Silver Solder Torch Selection

[ChazzC]

Got an answer from Bernzomatic on the output of the 8250-series torches:

Actually, they replaced the original answer which was this:

"Thank you for your question! If you’re currently using propane, which has a maximum burn temperature of 3,600°F, you might consider switching to MAP-Pro fuel. MAP-Pro burns slightly hotter, reaching a peak temperature of 3,730°F, which offers a modest increase in heat."​

​

When I checked the "No" button under "Helpful?" yesterday morning, they replaced the response with the actual answer to the question just now.

 

[Danuzzo]

Interesting that you should post this, because I contacted Bernzomatic as well last night and was emailed the specs as shown below. So, I cancelled the order for the 8250 just got back from a local store and bought the 8000 with a hose kit. Should be a little better. Going to try it out later after playing some pick-up hockey.

"What is the BTU rating for the BZ8250 HT torch? Propane 10229 – MAP Pro 9250"

"What is the BTU rating for the TS8000 T torch? Propane 14282 – MAP Pro 12915"

 

[ChazzC]

That's interesting since they both have the spiral burner (I forgot to go back to my earlier post on the 8000); I would have though the only difference was the permanently attached hose with remote regulator.

Although the 8250 has less heat output, with the remote regulator you have the freedom to use the touch head at odd angles, which is an important consideration.

 

[Danuzzo]

That's interesting since they both have the spiral burner (I forgot to go back to my earlier post on the 8000); I would have though the only difference was the permanently attached hose with remote regulator.

Although the 8250 has less heat output, with the remote regulator you have the freedom to use the touch head at odd angles, which is an important consideration.

I hope that the hose kit I purchased takes care of that. Please let me know what you think.

 

[ChazzC]

Hose kit is just that, a hose with a shut off valve at the cylinder end; the regulator is still in the base of the torch head. As long as you don't tip the bottle you should be ok?

 

[The Ignoble Troll]

Heating is complicated and BTU's are as useful to judging a torches performance as gas tank volumes on cars.

Max flame tempurature, flame front speed etc... all play huge rolls in getting the heat where and into what you want to heat.

 

[kwoodhands]

Well, I ordered the Harris 56%. https://www.amazon.com/Harris-Troy-Ounce-75310-5631/dp/B0713Y6V2F?tag=forumyield-20, and the Harris Stay-Silv white flux. I hope I got the right stuff.

Still have to figure out the torch. I think I want a propane with hose that connects to a small 1lb tank. More suggestions and links are welcome. I did look at the Sievert, but only could find one that hooked up to the 20 gal. tank. The Orca linked by Chazz is nice, but a little pricey.

I use a Victor torch that comes with two burner torch heads. Also has hose , regulator.
I use 20 % vinegar for a pickle. Regular vinegar is 5 % and will work but takes longer.
I have both white and black flux. Mostly use black flux, no particular reason. I use both Harris 45 & 56 solder. . I have found that cleaning the solder with a Scotch Brite pad and dipping the solder in flux first before cutting into 1/8" /3/16" long pieces then placing them on the joint helps .
Areas that you do not want solder to adhere to are coated with Whiteout .
Most of my solder is 1/16" diameter, also have 1/32" diameter that I use around bushings etc. Easier to form . The Victor torch connects to a 20lb tank. I think a 1 lb tank is too small unless your soldering is on the small size. There are hose connections to small bottles. The one I have is inherited.

 

[Steamchick]

Must get some "white-out"... my soldering looks a mess as the silver solder runs everywhere!
K2

 

[Steamchick]

Is T-cut just Rouge? - Will that work as a solder anti-flux?

 

[ChazzC]

Is T-cut just Rouge? - Will that work as a solder anti-flux?

Yellow Ochre is traditionally used by jewelers as an anti-flux, mixed with either water or alcohol as a carrier. If not ordered from a jewelers’ or artists’ supply, it’s reasonably priced:

https://a.co/d/iZBR8Iu

 

[GreenTwin]

Heating is complicated and BTU's are as useful to judging a torches performance as gas tank volumes on cars.

