Ever wonder about Non-Ferrous metals?
written by Greig Fors
Today we are tackling alloys, fluxes, and brazing/solders
Non-Ferrous is any metal that isn’t iron. I will be talking about brass, nickel silver (cupro-nickel) and copper. Other metals like aluminum and bronze may or may not be brought up later. There is so much to cover, so this is going to be an introductory blog in two parts, just to cover the basics.
Metal is metal is metal…All metals share some of the same properties, there is ductility, malleability, conductivity, luster to name a few. Some conduct heat or electricity better or worse than other metals. There are only two non-white metals, gold and copper. Brass is any number of combinations of copper and zinc, while bronze is any number of combinations of copper and tin. There are hundreds of different alloys of each. Specifically, brass, you will probably use one of the two most common alloys that are currently produced: navy brass (also known as yellow brass or common brass) which is the most common form of sheet brass. The other is free machining brass (or navy brass with a smidge of lead in it) that is found in rod or bar stock and in many different shapes. The real downside to Free Machining Brass is that it will crack if it is bent more that 70-80 degrees. Annealing doesn’t seem to help; however, it will bend rather well at temps around 1000°F. Navy Brass in various shapes can be found, but it will be older stock and most likely at a scrap yard. Alloys will change over time as to their availability because of manufacturing needs.
Brass wire is usually navy brass and brazing rod is a brass (Cu-Zn) alloy that has trace elements for good flow characteristics and strength. There are a number of other alloys for wire and commercial braze rod that will not be discussed at this point.
This seems like a good point to also discuss fluxes. Soft solder fluxes are generally two types, those being: acid fluxes (usually zinc chloride or muriatic acid) and rosin fluxes. The old time flux was Sal ammoniac which can possibly still be found, but went out of common use forty or fifty years ago. Soldering is the term for melting a filler metal into a joint at under 842°F. These fluxes will also burn at temps above 600° F or so. The other fluxes are those for over 842°. The most common is borax. It has been used for centuries. A cheap source for borax is a box of “Twenty Mule Team” pure borax laundry soap. When melted, it forms a glass-like coating over the metal to be brazed. The other type of brazing flux is hydrofluoric acid. This flux “eats” away scale during the heating process while also covering the metal, preventing re-oxidation. There are many brands of fluxes and they come in liquid, paste or powder. There is a high temp black flux that is great for those hard to solder pieces that require an IT braze or a large mass that requires a lengthy heat time. All of these fluxes are either borax or hydrofluoric acid or some combination of both. For most of my work, I prefer to use a commercial borax/hydrofluoric acid paste flux (usually Harris brand) or their black high temp flux. The one main drawback from using the hydrofluoric acid flux is that it goes everywhere, so you must be diligent in your soldering technique, and on silver, it will eat away the silver, leaving a copper fire scale that is rather tough to get rid of.
I guess that solders/brazing filler are the next on the list. As mentioned earlier, solders are a metal filler whose flow points are under 842º and brazes are over that temperature. There are many, many alloys of solder. Flow points start at around 120ºF and go up to around 650ºF. Tix ® is one of the commonly sold low temp. solders and is used in repairing pewter and paste/costume jewelry. There are a number of others that have similar flow temperatures and bonding characteristics. The next batches of solders are the most commonly used and have flow points of between 400º and 630º. They fall into the tin/lead, tin/antimony, tin/bismuth and tin/silver categories. While lead and antimony solders are useful in industrial applications, those metals are toxic and should be avoided, along with cadmium solders. Bismuth is generally OK. When using the low temp. solders like Tix, the MSDS (Material Safety Data Sheet) is a must read as it will tell you what is in your solder and will also advise you on toxicity. If you don’t get it with the product, it is always posted online. The solder that I generally use for soldering is the 95-5 tin/silver. It is non-toxic and has a generally higher tensile strength and better flow characteristics because of the silver and a comparatively low flow temp of around 430º. One of the great advantages of this 95-5 solder is that if you decide that you need to braze the piece, unlike the other solder alloys, you don’t need to remove it before brazing. Just make sure that all the soft solder flux is removed. Simply flux and braze with silver braze and the tin/silver alloy will re-alloy itself with the silver braze.
