Silver brazing / soldering?

[Michael J Evans]

Anyone have experience with silver brazing / soldering?

This is actually something for work, but I've been thinking about trying to learn silver brazing / soldering to expand our capabilities and offering. Mainly this would be used on high pressure hydraulic steel & stainless steel tubing, with carbon & stainless fittings. I've watched various YouTube "sales" videos on braze products, but it almost seems to good to be true in how easy it is to do. Can anyone confirm how easy it is to braze dissimilar material thicknesses & create strong leak free seals? Also what tools are truly needed besides a torch & the braze rod / flux?

Thanks

[Bill Dufour]

How about TIG?
Bill D

[Stan Coryell]

Silver Brazing and solder are very different.

Silver Brazing is reasonably easy. Clean, Flux, heat, and apply filler.

Harris has good information and good products. The AWS publishes a Brazing Handbook. Dissimilar metals usually use 45 Silver and white paste Flux. Don't let the flame touch the Flux, it will burn. Production fittings are done in a vacuum furnace.

I'm not sure why you would braze hydraulic lines vs using mechanical fittings. Careful joint design would be required. You would also need a welding procedure to ensure repeatability. I think it would be more cost-effective to use Swagelock or Parker type fittings.

What's your idea of high pressure? 10k psi? What are you testing to? 2x?

Manually tig welding tubing is tricky. Any underfill (under cut) creates stress risers and leads to failure, especially in hydraulic service, where pressure (loading) constantly cycles.

If you provide more information and specifics, like base metal groups, pressure (design and test), temperature, and joint design, I may be more helpful.

[Michael J Evans]

How about TIG?
Bill D

Our other store is currently setup to tig. We're trying to replicate that without the expense of all the equipment, not to mention having a welder.

[Michael J Evans]

Silver Brazing and solder are very different.

Silver Brazing is reasonably easy. Clean, Flux, heat, and apply filler.

Harris has good information and good products. The AWS publishes a Brazing Handbook. Dissimilar metals usually use 45 Silver and white paste Flux. Don't let the flame touch the Flux, it will burn. Production fittings are done in a vacuum furnace.

I'm not sure why you would braze hydraulic lines vs using mechanical fittings. Careful joint design would be required. You would also need a welding procedure to ensure repeatability. I think it would be more cost-effective to use Swagelock or Parker type fittings.

What's your idea of high pressure? 10k psi? What are you testing to? 2x?

Manually tig welding tubing is tricky. Any underfill (under cut) creates stress risers and leads to failure, especially in hydraulic service, where pressure (loading) constantly cycles.

If you provide more information and specifics, like base metal groups, pressure (design and test), temperature, and joint design, I may be more helpful.

Hi Stan
I have read some of Harris info. I think we would use their stay silv 56 for what I am hoping to accomplish. I spoke about tube assemblies above, but my main reason is to be able to reuse customers old hose ends. We deal in all kinds of custom assemblies but our main gig is aftermarket hose replacement on heavy equipment / automotive. Oems like to make their own special bend configurations, drop lengths, etc. I am hoping to be able to cut off customers old ends and reuse them either on a new hose stem via socket brazing or onto a jic adapter also via socket brazing. This provides a service to my customer base as 1) then they don't have to go to the OEM= another trip 2) most heavy equipment dealers don't have these specialty hoses / ends in stock and have to order from the factory, causing the customer further delay.

As far as tube assemblies go. It would mainly be j514 carbon steel (going by memory on the code)

Temperature can vary but max would be 212f in most applications. Pressures generally speaking are going to be under 6k psi.

[Stan Coryell]

The main difference between 45 and 56 is joint tolerances. 56 is for tighter joints, 45 is "thicker" in it's liquidous state, therefore more tolerant to poor fit up. 45 maybe the better choice because I believe it is more ductile, important in medium pressure and high vibration environments. 56 melts at a lower temperature, not much, and is a close color match to stainless steel.

J514 is the SAE spec for the fittings not the base metal

Stainless won't be a problem. Coated steel maybe. At 1200 degrees zinc could be diffused into the steel. This may lead to porosity or enbrittlement (hard spots). Porosity may cause pinholes and enbrittlement may lead to cracking. Any coating shall be removed mechanically, grinding or sandblasting.

I would do a couple samples and test to 10k psi.

I'd be happy to help with any other questions. I'm also curious of the outcome.

[Ronald Blue]

How high of pressure and how large are the lines? I work with hydraulics almost daily. Brazing has never been an acceptable repair method. Whatever material you use for the filler. The larger than line the greater the stresses. Gas welding with steel is acceptable but very challenging on tubing. Modern hydraulics typically run around 2500 PSI. Depending on the application it can be significantly higher. Power packs like for the jaws of life can be 10,000 PSI.

[Michael J Evans]

The main difference between 45 and 56 is joint tolerances. 56 is for tighter joints, 45 is "thicker" in it's liquidous state, therefore more tolerant to poor fit up. 45 maybe the better choice because I believe it is more ductile, important in medium pressure and high vibration environments. 56 melts at a lower temperature, not much, and is a close color match to stainless steel.

