PGK's 1" Minnie

HT5 and I thought a good layer between the 2 bits of copper but to be honest i never saw it bubble/melt as such. I did wonder if the flame was blowing it away at the edges. I need to practice more. I couldn't run the flame from underneath as intended 'cos with the gas cannister upside down the flame size surged but with a poor low temp burn (liquid phase)

"I did wonder if the flame was blowing it away at the edges"

Did you apply it as a powder? should be mixed with water to a paste.

Also when soldering two flat items together put a few punch marks in one as the burr around the punch mark will leave a small gap between the two

Hi pgk pgk,

Exactly what grade of silver solder were you using for the above joint?

Cheers,

Julian

Yes it was mixed with water and i also warmed the rod and dipped it in powder. High temp solder.. can't remember the exact grade number.. but was the somethingC to 800C stuff

Its supposed to be dry for a few days here so I'll play some more (between farm chores)

Hi pgk pgk,

I presume you are trying J&M silverflo 24 or cupalloys equivalent, which is only one of 2 grades ductile enough and suitable for boiler work in the UK (the other is silverflo 55).

Silverflo 24 has a melting range of 740 to 800 degrees C. It is not easy to use, and takes a bit of getting used to.

It requires a considerable amount of heat, and the heat really needs to be whacked up to a considerable degree, and as quick as possible. Use lots of Tenacity 4A or Thessco F flux or cupalloy's HT5 mixed to the consistency of melted ice cream, and you can let it dry out a bit after applying before lighting up, so that the flux doesnt run off where it wanted when the job is heated up.

The copper needs to be glowing bright red in my experience for Silverflo 24. Higher than the temperature colour than for annealing copper.

Silverflo 55 (or Easyflo 2 if you have any) is considerably easier to use. In fact it is a doddle compared to using Silverflo 24. Since the cadmium ban I have built 2 new boilers using Silverflo 24 on step silver soldering.

Cheers,

Julian

Your throatplate and barrel joint should look something like the above when done with Silverflo 24.

Cheers,

Julian

When i did the annealing with the same can blowlamp I went through the silver to the stage where one ould chase the oxide film around with the flame with an undr colour of plum and it anneled nicely after that first poor attempt. For this solder try it was way way hotter than that ..as said bright satsuma orange but it did take a while and I'm guessing the flux either was hck enough or got used up/blown away. So I need soem more practice to get used to the changes and with my new bigger torches.

If you would like to move close to midwales you can give ne lessons in xchange for a bootful of leeks

There is a problem with flux exhaustion if the job is not heated up and the silver soldering completed within a certain timescale.

I aim to get the job up to heat in no more than 10 minutes with propane, and the actual silver soldering a few minutes more.

The temperature required for Silverflo 24 can be a bit frightening. Do not attempt the whole boiler with it, silverflo 55 can be used for later joints. Do not use Silverflo 24 for the tubeplates or tubes.

Cheers,

Julian

Indeed. I've got 3 temp ranges to get used to.

For other novices that may be reading along:

I had another go at the high temp solder.. with some success. To be sure I cleaned up the failed attempt pieces and then dunked them in dituted sulphuric acid.. rinsed, then scrubbed with wire wool. I made up a larger batch of HT5 flux and soemwhat thicker than before.. coated both surfeaces, sprinkled a few fragments of fine copper 'dust' to space them, left a step between the parts as somewhere to apply the solder rod.. and fired up an 8KW torch.

It still took longer than i expected to really heat up and I had it all well confined on vermicultie bricks. It got to orange/yellow before the solder would flow.. and having been excessively generous with the fux it was buubling and spilling onto the hearth. Next time I'll wear welding gloves.. It was probably reflection at night ( outside my shed with an eves security light) but it looked like the vermiculite was glowing.. and with just that torch some serious heat affecting my torch hand.. defo need gloves for the 25KW goes in future.

When the rod flowed it flowed well. I could assess and prove the concept of solder flowing towards the heat source (now directed at one end)

I suspect that my copper dust had flowed out with the flux.. the solder line between plates is almost invisible after milling the edges but hammering a screwdriver into the gap doesn't penetrate.

I reckon it's a lot easier to handle on fillets and curved edges.. will have a go at samples like that next and try to asses an optimum on flux which washed onto the bricks and under the part so I had unnecessary solder attached under there too - but I was determined to use too much rather than too little.

At worst i have a feeling for the colour temp needed for 800C and repetition should get away from the anxious newbie instincts of rushing with the solder and splashing it about.

Yesterdays preactive attempts were disasters (to learn by?).

I made a thinner flux mixture to solder two small 1" plates to each other.. a total failure. It still takes 2-3 minutes to heat up those little plates with an 8KW torch and the flux was exhausted in that time. Second attempt was with an angle piece riveted to a flat piece but spaced with two tiny bits of silver foil but the same flux thickness.. again exhausted before temperaturereached and one could see the solder just ball and sit there.