Brazes are the filler metal for over 842ºF. I will not get into brazes that do not relate to brass working, like gold and platinum. While they can be used, it is not cost efficient to use them on brass or copper. I will also not use the standard brass braze rods that are sold commercially, as their flow point is almost identical to the brass we work with, and the risk of melting the piece is very great.
There are the silver brazes like low, medium and hard, plus Extra low and IT. These are all silver/copper/zinc alloys. The melt and flow temps. are approximate and go as follows: Extra Easy-1125ºM(melt) & 1145ºF(flow), Easy-1235ºM & 1325ºF, Medium-1265ºM & 1390ºF, Hard-1365º & 1450ºF and IT-1330º & 1490ºF. These temperatures are gathered from a couple of different sources and since different manufacturers may alloy their brazes a little differently than other manufacturers, I can say that these temps. are average. Silver brazes are used by manufacturers outside of the jewelry field so the next place we can purchase silver braze is a welding supply. There, silver braze is sold by percentage of silver, so you won’t see easy, medium or hard, but rather, 36%silver or 50% silver, etc. These are normally sold in one ounce coils and are about a sixteenth of an inch in diameter (16ga). The last types of brazes I will cover are the copper phosphorous alloys. These are used in plumbing and refrigeration/air conditioning. They come in sticks that are either an eighth of an inch square or an eighth by a sixteenth and in either 18 or 36 inch lengths. These are called copper-phos, or if they contain silver (to give a better flow rate), are called Sil-phos. These are interesting as they do not require a flux when used on copper, although when used on brass, do require a flux. The will not work on ferrous metals. Also, left untouched, or if pickled it is a copper color, but if polished, becomes silver. These last brazes, while great for industrial brazing, do not work well for anything that needs a fine touch. They are kind of globby. There are two reasons that I bring them up: 1- they are not well known by artists, if at all. 2- They can be used quite well to build up metal and can be used for sculpting. I have a line of “Mushroom Bells” where I take a round dome and make a drip formed stem and “roots”. For the ringer, I take a piece of standard eighth inch brass rod and melt (with flux) a drop of the copper phos and melt it on the end. Then I reheat the glob and let it begin to drip and harden. When upright, it looks like a very small mushroom on a stick.
Solders are used to join parts that either cannot take high heat or don’t need to be as strong as the base metals. If you are connecting two flat pieces together face to face, then solder may be perfectly adequate for the job, however, when strength and sometimes color is an issue, then braze is very much superior. It is harder and has a much higher tensile strength than solder, plus it takes a better polish and will blend in better as far as color, although both solder and braze will stand out when the piece tarnishes.
These are the basics which you will need as far as brass, solders, brazes and fluxes. The next chapter will be constructing with brass. Copper and nickel silver will also be discussed in the next chapter as the soldering and brazing techniques are pretty much the same.
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Growing up, my mother was a single parent and we lived with my grandparents. My grandfather was the chief engineer for a large commercial laundry in San Francisco that took up a city block and was three stories high. I would go and visit, usually with my grandmother, and to me; it was like going to Disneyland. There were all these huge washing machines and boilers. I had a bottle of mercury to play with and then there was the machine shop. The shop had all these wonderful tools; there was a lathe, drill press, grinders and an arc welder. It was the old style shop that was run by a donkey motor that had a wide leather belt that went to a series of pulleys on the ceiling. From each pulley, there were other leather belts that went to each of the machines. Each of the machines had an idler pulley that simply rotated freely and there was a leaver to engage that pulley to make the machine run. When the donkey motor was turned on, there was this wonderful cacophony of sounds: the leather belts slapping, the whine of the pulleys and the clatter of the machines. Those sounds drowned out the rest of the world for me and were the beginning of a love affair that would last me the rest of my life.