Off topic metal question

[Great Lakes Greg]

I am going to fabricate an intake manifold out of copper pipe. If I use steel flanges, can I solder the copper to the steel? Thanks for the metallurgist clinic.

[tbirdtbird]

you can solder steel using acid flux. I use a brand called Ruby Red. Tom W has been able to use rosin core flux but I could never make that work on steel.
So, yes, you could tin the steel first with solder, and then solder the copper to the steel.

But, having said that, the nearby exhaust temperatures will surely melt the solder.
If you used a brazed connection, it would withstand the heat. Braze will take to both copper and steel.

When brazing, great care must be used to prevent the project from warping

[SSsssteamer]

Silver solder has a higher melting point and it is stronger than lead solder.

[tbirdtbird]

yep, that would help.
In order for silver solder to bond to steel, he would need special borax flux or a silver content of 45%.
Silver solder bonds easily to copper and brass.

You could use a propane or MAPP torch, but an OA torch with a fine tip can be adjusted to a neutral flame and make the job way easier. Propane and MAPP flames tend to be very oxidizing and make it harder to work the metals

for the non-metal workers in the crowd, silver solder is way closer to brazing than it is lead soldering

[Great Lakes Greg]

You have both been very helpful. Thank you.

[Tom Wesenberg]

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I agree that silver solder or brazing is the way to go, but not common lead solder.

Have you also considered steel pipe and mig or tig welding?

[billy myers]

Tig weld with silicone bronze rod

[Great Lakes Greg]

It has to be copper. I am going for the weathered industrial look on an engine. I'll post a picture when it's done, but it may be a while.

[hardtimes]

Originally Posted by Great Lakes Greg

It has to be copper. I am going for the weathered industrial look on an engine. I'll post a picture when it's done, but it may be a while.

Hey Greg,
You can use copper , brazing the copper with good flux.
Your problem here, as I see it, is that the 3/8 in thick flange is going to have to be heated mightily to make that work. I don't think that you can get enough heat from mapp or propane. Oxy Acet torch with proper tip will be needed , IMO.

[aermotor]

I was under the impression that silver solder had to be a sweat fit to work properly (false?). Perhaps given different materials and thicknesses a thicker plate countersunk on the back and flares on the pipes inserted from the back would work.

John

[Sparky]

I happened to have this photo in my collection. It looks like the copper intakes are attached to a casting at the cylinders using a clamp. Might give you some ideas.

[tbirdtbird]

"I was under the impression that silver solder had to be a sweat fit to work properly (false?)."

This concept applies to lead soldering.
Silver 'soldering' is a bit of a misnomer since it is way closer to brazing, and hardly resembles soldering, and can easily fill small gap imperfections, unlike lead based solder where it will just all run out. As always, heat control is very important. Which is another reason for using O/A with a fine tip.
Having said that, it is always better to keep gaps to a minimum, but sweat fitting is not necessary.

Much higher heats are needed with silver solder, akin to brazing.

If you have never done this before, strongly suggest you set up test pieces of steel and copper and practice, this is a definite skill. Guys in the refrigeration trade silver solder all day long, and are very skilled, which is how i learned. Sometimes they have tight gaps, but sometimes not so much

[Great Lakes Greg]

Thanks for that picture Sparky. That is the "look" I am gunning for. I am using acetylene, and plan on some practice before attempting the real deal.

[Art Newland]

Originally Posted by tbirdtbird

yep, that would help.
In order for silver solder to bond to steel, he would need special borax flux or a silver content of 45%.
Silver solder bonds easily to copper and brass.

You could use a propane or MAPP torch, but an OA torch with a fine tip can be adjusted to a neutral flame and make the job way easier. Propane and MAPP flames tend to be very oxidizing and make it harder to work the metals

for the non-metal workers in the crowd, silver solder is way closer to brazing than it is lead soldering

We used a brand call sil-fos or silvaloy 15% silver and generic borax flux when a copper to steel tubing connection was needed. We used an acetylene "turbo torch" with a dual tip to heat from both sides at once. You need about 1500F. Regular old propane torch won't cut it. We were only dealing with tubing less than .5 inches, YMMV. BTW, the borax makes it very hard to get a "pretty" looking joint.

[tbirdtbird]

There are 2 more options.

1) use 1/4" copper plate for the flange instead of steel. You won't need the pricey 45% silver solder, which wholesale is 100 bucks per coil. Regular sticks of 15% silver solder will be fine.
https://www.mcmaster.com/#copper-plates/=15jenzp

2) if using steel plate, tin the affected area ahead of time with the 45% (if you skip the borax). Once tinned (which is the hard part), joining the copper pipe will be easy.

Art you just gave yourself away as a refer man. Agree about the borax flux

The flux and the sil-fos are available at any refrigeration supply shop such as Johnstone or Baker. These items are usually right on the shelves in the front of the store

[Art Newland]

Originally Posted by tbirdtbird

There are 2 more options.

1) use 1/4" copper plate for the flange instead of steel. You won't need the pricey 45% silver solder, which wholesale is 100 bucks per coil. Regular sticks of 15% silver solder will be fine

2) if using steel plate, tin the affected area ahead of time with the 45%. Once tinned (which is the hard part), joining the copper pipe will be easy

Art you just gave yourself away as a refer man. Agree about the borax flux

Yup, the R-134A has been let out of the (recovery) bag.

I'd go all copper if he wants it to look nice.

[Art Newland]

He could probably walk into an appliance repair outfit and they'd hook him up with the rod and flux if he shows them the cool thing he want's to make... I know I would've.

[mike657894]

I use a chunk of copper buss bar as a backer when welding thin sheet steel. as it never sticks to the welds. what you want may be possible but I think it will cause you problems down the road. maybe make it out of steel and have it coated in copper or bronze.

[Art Newland]

Also, most use way too much flux, clean parts shiny, a lite coating of flux then join the parts and heat just enough to flow the solder... too hot and it will just dribble on the floor.

[Art Newland]

Originally Posted by mike657894

I use a chunk of copper buss bar as a backer when welding thin sheet steel. as it never sticks to the welds. what you want may be possible but I think it will cause you problems down the road. maybe make it out of steel and have it coated in copper or bronze.

That could work, the "nice" compressor companies copper plated the steel tubing nubs to make the process a lot easier... no flux needed.