The I made up a thicker mixture again.. on two plates with a slightly larger 3 chips of copper as spacers. That way the flux persists but it does run everywhere.. a messy visual result and the sp[ace must have been too wide for good capillary flow..didn't flow the full width.

Next I plan to try letting the flux dry a lot more before cooking up in case it's the water boiling some of it away.

I'm having to consider downgrading my plans of using 3 temp ranges of solder. The original book used just c4 and easy flow.. so 2 temp ranges although he does soft solder too.

More practice needed.

Can I ask about the set up. Are you just plonking your boiler on a flat surface and getting on with it. You should realise that copper being such a good conductor will act like a radiator and disperse much of the heat you are putting into it with your torch. If you surround as much of the copper with insulating materials leaving only the joint exposed you will do better. You will find that you need to get pretty much the whole job hot before getting on with the joint. In order to not exhaust the flux heat the boiler away from the joint first then once every thing is nice and hot you will be able to raise the temperature of the joint area reasonably quickly. Many people have said before its not the heat you use it's the heat you lose that makes the difference.

Keep going, you will get there.

regards Martin

What flux are you using?

Easyflo flux will be exhausted by the time you get the far side of 800C, try using Tenacity flux (for alloys up to 880C) instead.

www.jm-metaljoining.com/pdfs-products/Tenacity%20No.5%20Flux%20Powder.pdf

Easyflo for melting up to 750C.

www.jm-metaljoining.com/pdfs-products/Easy-flo%20Flux%20Powder.pdf

Neil

Flux is HT5 and at the moment this is practice on small pieces rather than plonking the boiler down,

Hearth setup is a plank across 2 trestles outside my shed.. a layer of low density breeze blocks on the timber and a wind break built around the job from the same .. then vermiculite bricks surrounding the actual soldering job.

If and when I think I have the hang of doing this stuff then i also have loose vermiculite gravel for packing into spaces

Well done, you sound like you are already thinking about heat loss. Keep at it.

Martin

You could also think of a thermal blanket to wrap around the outside of the boiler.

Ian S C

I dont see anything wrong with pgk pgk's containment of heat method using Silverflo 24.

With Silverflo 24, if you have too much heat containment you get substantial heat throwback which makes it very difficult to apply the silver solder when the job is up to heat. Pgk pgk has already alluded to this with his burnt hand the other day.

Neil, there is quite a world of difference between using Easyflo 2 silver solder at 608 degrees C, and Silverflo 24 at 740 degrees C and above. In theory the extra 132 (plus) degrees ought not to make much difference, but believe me it does! I actually think using Silverflo 24 is pretty similar to using Sifbronze brazing rod. Those who have done Sifbronzed joints with propane will know what I mean. I dont think Silverflo starts to flow properly till well above 740 degrees C

Cheers,

Julian

Edited By julian atkins on 18/04/2016 19:34:28

Here's me being negative again, but I only ever use sf24 if I absolutely have to. As Julian says, it is not easy to work with and I only ever use it with oxy and a big propane torch, and then its all I can do to get it to temperature. When at temperature it doesnt flow as well as the lower temp does, and the Tenicity flux doent seem to promote good flow either. Im a bit perplexed re the flux bubbling and spitting - never had that occur. Dont forget that if you get the copper too hot it will burn, and you will never recover from that.

Julian. Is it acceptable to put strip joint covers on the outside, I have always put them inside which does take up waters space between the wrapper and the fire box on small boilers.

Bri

I totally agree with Fizzy re Silverflo 24 being 'difficult'. John Baguley (Baggo) described using same on his 'Helen Long' boiler in 2.5"g and even John admitted it wasnt easy to use.

I would not personally advise a beginner to use Silverfo 24. My first boiler (5"g Don Young No.1 Railmotor boiler started when 16, and started at 18 on the boiler) was done throughout in Easyflo No.2, but the stays were caulked with comsol.

For flux running when heated up, please do let it dry out before lighting up.

I have never had a problem with Thessco F which is what I use (JM Tenacity 4A, and Cupalloys HT5 being the same) with Silverflo 24.

(as an aside to Neil's previous post re ordinary Easyflo flux it is totally unsuitable for miniature loco boiler work using Silverflo 55 630 degrees C or even the old Easyflo No.2. Anyway that is what Alec Farmer of Reeves fame told me in 1984!)

In the over all scheme of things the cost of silver solder isnt that bad, and there are only 2 grades recommended by JM for silver soldered copper boilers since the Cadmium ban (unless you still have old stocks of Easyflo or Easyflo No.2).

Cheers,

Julian