Alternatives to Soldering Gold

[SamIveson]

Hello all,

I have searched and I don't think that this has been asked before so here goes! (Well, actually that's a lie, it has been asked but not in this context!).

I am looking for an alternative to soldering gold as another metal in the assembly cannot be heated above 400 deg C which is above the melting temperature of the solder.

What I am making is stainless steel rings with a gold band inlaid in the centre. There is a join in the gold which is then soldered. The problem is that, if heated to between 400 & 800 deg C the type 304 stainless steel looses its corrosion resistance and I have had one customer complaining of their ring rusting as a result of this. Unfortunately it is not possible for me to substitute the 304 stainless for another grade so I need to find an alternative to soldering. I can restore the corrosion resistance of the steel however this requires that it is heated above 1040 deg C which is above the melting temperature of the gold!

The join does not have to physically hold the metals together, it is more of a filler so that you cannot see the join in the finished article so a resin of some description may be suitable but I am not sure if such products exist that will blend seamlessly with the gold. I work in yellow, white and rose gold so ideally would need a solution for each.

I look forwards to your thoughts!

Cheers,

Sam

[ps_bond]

Is it possible to swage a too-large band onto the inlay or (better result but more troublesome) expand the stainless band into the gold inlay?

Other alternatives that spring to mind - which of course may or may not be suitable - are:
Weld the ends of the inlay (laser or TIG, very limited HAZ)
Use pure gold wire, undercut the inlay channel and hammer the wire into place, then undercut the end & lock the inlay in place. Very clean pure gold will bond to itself at room temperature but any oil on it will scupper that.

[SamIveson]

Hi Peter,

Thank you for your reply. Currently I undercut a groove, hammer in 18ct gold wire and solder. Presumably the impurities in the 18ct gold will prevent it from bonding to itself or is this a possibility?

Swaging a band into the inlay groove (by this I assume you mean soldering a ring of gold and working this over the steel ring and into the groove) is a good possibility that I had not considered and is something I will definitely try. It's possibly a bit more work than my current method however if it gives good results then it would be an excellent alternative method.

As for welding, this is not something that I had considered but will definitely look into. A small HAZ on the OD shouldn't cause a problem as it seems to be the inside of the ring that is most susceptible to corrosion (probably due to the fact that moisture / sweat gets trapped here). If it came to it I could leave the steel a little over size and machine back to remove the HAZ.

Thank you,

Sam

[ps_bond]

18ct will bond to itself eventually, but it's much easier to start with pure (well, 999) gold. It'll also be easier to hammer into the undercut than 18ct.

It'll be easier (ignoring the minor issue of it being steel...) to expand the ring into the gold than vice versa - getting the gold seated is always going to be a bit of a swine. I'd still prefer to hammer it into place though even if it is shrunk onto the ring.

With my laser I can go down to 0.20mm beam diameter, so with care there shouldn't be any overlap onto the steel (still only joining the gold to itself). While obviously any HAZ on the steel is going to create a stress cell, the amount of heat shouldn't cause any problem that can't be polished out rather than needing turning.

BTW - 416 is pretty forgiving, but at least you aren't trying to work 316L...

[SamIveson]

Thanks Peter,

I am working with pattern welded steel which is half AEB-L and half 304 with the AEB-L being fairly tough (It was originally developed for making razor blades). One of my concerns would be distorting the pattern if trying to expand the steel (as well as dimensional control) and whether I could successfully do this without adding heat.

I have looked into TIG welding and have found a small welder designed specifically for jewellery applications however it comes direct from china so I'm still not 100% sold on that idea. I think laser welding systems are out of my price range for the moment although one would be nice! Maybe in a few years once things have taken off! Certainly they seem to be able to offer levels of precision miles ahead of what I would be able to achieve with a micro-TIG unit.

Thanks again for all of your help!

Sam

[ps_bond]

AEB-L & 304 - not Devin Thomas' steel, is it?

I've seen the Chinese welders and they make me a bit twitchy too - the safety/support or lack thereof.

The other option on the welding would be to contract it out until your volume makes it a better bet to do it in-house... It's the sort of thing I do for others (subtle, aren't I?!).

[SamIveson]

You certainly seem to know your materials - I'm impressed!

I have found a few American companies selling these welders who seem to at least offer some form of after sales support but yes, the quality control (or lack thereof) on items coming direct from China does concern me slightly. After my last post I did spot an Orion M Pulse welder that goes for a reasonable price (well, under 2k!) which I think I will look at in the future however at the moment the volume of rings that require welding (most of my orders are for plain bands without any precious metals) doesn't justify the expense so subbing them out could well be an option for the short term. If only there was some-one who undertook this kind of work!

Joking aside, I don't have any orders at the moment that require welding however I may be dropping you a PM in the near future!