Brazing 11 gauge steel

If it were me I would buy some silver solder and flux from a jewelry supply company or a welder's supply company. It will be strongest. There are silver solders which are mostly silver and "silver bearing" solders which are not mostly silver. Stay away from the silver bearing solders, they are not strong enough. You won't need much solder. You will need to read about and practice silver soldering. Check out the book "The Complete Metalsmith" from the library. There is a section in the book about silver soldering. Short and to the point. Remember, you will holding your work in your hand. You don't want it to come apart. Eric

Thanks, good advice.
My library has one copy of the book. I placed a hold on it, might get it next week.
I don't want to spend more money on the solder than I do on the other materials, but I do like the idea of using a propane torch instead of O/A.

With one of these.
Was any of the brazing rod on the Home Depot site high enough in silver content? The local welding shop doesn't have a website, maybe I can look there tomorrow.

(snip) bernzomatic+torch
I use a modified BernzOmatic Oxy-propane torch. Only I cut off their O2 regulator for their crappy O2 bottles and used a real regulator with an R sized bottle.
I'm finally breaking down and buying a Smith jewelers torch for my jewelry work.
I don't think Home Despot carries anything with enough silver for you.
Try here:
You should be able to google the melting points of the easy to hard solders.

That torch may work. I don't have any direct experience with it and so can't say.The silver solder at Home Depot probably is low silver content. Since you don't need much solder it won't be too expensive. When you get ready to solder remember, and this is important, that you need to get the work hot fast. Don't pussyfoot around. The flux can only absorb so much oxygen and the longer it takes to heat the part the more oxygen the flux will absorb. When it quits absorbing oxygen the metal starts oxidizing and the solder will not flow. Once this happens your only choice is to let the work cool, clean it back to bright metal, and start over. I like to use firebrick or ceramic blanket to make a little "oven" around the work. This allows the work to be heated much faster. Using regular old brick is dangerous, it may explode when heated. Fire brick is cheap. Get it at a pottery supply or similar. Get the light stuff. Get the cheapest stuff. It cuts easily with a hack saw. Use an old dull blade if you have one. But read that book. You will understand what is going on and have much better chance for success. I learned how to silver solder when I was 14 and I was making precious metal jewelry good enough to sell. So it doesn't take a genius or lots of skill, just follow directions and pay attention. As to strength, Harris Safety Silv 56 is a solder that's usually available at a welders supply and it has a tensile strength of at least 70 ksi. Mild steel is 60 ksi. So it is stronger than mild steel. Other silver solders have even higher strengths. You will probably be better off with the lowest melting temp solder that is at least 70 ksi tensile strength. This is because it is easier to get it hot enough fast enough. And do practice a couple times. A little solder goes a long way because the gap it has to fill is so small. Eric

Thanks for the link. It makes sense to buy by the foot, couldn't see how much shipping runs.

Thanks again. SS 56 lists at 1,200 deg.
I'll practice on similar metals before I waste a $15 part.
I guess I should buy the flux coated, try with propane, and pick up the tanks for O/A just in case.

It must be amazing stuff all right. Harris states that Safety-Silv is comprised of 56% Silver, 22% copper, 17% Zinc and 5% Tin. Where did that 70 Ksi come from?

It depends on what you are going. If you simply butt two pieces end to end then the approach would be much like torch welding and flux coated or not hardly matters. If there is overlap and you want the silver to penetrate then you probably should use a different approach.
For this technique the flux is mixed with water to make a paste and the parts are painted with flux and then assembled. A spacing of approximately 0.001 - 0.002 is usual for carbon steel. the assembled parts are heated and as they become hotter you will see the flux liquefy - you are nearly there. You want the part to be hot enough to melt the silver. Don't melt it in the torch flame and glob it on, just keep heating and quickly touch the rod to the work from time to time. Eventually you will reach the desired heat and the silver will melt and capillary attraction will suck it into the joint. If you have heated the parts uniformly and evenly you will find that silver applied to one edge will flow completely across a one - two inch joint.
The main problem is heating things evenly. You will need to keep the torch moving and linger a little on the thicker parts to let them heat a bit more than the thinner sections. If you have ever made "sweated" tubing connections then you probably already know the technique.
By the way, assuming sufficient space for the silver to penetrate between the two sides the thinner the gap the stronger the joint.

