Help with brazing aluminum

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Old 01-09-08, 02:13 PM
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Help with brazing aluminum

Ive never brazed aluminum before but I need some help. I got some rod that supposed to work on aluminum and most cast aluminum. Ive tried it 3 times and so far all I have to do is breath on it and it breaks. The last try I got the alumimum so hot it started to melt. The joint looked good but after it cooled it breaks so easy becuse the rod never fused together. And I cleaned it very well to. I tried both aluminum and cast and no luck on either.

Anyone have any idea on what Im doing wrong? I would really appreciate the help.
 
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Old 01-09-08, 04:00 PM
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michaeljp86,

Aluminum is extremely difficult to braze successfully.
The temperature range that you can create a bond is very narrow which makes it easy to overheat.
I have a drawer full of various rods, fluxes and brushes that claimed to work well but don't.

I am familiar with two processes for brazing.
One has you clean the area well and apply a flux to eliminate oxidation.
You then need to heat a somewhat larger area than the braze point until the rod will flow but not applying too much heat that the flux will burn.
Problem with the fluxes I have the melting point of the rod is not too much lower than the point that the flux burns.

Another type I have uses a fine stainless steel brush that you use to brush the surface while heating and then apply the rod heat the braze area and brush some more.

Controlling the heat is the key as it is very easy to overdo it.
Also, sometimes what the aluminum piece is can be a problem.
If it is a piece that may be oil impregnated it could be very difficult to clean it properly.

I had been able to get the flux type to work after some practice but the resulting braze was never very strong.
I had much better luck with welding aluminum with a mig welder.

Let us know what you are trying to repair and exactly which brazing product you are using.

Maybe someone else has a trick for this product.
 
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Old 01-09-08, 08:28 PM
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The part I need to fix is a cast aluminum plate that holds a crankshaft seal on a engine.

The kit I bought came with a stainless steel brush. It said all you have to do is brush it clean and then heat the basemetal until the rod melts and your weld will be stronger then the aluminum.

I tried 2 types of flux with it and no luck. Ill play around with it tomorrow again.

Im thinking about just taking the part to a welding shop and have them tig weld it. If I cant get the hang of it thats what I'll do. All I have is a torch and a stick welder.
 
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Old 01-09-08, 08:38 PM
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brazing

ahhhh sounds like "alumalloy" has struck again...
 
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Old 01-09-08, 08:40 PM
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Originally Posted by Gunguy45 View Post
ahhhh sounds like "alumalloy" has struck again...

I think thats what it was, Im pretty sure I have the directons down the basement still.
 
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Old 01-10-08, 05:07 AM
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From what I remember you brush the weld area as you are heating the aluminum right up to the point you apply the rod.

If you are going to have it properly welded you would do well to not use any more of that rod on it.
It may make welding more difficult.

The fluxes I have for aluminum have a higher temperature rating that soft solder fluxes.........all were kind of a sticky liquid...... syrup like.

I was the brave soul at a trade show that went up to the demonstration table in front of a crowd of tradesman to try my hand at using one of these wonder aluminum repair rods.

Brazed a boat prop with a flux type rod with the sales guy standing at my shoulder coaching me.
The job looked like I had been repairing props for a career.
Bought that product along with several people at the demo, went home to use it and have never been able to duplicate the show results.
 
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Old 01-10-08, 11:01 AM
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I didnt try the piece I need to fix yet, I didnt want to screw it up. Ill go out and try the brushing thing and see how it works.
 
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Old 01-10-08, 12:21 PM
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I did a lap weld with both cast and regular aluminum. It seemed to go pretty good so I let it cool. It snapped of the cast wat to easy then I took the vise grips and popped the bead off the aluminum. This was the best one so far. Ill keep trying it and see how it goes.

I went to a welding show and a guy had something like this and would weld 2 pop cans together dunk it in water and hand it to you and it would not come apart. He also would melt a puddle on a can and leave the rod on it and you could not pull that rod off. Why cant I do that
 
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Old 01-10-08, 02:29 PM
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Well I sortof got somewhere. I did another lap weld and it was somewhat stronger but not much.

Then I took the cast heated it up and brushed it and then dropped a chunk of a weld that didnt hold on there and put the torch on it. Then while it was melted I took the needle nose pliers and stired it up and really shove it into the base metal. I cant pull that glob off.
 
