Post by nobbysideways on Apr 12, 2019 17:14:54 GMT
I'm making a spirit burner for my Stuart boiler, and intended to mimic the original design but using thicker gauge metal.
I've got a pretty good Sievert Propane torch and a variety of nozzles, would the best thing to be solder, silver solder or Braze?
The tube is Mild steel, 2mm wall thickness. I have attempted to solder in an eccentric plug I made for the end out of steel stock (to keep it off the floor, I made the plug eccentric as I thought it would look nicer than the original wedge design). I couldn't get it to wet despite trying a couple of different flux compounds, however I think my technique may be lacking in many other areas (about to attack youtube for some how-to videos).
Any suggestions please? Especially on skills worth learning.
Silver soldering steel is ok but you do need a lot of heat. You'll need a thick mix of the flux. If I understand your description of soldering and end to a steel tube, I would make sure it's very clean, no oil/grease deposits. Mix the flux and coat both parts before putting together, use something like 1.5mm 55% silver solder, make it into a ring that is a spring type of fit inside the tube. Push it down to meet the end, put more flux on top and heat from below, no direct heat onto the solder until it's liquid and then only if you think it needs it... It wl take time to get the metal hot enough, best use your largest nozzle..There may be specific fluxes which will work better I'll leave that to the experts, I just use normal flux as supplied by cupalloy...
This shouldn't be a big problem Silver Soldering as long as you do a few key things.
1) Get everything spotlessly clean then use Tippex to mark where you want the Silver Solder to stop. 2) Mix up plenty of flux, it doesn't have to be particularly thick in my opinion. 3) Cover absolutely everything with flux else you'll have Black oxide to clean off everything. 4) Make Silver Solder rings that very closely fit the joints. 5) Warm it gently and make sure there's plenty of sticky flux holding the Silver Solder in place, add more if necessary and poke the Silver Solder to make it stay where you want. 6) Once the flux has stopped bubbling, get cracking with getting it hot, playing the flame on the parts with the biggest mass. Don't blast away at the area to be Silver Soldered. 7) Although you might need a lot of energy to get it all hot, you don't need to get it more than a very dull Red heat if you're using 55% Silver Solder. You'll see the flux go clear and then soon after the Silver Solder will melt too, probably before it even glows Red. 8) Hold it at a very dull Red heat for a few second, adding any further Silver Solder if it's not gone everywhere you want it. 9) Allow to cool and then soak in water or us an ultrasonic tank.
I took ages to figure this out. I was blasting away getting it all way too hot and then wondering why it ended up as a black mess which was a nightmare to clean up.
Post by nobbysideways on Apr 12, 2019 18:41:21 GMT
Thank you gents. Obviously I've been following your exploits but in this case what I'm soldering is quite beefy. Also I suspect I'm not using the right solder. I'll look into this further. I've got a large stock of silver solder my grandfather left me but I don't think the flux is right.
How old is this Silver solder and how old is the flux. As you say it was your grandfathers it could well be cadium based which today is banned. Unless your flux is also old, something like easyflow 2 then it won't work so well if at all I'll leave it to the experts to say which. I'd buy some new solder and flux and try again..
If it is a big (0.5kg) lump then that is more difficult to heat with propane/air - you will need a 30kW Sievert to pump the heat in. It needs to get red in around 120 seconds IMHO. Roger has explained it very well with regard to getting up to heat but not burning the flux. I use oxy/acetylene for large jobs and heat locally, but you need to use what you have. Also, with steel it can be done with Easyflo but the high temperature fluxes do cope better and just need a bit more grunt to wash off.
You won't die if you use Cadium based solver solder in a well ventilated area. If you are really anti using cadmium based Silver solder then I will pay the postage to have it picked up and will personally dispose of the dangerous stuff by using it myself. My Easy Flow 2 and Tenacity No 5 fluxes are now well over 30 years old and both still work very well, Tenacity No 5 takes heat better for longer.
Steel silver solders very well. Too small a burner will not heat the item fast enough and will "kill the flux" = burn it off before the solder is able to flow and it forms a solder proof barrier If you are heating a large area which can radiate heat then shield it to keep the heat in around the item. Put your spare stick of silver solder in a bit of copper tube with a kink in the end and with only a short length sticking out, use this to poke extra silver solder on the joint as it runs round and also use it to dab on extra flux.
It is difficult to describe getting the knack of silver soldering as one person's "a lot of heat" is another person's tickling it with a propane torch Do a few practise pieces before tacking your prized new burner.
You could put a small piece of the Silver Solder on a piece of Copper or Steel with some flux and see how hot it needs to be before it melts. If you don't get a puddle and it's all glowing a dull Red, it's not 55% because that melts almost before it gets Red hot. By the time you get to say 24%. you're going to have to get it almost Orange before it melts. This is all fine but you'll need a high temperature flux because the usual stuff you have for 55% Silver Solder won't last long at those temperatures.
To be honest, in my opinion there's little point in having these really high temperature Silver Solders for our purposes, they're more trouble than they're worth. 55% Silver Solder is probably strong enough for just about anything you're likely to need it for. If what you have is high temperature stuff, personally I'd label it, put it away and buy some 55%, it will save you a lot of hassle.
Roger Your nine point lesson is briliant. I will try it this afternoon as I have some work to do and perhaps they will not be black and horrible. Will report later! D
The Princess Royal has muscled into top position. The Aspinal is in the box. The Princess of Wales is well and happy, with the 990 alongside. The little 3 1/2" part built 4F waits and still need a rake of clerestory coaches. Southampton Society of Model Engineers www.southamptonsme.org
Post by nobbysideways on Apr 13, 2019 10:22:37 GMT
Fresh material would give me a very definite starting point, it just will put things on hold until its affordable. It's no great problem, I've got other things I can be doing. I suspect the older stuff will be useable by me once I'm more experienced, but as a novice the fewer variables the better.
Post by nobbysideways on Apr 27, 2019 20:05:22 GMT
I've just purchased some HT5 flux and a hearth from CUP Alloys. Their website looks very helpful, I'll keep watching some videos and practising. I've got to solder up my motion brackets. I wondered about brazing it but I don't have the equipment and it's just not a viable purchase right now.
And if you want any more information then simply give us a call. Better still, if you are going to Doncaster come and see us. We will make sure that you have all the knowledge to be successful. Regards Keith
Your initial question was solder or braze so why not go for the braze option. Steel can be readily joined with brass using borax as flux .If you have a blown torch or oxy-acetylene , a bit of copper wire can be used rather than the brass. This is how we were taught to braze in metalwork at school and it is still the way I join steel parts together if welding is not an option. It is very cheap on materials but a bit more demanding on the heat supply. Dan.
Copper melts at 1083 Deg C. It requires oxy-actylene torches with the associated problems of gas storage and insurance. They are amongst the most expensive form of torch. The cost of the gas is high. It can only be used to join steel. Anti-glare goggles, gloves etc.
Brass as the brazing alloy is better only as far as you can now braze copper. But you can't join brass!
Propane torches are cheaper, more versatile with none of the above restrictions except you need to use a lower melting point brazing alloy (silver solder) or soft solder. You can now join brass components.
Ok - silver solder is more expensive but used properly will produce the cheapest joints.
Cheaper equipment, cheaper running costs, easier to use it's the go-to system for the model engineer.
50 years in the brazing business has taught me that an oxy-actylene torch in the hands of the average model engineer causes more problems than it solves! I've picked up the pieces!
But buy your torch from a source that can and will guide you. Another money saving tip.