J514 is the SAE spec for the fittings not the base metal

Stainless won't be a problem. Coated steel maybe. At 1200 degrees zinc could be diffused into the steel. This may lead to porosity or enbrittlement (hard spots). Porosity may cause pinholes and enbrittlement may lead to cracking. Any coating shall be removed mechanically, grinding or sandblasting.

I would do a couple samples and test to 10k psi.

I'd be happy to help with any other questions. I'm also curious of the outcome.

Thanks stan I will review the info on the 45. We are obviously going to need to do some testing to see if this will work and how reliable the method is.
Another tool we would likely need is some kind of parts washer. From what I've read brazing seems very intolerant of and residues.

[Michael J Evans]

How high of pressure and how large are the lines? I work with hydraulics almost daily. Brazing has never been an acceptable repair method. Whatever material you use for the filler. The larger than line the greater the stresses. Gas welding with steel is acceptable but very challenging on tubing. Modern hydraulics typically run around 2500 PSI. Depending on the application it can be significantly higher. Power packs like for the jaws of life can be 10,000 PSI.

Hi Ron

It depends but yes 3000psi is a general hydraulic pressure, but we do assemblies up to 6k and most of our customers have machines running 4 and 5K. Mostly 1" and less.

I'm not trying to do this to repair hardlines. This would be for reusing customers hose ends if the situation arose.

It would also be for making new tube assemblies.

[Stan Coryell]

Ron,

"The larger than line the greater the stresses."
This is incorrect. Pressure is measured in square inches. Larger pipe has more surface area, so less stress.

[Ronald Blue]

Ron,

"The larger than line the greater the stresses."
This is incorrect. Pressure is measured in square inches. Larger pipe has more surface area, so less stress.

That is not incorrect. The greater the diameter the less pressure a tube of the same wall fitness can withstand. Hydraulic hose for example. The larger the hose the lower the burst pressure. So 1" hose has to be upgraded to 4 wire to withstand the pressure pulses that a 1/2" 2 wire hose can handle easily. I'm attaching a chart that clarifies tubing working and burst pressures. We recently had a hydraulic pump compensator failure which caused the pump to not destroke when the preset pressure was reached. So the pressure kept building on the circuit. Multiple hydraulic cylinders in this circuit ranging from 2-6 inch bores. Guess what blew. The 6" cylinders swelled like a balloon and split. Fortunately no one was near them when they blew. They were the weak link.


https://eagletube.com/wp-content/uploads/2015/07/Theoretical-Bursting-Bulging-pressures.pdf

[Michael J Evans]

Ron is correct.
The smaller the line the more pressure it can hold.
The "per square inch" is spread out over a much larger area in a smaller line.

[Stan Coryell]

Ron,

We are talking about two different things.

Your are correct that small pipe can withstand higher pressure than large pipe (Barlow's Law). This is hoop stress and is irrelevant in lap joint design. Hoop stress is porpotioninate to wall thickness, doubling wall thickness will double allowable pressure. A lap joint doubles wall thickness.

Michael, in my understanding, you plan to use a manufactured "socket" (swedge). This swedge doubles the wall thickness and gives us a brazed lap joint. The braze joint is a combination of shear and tensile strength.

Weld strength is calculated by faiulure over a surface area. System pressure is a constant. As pipe size increases so does surface area. Increasing surface area effectively reduces stress on a joint (Pascal's Law) and increases joint strength.

Even though Michael is repairing a hydraulic assembly, the braze joint is not a repair. It's a production joint, as in producing a new assembly. As long as the production joint is properly designed, preformed, and tested I don't see any reason this isn't acceptable. In my experience, failure would be at the minor diameter of the swedge.

I apologize for not elaborating more in my previous post.

Ron, do you have any experience with Delem controls?

[Michael J Evans]

Stan
The fitting would be socket weld / braze style like this - https://brennaninc.com/fittings/tube-fittings-and-adapters/0403/

(Hopefully the link is okay)

[Ronald Blue]

Stan I've not had any experience with Delem controls. They look sophisticated but also more likely to be used in an indoor environment. Our equipment is mobile on track for the most part. We use primarily Vickers, and Rexroth controls but there may be another brand but not I am drawing a blank now. While we have some somewhat precision control in track surface (cross level and elevation) and smoothness (no roller coaster track) it's still loose tolerances compared to manufacturing. If it's less than 1/16" for cross level that's good. The valves we use to control this are Moog servo valves like used on air craft. I'm far from an expert on hydraulics but I have good general knowledge.

[Ronald Blue]

Michael, what type ends are you speaking of that isn't stocked by the OEM? There are all the standard stuff. ORS, ORB, Split Flange with J61 and J62 bases, JIC, and the dreaded and hated pipe thread/inverted pipe fittings. There are also some European or British ones but I don't know the correct terminology for them but they are different from everything else and sometimes hard to find.

[Stan Coryell]

Michael,

Those fittings look fine. There are ways to vacuum braze in production levels. I don't have any experience with this.