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Old 01-10-08, 03:11 PM
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Glad to hear how you are making out.
What you are experiencing is about how far I got.

Why don't you try soldering a pop can to see what happens.
Maybe that is all it's good for.
 
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Old 01-10-08, 08:14 PM
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Originally Posted by GregH View Post
Glad to hear how you are making out.
What you are experiencing is about how far I got.

Why don't you try soldering a pop can to see what happens.
Maybe that is all it's good for.
I did alot of playing around, I was going to try a pop can and never got around to it. It seems to hold good until it cools. I had a little stub of rod and held it with the vise grips and had a nice silver puddle swirling around like the guy at the show. I left about 1/2" of rod out with the vise grips and blew on it and it cooled and held the vise grips up and I wiggled it and seemed to be good. But once it cooled it popped right off.

The directions says it works on cast aluminum so I wouldnt think its only good on pop cans.

I'll keep playing with it.
 
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Old 01-11-08, 12:31 PM
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Originally Posted by GregH View Post
Glad to hear how you are making out.
What you are experiencing is about how far I got.

Why don't you try soldering a pop can to see what happens.
Maybe that is all it's good for.

The pop can works great, it held so good when I tried to peel it off the can ripped.

But my problem is I need to fix a cast part.

I took a wood chisel to the glob on the cast and it wont come off so maybe there is hope for me.

Ill keep playing with it. Using it on the cast I have to use a cutting torch to get it hot enough to melt the rod.
 
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Old 01-11-08, 12:43 PM
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Originally Posted by michaeljp86 View Post
Ive never brazed aluminum before but I need some help. I got some rod that supposed to work on aluminum and most cast aluminum. Ive tried it 3 times and so far all I have to do is breath on it and it breaks. The last try I got the alumimum so hot it started to melt. The joint looked good but after it cooled it breaks so easy becuse the rod never fused together. And I cleaned it very well to. I tried both aluminum and cast and no luck on either.

Anyone have any idea on what Im doing wrong? I would really appreciate the help.
cleanliness is next to Godliness!!! if it is not clean, it WILL NOT stick!.. preheat the part thoroughly, keep the heat on it after you weld but back off so it will cool slowly. if it cools too fast, it will crack. something in the stainless brush makes a chemical type reaction to the aluminum. who knows what??? good luck. as a last resort, take it to a welder who has a heilarc machine and knows how to use it.
 
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Old 01-11-08, 03:45 PM
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I think I may have it figured out, on the cast anyways. Heat it up and while heating it youll see it get a little dark. Thats when it starts to melt. Take the brush and brush it and the top layer will come off and you will see a soft silvery layer which is where this stuff seems to stick. If you get to much heat then you have to much molten aluminum and it wont stick to that. It only sticks to the clean layer under where you brushed what was molten off.
 
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Old 01-17-08, 09:43 PM
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Today I fixed the engine part, it looks like crap but it worked. I also learned dont stick the brush into the melted puddle. You can braze stainless too and I brazed the brush bristles together .
 
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Old 01-18-08, 04:44 PM
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Brazing of aluminum

MichaelJP86, I'm sorry this is a little after the fact, but I just happened upon this website. It looks interesting! I hope I can help with your brazing questions. aluminum, no mater how you plan on welding it ,can be a real pain. It has to be clean. Even a casting that appears clean, the dark film your seeing are impurities. There are etching acids available from your local welding supply that do a good job of preping the base metal. As with any cleaning agent, caution is first and upmost important.With hand and eye protection, good ventalation,and following the instructions on the label, these products work well.Castings are very porus and there are many grades of aluminum, some of which are more apt to crackinig. Joint preporation is another factor in a sucessful weld. If your piece is say 1/4 inch thick, you want to make sure your joint is beveled so you get full penetration. On thick stock preheat the area around the joint,or it will suck the brazing temp. out of the joint. Aluminum of course is not like a ferrous metal.It will not turn red , when it gets to hot it just disappears! The big advantage to using a flux with brazing is picking a flux that has a higher melting temp. than the wire. When the flux melts, With Out direct heat from your torch, your ready to add wire. Keeping the puddle molten,without burning thru your piece,can be accomplished by moving the torch in and out of the area.Also you want to have a neutral flame. If you're puddle still looks dirty, try laying the torch over at harder angle to allow the impurities to move ahead of the puddle. Also increasing the oxygen flow slightly will help.On larger castings that are very porous try doing what is called "buttering" the edges. Preheat the piece, then weld both edges trying to get new metal on each side before joining the seam. Never quench alunimum to cool it after a weld, and on a heavy weldment a little post weld heat can go along way. I hope this helps.
 
