Soldering, Flux burns before solder flows => Success !!!

Hengelo_77

Hengelo_77

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I'm trying to solder stainless bolsters on to stainless liners.
First I heat the piece from the underside, then apply flux, then I put pieces of solder on to the fluxed steel and apply heat it with a torch from the underside.
I'm using 5%silver solder.

While heating the flux turns black before the solder flows. Then I have a hard time hitting the solder to flow there.

What am I doing wrong?
 
I think you are getting it too hot. I use a large soldering iron because I feel I have more control over the heat.
Soldering stainless to stainless is a lot harder than stainless to brass.
I use Alstate 430 solder.
 
Tom Lewis said:
I think you are getting it too hot. I use a large soldering iron because I feel I have more control over the heat.
Soldering stainless to stainless is a lot harder than stainless to brass.
I use Alstate 430 solder.
Click to expand...
Do you just touch the bolster/liner with the soldering iron from underneath to heat them?
 
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interesting vid
I'll try heating slower with a torch first before I buy more stuff, but it is a good one to keel in mind
 
A soldering Iron doesn't take forever. Bob Loveless used a soldering Iron. I use a large one and hold it underneath the bolster.
My soldering Iron is 200 Watts.
Also it is really really important to have the surfaces absolutely clean.
 
There are several things that make or ruin a solder joint in a guard or bolster:
1) Cleanliness - Sand all joints flush and clean. Wash well and clean with denatured or isopropyl alcohol. Keep your fingers off the mating surfaces.
2) Herat source- A big torch is WAY too much heat. The solder melts around 400° or less, so a big flame at 3000° makes no sense. A small butane refillable torch works well. The best choice is a small jewelers propane/oxygen torch like a Smith torch or a Little torch. A heat gun also works quite well. A large wattage soldering iron will work if the joint isn't too large.
3) Temperature - The solder flows around 400° The flux burns around 600°. If you overheat the joint, the flux burns and the solder won't flow.
4) Feed the solder into the joint form the side opposite the heat source. It will flow toward the heat.
5) Clamping - Don't clamp the parts together hard. The solder needs enough room for capillary action to let it flow through the joint. A pair of medium tension soldering tweezers is plenty enough clamping force. If the joint is riveted really tight prior to soldering it may be too tight to solder. Slip the pins in place, clamp the bolsters with soldering tweezers, solder, then trim and lightly peen the rivets.

Final comment:
If the flux burns or the solder just balls up - STOP! Take the assembly apart, clean and re-sand everything, and start over. Adding more heat will not help, it will only make it worse.
 
Everyone does things differently, but that video really over complicates soldering a guard on. It's a 5-10 minute job.
He heated the joint 4-5 times, added flux 4-5 times, kept adding solder. Wow!
 
Short answer - cleanliness and too much heat.
The surface it is on has a layer of oxide, dirt, or burnt flux - which prevents the solder flowing. Due to surface tension, it thus pulls itself into balls.

The wrong flux can also be an issue. Use the flux that is for the solder you are using.

I prefer Tix solder. It has its own flux. It flows wonderful and at a much lower temp than Say-Brite - 275° vs 430°. It only requires evenly heating the items to be joined and a perfect solder joint happens effortlessly. A heat gun with a small nozzle works great as well as a jeweler's torch.
 
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Another good thing about the tix solder is thin rods it comes in. I hardly use any solder and end up with a tiny solder line.
A last step prior to cool down with a wipe of a q tip leaves little cleanup. I think most end up with their own method.
The perfect puddle of solder look hides the good fit of the guard and requires more patience and skill than I have.
My soldering is like when I use jb weld, a sealer that the less seen the better. Interesting video, thanks for posting it.
 
I'm still practicing and I believe I'm making slow progress.
Sometimes the flux builds some kind of foam on the steel.
Does that mean I use to much flux?
I'm using a (German) stainless to stainless flux for soft solder
 
This is the setup I'm using, I have a small burner fixed and pointing upwards and I move the piece over the flame.
It is not pretty and I cooled, cleaned of burned flux and reheated twice but I have solder all over.
Is this acceptable?

IMG-20230103-094705.jpg


IMG-20230103-165643.jpg
 
Have you priced Tix solder recently? Rio Grande has it at $32 for the little container!
 
Which will do well over 100 guards. The Dr. Pepper I drink while doing a solder job costs more than the solder.

Itis $22 from Stuller and the flux is $5.
 
hello. some solder flux's have a shelf life. how old is yours ? are you sure the surfaces were clean enough? looking below where you soldered on that liner its hard to tell. i have noticed if surfaces are too rough, or too shiny ( mirror) the solder has more difficulty taking hold and spreading. i found a clean 1000 grit surface works nice on stainless. also as stacy mentioned, make sure that flux is specifically made for that solder, by the same company. somehow things get much more difficult when soldering stainless versus other metals. another thing to try is while you are heating your work piece and the solder melts, take a long piece if 1/8" brass pin stock wet with the flux and use it to wipe the solder around, trying to spread it evenly while heating it. sometimes that helps the solder grab on a wide flat surface and get less blobs. even with a heat gun, its still easy to burn the flux. once the solder starts to bubble, move the gun back another 3 inches. another issue may be too much flux. flux actually starts to eat into the metal before you heat it. it will make a frosted line on your stainless if you leave it there for a few minutes. the heat speeds up and finishes the process. it just needs to be wet when you start heating it. if you have a puddle of flux on your bolster when heating it, there is gonna be a thick hardened patch of flux your solder has to get through to contact the metal. that excess flux never touched the metal, so it never did anything helpful to begin with. it just needs to be wet enough so you can see the metal changed color when you wiped it on. good luck !
 
john april said:
i cannot figure out how to get rid of that gallery link, its not supposed to be there without a paid subscription. can you help me out stacy ? thanks.
Click to expand...
click on your name at the top, go to "Signature" and then delete it and then click save
 
It was a battle of wills but I soldered a pair of bolsters!
This is an older slipjoint I made that I took apart to rehandle and practice something else.
Now it is going to get a pair of soldered bolters as well.

The biggest game changer I think was getting fresh flux. I got the same brand as before but maybe the older flux has gone bad over time.
It came with new solder, 3,5% silver rest tin.

What I have learned and may help somebody else:
Don't overheat, heat doesn't disapper immediately when you move the piece away from the flame.
Get the solder liquid and move it around with a (titanium) pick. The piece doesn't need to be in or above the flame for that.
If it doesn't take somewere, heat that part up and drop just a little drop of flux with the pick and while it bubbles move the liquid solder over it with the pick. (flux is colder so heat that part up a bit more)
I've re-heated a bolster that had parts not tinned correctly and moved the solder over those spots with success.

Also don't have huge blobs of solder sitting on top it prefents the two parts adhering well. Just have everything covered in solder and whipe the rest of with the pick.

Now that I'm getting some controll over the process I'm actualy enjoying it.

I'll be doing some slipjoints with solderd bolster and maybe try different metals after that.
Here is my result and the flux I used. I got it in Germany, it may help someone (the "ST" is important!)

IMG-20230109-142601.jpg


IMG-20230109-142609.jpg


IMG-20230109-142718.jpg


IMG-20230109-142813.jpg
 
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