Welding Tips and Tricks

Hello everyone,

I have this ongoing project I have been working on as I get free time. I am attempting to make a hatch style liftgate for my car using the existing liftgate and tailgate. My plan is to fabricate a frame for the tailgate and liftgate to bolt onto. I decided to use 6061 T6 aluminum and 5356 rod.

ISSUES:

In the last few days I learned that when welding 6061 T6 that it loses its strength.

I also learned that 5356 doesn't hold up well when subjected to degrees of 150 Farenheit or above Temperatures get 110 degrees farenheit in the summer where I live and have put thermometer's in my dash to observe temperatures between 130 to 160 generate inside auto cab space areas.

Further, if I were to proceed and weld the frame together, aluminum fails instantly instead of gradually giving me a chance to observe that the welds or aluminum base will fail.

The liftgate and tailgate weigh about 50 pounds each on their own. The hatch will weigh about 100 pounds. I plan to get custom gas struts with a high pressure rating to open the hatch.

I guess I am confused because I see people online welding 6061 w/5356 on things that look structural but I'm scared if I proceed that the hatch will fall apart when in use and injure someone in addition to damaging my car. I read that 4643 rod will just about match the strength of the base metal; however, you have to send your part some where for heat treating. My concern for heat treating is warpage. I tried searching online and couldn't find and heat treatment services near me (Fresno, Ca).

Lastly, I also read 4643 rod is not usually stocked in welding supply stores.

Any help or insight is appreciated.

Your makin a what?

Welcome to the form Michaelmotorcycle.

I get the concept your doing but more details or pictures would help - I assume this is a station wagon style or maybe a LandCruiser ? - I'm not an expert on aluminum frames - I do a bit but they are usually not critical - hopefully other members will chime in as time differences & work patterns allow - a few thoughts on your general questions are.

If you join the 2 existing pieces you are doubling the weight on the top hinges - are they & the surrounding frame up to it ?

you say 4643 filler ? never seen it here ( UK ) did you mean Maxal 4943 ? - generally 6061 will weld with 4043 or 5356 - most non code welds it won't effect that much - we have 4743 here which is just a higher %silicon than 43 - not sure it would have much effect - only time I've had it recommended here was on some unknown dirty material we had to weld.

T6 grade is heat treated so the HAZ will always be softened - design of the frame could however place the welds in less strained areas with careful planning - I don't know of an easy way to re-heat treat post weld - maybe other members will.

If you really want a project which seems a lot of work for the benefits maybe you could look at fabricating a complete frame & skinning it aluminum to create a lighter weight replacement for the original 2piece tailgate - then the strength issues would be much less - just ensure you have sufficient material thickness where the hinges will bolt on.

Best of luck with your project.

Michael,

I've welded loads of 6061 in T3 through T6 temper in code vessel and structural applications, and only once have had anything other than 5356 called out for it. That one case was a cryogenic application for -320*F, but I've done cryo welds with 5356 as well.

There's a lot of mythology and alchemy involved in aluminum, if you believe the internet.

Here's the skinny: 6061 will age-harden.

The trick to what you want to do is simple. Prep carefully so you use as little 5356 filler as needed to achieve the joint with inner and outer reinforcement, while welding hot enough for good dilution with the parent metal, and the rest will take care of itself. A pre-heat will help, but 275*F is more than adequate for thin material.

If you have enough experience to be confident in your aluminum welds, you should not let this scare you because of the alloys involved.

Steve S

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Given what I've read from responses here, talking to a local shop that fabricates with aluminum, talking to a shop that does heat treating, and additional research, I guess I'm going to attempt welding the 6061 T6 frame together with the 5356 rod. My next concern is prep work so that my welds can be as strong as possible. I remember reading that you don't want to use sanding discs on aluminum to be welded as it puts impurities in the aluminum and also because it smears the aluminum causing for a weaker weld. I will need to fill some really bigs gaps. I was thinking of welding ontop of welds to build up material. I have used a skill saw w/ a blade to cut wood to cut the 6061 T6 3/4" bar and the 1/4" thick angle aluminum w/legs that are 1 1/4". I see little pieces of extra cube like metal on the skill saw blade but I'm not certain their carbide (I was told that a skill saw blade would be fime to cut aluminum; however, recently found out that it needs to be carbide tipped in order to cut clean enough so I can weld at the cuts). I purchased a container of acetone and new wire brushes to aide in cleaning metal. I was told there are aluminum specifice angle grinder discs but I don't know if I can weld on an area that I grind on using an aluminum specific disc. I took pics w/ my phone but I'm not sure how to upload them.

+1 to Steve.
6061 will substantially "harden" in about 2 weeks after welding\annealing. However it depends on how much heat was pumped in it.
The nature of "hardness" in cast and rolled 6061 is different.

To weld 3/4 bar to 1/4" flat you need a lot of juice and possibly an argon-helium mix...

aluminum specific discs usually contain agents to prevent the disc from loading-up/buildup on the disk itself, and has little to do with the surface that was just ground down. You still need to do a good acetone cleaning, then wire-brush, and again acetone.

Oh and by the way, Maxal ER4943 is the way to go. This one does not depend on base-metal dilution for decent strength. Can be PWHT but not necessary.

Maxal ER4943 Datasheet

1/16" 10lbs box Part#: 494306270
3/32" 10lbs box Part#: 494309470
1/8" 10lbs box Part#: 494312570