cast aluminum?

[wagin]

It is rare that I, in a conscious effort, shoot off my mouth. Here is a perfect example why. My neighbor which I've fabricated-repaired many "friend" jobs for asked me if I could repair the broken door on an antique mail box. I said if I can't weld it, no need to look more, it can't be done. Turns out the mail box is a reproduction, not a true antique, and is made of cast-pot aluminum, 3/16". So, another lesson reinforced. Can this be done using any type of dc tig with ever-do filler or brazing. I do have ac, hf ability but it is set up for portable service and I try not to run the loud monster in the neighborhood. Any tricks? Here are pics.
Thanks
Wes

[rode2rouen]

It's likely made of pot metal which usually has lots of zinc..................welding would be dicey, at best.
This might be a good application for one of the Devcon (kinda like JBWeld) epoxies.


Rex

[A_DAB_will_do]

X2 on using an adhesive. I predict nothing good will come from trying to weld on that door. If you were to get an analysis of the alloy, you could make a better run at picking the right filler metal. But I'll be the first to say the job is likely not worth paying for a lab to analyze the alloy composition. Without that you're shooting in the dark, and likely to have all sorts of hot-cracking issues.

If I were in your shoes, I'd take the whole door off. Clean well with solvents and handle with gloves going forward. Press the corner and broken piece into a block of warm wax, to make a simple, easy way to hold the pieces in the correct position. Take a dremel and put a shallow groove in the back side, where it won't be seen most of the time. Then take apart, coat crack with a thin layer of expoy on both sides. Set together in the wax 'jig' and allow the first coat to cure. Then fill up the groove with 1 or more layers of epoxy. Allowing time for full cure between multiple coats.

With some luck the front side of the crack will be hard to see. Could be painted when done to completely hide the repair. Hopefully the light weight of the door will mean that the repair has a long life....

[yorkiepap]

Hey wagin,
I did a repair on an identical mailbox last summer that had a broken base because the garbage hauler wasn't paying attention & ran into it. The customer unbolted it from the concrete base & I brought it to my shop. Yup......zinc diecast. I used the HTS-735 "garbage alloy" rods that are also known as Alumalloy or HTS-2000, & others found on E-Bay. I prepped the break the same as I do regular aluminum.....bare, clean, & brushed vigorously w/acetone. I used O/A since the break length was 4.5". The small repairs I usually do with Oxy/Mapp. Surprisingly, the rod works quite well & does make for a strong joint. You really have to do serious flame/heat control continually moving the flame to reach the brazing liquidus of the rod. The rod melts very smooth once the metal reaches temp & a brisk pushing/pulling of the rod end to the repair surface will allow a nice fillet.

I did a test to determine strength of the alloy with a couple pieces of 6061 angle.....the joint did not break from my 2# ballpean hammer. That would also help you get the feel of the alloy & its' brazing characteristics prior to doing the repair if you choose to try it. Anyway, here's some pics of the rod & test I did.

Denny

[wagin]

Thanks for the info guys. I wish I had a scrap piece of this metal to experiment with. But I don't. Would silicon-bronze filler work? The mail box metal is a cast aluminum of sorts. It's not magnetic and very light. I've found a few assembly welds. Here's pic.

[castweld]

Originally Posted by wagin

Thanks for the info guys. I wish I had a scrap piece of this metal to experiment with. But I don't. Would silicon-bronze filler work? The mail box metal is a cast aluminum of sorts. It's not magnetic and very light. I've found a few assembly welds. Here's pic.

Its cast al, bevel it then tig or mig. No need to heat it being its a corner repair. Combines and tractors hit a few around here each year. Farmers bring them in for repair, they are trying to avoid having to buy owners new ones. 4043 is my choice for filler.

SI bronze won't work.

Peter