Brass Alloy Additives

How are brass properties affected by alloy additives?

Brass hardware
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Brass, a binary alloy containing copper and zinc, is made of various compositions depending upon the hardness, durability, machinability and corrosion resistance properties required by the end-user.

Lead is the most common alloying agent used in brass because of its ability to make the alloy more machinable. Free machining brasses and free cutting brasses, such as  C36000 and C38500, contain between 2.5% and 4.5% lead and have excellent hot forming properties.

Eco Brass® (C87850 and C69300) is a lead-free alternative that uses silicon in replace of lead to increase machinability.

Section brass contains a small amount of aluminum, giving it a bright golden color. The EU's 10, 20 and 50 cent coins are made of a section brass, known as "Nordic gold" that contain 5% aluminum.

Arsenical brasses such as C26130, not surprisingly, contain arsenic. