Soldering White Metal

[LinnS]

     After I posted pictures of a Ford rail truck kit, in "The Gallery" section of this forum, along with a comment that it was my first experience with white metal, and that soldering white metal was easy, it was suggested that it might be of some use to start a thread on the subject.  This is the beginning.
     I recommend reading a very informative soft bound book titled 'Whitemetal Locos, A Kitbuilder's Guide', published by the British firm Wild Swan Publications.  I purchased a copy from International Hobbies, which I found on the internet.  There are probably other sources. 
     Seventy degree centigrade solder, which melts at 158 degrees Fahrenheit, is the traditional solder recommended for soldering white metal.  It usually flows at less than half of the melting temperatures of the white metals used in kits.
      On YouTube, I recently saw a demonstration of how to solder a white metal loco kit using a mini-torch. I had never seen or heard of this method, which looks useful.  However, I would think that attaching details parts, either brass or white metal, or soldering thin white metal parts together with a flame would be more difficult than with a soldering station, only because a soldering station provides a more localized controllable heat. 
     To avoid melting white metal while soldering with a soldering station, it is convenient to know its melting temperature, which may vary among manufactures.  For example, the melting temperature of the white metal in the Ford truck kit was about 360 degrees Fahrenheit, and for the West Side Lumber Company Plymouth loco kit was about 435 degrees.  Pictures of the Plymouth kit are also in "The Gallery" section.  If you build either of these kits, I recommend testing for their melting temperatures since the manufacturers might change the alloys.
     I test for melting temperatures using a soldering station usually with a 1/8 inch wide chisel tip, but a smaller tip may be used for small parts.  I start with a low temperature, about 300 degrees Fahrenheit, and raise it in 3 to 5 degree increments until a test piece of metal just begins to melt when the hot tip is rubbed on it.  The safest way to test is to use a piece of scrap.  In the absence of scrap, I test on the back side of the thickest part in the kit, where a little smearing of the metal will not show.  The idea is to sneak up on the melting temperature.   
     I also use the sneak up method to find the safest soldering temperature.  I might initially set the tip temperature at 325 degrees Fahrenheit, or less, if the metal's melting temperature is 360 degrees.  The initial temperature depends on the heat sink effect caused by the size of the metal being soldered.  The more massive the parts the higher the initial temperature.
     Another thought on the flame method is that since the melting temperature of the white metal is unknown and does not have to be known, the flame must be moved quickly on and off the base metal, over the area where chunks of solder have been placed, until the solder melts. 
     An advantage I see with mini-torches is that they cost less than electric soldering equipment.  But, a soldering station having a range of about zero to 840 degrees Fahrenheit will do about 90% of the jobs needed in the model railroad and probably other hobbies.  I build in quarter inch scale and have found that other soldering jobs frequently require the kind of heat that a standard sized propane or Mapp gas torch generates.  Those torches are safe to use for soldering metals that melt at high temperatures, like brass and steel, even when the metal has to brought to a red color.  But, they can quickly turn white metal into a puddle.
     This should get you started.  After that it is all practice.  Let me know if this is useful, and let us know your experiences.

Linn

[Mr Potato Head]

I had never soldered white metal before and I had a lot of white metal kits that I just didn't want to super glue or epoxy, so when I was at O scale west a few years ago I met the guy from International Hobbies and he sold me Carr's "Yellow Flux" for low temperature metal and it's a dream to work with, that along with their low met solder.
I use a resistance soldering unit and you only need a few watts for a perfect solder joint, the flux is the key, so even though I would never use a torch, the flux and solder make it really easy to weld white metal to any solder-able metal
try it, it works
MPH

[lab-dad]

Thanks Linn!
I have several different soldering tools but none I can adjust, need to look into that!
I will have to get the supplies and give this a try.

-Marty

[Chuck Doan]

Thanks Linn! Good info, I would never have thought of soldering soft metal.

[LinnS]

MPH 

Thanks for the tip on resistance soldering.  I'll have to try it.

