Model Railway Forum

I hope somebody on the Forum can help me here. As we discussed in an earlier thread ("Nickel Silver or Steel"), I have laid a bank of sidings with Peco Streamline steel track. Since these tracks go across dismantlable board joins I need to put in connecting cables betwen the boards, and that means soldering wires to the steel rails. I see the need to pre-tin but I'm having the devil's own job trying to make the solder "take". Is there an optimum size of soldering iron, working temperature (my soldering station goes to 400°C but the bit's a fine pointy thing, won't hold any real heat, which leaks away before you can say knife), type of flux etc? I'd be grateful for any advice I can get.

Cheers and many thanks,
Artur

Hi, i have a lot of steel track. It needs to be very clean, and i use flux. I changed my solder to make it easier. My iron is a cheapo from Aldi, but i keep it plugged in when soldering.

Artur you did not say what wattage your iron has, I would say a 40 - 50 Watt iron should do it. Remember whilst soldering heat is drawn out of the iron into the rail, a higher wattage iron is able to replace that heat quicker. Higher wattage does not mean higher temperature, although on a temperature adjustable iron adjusting the watts sets the temperature.

Richard

From your description, my feeling is the same as yours, the bit is loosing heat quickly, and not being replaced fast enough to maintain a working temperature. A lower temperature solder might help.

If you take a look at Rapid on line , the range of solders melt temperatures range from 180 to 240 Deg c

Can you change the bit in the iron to a large one that holds more heat ?

Some solder stations, the bit can be changed, or the iron itself to provide a range of soldering requirements. Depends on the temperature/ heat supply on how the temperature at the iron tip is monitored / supplied.

Just to add, the rail should have a good scrub with something like a fibreglass pencil, and a none corrosive flux used (Gaugemaster , other suppliers are available)

Rgds

Thank you for your feedback, gentlemen.

What I'm doing corresponds roughly to what you're advising (fibre glass brush, flux). I tried to attach a larger bit to my iron (42W, according to the label on the bottom) but the shank didn't fit; I suspect some kind of H & S conspiracy here. By raising the temperature of the iron to 370°C I achieved solid joints but they look very rough - OK for sidings parked full of rolling stock, I suppose (out on the main line the rails are nickel-silver). Maybe the iron is just not hot enough to compensate the heat loss into the steel rail. There's still quite a bit of work to do, so I'm going to up the temp to 400°C and hope that heats the job up enough to melt the solder properly before the sleepers disintegrate.

Cheers,
Artur

I do not know what the difference in heat conductivity is between nickel silver and steel is but the technique should be the same maybe steel needs a slightly longer application of heat?

For nickel silver rails I normally clean the rail surface with a fibre glass pencil and tin the rail surface with a thin coat of solder. I tin the end of the wire and simply hold the wire in place on the tinned rail and apply the iron until the two soldiers run together it is not necessary to have a blob of solder. I find using multi core solder has sufficient flux in it for the task but adding additional flux will not do any harm but only help.

You need to localise the heat to the area you are soldering and the actual time the iron is on the work should be for a count 1-2-3. Keeping it on longer runs the risk of heat spreading along the rail and melting sleepers. Most people I have observed having this problem is usually because of using an underpowered iron and having to hold it on long to get sufficient heat into the join. Those that take my advice and use a more powerful iron usually find their rail soldering improves.

I am surprised that a 42watt iron is not up to the job but I have never soldered steel rail to compare only steel cored wires and larger steel components using a gas torch. I do not think raising the temperature is the issue more the ability to deliver the heat is the problem and that is down to power. When soldering two components together you need to bring the temperature at the joint to the point where the heat in the material is sufficient to melt the solder only then will solder fuse to the surface. If you are lingering over the soldering two things are happening heat is dissipating along the rail and the flux is burning off which is what the smoke you see whilst soldering. Adding more flux slows the burn off but once the flux burns off you have problems. Fluxes used in electrical work by suspending oxides in the liquid keeping the heated area clear, once the flux burns off those oxides settle and then you have problems the soldered join looks rough and dull and usually fails if not immediately certainly over time.

I still think it is a power issue by cleaning and fluxing you are doing the right thing but getting a dull rough finish suggests flux is burning off due to extended heating. I hope you are not moving the soldering iron about as that does not help the heat transfer, remember your soldering iron is merely a heat source not a solder spreader and only needs to be held in place where the solder is needed.

Richard

Thank you for your feedback, Richard. Sorry to be a bit slow here. I am coming more and more to the realisation that what's needed for work that drains the heat (like steel rail) is a bit that's big enough to have heat in reserve. As I mentioned, the iron I have has a fine-pointed bit which apparently just cannot transfer enough heat to get the solder flowing properly. Even joining wires is a pain. I noticed another thread about soldering where an Antex iron is recommended and a Wellnyk soldering station as well. I'm going to have to shop around a bit and see what I can see.

Cheers,
Artur

P.S. My flux always smokes. Does that indicate faulty technique as well? I'm clearly doing something wrong.

Hi, i solder mine with 10 Euro iron bought from Lidl. It is my 3 rd one in 15 years. They work fine, and sleepers dont melt. I understand people buy expensive ones, thinking they must be better quality, and i am sure they are, but nip to Lidl or Aldi, buy one, and see how you get on. It could save you a lot of money,and give same result.

RSR Engineer wrote: ↑Tue Feb 18, 2020 11:03 pm

P.S. My flux always smokes. Does that indicate faulty technique as well? I'm clearly doing something wrong.

Hi Artur
I was not implying that smoking flux indicates bad technique, all fluxes smoke or evaporate off when heat is applied. I was just making the point you have a finite time to complete soldering and the longer you linger the more the flux burns off. Once the flux burns off any oxides suspended in it will settle on the join and form a barrier to the metal and solder fusing. Hence you can see why I advocate the power issue it’s all about getting the heat in there quick.

You might be right about the bit profile and a heavier bit with a wider tip can help the heat transfer. I have a cheap 40W iron with a number of tips and have used the pointed tip to solder to nickel silver rail without problems but can understand how that might not work on steel rail owing to different conductivity of the two metals. If you have wider tips try them before upgrading your iron.

Richard

I have put on another sight that my first job when I left school was as a sheet metal worker.
Back in those days all the metal we used was lead coated 20 and 22 gauge steel so every thing we made had to be soldered together. We used really heavy soldering irons. Wooden handles and solid copper tips so large you could file them into any shape you needed, they were stuck into a gas flame on your bench keeping them hot all the time and each time you used them you plunged them into a pot of liquid soldering flux to keep them clean. Keeping every thing clean was the secret of a good soldered joint we pulled the solder through a sheet of very fine sand paper before using it to keep it bright and shiny we also wire brushed over the lead coated steel to brighten it. So keep your solder clean, your material clean and your ion clean with plenty of flux and you should be able to make a decent joint.
When soldering wire always tin it first and also putting some solder on the item you are fixing it to first will also make a good joint.

Puddles