Non-ferrous metals are defined as those which have little or no iron in their composition. They include aluminum, brasses, bronzes, as well as the precious metals such as platinum, gold and silver. The non-ferrous metals are generally used in alloy form, being alloyed with elements common to the steels, such as nickel, manganese and silicon. Alloying two different non-ferrous metals to create a third is frequently done as well.

Due to their higher conductivity, heating in a gas forge rather than a coal forge provides a greater degree of control over the result. A medium heat rather than a welding heat provides more control as well.

The most commonly available alloy of aluminum is designated 6061-T6. The suffix refers to the level of initial heat treat, with T6 designating solution heat treating and artificial aging. This alloy is referred to as a wrought alloy and has a nominal composition of .6 Si, .28 Cu, 1.0 Mg, .20 Cr., remainder Aluminum and impurities, always including trace amounts of iron. This alloy is heat treatable.

Forging 6061-T6 requires considerable attention to the temperature. Forging begins at 750F and ends at 950F. As this is below the incandescent range and aluminum doesn't oxide in the same way as steel with temper colors, there is no color indicator during heating. Thus there are a number of methods to determine when the material is ready for forging.

A pine stick, such as a paint stirrer or door shim when dragged across the surface of 750F aluminum will leave a black scorch mark. A mark made on the aluminum with a black felt tip pen prior to heating will turn brown in the forge upon reaching approximately 750F. This method seems to have more variability than the pine stick method. Thirdly, there are commercially available "tempilsticks" with highly refined temperature ranges. The pine stick method yields the best results because it requires active diligence in monitoring the temperature. It is very easy to overheat the material, and it is immediately obvious upon beginning to hammer as the material crumbles under the first blow!

Aluminum, because of its unique structure, retains and conducts heat readily. As well, it has a low melting temperature (1220°F). This feature can cause overheating of the work as forging with power progresses. Thin sections can overheat, causing cracking and crumbling. Restraint should be used when working thin sections to ensure that the aluminum stays within the forging range. Gentle heating yields good results when doing scroll work, as aluminum can tend to bend unevenly if not allowed to come to temperature slowly. Again, patience and diligence will yield the best results.

Welding aluminum is best achieved with the shielded metal arc process (MIG or TIG). Clean the surfaces by abrasion or wire brushing immediately prior to welding. This is extremely important when welding aluminum. Designate a stainless wire brush specifically for this task. Use 100% argon shielding gas. AC TIG welding is generally preferred for manual welding of material up to 1/2" in thickness. Use a pure tungsten electrode. For DC TIG use a 2% thoriated tungsten electrode. For thick sections MIG welding provides much faster welding with deeper penetration. A spool gun makes it easier, although a short cablehose kept relatively straight (to prevent kinking the soft wire) also works adequately. Refer to a welding manual (see references) for complete information on welding practices.

Grinding aluminum is best done with zirconia (blue) discs or specially designated hard discs that reduce loading. Also, belt grease/lubricant in conjunction with reduced pressure prevents loading on the abrasives. For die grinding there is a line of special coarser burrs that don't load as much as double cut burrs. Sandblasting and wirebrushing finished works gives an attractive satin finish. The use of solvent dies in acrylic lacquer is another interesting way of finishing. Polished/brushed aluminum should be top coated with a clear acrylic lacquer to prevent surface oxidation.

Two types of bronze useful for forging are silicon bronze and aluminum bronze. Aluminum bronze C954 has a composition of 85 Cu, 4 Fe, 11 Al. It is, technically speaking, not a true bronze as it contains no tin but is referred to as a binary alloy. Stock for forging is available as continuous cast and hot rolled squares and flats, sold oversize. This material is rather rough looking and the surface has a pattern of very small fissures that disappear upon forging or which can be removed by rough grinding. It is recommended that stock be purchased oversize and forged under power to the desired nominal size. Alloy 614 is the sheet form of Al Bronze: 91 CU 7 AI. Its slightly different composition means that there may be a slight color variation between 954 and 614.