For those wanting to learn to solder white metal, a convenient source of material to practice with may already be on your work bench, 63/37 solid wire solder.  It is eutectic at 361 degrees Fahrenheit, that is, it is liquid and solid at 361 degrees.  One-sixteenth wire is suitable although thinner may be used.  You will also need Carr's yellow acid flux, 70 degree centigrade solder, and a few small pieces of thin sheet brass.  Thicknesses of .015 to .020 inches are useful, since those sizes are usually used in kits, at least in On3 kits.  A small low cost sable artist's brush works well for applying acid, and will last a long time if cleaned with running water.   

White metal can be soldered directly to itself with 70 degree solder.  But, brass must be pretinned with a higher melting leaded solder, such as 63/37, 50/50, etc., before applying 70 degree solder.  This is because 70 degree solder will not adhere to brass but will adhere to leaded solders.  Seventy degree solder also may adversely affect brass when in direct contact with it.

Thick test pieces can be made by folding the 63/37 wire into large blocks and hammering or just pushing them into shape. A thin test piece can be as simple as a strand of the solder.  Use a lot of flux, 70 degree solder seems to flow best when a lot is present.  The same techniques used for soldering brass may be used with white metal, that is, solder may be transferred off the end of an iron, or put on the parts to be soldered, flux applied, and then the iron touched to the solder.  The only difference is that less heat is needed.

If white metal is clean, flux alone may be enough to make a good solder joint.  I prefer cleaning every kind of metal I solder using some kind of abrasive.  White metal is easy to scrape clean with, for example, fiber glass brushes,  hobby knives, chisels, and abrasive papers.

This is something that I haven't seen much about in hobby articles.  All molten metals and fluxes emit unhealthy fumes.  Fluxes for example frequently contain acids or chlorides.  The warnings seen on product labels should be heeded, even if they are not always completely explained.  For example, years ago, one manufacturer of commonly used paints, published a description of what it meant by "adequate ventilation."  It was defined as having a 40 mile per hour wind at your back.  When I read that, I considered that I could dispense with a spray gun and just throw an open can of paint into the air.  That isn't practical, but what is is at least working near an open window, or using an organic or acid respirator, or a fume extractor.  I use a small portable Xytrnoic Fume Extractor, Model 426DLX.  If placed within a few inches of fumes it makes soldering a safer and much more pleasant experience.  If you get one, or something like it, remember to replace the filter from time to time.  I also recommend making a flux jar holder out of wood or plastic.  It should have a large base, support the jar almost to it's top, and not easily slide on your work surface.  This is a little off the subject, but silver brazing in the 1200 to 1300 degree Fahrenheit range requires a chloride flux.  For that I prefer working near an open garage door.

Linn





   

[davidb]

C&L in the UK now have 100^oC solder which will solder white metal directly to brass without the need to tin the brass. 

I have used resistance soldering to solder brass to white metal, tinning the brass with 100^o first.  You need a very low setting on the RSU and keep the carbon probe away from the white metal, letting the heat flow through the brass to melt the solder then promptly taking your foot off the switch!  It is best to practice on some scrap first.

I have soldered white metal for years but it was not until I got a temperature controlled iron that it really became easy and reliable.  I set the iron to 180^oC, use 70^oC (low melt) solder and Carr's yellow label flux.  

A rule of thumb setting for the iron was suggested to me some time ago and I have found it invaluable.  It is: take the melting point of the solder, double it and add about 25-30^oC.  Hence for low melt solder this comes to about 170^oC but with experience, you can adjust this and have a higher setting (and larger bit) if you have a lot of metal to heat and I often set my iron to 200^oC.

As an aside, I have found this very useful site for making metric / imperial conversions.

70^oC is 158^oF
100^oC is 212^oF
180^oC is 356^oF
200^oC is 392^oF

[Mr Potato Head]

here is the states they make you take the SAT to go to college the formula that you must remember is:

F to C Deduct 32 then multiply by 5 then divide by 9
C to F Multiply by 9 divide by 5 and add 32

now you know why I went to a state college

Like I said before I use resistance to solder an I start with the lowest wattage and then go up till I find the correct setting and then 2 seconds and viola! done deal, that and Carr's yellow low melt flux and their low melt solder I think its 170 degrees
MPH

[Bexley]

It's a little-known feature, but Google does unit conversions. Just type in "45 f to c." Or "20.4m to feet." It's actually a really comprehensive converter and calculator. It can even use the Potrzebie system of measurement.