Soldering Solder Soldering

[garethevans1986]

Hi all

 

I'm currently trying to build 7mm brass kits aattempting to solder using flux but I keep finding that when I try and "drag" the solder along the line of flux that it ends up in a blob of solder.

 

Soldering Iron - I'm using a BlackJack BK 2050+ 70W Soldering Station with the biggest tip I've got at 400C.

Flux - Powerflow flux (Yellow tub from B&Q)

Solder - I've tried a few, some are better than others but mostly "lead free solder", Ag 4%, Sn 95.5% and Cu 0.5%, 1mm from Maplin.

 

The kit I'm trying to build is the GWR Loriet M Low Machine Wagon by Connoisseur Models which also happens to be a skill builders kit.

 

Any ideas? I've tried practising using offcuts of brass and it sort of works on them.

 

Thanks

Gareth

[Ralph R]

Get rid of the solder and get some 145 solder which contains lead. That will flow very nicely with what you have for the job. Eileens or most model shops will sell solder for kits.

[Guest baldrick25]

Lead-free solder is your problem... Try 60/40 tin lead . Its a well documented problem- try a search of the forum for many previous threads.

[Kempenfelt]

Possibly a silly response but make sure you're not soldering onto anything that can act as a heat sink, wood, paxolin or glass are all preferable surfaces.

 

If you do change the solder try and get a high silver content, the 2% stuff is usually pretty good!

 

The rest of your setup sounds pretty good! Some tip tinner and solderwick is also useful to have to hand!

 

Finally ensure the suface of the etch is clean, ideally polish up the etch with a fiberglass brush prior to soldering. Equally scrub the joint clean to get rid of the flux residue once finished.

 

It may be worth trying on a small off cut of etch just to make sure the iron is working corrrectly. The smaller the etch that you're trying heat up the easier it should be to solder.

 

Good luck!

 

Paul

[corax67]

The B&Q flux is not helping really as it is a plumbers flux paste and as such designed to work on copper joints with a blowtorch rather than a soldering iron.

 

 

 

You will be much better served by purchasing a liquid acid flux designed for brass such as Carr's Yellow or Green flux:

 

 

http://www.nairnshire-modelling-supplies.co.uk/solder-and-flux-flux-c-81_126.html?zenid=82179c3c53bfda58aeaccfe466abbf44

 

 

You also need to spend time preparing the brass parts and ensuring the surfaces to be soldered are really clean, a fibreglass scratch brush is perfect for this job, for example:

 

http://www.osbornsmodels.com/expo-705-10-4mm-propelling-fibreglass-scratch-brush-7991-p.asp

 

 

At 70W your iron is more than powerful enough for kit building but you possibly don't need the largest tip you have, rather one with a shape that enables you to effectively get into the joint to apply heat. The tip also needs to be clean and lightly tinned before you make the joint.

 

 

A handy guide to soldering is here at:

 

http://www.doubleogauge.com/journal/soldering.PDF

 

 

Hope this helps.

[Kenton]

Have to agree with the above.

Dump the solder AND the flux they are not for kit building - they may work for some but are not ideal.

 

Also watch out for cleanliness. If the solder is good and the flux liquid yet is still not flowing along a join the usual cause is poorly cleaned brass. If the brass is mechanically and chemically clean the solder will just wizz along wherever there is heat (and in a 70W iron there is far more than enough heat - assuming it is also clean and tinned).

 

If everything is clean then even Powerflux works and even lead free solder.

Some brass used in some kits leaves a lot to be desired and the time it sits around in store tarnishes it.

[Lady_Ava_Hay]

The solder and possibly the flux are destroying the iron's tip and its heat transfer capability. That sort of power in an iron will need a fairly high melt solder. i would use 176 but make sure it has lead in it. If you really want to use resin cored solder you will need to hunt up a tube of Ersin Multicore. Possibly not right for 7mm brass kits but I have used it on smaller brass components. I find the resin style flux is not flowing enough for a good long soldered joint.

[bertiedog]

I would never recommend Powerflux, or any "grease" flux for models, they are, as said, for plumbers and are meant to remover tarnish and then keep air off the clean surface, neutralise themselves and set with the grease still there to help protect the joint.

 

The normal precision soldering flux is acid, with a zinc content dissolved in it, it acts to remove oxide and tarnish, boiling away, and as it boils the solder will run along the hot area forming an alloy in the joint.

 

It remains acid and should be washed away, which it does easily, unlike powerflux types. The classic brand is Bakers flux, still made, this is a killed spirit with zinc phosphate type, as are Carr's etc in various versions, which add buffers etc to control the acid, or used different types of acid and additives, like phosphoric acid.

 

The whole process of soldering is often misunderstood, the flux does not aid the solder to flow or adhere to the brass or other metal it is melted on, the action is Eutectic, the heat will cause the metal to alloy together,...if all else was perfect....but the tarnish and other oxides ruin the eutectic approach, and the flux is there to ensure a clean surface, no more than that.

