Loosing Strenght

[mutang460]

I'm in the process of welding 1/8 thick x 2" flat plate x 7" long... TIG ing a 1/8 thick X 2" leg together forming a 90 degree angle. I'm not having trouble welding the two together but after I'm finished. About 1/2 inch from my weld on both peices the peices are becoming very weak and pliable. How can i fix this. I'm not sure what series of aluminum i'm using.
I've tried different ways of prepring the paterial from cleaning it to pre heating. tried different tungstens I'm running 100 percent argon. I've never had this problem with this setup before.... but its been about a year and half since i've welded aluminum tring to figure out what the heck im doing wrong. or whats going wrong.... any ideas... I've changed out the peices of aluminum with new strips but i've bought them at the same place...
What series of aluminum would be the best to use...
I've always been given the aluminum and been told to weld them together in the past. I've never actually went out and bought aluminum for my own project.

[atlantafab]

series of aluminum would depend on the end use of the product but, you can expect to get 6000 and 7000 series from most vendors. If you don' have to comply with specs for the project then focus more on the process of welding to fix the problem areas. Add filler as long as you can at the start then at the end of the weld and back off the pedal (if you're using one) to let the puddle cool before extinguishing the arc.

BTW - why not cut buy the angle and cut it?

[mutang460]

its a 7 1/2" long peice with a 2" long peices welded to it to form the angle

2" rise 7 1/2" run dont want to have to buy a 8" angle and then cut awya most of it.

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[atlantafab]

How about calling someone or using a press brake to form the angle from sheet?

[JoeS]

just remember, aluminum is usually tempered to get the required strength. Any time you weld it, you will lose some or all of the temper.

the best thing to do is to design the part so that a weaker section of the assembly will not cause the part to fail.

additionally, you can try and run the weld hot and fast, and hopefully reduce the amount of time the material is heated, and also use some damp cloths or heat sinking of some type to avoid overheating localized areas.

if you start with something like 6061 T6 tempered, you might end up only losing some of the temper.

i beleive you can retemper the part, but it required a specific heat/cool cycle in programmable ovens, and not easily accomplished by the home shop fabricator.

[B_C]

I used to weld Harley cylinder heads for a dealer near by and he would send them out to be heat treated......They get soft from the heat of welding and have a weak thread if one needs to thread a hole before treating...(Spark plug holes)

[mutang460]

Thanks guys, I was hoping i had just got some crummy metal or i was laying a bad weld trapping in procity. But realizing the aluminum just is holding its strengh and wont work for this application with out some major work and excess time which i'm trying to stay away from... I'm just going to have to go back to steel or stainless steel. :mad: