Thread: Jigs for Silver Soldering

In the 60's I used silver solder inside hydrogen bells to join copper, nickel, kovar, monel, metallised ceramics and other exotics for high vacuum applications using green stainless steel jigs and induction coils for heating.

The green layer on the jig was resistant to the solder and was, I think, generated by heating the jig up in water saturated air to create a tightly adherent oxide layer.
Can anyone confirm how to do this ?
Type of stainless, temperature, atmosphere etc.
Is this approach suitable for workshop propane torch use ?

Does anyone have any suggestions on alternatives ?
Machinable ceramics, for example.

John.

Hi electrosteam
Can you tell us what it is you wish to achieve?
Would it would be silver soldering-( silver brazing-same thing) some carbide to a tool bar or cutting bar ? This subject has occupied a thread or two of late.

If we know what you trying to do it is much easier to help you. Induction coil heating is production line stuff .I recall induction heating bobbing up in study notes ,but I have never seen one.

Funny how things work out .I was just looking for the bullfinch LPG torch for some silver solder work but they don;t appear on the net-leastways where I looked.

Grahame

Grahame, try

Bullfinch Gas - Home


These guys colour S/S. From the attached PDF http://www.rimexmetals.com.au/PDF_da...nlessSteel.pdf
It sounds like green is just the S/S with the thickest oxide coating available. Thicker oxide = less likely to have things stick to it.

Michael

Hi Grahame,
Thanks for taking the time to respond to my query.

The vacuum applications referred to were power electronic valves typically used in TV and other high-power transmitters.
It was not a production line, rather a batching system with batches from 1 through to about 10 units in a group.
However, the actual silver soldering, almost assuredly cadmium free because of the vacuum, was done one unit at a time.

The problem raised itself today whilst using some grade 245 silver solder to join some 6 x 6 brass blocks to 4 mm brass tubes using an air/propane torch.
The block had machined features that required correct squareness to be maintained.
A nice jig would have made it so much easier.

I learned the lesson: solder raw block to tube first, then add the features.

Michael,
You could well be correct with the Rimex reference to chemical colouring of stainless steel.
We had available a wide range of chemicals and an extensive electro-plating section available for all sorts of odd things.
(We even mixed up some automobile fuel during one fuel strike).
The oxide that we had, however, was not especially prone to scratching, as noted by Rimex.

John.

G'day John
On a wild whim, I just had a look at a copy of the Soldering Handbook (AWS, 3E, 1999). There is nothing in there about making up fixtures but it does say that Stainless steels are difficult to solder and need an agressive flux for the solder to take, so provided flux was not splashed around you may just be able to use S/S. The other interesting one is Copper - Aluminium. These alloys are listed as difficult to solder, especially with high Al content. My last thought was that hard anodising may be worth looking at (uses oxalic acid I think) as that gives a hard damage resistant coating to Al - I don't know whether there is a S/S equivalent.

In your original post you mentioned ceramic. With the temperatures involved metals and ceramics are probably the only common items that will last (I have made one off weld jigs with wood, but sooner or later something gets too hot...). The main problem with ceramic material is that typical shaping is done by grinding. However, it does make me wonder whether one of those modelling clays that harden up in a domestic oven could be used for making up simple fixtures. Might be worth experimenting with.

Michael

Aluminium would be a pretty poor choice for a soldering jig - the amount of heat dissapated by the jig would be an issue, along with the jig moving with heat. Stainless is a much better choice - it's not nearly as efficient at dissapating the heat of the torch, and has a much lower coefficient of thermal expansion.