Brass – a multi-purpose material
Brass is a copper zinc alloy, harder than pure copper, but not as hard as bronze. In opposition to steel or aluminium it is not thermosetting by heat treatment. The strength is only controllable by an appropriate alloy or mechanical deformation (rolling, forging, drawing in cold condition). Brass is characterized by very good hot conversion and also by excellent forgeability.
Brass, a versatile material
Due to its respective copper amount the range of colours varies from steel glossing rouge (high copper amount) to light yellow (high zinc amount).
As well as copper and bronze, brass is able to cover itself with a naturally patina in the course of time. This Patina is an anti-abrasion layer against corrosion.
The most common brass-alloy is CW508L, with a zinc amount about 37 %. Brass contains a copper amount with minimum 50 %, with a lower limit it becomes refractory and bad workable. Brass alloys with a copper amount above 70 % are also known as „Tafelmessing“, tombac or gold-brass. This alloy is frequently used in e.g. jewelry making or in the military for steel metal jackets.
The lead amount ranges between 0,5 – 3 %, if this range will be exceeded, the alloy will be attributed to the special brass classification. Some kinds of brass, which have lead as a third component are also known as free cutting- or chipping-brass. Due to this component, brass is unsuitable for welding.
Nowadays, this free cutting brass is also named as CW614N, but this term is actually ineligible because this quality doesn’t exist in norms anymore. Since 1974 CW614N is the genus of 3 materials: CuZn39Pb2, CuZn39Pb3 and CuZn40Pb2. These materials are different as follows:
- CuZn39Pb2 (CW612N in accordance with EN, 2.0380 in accordance with DIN): good hot conversion, confined cold conversion (banding, staking, beading); good blanking boring and milling quality;
- CuZn39Pb3 (CW614N in accordance with EN, 2.0401 in accordance with DIN): good hot conversion; main-alloy for machining on machines;
- CuZn40Pb2 (CW617N in accordance with EN, 2.0402 in accordance with DIN): good hot conversion, confined cold conversion; alloy for all metal cutting machining operations and accurate drawn extrusions
Ms58 is presenting a popular material, which is mostly available from stock.
Due to its gold-colour, brass is used as a preferred material for decoration and crates. Furthermore it has a technical importance because of the good electric conductance and mechanical stability. It is also frequently used for the sanitary installation, because of its very good chemical corrosion properties.
If there are more alloying elements than copper-zinc in a brass alloy (like aluminium, iron, manganese or nickel) it‘s called special brass.
These alloying elements conduce to the strengthening as well as the improvement of the floating properties and corrosion resistance.
Aluminium (Al) for example, increases the strength (without influencing the warm-form-property) and resistance to seawater (e.g. CuZn40Al2).
Silicium (Si) enhances the mechanical properties as well as tarnish-proofness (e.g. CuZn31Si).
If a copper-zinc alloy has a Nickel-constancy about 9-26 % it is called: German silver.
In cause of this, it also enhances mechanical properties (even by higher temperatures) and the deformability. Furthermore it enhances the corrosion resistance (e.g. CuNi12Zn24).
Similar to Nickel, Manganese (Mn) enhances mechanical properties and corrosion resistance particularly against atmospheric influences (e.g. CuZn40Mn2Fe1).
The component Iron (Fe) is generally up to 0,5 – 1,5 % and effects normally a grain refinement (e.g. CuZn40Mn2Fe1).
Special brass has got a high strength (therefore it is qualified for gliding loading) and a good resistance against atmospheric influences.
It’s usually used for structural parts. In other words: It is a heavy-duty mechanical material (e.g. for journal bearing with high encumbrances at a slow rate).