Max flame tempurature, flame front speed etc... all play huge rolls in getting the heat where and into what you want to heat.

From my limited experience with silver soldering steel parts together with high-temperature silver solder, there is a bit of an art to getting the two (or more) pieces hot enough to flow the silver solder, without overheating the flux at the joint line.
The thing that really needs to happen (in my opinion) is that the pieces (complete pieces, not just edges of the pieces) need to get to the right temperature to completely flow the silver solder all the way through the joint.
It is very easy to make a good looking superficial silver solder joint, but a few whacks with a hammer on a test piece will tell the tale.
For a high-strength connection, you need a very thin joint, and a completely flowed joint.

As I mentioned, I use any oxy-acetylene torch, and while that may be overkill for hobby work, it should be noted that there are a wide variety of tips available with an oxy-act torch, to provide anywhere from pinpoint heat, to very wide flames.
You can also use various sized tips, for large or small projects.
And by adjusting the regulators, you can dial in the heat you need for the particular application.
There is no downside in my opinion to having excess heating capablilty, since it is like the accelerator pedal in your car; nobody says you have push the pedal completely down when you use a car, and controlling the excess power is easy.

From a cost standpoint, the least expensive equipment that will do the job at hand makes sense.
If you have an overlap of other repair types in your shop, then the least expensive option is the one that will do all the types of repair you want to do, not just model work.

A very hot flame that is too localized/pinpointed will just burn hot spots on the metal pieces without getting the overall pieces hot enough for a complete flow.
The approach for silver soldering is the opposite of gas welding.
With gas welding, you want a narrow tip that concentrates all of the heat into a very small area, where you create a puddle and sort of pull/walk it along around the joint. The joint should be V-cut so that you are assured of complete and full weld penetration.

For silver soldering, you are trying to bring up the temperature of all of the pieces to a uniform temperature that is hot enough to get complete joint flow, but cool enough to not burn off the flux.
The joint is typically two flat surfaces that are separated by a very small distance, with the separation often obtained by using slight punch marks across the faces of the joint.
The brown flux helps with avoiding flux burnoff, since it has a higher temperature rating.

You don't want to pinpoint high concentrations of heat or temperature into a small spot when trying to silver solder.
Focusing high temperatures on the joint itself just burns off the flux and ruins the connection.

Try some test pieces, break/cut them apart to verify full penetration, and I think you will get the hang of it quickly.
.

 

[Danuzzo]

I did try some silver brazing today with the new Bernzomatic torch and propane, on a practice piece before I do the crankshaft. It is a very strong connection; however, what was once the color of steel is now a dark grey, and it doesn't wire brush out. I did get both pieces of steel red hot, maybe too hot?
What went wrong?

 

[GreenTwin]

The discoloration sounds normal to me for steel.
I can't comment on what to do about that though.
Congrats on the silver soldering; you are on a roll !
.

 

[Jasonb]

If you are seeing scale then you have got it too hot, the solder should flow just as the metal gets to a dull red (don't do it in bright light) You will get discolouration but it should come off with Emery cloth or wire brush.

An acid pickle can be used to remove the black deposits as well as flux but if you have too much scale that can result in some metal loss so not what you want on a crank built up from finish size metal.

This is the amount of discolouration of the steel you should be seeing, straight after soldering it's a bit bigger at 5/8" diameter

End of crankpin filed flush showing the ring of solder in the chamfer that was cut on the hole

And after a clean up with emery, nothing excessive and no acid used

 

[Jasonb]

Another steel fabrication showing light discolouration after silver soldering on the bottom plate, it's 8" wide x 12" tall

And the dide mark where it was stood in about 1" depth of acid to clean off the flux which also cleaned the steel

 

[Jasonb]

Have a read of the posts on this page, they start with a poor solder joint and lots of black scale, his second attempt is a bit better then further down I show a similar joint being done where the solder flows well leaving a neat fillet.

