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  #21  
Old 06-25-2017, 03:01 AM
elavir elavir is offline
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Originally Posted by crystallographic View Post
Leaks happen in clean-room environments, with excellent back purge, and cameras inside the tanks, as I learned from the guys who build Kenworth and Peterbilt tanks. Perfect appearing TIG welds, inside and out - leak - because of weld density issues. Welds are sliced open along their lengths, and voila! - porosity inside the weld, invisible from outside.

It's a problem that the most expensive tig machines are only just now starting to overcome.
Thanks for the explanation Kent, just now I am making a tank and tried to weld with and without flux . In both cases the penetration was good but as you described this can be misleading. I am going to flux the remaining welds just to be sure.

Cheers Richard.
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  #22  
Old 06-25-2017, 03:17 AM
elavir elavir is offline
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Originally Posted by Rick Mullin View Post

Seldom do I have porosity when welding with 1100 wire on 1100 or 3003 sheet metal. 1100 was not the correct wire for the alloy of the tanks I have built so I was using the harder wire as Kent has mentioned (4043 or 5356).

Rick
Hi Rick, I am using 1050 aluminum for the tank and for the correct "color match" I am using strips from the same sheet as the tank. In combination with back fluxing I guess It would be OK. I can't find it but I thought to remember that welding with 4043 could crack sometimes.

Cheers Richard.
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  #23  
Old 06-25-2017, 08:36 AM
crystallographic crystallographic is offline
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Originally Posted by elavir View Post
Hi Rick, I am using 1050 aluminum for the tank and for the correct "color match" I am using strips from the same sheet as the tank. In combination with back fluxing I guess It would be OK. I can't find it but I thought to remember that welding with 4043 could crack sometimes.

Cheers Richard.
Richard,
4043 is a Silicon-bearing rod that has a low solidus (low re-solidifying temperature). 4043 was designed for welding castings. It is a hard, brittle filler that cracks when it is hammered / wheeled.
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  #24  
Old 06-25-2017, 08:37 AM
crystallographic crystallographic is offline
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Thanks for the explanation Kent, just now I am making a tank and tried to weld with and without flux . In both cases the penetration was good but as you described this can be misleading. I am going to flux the remaining welds just to be sure.

Cheers Richard.
Thanks Richard. Good luck and please post your results with the back-up flux.
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  #25  
Old 06-26-2017, 07:40 AM
Rick Mullin Rick Mullin is offline
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The fittings that I machine are 6061 so that is where I am using the 4043. Most tank are made from 5052 so I am using 5356 wire. Generally no hammering or crushing of the welds. On a few tanks that I made for D types, I used 3003 (butt welded) which did require some planishing and the wire I used was 1100 with great success. The bulk of the alloy tanks that I am making require edge welding of a flanged seam thus no planishing required. I am anxious to try fluxing. Kent- What do you suggest to thoroughly clean the flux form the inside of the tank (particularly the edge flange joints)? Flux is always my worry. I have seen far too many coachbuilt cars with flux corrosion that leaves me a bit nervous.
Rick
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  #26  
Old 06-26-2017, 03:07 PM
elavir elavir is offline
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Originally Posted by crystallographic View Post
Thanks Richard. Good luck and please post your results with the back-up flux.
Hi Kent, I'm not sure if I can make pictures of the remaining welds because they are inside the the last sheet to close the tank. Maybe through the filler neck.
The pictures below are the ones I made with and without the flux( bottom weld is with and top weld without flux)
IMG_20170626_084007.jpg
IMG_20170626_084023.jpg
I had difficulties to see the puddle that was fluxed because of the orange flair but then again it was probably too thick.

Cheers Richard
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  #27  
Old 06-27-2017, 12:12 AM
crystallographic crystallographic is offline
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Originally Posted by elavir View Post
Hi Kent, I'm not sure if I can make pictures of the remaining welds because they are inside the the last sheet to close the tank. Maybe through the filler neck.
The pictures below are the ones I made with and without the flux( bottom weld is with and top weld without flux)
Attachment 42229
Attachment 42230
I had difficulties to see the puddle that was fluxed because of the orange flair but then again it was probably too thick.

Cheers Richard
Richard,
It looks to me as though the flux is helping your welds. Sorry about the flare - it is a problem for electric welding that I have been working on.
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  #28  
Old 06-27-2017, 12:25 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Rick Mullin View Post
The fittings that I machine are 6061 so that is where I am using the 4043. Most tank are made from 5052 so I am using 5356 wire. Generally no hammering or crushing of the welds. On a few tanks that I made for D types, I used 3003 (butt welded) which did require some planishing and the wire I used was 1100 with great success. The bulk of the alloy tanks that I am making require edge welding of a flanged seam thus no planishing required. I am anxious to try fluxing. Kent- What do you suggest to thoroughly clean the flux form the inside of the tank (particularly the edge flange joints)? Flux is always my worry. I have seen far too many coachbuilt cars with flux corrosion that leaves me a bit nervous.
Rick
Hi Rick,
Flux has been an issue with welded aluminum cars since 1910, to a greater or lesser degree. Less flux into a weld means less flux to clean up.
I have seen pre-war Alfa bodies with only slight residues left where they could not be cleaned on the back side - and only slight corrosion left, after 50 years. But, on the other hand .... I have seen serious backside corrosion from excessive flux ...... Maybe better to use a little less of the good flux rather than a lot of the avgerage flux?

So, I flux only the rod when welding clean and fresh stock.
And I rinse first with hot water, and then I rinse with 25% phosphoric - whatever available brand, MFR, Ospho, Dairyland rinse, etc.
I don't try to rinse the phos. completely clean because it adds protection against corrosion.

For joining 6061 to 5052 the 5356 is recommended by the AWS filler charts. 4043 is a second choice, or third.

Many thousands of aviation fuel tanks were gas welded from 1920 onwards. Rinsing with hot water was S.O.P. in the factories.
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