Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old May 9th 04, 11:39 PM
Racer X
 
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Default Soldering aluminum tubing to steel sheet metal

I've got a tank made of mild steel sheet metal, and I want to
permanently attach some aluminum tubing to the bottom surface of the
tank. The tubing is for some hot fluid (200F-250F) that will be used
to heat the contents of the tank. The aluminum tubing is only 3/8"
diameter, with a wall thickness of about 0.060" (maybe 1/16"). I
estimate that the sheet steel that I'm attaching it to is about 16
guage, maybe 18 guage (0.050" to 0.060").

What's the best way to do this and the best tools to use for the job
for a DIY type person like myself. I'm not a professional, but I do
have some experience welding and soldering. I have both an
oxy-acetylene torch setup and a cheap Propane torch that mounts on a
small hand held propane cylinder.

I've done a bit of reading and research, and I think I should probably
use some Cadmium/Zinc solder, probably 30% or 40% Zinc. I'm not sure
exactly what flux to use on the steel, or on the aluminum.

I'm kind of guessing that the propane torch would be a better choice
for this job because I'll need more general heating of the materials
and indirect heat. I've got some extra material of both types to
practice on as well, so I won't start out ruining my main project.

I'm just asking for advice or confirmation that I'm on the right track
here. Also, would a normal welding supply place have the appropriate
solder? What kinds of flux would I need for this? I plan on calling
them tomorrow and asking, so I guess I'll find out.

One resource I checked said not to use flux on the aluminum, but to
apply the solder with steel wool to scrape away the surface oxidation
on the aluminum. The procedure described was to heat the aluminum with
the torch, drop a few drops of melted solder on the aluminum, then use
steel wool to work the surface of the aluminum while continuing to
apply heat to maintain the temperature slightly above the melting
point of the solder. As the oxides are scraped clean, the solder will
wet and tin the aluminum. I'm probably going to be soldering down 12
to 18 feet of this tubing, so that sounds like a lot of work with the
steel wool. Would there be a better method using some kind of
chemical treatment or flux to remove the surface oxides from the
aluminum?

I plan to tin both surfaces to be joined with the solder, then sweat
them together and apply additional solder to fill any gaps and build
up a little under the tubing. I want as much heat transfer as possible
from the aluminum to the tank in the finished product. I'm assuming
that I'll need 30% to 40% zinc in order to have some decent paste
range to work the extra solder into the gaps and build up around the
bottom half of the tubing.

Also, this surface will be exposed to weather (after painting), so
corrosion resitance is fairly important, as well as strength.

So, am I on the right track? Or am I about to make a huge mistake?

  #2   Report Post  
Old May 10th 04, 03:58 AM
John
 
Posts: n/a
Default Soldering aluminum tubing to steel sheet metal

Racer X wrote:
I've got a tank made of mild steel sheet metal, and I want to
permanently attach some aluminum tubing to the bottom surface of the
tank. The tubing is for some hot fluid (200F-250F)
I've done a bit of reading and research, and I think I should probably
use some Cadmium/Zinc solder, probably 30% or 40% Zinc. I'm not sure
exactly what flux to use on the steel, or on the aluminum.


Could you use copper tubing? In that case you can
use regular lead/tin solder. Cadmium fumes are
unhealthy to say the least, they can kill you. HTH
--
SATOR AREPO TENET OPERA ROTAS
Have 5 nice days! John
******************************
--- ILN 000.000.001 ---

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Old May 10th 04, 04:15 AM
jim rozen
 
Posts: n/a
Default Soldering aluminum tubing to steel sheet metal

In article , Racer X says...

So, am I on the right track? Or am I about to make a huge mistake?


This sounds like a great deal of work and you may be unhappy
with the results. I would substitute copper or mild steel
tubing instead for the heater coil, and solder with regular
soft solder.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

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Old May 10th 04, 05:08 AM
PJ
 
Posts: n/a
Default Soldering aluminum tubing to steel sheet metal

Racer X typed:
I've got a tank made of mild steel sheet metal, and I want to
permanently attach some aluminum tubing to the bottom surface of the
tank. The tubing is for some hot fluid (200F-250F) that will be used
to heat the contents of the tank. The aluminum tubing is only 3/8"
diameter, with a wall thickness of about 0.060" (maybe 1/16"). I
estimate that the sheet steel that I'm attaching it to is about 16
guage, maybe 18 guage (0.050" to 0.060").

