Brass Technical Information

Brass is the best material from which to manufacture many components because of its unique combinations of properties. For example, good strength and ductility are combined with excellent corrosion resistance and superb machinability. Brasses set the standard by which the machinability of other materials is judged and are also available in a very wide variety of product forms and sizes to allow minimum machining to finished dimensions. Brass's availability in near net shapes can result in significant production cost savings.

As rod or bar, brasses are readily available from manufacturers and metal distributors. For longer runs, it is frequently worth considering the purchase of special sizes or extruded shapes designed to minimize machining costs. Brass rod manufacturers are able to produce a very wide variety of shapes and sizes of product—commonly called "shapes" or "profiles"—with minimum order quantities that are very low compared with many other materials. Custom-shaped profile dies are not very expensive, and many styles can be produced and be ready for use within a few days.

Die costs for special extrusions are especially inexpensive when spread over a long production run, particularly if they do away with machining or assembly operations. Hollow extrusions, for example, can save excessive boring operations. As in the case of extrusions, die costs for hot forgings are much lower than those for die casting or injection molding techniques used with aluminum, zinc alloys or plastics. For special shapes, hot stampings can provide a very economic feedstock. Manufacturers welcome discussions regarding optimum alloy, sizes and tolerances at an early stage in the design of components. Brasses, having various combinations of strength and ductility, corrosion resistance, machinability, conductivity and many other attributes are very widely used in the manufacture of components and finished goods. Alternative materials can be considered but it must be remembered that the main criteria to be assessed are those that effect the overall lifetime cost-effectiveness rather than first cost or raw material cost.

The off-the-shelf price of brass may sometimes be higher than some alternatives, especially leaded steels, but the raw materials cost is only part of the overall cost picture. The higher production rate that brass allows, the availability of brasses in precise near net shapes such as extrusions, hot stampings and die castings, plus the considerable value of recycled scrap and turnings often results in items made from brass costing less than those in other apparently lower cost materials. Brasses also frequently offer better and longer service performance, avoiding consequential service and guarantee claims.

Strength
In the softened or annealed condition, the brasses are ductile and strong but when hardened by cold working processes such as rolling or drawing, their strength increases markedly. Strong, stiff structures can be assembled from extruded-and-drawn sections. Bars and rolled sheet and plate can be fabricated into containers and other items of equipment which work under pressure. The strength of brasses is substantially retained at temperatures up to around 200ºC (3900F) and reduces by only about 30% at 300ºC (5700F), which compares favorably with many alternative materials, and easily exceeds the properties of plastics. The brasses are very suitable for use at cryogenic temperatures since the properties, especially strength and toughness, are retained or slightly improved under these conditions.

For applications demanding higher strengths, the "high strength brasses" are available. These contain additional alloying elements such as manganese, which further improve the properties. Some high strength brasses attain strengths that are comparable with steels.

Ductility and Formability
Brasses with a copper content greater than 63% can be extensively deformed at room temperature, and are widely used for the manufacture of complex components by pressing, deep drawing, spinning and other cold forming processes. If the copper content is below 63% and no other alloying elements are present, the room temperature ductility is reduced, but such alloys can be extensively hot worked by rolling, extrusion, forging and stamping. Strength, ductility and formability are retained at low temperatures, making the alloys ideal for cryogenic applications. Alpha brasses, i.e., those containing more than 63% copper have excellent cold formability and can easily be drawn into deeply recessed components such as the automotive radiator tank shown here.

The ability of free-cutting brass to permit the rapid clearing of machining chips makes it possible to create deep blind holes and recesses containing complex profiles. The hose fitting shown here was formerly made from several deep-drawn steel components, welded together. Making the part from alloy C36000 allowed the fitting to be made in one piece, thereby reducing manufacturing costs. Brass also eliminated electroplating, otherwise necessary for steel, and resulted in a product with naturally high corrosion resistance.

Machinability—the standard by which others are judged
While all brasses are intrinsically easy to machine, the addition of small amounts of lead to brasses further improves this property and the well-known "free cutting brass" (UNS Alloy C36000) is universally accepted as setting the standard by which other materials are judged when machinability is being assessed. Higher machining speeds and lower rates of tool wear mean that overall production costs are minimized, tolerances are held during long production runs and surface finish is excellent

Machinability—the standard by which others are judged
While all brasses are intrinsically easy to machine, the addition of small amounts of lead to brasses further improves this property and the well-known "free cutting brass" (UNS Alloy C36000) is universally accepted as setting the standard by which other materials are judged when machinability is being assessed. Higher machining speeds and lower rates of tool wear mean that overall production costs are minimized, tolerances are held during long production runs and surface finish is excellent

Corrosion Resistance
Brasses have excellent resistance to corrosion that makes them a natural, economic first choice for many applications. Atmospheric exposure of the brasses results in the development of a superficial tarnish film. Outdoor exposure will ultimately result in the formation of a thin protective green "patina" which is frequently seen as a visually attractive feature in buildings, but the brass will remain essentially unaffected for an unlimited period of time, i.e. it will not rust away like iron and steel. Seawater can be handled successfully providing the correct alloy is chosen, and there is a long history of the use of brass tube and tube fittings, valves, etc. in domestic plumbing, central heating, seawater lines, steam condensers and desalination equipment. High strength brasses containing manganese have particularly excellent resistance to atmospheric corrosion, continual exposure resulting in a gradual darkening of the bronze color.

Conductivity
Brasses have good electrical and thermal conductivities and are markedly superior in this respect to ferrous alloys, nickel-based alloys and titanium. Their relatively high conductivity, combined with corrosion resistance, makes them an ideal choice for the manufacture of electrical equipment, both domestic and industrial. Condenser and heat exchanger tubing also require the good thermal conductivity of copper and its alloys.

Brass has higher electrical conductivity than steel and many other metals. This property, combined with brass's good formability, It has long made it the material of choice for a huge variety of electrical and electronic products.

Wear Resistance
The presence of lead in brass has a lubricating effect that gives good low friction and low wear properties utilized in the plates, pinions and gears used in instruments and clocks. Special brasses are available with additions of silicon that make the material ideal for use in heavy-duty bearings.

Spark Resistance
Brasses do not spark when struck and are approved for use in hazardous environments.

Magnetic Permeability
Brasses are essentially non-magnetic, a property which has gained them extensive use in electrical and electronic equipment, as well as instrumentation such as geological and survey equipment.

 

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