silver soldering steel to steel

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NP317
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Re: silver soldering steel to steel

Post by NP317 »

Caution on using the drill rod.
The heat of silver brazing will result in the rod becoming dead hard after cooling.
The rod/pins can easily break if stressed. That happened to be on a project.
If you plan on tempering the rods after the brazing operation, the required heat is likely to melt the silver solder!
I suggest a different steel for the pins.

Maybe there's a specific drill rod alloy that will work for you. I'm not educated about the alloy specifics.
~RN
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Builder01
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Re: silver soldering steel to steel

Post by Builder01 »

I thought tool steel becomes dead hard only after quenching?
David
John Hasler
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Re: silver soldering steel to steel

Post by John Hasler »

There are air-hardening alloys, though most are water or oil hardening. Silver brazing shouldn't get the steel hot enough to harden, though.
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Harold_V
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Re: silver soldering steel to steel

Post by Harold_V »

Just don't quench, and don't use an air hardening drill rod. Even if you happened to hit a critical temperature, it won't get hard enough to be a problem if you allow it to cool slowly. Also, ensure that the entire piece is heated, so the unheated portion can't draw heat from the heated portion too quickly.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
RET
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Re: silver soldering steel to steel

Post by RET »

Hi,

What Builder01 is showing is the right stuff. Insulating brick is white, it is very light (because it is mostly air) and has no mechanical strength to speak of. Anything between G20 to G23 are the designations you want. If I remember right, the higher numbers are more fragile but insulate better. The "hearth" I've made is very simple, just 3 bricks side by side, sitting on a piece of plywood. Works just great if you try and make sure that the wash from the torch doesn't get down between the bricks. If you keep the bricks together, that doesn't happen.

If you want to make a proper furnace, you have firebrick on the inside because of its mechanical strength and then you have a couple of courses of insulating brick outside to keep the heat in. Its easy to tell the two apart. Firebrick is quite strong and has good thermal conductivity, but is a very poor insulator and is heavy. On the other hand, insulating brick has very poor mechanical strength, but is a very good insulator and is very light. I have a box or two of the insulating brick in case I want to make some sort of a temporary "oven" for silver soldering or brazing large parts (the two are not the same).

The main cautions are; don't be in a hurry and don't overheat the work. I put the flux on before the part gets red. The right time is when the flux turns clear almost as soon as you add it. The technique varies a bit depending on the material you are using. With copper, you pretty well have to heat the whole thing because of copper's high conductivity (silver would be even worse). On the other hand with stainless, it is easier because of stainless's low conductivity. You can hold one end of a stainless rod while you silver solder the other end; just don't try the same thing with copper!

When Don & I were doing the Big Boy boiler, we found that the wash from the torch did a very good job at protecting the work. Keep the torch moving.

I agree with what Harold says. I wouldn't use drill rod for an axle and if you do, you have the problem with what you do with the unheated portion.

There is a whole range of hardenable steels from drill rod all the way through to tool steel which is an air hardening steel (there is still some iron in it). If you get a tool bit almost white hot, you can bend and shape it but when you let it air cool, it will be as hard as it was before you started.

Maybe some of this will help.

Richard Trounce.
JohnHudak
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Re: silver soldering steel to steel

Post by JohnHudak »

Thanks to everyone with the great replies.. I suspect that my previous failures with cold rolled steel was that I was probably using 12L14, as I have it on hand because of it's ease of machining.. Knowing this, I'm going to attempt it again with a test piece first on 1018..
Thanks again; John
piedmontg
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Re: silver soldering steel to steel

Post by piedmontg »

Hi
Thanks for the tips, I had not thought of citric acid, I will try that as I do not want to destroy the finish on the rods. I have rarely done steel silver brazing and had Sparax 1 at the time. I will see about picking up some of those bricks and get rid of my heavy firebricks.

As for the drill rod, I am using O1. To get into trouble I would need to get it to 1450+ degrees and hold for a bit and then quench. A1 requires 1700+ degrees to reach hardening temp. I am using easy flow at 1140. I am also using a Sievert Propane torch and can control heat placement good. The silver braze would burn bad at that elevated temp. Once done it will be covered for a slow cool down, I need to minimize distortion. Unfortunately it is too long to go into my heat oven, otherwise I would slow cool it inside the oven. As I mentioned my test braze went well. The only difference when I do the final braze is I am going to use some Cd bearing braze as I really want it to flow well into the joints.

Thanks again for the input

Bob
Abby
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Re: silver soldering steel to steel

Post by Abby »

It really isn't difficult , use plenty of flux and let the heat radiate back from the firebrick and don't over heat.
http://www.youtube.com/watch?v=o07KqhQ0u-I
https://s5.postimg.cc/9hyy27lo7/DSCF5394.jpg
https://s5.postimg.cc/uu6fzw5mf/DSCF5400.jpg
Dan.
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Harold_V
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Re: silver soldering steel to steel

Post by Harold_V »

Pretty assemblies, Dan. Looks like crankshafts. Would you mind telling us a little about the project?

H
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dajt
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Re: silver soldering steel to steel

Post by dajt »

I have been doing this recently and found the grade of solder is important. Down here we can buy silver solder with 15% silver in it, as well as the stuff with 45% or 55% silver.

The 15% silver solder us useless for steel. It will not flow, it will not stick, it will not do anything. I tried a joint 3 times recently before turning the solder packet over and seeing the 15 on it. As soon as I used the solder with more silver in it the problem disappeared.

I use a flux labelled 'tenacity' that withstands high heat for longer than normal and it works well.

https://www.boc.com.au/shop/en/au/boc-t ... flux-paste
piedmontg
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Re: silver soldering steel to steel

Post by piedmontg »

Since I got some much appreciated advice on pickling solution for steel thought I would show you the result. I used about a 10% citric acid solution slightly warmed. It cleaned up the metal real nice. I used the Harris Black Flux since I was doing this all in one shot and it tends not to turn liquid and disappear until you get near the area for brazing. I used up the last of me 1140 CAD bearing Braze on this. It went very well, took about 5 minutes once everything was hot. The picture is of the finished crank, crank and pins are not polished yet.

I included a picture of the crankcase for the engine. It was 19 pieces of brass varying in thickness from 1/4", 1/8" , 3/16" and other. I used 3 different temperature silver Braze. Its hard to see but all the sides are tapered to the top. Took a couple of days and lots of heat. What you see is the after machining crankcase.

Again thanks for the input.

Bob
Crank-2a.jpg
Parts-Ready-For-Brazing-EM.jpg
Crank-Case-Machined-1.jpg
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