Solder for steam pipes

I am looing for advice on soldering locomotive copper steam pipes and or finding a suitable solder. Steam at 100psi is at about 170'C. Solder weakens about 50'C below its melting point. So solder with a melting point well above 220'C is required which means typical soft solders leave no safety margin. I therefore intend to use 93.5%Pb, 5%Sn, 1.5%Ag melting at 296'C. I need to use a gas flame to do the heating. So far so good. The problem though is that all 296'C soder I can find is rosin cored and if the flame touches it the rosin burns so fiercly that the heat from the rosin flame melts the solder wire beck up to 10mm and the burnt rosin contaminates the joint. Can anyone advise where to get 296'C solder without flamable flux? Or do I need to use a soldering iron? Or do I have to silver solder? Or any other advice would be appreciated.

Try a search for Comsol. Most of the Model Engineering suppliers in the UK stock it as well as CuP alloys who stock their own version in both cored and solid.

HTH,

Rod

Hi Eckart i always silver solder steam joints on fittings and pipe work. I have a very small gas torch and use low melting point silver solder and flux. It is very quick and I don't have worry about joint failure.

David

Plus one for that!. I would not feel too safe around soft soldered copper pipes carrying steam at 170 centigrade!

I find silver soldering joints easier and quicker than using soft solder, as a bonus.

Andrew

+1 for the advice to Silver Solder!

Steam at 170C will do a lot of damage when it hits you, should a joint fail. Possibly remove skin!, as well as burning.

It takes 536 calories to change 1 grm of water at 100 C into steam at that temperature. That heat will return when the steam condenses on you.

And you are talking not only Latent Heat of vapourisation, but another 120 C above your temperature, so 120 calories per grm of steam, as well!

That is an awfully dangerous amount of energy.

Don't chance it!

Howard

Hi all. Thank you for your replies. Some of you missed the fact that I am not talking of normal soft solder but high temperature soft solder. But I did get some useful information. CupAlloys does sell what I want but I missed that because I was looking for a reel and they only sell it per meter. Comsol and Johnson Mathey make it but I have not yet found a seller for the unfluxed stuff. On balance I tend to go with the advice of silver soldering.

For those who are wondering - I am making a Garratt locomotive so there is quite a lot of pipework.

I have a small Proxxon Microflame Burner Hand Torch and find it perfect for pipe silver soldering pipes etc so easy to use with piezo ignition and not expensive.

David

I did note that you were talking about high temperature soft solder. The advice is still the same, don't do it, use silver solder instead.

Andrew.

Hi Eckart, CuP can supply 500gr reels both flux cored and solid. We call it CuPSol but it is only a rose by another name. Please call for a price. However, I must say I agree with the majority on here, silver solder would be my recommended method.

I use 45% silver solder for joining steam fittings and fabricating valves but it is expensive.

15% Silver alloy rods are normally used for plumbing applications like copper pipe, hot water tanks, plumbing fittings, etc. Excellent for gap-filling where close fit-up does not exist, and where thermal expansion and service vibration are involved. Melting Range: 645-800°C.

45% silver alloy rod for general purpose, high-strength joining of all ferrous and non ferrous metals, including steel, stainless-steel, copper, brass, nickel, etc. High fluidity & rapid capillary flow, good choice where parts have a close fit. . Melting Range: 640-680°C. (used for making copper boilers)