Soft Solder v Silver Solder

I am making the cylinders for a twin cylinder oscillating engine. Each cylinder consists of two pieces soldered together. As I will be running this on steam would I need to silver solder or would soft solder be OK? I thought to tin the surfaces first as steam ports would be drilled through and want to be sure of a complete seal/joint. Many thanks for any help views on this, John

Edited By JC54 on 08/05/2019 12:51:03

Silver solder would be the best option but as you are unlikely to be running on high pressure super heated steam then one of the soft solders in the higher end of the temperature range would be OK. Something like the 40/60 tin/lead that CuP do will melt between 180-230 degC.

Yes if soft soldering the joint should be tinned first, not needed if silver soldering

Edited By JasonB on 08/05/2019 13:24:09

GOSH !! I thought lead solder was banned ?

BobH

Lead solder is only banned from plumbing for potable water.

David

This makes it clear then :-

**LINK**

The driver for the move to lead free solder is the desire to eliminate lead from land fill where it contaminates surface water. Much of the consumer electronics ends up in landfill so commercial electronics is now produced using lead free solder. As to the word for word details of the legislation you can look this up for yourself. But that is the why. Leaded solders are still freely available.

regards Martin

Hi all.

Let's open the can of worms and disturb the hornets nest!

Lead bearing soft solder has been banned from potable water systems for years. No problem.

It has been banned from electronic products due to a perceived increase in the lead build up in the water table as these products find their way to landfill sites. No problem.

It has not been banned from sale to the professions eg plumber, metal sculptors. The key word is professional.

It has been banned from sale to the amateur and that includes the man in the street- Joe Public.

The fact that tin-lead solder is still readily available does not detract from that. It is simply testament to another fact - it is proving impossible to monitor and police.

If necessary, you can always create a letterhead describing yourself as a plumber or get a friend to get it for you who knows someone that uses it professionally!!!

You couldn't make it up!

It is not my place to go into more detail regarding conversations / discussions / instructions / warnings with and from Trading Standards and HSE..

Regards

Keith

PS If there are any readers who want to fight the above or challenge the ruling in the UK or Brussels, please send me an email. I will provide bank details for all financial contributions to the war chest. Shall we say a minimum sum of £10,000 per person! 500 contributors should set the ball rolling.

Let's not! There's a good chance everyone will be stung...

But there's a technical question Keith might be able to answer.

I think Jason may have recommended 60/40 solder for historical reasons. It's easier to use than either pure lead or pure tin because it's melting point is lower. I believe tin strengthens the joint but the weaker mix is commercially attractive because lead is cheaper than tin. It's good for electronic and tinplate joints and other general work where high strength isn't needed. As such 60-40's been widely available for donkeys years, whereas tin was once hard to get.

But is not modern electronic tin solder better than 60-40 for soldering John's small cylinder? I believe tin bonds to steel without problems, I think the joint is stronger than 60-40, and the melting point is certainly usefully higher.

Being a Silly Old Duffer myself, I'm all too aware I believe old ways are always best even when this is obviously wrong. Therefore I question everything. What's the truth about the pros and cons of high-tin solder versus 60-40 for this particular job?

Dave

Back to the original question. Silver solder or soft solder for cylinder fabrication. personally I would bo with the lowest melting point silver solder.

Brian

It's a bit more complex than that. The 60/40, or to be precise 63/37, mix used for electronic work is eutectic, ie, the freezing and melting points are the same. So the solder goes from liquid to solid almost instantaneously, which is good in preventing dry joints. In contrast some mixes used in plumbing had different freezing and melting points, so there was a range of temperatures where the solder was 'pasty' allowing for the joint to be wiped to leave a neat fillet.

Andrew

Not Guilty. I suggested 40/60 as it has a higher liquid point than 60/40 so better able to resist heat from steam, simples. That is why I also said use a soft solder that is towards the higher temp range.

As also said silver solder is the best option (and what I would use) but a beginner may find that more difficult to use, need to spend out on a torch to get the wattage and for something that may run of a simple boiler at 50-60psi will never see enough heat to weaken the joint.

Edited By JasonB on 09/05/2019 11:45:21

Not sure it'll make much difference? The 40/60 solder starts to go 'pasty' at about 180°C, at which point I suspect it will have very little strength. The 60/40 eutectic melts at 183°C. A better soft solder choice might be CupSol that melts at 305°C.

My traction engines will run at 170psi and if I recall correctly that's a wet steam temperature of about 190°C. So operating at lower pressures, and remembering that the cylinder will be at lower temperature than the steam, ordinary soft solders of whatever constitution should be fine.

Andrew

Thank you all for your replies and advice. The engine will run at a maximum of 60psi (ME upright boiler) and as I have some good quality "soft" solder I will try that. According to the spec melting point is 221C. Yes Jason I will be looking for a better torch at Doncaster Saturday.

Good job I won't run out of cadmium containing silver solder soon, someone in the Health and Safety department is bound to have a pop about that

There is nothing illegal about using cadmium or lead bearing solders.

To supply or "place on the market" is when the fun starts. A trading entity cannot provide samples.

Like you, I've got enough of both to meet my needs.

So, I do not have a problem.

The generals in Brussels who control the number of holes in the salt pot and outlawed refillable olive oil bottles, do not have a problem.

They do not have to try to enforce the law.

Keith

PS The war chest now stands at £0.00

I am fast running out of Cadmium bearing Silver Solder. I travel to the USA regularly -Cadmium bearing Silver Solder is still available there. So from the statement above, it would be legally OK to bring some back for my own use -for the information of anyone with delicate H & S sensibilities, I won't be inhaling whilst using it.

Apparently Bill Clinton does all his brazing like that.

N.

Purely off topic, Lead pipe is non grata for potable water, because it is a cumulative poison. (My grandparent never drank water other than via lead pipes, and they died in their 80s!) However, a vast amount of plumbing (if that's the correct word now ) is in copper pipe. And Copper is also a cumulative poison. My houses have always had copper pipes, so at nearly 81 there can't be much hope for me!

Howard

I saw mention of Cadmium in posts above.

In Australia I recently bought some Silver Solder rods with Cadmiuim, seems to be easily available in shops.

Did my first silver soldering and quite chuffed with results, however am aware that some people appear to be very wary of Cadmium whilst others are not so concerned.

Any good risk assessment worksheets associated with Cadmium bearing solders that you chaps can recommend ?

If I am in a well ventilated space and use the solder for less than 30 minutes a week doing very small occassional jobs ( ie tiny little wobblers and boilers less than 1 cubic inch of material being heated and soldered surfaces of less than 0.5 sq inches) - how do I calculate my exposure and associated risk ?

Bill

"......... - how do I calculate my exposure and associated risk ? "

VERY unreliably ! There are too many unknowns with respect to your actual exposure and translating that to the more important index of dose received. (dose received and exposure are not the same).
Risk = hazard x exposure
Plenty of data on the hazards (toxicity) of Cd once absorbed but without knowing your exposure, true determination of risk is not possible. Cd exposure in industry is normally assessed by area or personal monitoring. Actual dose received by bio-monitoring of workers.

But Cd is a relatively ubiquitous metal and we are exposed to it & its salts in vegetables, cereals and seafood.
So we're then in the sphere of risk assessment.
Given your exposure frequency in "well ventilated space" and the quantities of Ag solder employed, an assessment might be that your risk (of toxic effects) is minimal.