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Old 01-18-08, 08:24 PM
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One thing I didnt do was bevel the joint, when it started to melt and you brushed the melted aluminum off it made the bevel for you. I have some work on a aluminum boat Id like to try some time with this stuff. I think it could work really good if you do it alot.

One thing I did on this was keep it heated so it doesnt crack. Since its a ring I was worried about that so every few seconds I would run the torch around it.

I brazed up a old cast pan seat off a old piece of farm equipment. The center of it rotted out so I made a new center section and when I brazed it in it kept cracking. While barazing you had to run the torch around it to keep it warm and it finaly didnt crack. You had to hold the torch on the outside and make circles until you got to the center and braze a little then heat up the outside again.

This aluminum rod is neat stuff, Im going to try to braze steel with it.
 
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Old 01-24-08, 08:39 AM
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Welding Aluminum

A bit off topic but I used JB Weld to fix a bearing holder for the camshaft seal on my engine. Been holding for over 100,000 miles.

My high school had a tig welder, I used to be pretty good at welding anything. Aluminium was the toughest. Even with the new fluxes and rods wouldn't attempt it now.
 
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Old 02-07-10, 07:50 AM
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I am late to the thread but I am wondering if there is anything new since the last post in 2008. I want to try the rods that are available locally -

Alumiweld - HF
Bernzomatic - HD/Lowes
Hobart - Tractor Supply


Is any one of these brands of aluminum brazing rod material better than the other ? Do I need to use the stainless steel brush with all of them ?

- Thanks
 

Last edited by rkpatt; 02-07-10 at 09:27 AM.
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Old 02-07-10, 08:12 AM
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Originally Posted by rkpatt View Post
I am late to the thread but I wondering if there is anything new . I want try the rods that are available locally -

Alumiweld - HF
Bernzomatic - HD/Lowes
Hobart - Tractor Supply


Is any one of these brands of aluminum brazing better than the other ? Do I need to use the stainless steel brush witha all of them ?

- Thanks
I used my brazing rod the other day and it seems to have worked good so far. I used it on a cast aluminum door handle on a 1992 chevy truck. I dont remember the brand of mine but its in rods and you have no flux. I put the door handle in a bead blast cabinent to clean the paint off.
 
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Old 04-25-12, 10:57 AM
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Hi Michael, I'm presently in the process of brazing up 2 holes in an old Aluminum Boat that I purchased recently. It had 2 pretty good size holes in it and some leaking around some of the rivets. It has been a real learning process because it definitely is not as easy to do as implied in a lot of the videos on youtube. I used a propane torch to start with but it wouldn't heat the aluminum up enough to make the brazing rod melt, I then tried a MAPP Gas Torch but it produced too much heat and actually caused the hole to get bigger, because it melted the Aluminum. I then swapped the Torch I was using with the MAPP Gas and put it on the Propane tank and voila it produced enough heat on the aluminum so that the brazing rod would melt without causing the Aluminum to melt. I still had problems though so I made a patch from an old Aluminum Copy Machine drum and attached it over the holes with some Galvanized bolts and washers and then brazed it into place. This to me turned out the best and the patch is still thin enough that it's not unsightly. I tightened up most of the leaky rivets by using a Ball Peen Hammer and having an assistant hold a heavy thick metal Auto body tool as a backing while I hammered the rivet. This causes the rivet to spread slightly which tightens it back up. I'm also planning on putting some Road Warrior Bedliner from the Rustoleum Company in the bottom of the boat for added insurance that the boat won't leak around the rivets anytime in the near future. I used 2 different rods Alumaloy and TS2000.
 
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Old 04-25-12, 08:44 PM
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I had some brazing rod that work great but after a while it would just fall off. It seemed like you had to get the aluminum to the perfect temp which was right before it melted off.

I bought a tig welder now but it seems like in certain places like leaky rivets. Brazing rod would be perfect.

I know someone who did the bed liner on a alum boat and it peeled off. Id try washing it with vinegar first. Sure looked good after he did it.
 
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