What's the best way to do this and the best tools to use for the job
for a DIY type person like myself. I'm not a professional, but I do
have some experience welding and soldering. I have both an
oxy-acetylene torch setup and a cheap Propane torch that mounts on a
small hand held propane cylinder.

I've done a bit of reading and research, and I think I should
probably use some Cadmium/Zinc solder, probably 30% or 40% Zinc.
I'm not sure exactly what flux to use on the steel, or on the
aluminum.

I'm kind of guessing that the propane torch would be a better choice
for this job because I'll need more general heating of the materials
and indirect heat. I've got some extra material of both types to
practice on as well, so I won't start out ruining my main project.

I'm just asking for advice or confirmation that I'm on the right
track here. Also, would a normal welding supply place have the
appropriate solder? What kinds of flux would I need for this? I
plan on calling them tomorrow and asking, so I guess I'll find out.

One resource I checked said not to use flux on the aluminum, but to
apply the solder with steel wool to scrape away the surface
oxidation on the aluminum. The procedure described was to heat the
aluminum with the torch, drop a few drops of melted solder on the
aluminum, then use steel wool to work the surface of the aluminum
while continuing to apply heat to maintain the temperature slightly
above the melting point of the solder. As the oxides are scraped
clean, the solder will wet and tin the aluminum. I'm probably going
to be soldering down 12 to 18 feet of this tubing, so that sounds
like a lot of work with the steel wool. Would there be a better
method using some kind of chemical treatment or flux to remove the
surface oxides from the aluminum?

I plan to tin both surfaces to be joined with the solder, then sweat
them together and apply additional solder to fill any gaps and build
up a little under the tubing. I want as much heat transfer as
possible from the aluminum to the tank in the finished product. I'm
assuming that I'll need 30% to 40% zinc in order to have some
decent paste range to work the extra solder into the gaps and build
up around the bottom half of the tubing.

Also, this surface will be exposed to weather (after painting), so
corrosion resitance is fairly important, as well as strength.

So, am I on the right track? Or am I about to make a huge mistake?


The task you are trying to accomplish is very possible. You are
dependent on your choice of solder and flux's. I would recommend the
Harris brand. Harris Stay-Brite 8 silver solder would be my choice for
the solder. It will bond both metals.
http://www.jwharris.com/jwprod/solderalloys/#SBSolder

My choice for the flux on the steel would be Harris Stay-Clean flux.
It is available in liquid and paste forms.
http://www.jwharris.com/jwprod/braze...uxes/#soldflux

Additionally, Harris makes an aluminum flux for soldering using the
same silver solder mentioned above, Stay-Clean Aluminum. It is also on
the flux page I posted above.

The solder has very high strength and is food safe. The web sites I
posted tells it all.

I would "tin" the pieces with solder - using the appropriate flux -
and then join them together as a unit by adding additional solder. A
propane or Mapp torch should be more than adequate. I have tremendous
success with this solder and flux combination. I do a bit of work in
stainless steel, copper, brass and aluminum. Most heating/air
suppliers that I'm familiar with carry this brand.

I hope this helps.
PJ


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Old May 10th 04, 02:50 PM
Racer X
 
Posts: n/a
Default Soldering aluminum tubing to steel sheet metal

"PJ" wrote in message ...

The task you are trying to accomplish is very possible. You are
dependent on your choice of solder and flux's. I would recommend the
Harris brand. Harris Stay-Brite 8 silver solder would be my choice for
the solder. It will bond both metals.
http://www.jwharris.com/jwprod/solderalloys/#SBSolder

My choice for the flux on the steel would be Harris Stay-Clean flux.
It is available in liquid and paste forms.
http://www.jwharris.com/jwprod/braze...uxes/#soldflux

Additionally, Harris makes an aluminum flux for soldering using the
same silver solder mentioned above, Stay-Clean Aluminum. It is also on
the flux page I posted above.

The solder has very high strength and is food safe. The web sites I
posted tells it all.