 

Tallow and grease works with clean metal, as it heats it simply stays there as a protective shield, not allowing the air to oxidise the metal surfaces, with a spot of acid added that is the action of Powerflux. Vaseline and pure meat dripping, (tallow), work in the same way.

 

So the problem you have is the solder, the 148 or 60/40 electrical with lead types are better, and still both legal and still made. But the other issue is the metal, etchings often are sprayed with silicon oil etc., to keep them clean, and this interferes with soldering,

 

Some brass used for etchings may be the wrong grade, but these days most of the etched kit output comes from only a handful of companies, and mistakes few and far between.

 

The first thing to do with all etch kits is to take each sheet and wash it with hot water and detergent, and then to scrub them with vim cleaning powder and a tooth brush, till it all has a dull but clean surface, it will then solder brilliantly. Do not clean with Vim liquid or any cleaner that has additives like lanolin, the old fashioned scouring powder is the best.

 

Clean the brass!!! it will pay, if it still will not solder it must be the solder, get Frys or use Carr's, then there is no reason it will not flow.

• Couple of tips, use glass paper, or production ali oxide paper to clean brass, not emery cloth, when cleaning brass.

• Do not put Bakers or most acid flux near steel tools, it makes them rust, phosphoric based fluxes such as Carrs do not, It's rust proofer).

You may like to try the Citric acid based fluxes, they work fine and wash away instantly. You can make this at home if you want, a simple saturated solution will do, plus a drop of BPC grade detergent, but I use any pure detergent. like Teepol. This flux works on whitemetal very well., as does dilute Baker's, the best flux for whitemetal.

[garethevans1986]

Thanks for all the replies.

 

I've got some liquid flux somewhere which I bought the start of last year in the Gresford show.

 

I'll also get some decent solder and see how things go from there.

 

Thanks

Gareth

[burgundy]

I have been struggling to teach myself to solder and have been following this and other threads in the hope that they will shed some light on the dark arts.

Following up a comment in one of the discussions, I carried out a simple experiment this morning to understand a little more about the iron that I am using. It is a variable temperature soldering station, that was bought from Maplins about 12 months ago for £9-99. The dial to vary the temperature has a knob that rotates from about 7 o'clock in the off position, clockwise, to about 5 o'clock at the maximum, but it is not calibrated to show the temperature that is being produced. For the last 12 months, I have been simply turning it about two thirds of the way around (i.e. about 2 o'clock) assuming that that would be about right for lead based solder. This morning's results came as a bit of a surprise. Low melt (70 degree) melts on the absolute lowest setting - no great surprise there. 145 solder melts at about 9 o'clock and lead free solder (from a d-i-y store) melts somewhere between 10 and 11 o'clock. In other words, the iron has been working at a much hotter temperature than it needed, which may explain why it was so difficult to load the tip with a blob of solder. With luck, this will also reduce the incidence of singed fingers................

Eric

[craigwelsh]

It is a variable temperature soldering station, that was bought from Maplins about 12 months ago for £9-99. The dial to vary the temperature has a knob that rotates

It wont be variable temperature, its variable power which when set lower will give a lower temperature. Proper temperature controlled irons keep the tip at a set temperature via a feedback circuit and by varying the power. Its a small point but worth noting as these cheaper irons wont boost power to try to maintain temperature and are generally low power anyway and tend to drop off quickly when applied to large work.

 

I use one purely for white metal though and they are great for that at the sort of setting you have now discovered.

[Kenton]

Sorry, but soldering is not about just melting solder and carrying "blobs" around on the tip.

 

I actually think "temperature" controlled soldering stations are next to useless. I have never found the need for one and can happily use a non-temperature controlled iron on white metal. Perhaps that is because I was taught to solder with a normal iron and have never found the need to do anything different.

 

The Maplin solder stations are cheap for a reason and are being sold by a company that promotes itself as an audio and electronics supplier. So you can be pretty certain that what Maplins know about (or care about) brass/metal/w/m soldering is zilch.

[bertiedog]

which may explain why it was so difficult to load the tip with a blob of solder. With luck, this will also reduce the incidence of singed fingers................

Eric

And that quote might explain a lot to yourself and others with soldering problems, never apply solder to the work with the iron, it is purely the heat source. It is "tinned", a skin of solder is added to aid the fast transfer of heat to the work, helped by the flux.

 

The solder is applied to the already hot work is the golden rule, or a pellet of solder already there melts, or solder paint already there melts.

 

There are exceptions, in whitemetal low temp soldering the iron can transport a "blob" to the work, and filling in gaps on a brass kit might occasionally need a "loaded" tip.

 

There's a good reason for this, solder overheats on the tip of the iron, and deterioration sets in ....in seconds.

 

This only really affects electronic precision soldering, but if solder is transfered with an iron on models it leads to adding far too much solder to the joint, the blob may not be big enough, and the temptation is to add more from the solder wire, and the joint gets flooded.

 

I mentioned this before on other postings, but the key is that the soldering process is "eutectic", the metals we use have a natural affinity to join and form an alloy at the point they touch, it purely needs heat and the protective cleaning flux to encourage the process.

 

Hope this helps,

Stephen.