Posted by Brian Adam on December 19, 1997 at 13:17:42:

In Reply to: Re: Welding precious metals posted by Valerie on September 05, 1997 at 17:06:30:

:

: : So what tips do you have for welding metals such as fine silver, sterling silver, etcetera?

: Brian, this is a two-part question and I'll answer them briefly first and then elaborate later on the weldability.

: : What's required of a metal that it is weldable? Poor heat conductivity, I guess.

: There are quite a few considerations when you use the term "weldable". We can pretty much weld any metal, it is just that some properties obviously make one metal harder to weld than another - but with proper techniques you can get the job done. The trick is knowing the properties of the metal to be welded and then to figure out a weld procedure that will make a joint which stands up in service. Yes, if a metal has a high thermal conductivity (heat is sucked out of the joint quickly by the mass of the metal itself), it is harder to weld since it takes a high, fast heat (electric) or immense quantities of low heat (oxyfuel). Some also need a special atmosphere (such as argon or helium) to be properly welded.

: This topic is called the weldability of metals. There are special concerns for each type of metal and for different types of applications. I think that I will spread out this inforamtion over time because all of it at once is -how shall I say - pretty heavy stuff.

: As far as welding, what is it? Welding is when we melt the base material and have the material fuse or flow together. It may be done with or without a filler material. Some processes don't even use heat - such as ultrasonic (sound wave) welding!

: As far as welding the precious metals (by most books - gold, silver, platinum and palladium), they can all be welded. The oxyfuel process can be used for each of these metals. There is one problem with welding these materials, though: usually we are talking about relatively small objects. When you are working with a small mass of metal, it is easy for the material to get to the molten temperature. The heat is easily distributed through the piece. This makes the time to get the material molten fairly rapid. So, you are joining the pieces, but the rest of the material is awfully close to the melting temperature (which in pure metals is a melting *point*). In other words, WHAM, the piece melts down. There is no real color indication, either, as there is in steel turning red to let you know that you are close to temperature.

: So, the weldability handbooks that I have say that these metals CAN be welded. For Gold and Silver oxyfuel welding, use a reducing flame. This means that there is a slight feather left at the end of the blue "cone" of the flame as you adjust your oxygen at the torch. This reduces the oxides at the surface since this type of flame uses more oxygen from the atmosphere.

Valerie, thanks for this, and the comments on brazing,

but you didn't quite get to the actual welding of precious metals?

I'm sorry if I missed a later post.

On rec.craft.jewelry lately (19/12/97) someone was suggesting a way to

reduce the size of a red gold ring by using the piece cut out

as filler for welding the join. A�reasonable solution?

Regards

Brian

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