If you try to weld 17-4PH in the H900 or H950 you will likely get cracks.
So weld them both annealed, and use an austenitic filler (309L).
Then heat treat to harden the A286.
After the long age at 1325F the 17-4PH will be in the overaged condition with properties similar to the H1150M.

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Plymouth Tube

 

[metengr]

Good luck, A 286 is prone is weld heat affected zone microfissuring/cracking. This alloy is sensitive to cracking because of the chemical composition. Second, I would use an austenitic, Ni-base filler.

 

[SirCallipygous]

Thanks guys, I really appreciate the input.

I just had a supplier pop up that will provide some 17-4 tubing, so that should solve the issue and I can avoid the A-286. It was a little overkill, but it was available.

Just curious, how does the H1150M condition differ from H1150?

 

[OGMetEngr]

H1150 involves aging at 1150F, while H1150M involves a double age. The first is 1400F, the second is 1150F. H1150M results in, among other things, a lower strength due to the higher temperature temper step at 1400F. ASTM A564 details these conditions as well as others for this alloy.

If you are welding this you'll want to weld then age for full strength. If it's welded to 316L and aged, these temper temperatures may sensitize the 316L (Cr carbide precipitation at grain boundaries) which lowers corrosion resistance and impact strength.

Depending on application, this process may take some more careful consideration as there can be more issues/possibilities than I've mentioned above.

 

[EdStainless]

If the welds are not highly stressed you can weld 17-4 in the H1050 or H1100, or H1150 conditions.
The material will be softer next to the welds but not too bad.

Another thing about the H1150M, it has much higher ductility than even the annealed material. There are applications that overage, form, then re-anneal and age to a higher strength condition. Because the annealed material will not tolerate the forming.

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Plymouth Tube

 

[MagBen]

Ed, you got a typo? as for 17-4, weld in over-aged conditions (H1050-1150) is for high welding streses.

Solution-treated condition is 100% martensitic, prone to SCC. weld in this condition is normally fine, but need to age for application. but for an optimum combination of strength, ductility, corrosion, it 's better to solution again and aging.

Normal aging is to soften the alloy, no anstenic transformation. over-aging (e.g. H1150) is for obtaining some percentages of anstenite. M in H1150M stands for machinability, aging to 1400F leads to more antenite transformation (about 40%), so better machinability.

 

[EdStainless]

What I meant was that if the part was not under high loads you could use a part aged to lower strength as 17-4 is reasonably weldable in these conditions.

You are correct Ben, you cannot use 17-4 in the annealed condition. For many reasons, but the lack of ductility and sensitivity to SCC are the main ones.

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Plymouth Tube

 

[MagBen]

Ed, the emphasis we are talking about is a little different. two conditions of 17-4 can be welded:
1. solution treated condition: normally OK
2. solution + over-aged condition: may be better when high welding stresses is a concern.

How to heat treat after welding is a different story.


Aging at 900F could yield a bit of austenite, say 2%. So strickly speaking, my last post "normal aging yields none austentite" is not correct. Aging is to get small martensite precipitates, while increase in aging temp is to soften/toughen alloy

 

[EdStainless]

Sorry Ben, I had skipped over the weld in the annealed condition because the heat treatment of the two alloys are not compatible. But yes give the option welding in the annealed condition is preferred, followed with an anneal and age cycle.
If you want lower retained austenite and better toughness move from 17-4 to 15-5. 15-5 behaves just like 17-4 and it has the same strength but is engineered to have lower retained austenite and it is less sensitive to 'mistakes' in heat treatment.

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Plymouth Tube

 

[SirCallipygous]

Hi Guys,

Thanks for the wealth of knowledge! Sorry for just responding. It seems I needed to update my email filter for these notifications. I appreciate the discussion.