I would "tin" the pieces with solder - using the appropriate flux -
and then join them together as a unit by adding additional solder. A
propane or Mapp torch should be more than adequate. I have tremendous
success with this solder and flux combination. I do a bit of work in
stainless steel, copper, brass and aluminum. Most heating/air
suppliers that I'm familiar with carry this brand.

I hope this helps.
PJ


Thanks for the informative reply. I'll check into the Harris products.

Have you ever used the Harris Alsolder 500? It was on the same page
with that silver solder. Would that be a better choice for me
considering I'm working with aluminum?


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Old May 10th 04, 04:09 PM
PJ
 
Posts: n/a
Default Soldering aluminum tubing to steel sheet metal

Racer X typed:
"PJ" wrote
The task you are trying to accomplish is very possible. You are
dependent on your choice of solder and flux's. I would
recommend the Harris brand. Harris Stay-Brite 8 silver solder
would be my choice for the solder. It will bond both metals.
http://www.jwharris.com/jwprod/solderalloys/#SBSolder

My choice for the flux on the steel would be Harris Stay-Clean
flux. It is available in liquid and paste forms.
http://www.jwharris.com/jwprod/braze...uxes/#soldflux

Additionally, Harris makes an aluminum flux for soldering
using the same silver solder mentioned above, Stay-Clean
Aluminum. It is also on the flux page I posted above.

The solder has very high strength and is food safe. The web sites
I posted tells it all.

I would "tin" the pieces with solder - using the appropriate flux -
and then join them together as a unit by adding additional solder.
A propane or Mapp torch should be more than adequate. I have
tremendous success with this solder and flux combination. I do a
bit of work in stainless steel, copper, brass and aluminum. Most
heating/air suppliers that I'm familiar with carry this brand.

I hope this helps.
PJ


Thanks for the informative reply. I'll check into the Harris
products.

Have you ever used the Harris Alsolder 500? It was on the same
page with that silver solder. Would that be a better choice for me
considering I'm working with aluminum?


Alsolder is a possible choice for you, although, the Alsolder 500
does not produce joints as strong as the Stay-Brite 8 solder. I'm
also not too thrilled with the zinc content. My preference is the
Stay-Brite. It bonds very well with aluminum and has excellent
strength. It also has a liquidus temperature range that allows it to
be used as a filler metal.

Just my 2 cents. (BTW - I'm not affiliated with Harris. I just use
the products.)

PJ


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Old May 13th 04, 02:01 AM
Doug Goncz
 
Posts: n/a
Default Soldering aluminum tubing to steel sheet metal

I like the Stay Brite and a more active flux.

I'd lay lengths of Stay Bright aside the joint, adhered with a fillet of flux,
and heat the whole job in the oven.

Preferably, you can block up the metal and support it flat, weight the tubing
into contact with fire bricks, and just heat soak it at the reccommended
liquidus using an oven thermometer to go maybe 15 degrees over so it won't take
forever. You can shield the work from the infrared of an electric oven to
prevent overheating.

The more active flux must be hand brushed with hot water until spotless, or it
will corrode.

You can pull the lengths of solder to straighten them, then snip and handle
carefully. You can also tack the ends of each to the tank before putting it all
into the oven.

I have and recommend The Aluminum Association's Aluminum Soldering Handbook.


Yours,

Doug Goncz ( ftp://users.aol.com/DGoncz/ )

Read about my physics project at NVCC:
http://groups.google.com/groups?q=dgoncz&scoring=d plus
"bicycle", "fluorescent", "inverter", "flywheel", "ultracapacitor", etc.
in the search box
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Old May 14th 04, 08:11 PM
Dan Caster
 
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Default Soldering aluminum tubing to steel sheet metal

I agree with Jim. It would probably cost less to buy copper or steel
( see your friendly scrap yard or auto supply ) tubing than to buy the
solder and flux for aluminum. Soldering aluminum with ordinary solder
is possible, but a PITA for anything but small items.

If you do try this, you might try scrubbing the oxide off the aluminum
with steel wool or sandpaper under a film of oil. And leaving the oil
in place while you solder. Cleaning under molten solder work well for
small items.

Dan


jim rozen wrote in message

So, am I on the right track? Or am I about to make a huge mistake?


This sounds like a great deal of work and you may be unhappy
with the results. I would substitute copper or mild steel
tubing instead for the heater coil, and solder with regular
soft solder.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

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