welds failing on intake plenum need help/advice

[wallace]

I built an intake plenum for a 4 cylinder engine. I used .090" h3003 aluminum sheet and 4043 filler rod. I put x creases in the panels to stiffen them. I used 1/8" pure tungsten and 1/16" filler rod. This is a turbocharged application and it sees quite a bit of pressure. After I fabricated it I built a pressure tester. cycling the pressure to 30 psi a couple of times results in cracks in the long seams. I initially drilled small holes at each end of the crack, ground the weld down to base material and re-welded. cycling after the repairs results in cracks in other areas. I have done a couple of plenums prior to this using heavier 6061 t4 plate and 4043 rod with no issues. Have I chosen the wrong base material or too thin? I am not a professional welder but I have some experience and from what I can see I have good penetration. I'm using a syncrowave 180. I am at the point of scrapping the assembly and starting over. I don't have a way to post pics at this point but really I would like to know about the base material and my choice of filler. Thanks.

[chewinggum]

It's probably not your welds, it's your design. Thin metal, unsupported, will flex and fatigue at the joints. You need to brace it up or redesign to eliminate large flat surfaces, I suppose.
CG

[monte55]

It would help if you would post some pictures

[WookieWelding]

well 4043 is used when joining other alloys to 3003

AL 1100 filler is used when welding 3003 series aluminum's to other 3003 series aluminum's

try the right filler for the material and if your design is good the problem should go away with the cracking

[wallace]

Thanks for the replies. I think the material is just too thin for the design. I'm going to get some 6061 .187" flat sheet and start over. I did try making up some reinforcing angles and welding them across the seams and it did seem to keep it from cracking in those areas. I THINK if I applied them all over it might hold up. This is for my dd so not going to chance it.

[Cgotto6]

What kind of car is it?

[FusionKing]

.090 is WAY to thin for that

[jrscgsr]

Wrong filler, material to thin, possible design problem.

I built supercharger manifolds with 6061 .125" 4043 filler with no problems.

[awill4x4]

Yes, .125 or thicker should be ok.
Also look at your weld joint design, try to steer away from corner to corner welds and maybe look at using a lap weld design.
If not, can you get access to weld internally as well as externally?
I'd use 4043 filler unless the weldment needs to to anodised in which case 5356 is the requirement there.
Regards Andrew from Oz.

[wallace]

What kind of car is it?

Its a 1987 Plymouth Horizon.

I can't weld on the inside unfortunately. I'm going to the metal supply today and see what they have available in the drops bins in 6061. I tried the .090 because I could shear and bend it with the equipment I have. I'll try and post pics as I go along this time. Thanks for the replies and info!