https://www.model-engineer.co.uk/forums/topic/steam-engine-number-one/page/5/

Note the bits of thin angle iron I have it stood on are bright red but the parts only have a slight red tinge. As Pat says you need to get all the metal hot and that is why a good output torch is needed. That Muggyweld site mostly have thin tube and sheet being soldered which like the angle iton is easy to get upto temp but it is the solid metal you need to get right

 

[GreenTwin]

I have had better luck with the Harris black flux (pics attached).
When using the white flux, there seems to be a very fine line between getting the pieces hot enough to wick in the solder, but not so hot as to burn the flux.
Once you overheat the flux, or keep it hot too long, then the silver solder just beads up in a ball, and will not wick into the joint.
It is really annoying to have to cool the pieces back down, clean all the mess off of them, flux them again, and start over.

Similar situation with welding rods.
Some welding rod brands work infinitely better than other brands, even when they are the same type.

If the flux comes dried out, which I have found to be pretty typical, add a few drops of water to the top, and mix a bit of paste up.
.

 

[GreenTwin]

I think joint strength is directly related to joint thickness, if I am reading this article correctly.

https://kaybrazing.com/brazing-articles/1000978-the-famous-joint-strength-vs-joint-clearance-chart/

.

 

[Steamchick]

My experience... for what it is worth.

• I apply flux continuously during heating. Otherwise it is used-up and burnt before the job gets hot.
• I start with Easi-flo flux, but then change to Hi-temp flux as red heat starts to show, as there is less risk on contamination with burnt flux. The fresh flux washes away the old stuff.
• Cleanliness is next to godliness. - But most of the crap in joints is the oxide=flux residue. If not washed-out with fresh flux continually, joints can be weakened by contamination.
• The blue cone of the blowlamp flame is hydrogen combustion, and Carbon to Carbon monoxide beyond, in the start of the darker blue zone. The Carbon monoxide to CO2 is the outer part of the darker zone, but the hottest part is in the middle of the darker blue zone, before it expands and becomes feathery. The light blue cone doesn't have the highest temperature of heat supply, but does have more air = oxygen supply to oxidise the metal. So Keep the light blue away from metal, and use the darker zone maybe 1/2 in or 1.5cm beyond the end of the blue cone.
• Pre=heat the silver solder rod applying solder and dip into the flux powder, so it gets flux melting on it as it heats and this will help it flow.
• Simply: Blobs of molten solder sit on oxide at any temperature, but wet clean, fluxed metal when the Metal is hot enough.
• Do not continue heating after the solder has flowed. You are simple creating more oxide as crap in the joint. The oxygen is in the flame, hot and ionised ready to grab anything = fuel gas, solder and metal!
• Dull~mid red is hot enough for SILVER alloy solders. Bright red for COPPER alloy Brazing materials. Yellow hot melting steel and copper, and white hot for burning steel! Take a fine steel wire from a wire brush, and probe in your gas flame to see where it is hottest. remember that point in the flame and hold the torch with the hot spot just at the surface of the job to be heated, at the joint, or biased towards a thicker metal where there is a thick metal and thin metal to be joined. The whole joint should reach soldering temperature simultaneously.

Hopefully something here to help?
K2

 

[Steamchick]

A couple of views of ways to keep the heat in the job.

• Bury much of the job in a tin of DRY sand:

• Surround with firebrick:

This used 2 off, 3kw blowlamps to heat the body of the boiler, with a 5kW Propane blowtorch to heat the soldered joints on the end of the boiler. (I was adding stays to strengthen the end plates.).

• And another one...

This is during heating before I lit the Propane hand-held blowlamp. Notice how the copper adjacent to the blowlamp is looking coppery, not black, where the flame impinges. Most of the oxygen has been used in burning fuel, so there is little left to cause the metal to oxidise. But it is black oxidised everywhere away from the flame. It was all "pickle clean" when I started heating! On the LH blowlamp the light blue cone can be seen. It is clear of the metal by about 1/2inch.
The 2 pieces of firebrick sat on top of the larger bricks were lifted away for this photo, but sat on the sand tin during actual soldering. I think I decided to take this photo just after the soldering was finished, when I would normally remove the blowlamps and adjust the firebricks to cover the job for slower cooling. Hope it is useful?
K2