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Old 02-27-2018, 08:14 AM
dwmh dwmh is offline
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Default Aluminium gas welding and flux removal

First I am no expert but the following seems to work for me and hope it may help others to avoid problems.
The aluminium hardtop I made for my E-type (XKE) showed signs after a few months of residual flux where the sail panels met the roof, this flux was in crevices where the weld was poor. Having put a lot of time into shaping the panels, my mistake was to go too gentle on the welding. This meant not enough heat so the weld bead laid on top of the joint instead of melting into the joint. So when the weld bead was filed down the joint was still showing in places and flux was trapped in there. To rectify the problem I cut the poorly welded section out and made a patch panel to fit. I checked the piece removed under the microscope and could clearly see crystals of flux still in the crevices, this was despite steam cleaning and wire brushing.


DSC02512.JPG

DSC02513.JPG

DSC02516.JPG

DSC02520.JPG

I had previously used a #2 tip on my meco midget torch for welding this 60 thou 1100 aluminium but found it was very slow heating some areas, the temptation is to scrape the rod on to break the oxide film and often it will lay nicely on there, without the joint melting right through, giving poor to no penetration. So for the patch repair I switched to a #3 tip and cranked it up to give a roaring flame. With this the metal quickly melted and the weld progressed easily. The reverse side showing good penetration.
I then cleaned the flux off when the metal had cooled with phosphoric acid, which dissolves the flux easily, followed by steam cleaning and wire brushing. To check it was clean I moved the torch flame over the weld and looked for orange flares, which is a sure sign of flux left behind.


DSC02523.JPG

Below is the patch for the other side fully welded. Lots of distortion, but the soft metal easily reshapes

DSC02536.JPG

I do put a 45 degree chamfer on my patch panels and the mating part to ensure I do get some degree of penetration even in the worse case scenario. It seems to me that you have to get the weld area in enough of a fluid state that any flux will rise to the surface, this fluid state also gives a wide flattish weld bead without crevices or pinholes. I also use Kentís welding lenses which allow a perfect view of what is happening.
I would be interested to hear if there would have been an easier way of rectifying this. Using TIG is not the answer for me in this case.
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Old 02-27-2018, 05:17 PM
Peter Tommasini Peter Tommasini is offline
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Quote:
Originally Posted by dwmh View Post
First I am no expert but the following seems to work for me and hope it may help others to avoid problems.
The aluminium hardtop I made for my E-type (XKE) showed signs after a few months of residual flux where the sail panels met the roof, this flux was in crevices where the weld was poor. Having put a lot of time into shaping the panels, my mistake was to go too gentle on the welding. This meant not enough heat so the weld bead laid on top of the joint instead of melting into the joint. So when the weld bead was filed down the joint was still showing in places and flux was trapped in there. To rectify the problem I cut the poorly welded section out and made a patch panel to fit. I checked the piece removed under the microscope and could clearly see crystals of flux still in the crevices, this was despite steam cleaning and wire brushing.


Attachment 45741

Attachment 45742

Attachment 45743

Attachment 45744

I had previously used a #2 tip on my meco midget torch for welding this 60 thou 1100 aluminium but found it was very slow heating some areas, the temptation is to scrape the rod on to break the oxide film and often it will lay nicely on there, without the joint melting right through, giving poor to no penetration. So for the patch repair I switched to a #3 tip and cranked it up to give a roaring flame. With this the metal quickly melted and the weld progressed easily. The reverse side showing good penetration.
I then cleaned the flux off when the metal had cooled with phosphoric acid, which dissolves the flux easily, followed by steam cleaning and wire brushing. To check it was clean I moved the torch flame over the weld and looked for orange flares, which is a sure sign of flux left behind.


Attachment 45745

Below is the patch for the other side fully welded. Lots of distortion, but the soft metal easily reshapes

Attachment 45746

I do put a 45 degree chamfer on my patch panels and the mating part to ensure I do get some degree of penetration even in the worse case scenario. It seems to me that you have to get the weld area in enough of a fluid state that any flux will rise to the surface, this fluid state also gives a wide flattish weld bead without crevices or pinholes. I also use Kentís welding lenses which allow a perfect view of what is happening.
I would be interested to hear if there would have been an easier way of rectifying this. Using TIG is not the answer for me in this case.

I am not sure if you have done this already ? But make sure NOT!! to strike the hammer and dolly to adjust your tacks while the flux still on the panel or before washing off the flux inside and out with water and soap using a stainless steel wool pad ...then do the same when the weld is finished prior of any beating or filing..........PS do not forget to dry the whole panel from any water residue also I have been using this procedure for Years and NEVER had any flux problem
Peter
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Old 02-28-2018, 01:58 PM
dwmh dwmh is offline
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Thanks Peter I'm glad you chipped in. I do clean off after tacking and before touching with a hammer and dolly or file. I hadn't thought of using soap with any water though. I'll give it a try along with the stainless pad. Also I haven't been washing and drying the whole panel off. So I've stuff to learn.
Many thanks
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Old 03-01-2018, 06:45 AM
cliffrod cliffrod is offline
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Soap and HOT water with the stainless steel scrub/brush- that's what Peter showed us at Will's shop. The hotter, the better to both remove flux and help panel dry more quickly & completely.
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Old 03-01-2018, 07:26 AM
dwmh dwmh is offline
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Thanks 'cliffrod' makes a lot of sense.
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Old 03-02-2018, 07:55 AM
Jim Tomczyk Jim Tomczyk is offline
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Quote:
Originally Posted by Peter Tommasini View Post
I am not sure if you have done this already ? But make sure NOT!! to strike the hammer and dolly to adjust your tacks while the flux still on the panel or before washing off the flux inside and out with water and soap using a stainless steel wool pad ...then do the same when the weld is finished prior of any beating or filing..........PS do not forget to dry the whole panel from any water residue also I have been using this procedure for Years and NEVER had any flux problem
Peter
So is the best method to only initially flux where you tack? In case you need to adjust with hammer & dolly
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