Look at the strength of 70% copper - 30% zinc brass:
and bronze:

I should have said that generic 56% silver solders have a yield of over 60 ksi and ultimate yield of 70 ksi. I used the Harris name because it is available widely. And it's true, silver solders, AKA silver brazing alloys, are amazingly strong when used properly. Eric

I already own the propane torch and I'll try it first. Went to Home Depot this morning and was disappointed they only had Lincoln Electric KH515 brazing rod which has no silver at all.
I assume that the Lincoln Electric Stay-Silv 56 is the same as Harris Safety-Silv 56, but they don't stock it at my local store. I can't get to the welding shop today. 70,000 PSI sounds plenty strong.
The Depot did have a MAP gas rig for only $42. It is supposed to get significantly hotter than propane, and I would be willing to purchase one for this project - could probably find uses for it in the future.

I already own the propane torch and I'll try it first. Went to Home Depot this morning and was disappointed they only had Lincoln Electric KH515 brazing rod which has no silver at all.
I assume that the Lincoln Electric Stay-Silv 56 is the same as Harris Safety-Silv 56, but they don't stock it at my local store. I can't get to the welding shop today. 70,000 PSI sounds plenty strong.
The Depot did have a MAP gas rig for only $42. It is supposed to get significantly hotter than propane, and I would be willing to purchase one for this project - could probably find uses for it in the future.

I already own the propane torch and I'll try it first. Went to Home Depot this morning and was disappointed they only had Lincoln Electric KH515 brazing rod which has no silver at all.
I assume that the Lincoln Electric Stay-Silv 56 is the same as Harris Safety-Silv 56, but they don't stock it at my local store. I can't get to the welding shop today. 70,000 PSI sounds plenty strong.
The Depot did have a MAP gas rig for only $42. It is supposed to get significantly hotter than propane, and I would be willing to purchase one for this project - could probably find uses for it in the future.

I already own the propane torch and I'll try it first. Went to Home Depot this morning and was disappointed they only had Lincoln Electric KH515 brazing rod which has no silver at all.
I assume that the Lincoln Electric Stay-Silv 56 is the same as Harris Safety-Silv 56, but they don't stock it at my local store. I can't get to the welding shop today. 70,000 PSI sounds plenty strong.
The Depot did have a MAP gas rig for only $42. It is supposed to get significantly hotter than propane, and I would be willing to purchase one for this project - could probably find uses for it in the future.

"Stumpy" wrote > DAMN SERVER.

propane is hot enough, but on larger items can not supply heat fast enough. Erik has some good suggestions about using insulating fire brick to contain the heat. I have used more than one small propane torch to heat things faster.
Dan

Silver has an ultimate strength of 24,656 psi Copper 30,457 Tin 29,007 Zinc (wrought) 29,007

I think that you are getting the ultimate strength of the silver solder mixed up with the strength of the joint that can be made with it, which is far, far, greater then the strength of the silver solder alone.

If by "propane" you mean a torch that connects to a cooking gas bottle it will melt the solder but they need a bloody great flame to do it. If it is MAPP gas, I think it is sold as Benzomatic in America, then it will likely do everything you want to do with it. They don't sell it over here but I acquired a couple of bottles and the torch from somewhere and built two bicycle frames with it.... just ran out last week, now I'll have to buy an oxy-cooking gas rig :-(
I wouldn't assume, check the specs. I once bought some "silver solder" - got a fabulous buy on it too - only to discover that it is intended for copper tubing and didn't work reliably on steel.
As I said above I used MAPP gas to build two bicycle frames.