Silver soldering

I've tried to silver solder a steel Bush to steel several times but it will not take. I've silver soldered up three copper boilers with no problems at all, also brass to brass so have a basic idea of silver soldering.

The items were cleaned with meths and made sure they are clean, used the powder flux to paste, heated the under side until the flux took a watery look, applied the rod, but just balls of solder and would not take. I also tried different flames, slow heat, and a higher heat.

I've took it apart for another go as I have more steel to steel to do , the only thing I'm thinking is meths the best degreaser.

Bob

,

I have never found meths to be a particularly good degreaser. I had assumed it was, then left a couple of small ball bearings soaking in it overnight to get the grease out of the bearings and found it made no impact at all on the grease. Surprising, but since then have tried meths on various other bike bits and found it does not degrease particularly wellat all.

You might be better to use spray can brake cleaner from the auto parts store. It leaves no residue and it does a very good job of getting rid of grease, finger marks, oil etc etc.

Or petrol.

If still trouble, you might call the guys at CupAlloy. They seem to be the experts and very helpful on model engineer stuff.

Tend to agree with Hopper re: Meths. Brake cleaner or pure Acetone is much better. As you've sucessfuly SS before, your technique is probably fine, may be a dumb question (but we all miss the glaringly obvious sometimes!) what you're attempting to solder the bush to is ordinary steel and not stainless?

all the best Mike

I've found steel takes way more time heating compared to copper. The skin is hot but the inside is not.

Having heated the work up once already all the oil has gone so if that was the issue the 2nd heating of the de blacked steel would have worked.

Suggest you use a scrap piece and heat the steel to a brighter red till the solder flows and note the colour required.

On the degreasing point, I use and recommend an acetone/ethanol product called Holdtite A061; this is intended for parts to be bonded rather than soldered, however.

I have some surgical spirit left over from my cycle racing days and used it recently for degreasing with apparent success. Does anyone know how this compares to meths?

PS from brazing ignoramus: why not use a brass-based rod rather than silver?

Edited By ega on 21/12/2022 10:20:08

You may need high temperature flux eg HT5 ? I would never use meths as a degreaser, acetone or brake cleaner. Is the steel free cutting or stainless? Not enough heat to flow ? Noel.

I've silver soldered lots of steel bits over the years and have nearly always used emery paper followed by warm soapy water and a stiff brush as the final cleaning regime before soldering and never had any trouble. Agree also that you need considerable more heat for steel than non-ferrous metals, and need to apply it quickly before you burn off all the flux.

Bob - if the steel is of the leaded free cutting type you may find that is the problem.

You should have no issues with silver soldering mild steel generally but the leaded versions can prove problematic.

Strangely enough I have a piece of unknownium 'brass' that simply will not silver solder at all. I have no idea of its heritage but the solder, as in your experience, just sits in balls on it no matter what the approach. Takes soft solder without issue though.

Best - Tug

Edited By Ramon Wilson on 21/12/2022 10:46:37

are you using the right flux there many different fluxes for different metals even stainless steel is easy with the right one. sadly i can not give you any names as i am not at work now

Could be leaded bronze? (LG2, SAE 660 etc.)

As the man from JM will tell you, let the flux do the cleaning !

Much more likely the steel is leaded , as others have said.

Most likely it is isopropyl alcohol based. Meths is ethyl alcohol based, with nasties such as methyl alcohol mixed in to make it undrinkabe. (Shame.)

How large are the bits of steel and what is the heat output of your burner? Quite possible you are taking too long to get it upto temp and by then the flux is exhausted. Bigger burner or HT5 flux will help.

Unless you have had the part swimming in grease and oil the flux should remove any small traces just make sure the surface is bright not rusty or oxidised from previous attempts

I don't think so Hopper, - I've used quite a variety of brass and bronze over the years but whilst this has the appearance of a yellow bronze and machines as such soldering is a completely different matter to all the others. I don't recall it's source so it could be anything but leaded 'it aint' as they say - too hard for that.

Theres not much of it but it's clearly marked as such - no point in using it again only to realise later which is how I discovered it in the first place

Best - Tug

Thanks, Hopper.

I would never dream of silver-soldering ferrous alloys with anything other than HT5 or JM Tenacity No.5 as a flux. Ordinary Easy-Flo flux just doesn't cut it with steel. I just use water to wet the flux. Cleanliness of the steel is obligatory if you want a good joint.

Or rather it is not purified so contains metanol as a contaminant, hence cheaper than when more highly purified, hence dyed to deter drinking.

Quick search of 'Surgical Spirit' (site:.uk) gives 'Methyl Salicylate, Castor Oil, Diethyl Phthalate and Industrial Methylated Spirit' so worse than ordinary meths for de-greasing because it contains castor oil already.

I generally use soap and water and dry off in the oven or with heat gun. Start off with white spirit for very greasy jobs.

Seasons Greetings Tug,

I once had the same problem with a piece of Manganese Bronze, which would not take silver solder, difficult to machine as well.

Regards

Brian B

Bob, can you upload a picture showing what you're trying to solder to what, with what torch and in what micro-environment?

I've successfully silver soldered quite a bit of mild steel, stainless steel and cast iron using just Easy-flo flux and either Silverflo 55 or a similar silver solder.