Forge aluminum bronze in the red to yellow orange range. It is very forgiving and overheated stock can be allowed to cool without it disrupting. Unlike most other copper based alloys, aluminum bronze is extremely stiff when cold and straightening pieces when cold is problematic. When worked in the temperature range the metal shows very little tendency to edge cracking when drawn out thin and during hot bending. It scrolls very smoothly.

Weld aluminum bronze with A MIG, using Ampcotrode 10 wire (.035) and 100% argon. Higher wire speeds (amperage) and lower voltage than used in welding steel is generally the case. Preheating is usually not necessary except for very thick sections (1.5" +). The wire is very stiff and can be run in a regular cable hose up to 15'. Joints should be vee'd wider than steel, to around 55-60 degrees. Thinner sections can also be TIG welded using 2% thoriated tungsten electrodes, DCEP and 100% argon.

Grinding can be accomplished with the same materials as used for steel. Aluminum bronze is hard enough that loading of abrasives is not a problem. Drilling and tapping requires sharp tools. A dull drill bit will not work on aluminum bronze. Cutting this hard material on a bandsaw requires a higher blade speed (270 fpm) and more

Aluminum bronze accepts patinas, although testing is a must. The polished material has a beautiful golden hue, more yellow than silicon bronze. Flame oxidizing is another useful finishing method.

Silicon bronze, C655, is available in cold rolled forms as barstock and sheetplate. It has a reddish hue due to the very high copper content (97 Cu, 3 Si). Working temperature range for forging is slightly lower than for aluminum bronze, generally red to bright orange. It will fall apart at too high temperatures. It exhibits excellent forging characteristics, with little cracking in thin sections and bends. Because it is available in plate as well as bar it is an ideal choice for the construction of sculptural forms. Cold bending/straightening is more forgiving than aluminum bronze, but care must be used to prevent cold cracking.

Welding is similar to aluminum bronze and an exact matching MIG wire is available. It will work in a standard cablehose. TIG welding (DCEP) with a 2% thoriated electrode is an excellent choice for sheet and plate up to 1/4". Welds flow beautifully. Vee thick joints to 45 degrees.

Because of its softer nature, silicon bronze grinds easily and quickly with standard abrasives and burrs without loading. It accepts patinas more easily than aluminum bronze, although it has more tendency to change as it ages due to oxidation. Therefore a clear acrylic lacquer topcoat is recommended.

Pure copper is a joy to forge. It has a very long working range, essentially from cold to yellow. Because of its malleability it is rare for copper to crack during forging or bending. When worked hot there is no need to anneal because there is no work hardening occurring. And when finish working thicker sections cold there is usually no need to anneal. For sheet, anneal by heating through to red, then quenching in cold water. For thin sections cold planishing to work harden effectively adds stiffness and strength.

Because of its softness, careful planning of the work sequence is necessary to prevent deformation of previously worked areas. Even when cold it is possible to easily bend 1" x 1 " sections, especially when working in the vise.

Copper can of course be soldered or brazed, but these methods lack the strength necessary for joining larger sculptural shapes. Copper can be MIG welded using pure copper wire with a special gas mix tradenamed Blue Shield #5. Preheating is absolutely essential as the copper conducts the heat so quickly and has a high melting temperature (1980F).

For tapping threads into copper a thread forming tap rather than cutting tap works better. Copper can be quite "gummy” due to its softness when machining. When sawing use higher blade speeds (270 fpm) with a coarse blade.

Copper is very reactive and receives patinas wonderfully, both hot and cold.

Welding and grinding non-ferrous metals produce unique pollutants which may have deleterious effects on your body's health. The use of common sense, ventilation and the appropriate safety gear including respirators and safety glasses is essential.

Contact: Brian F. Russell 10385 Long Rd. Arlington, TN 38002 (P) 901-867-7300 (F) 901-867-7843

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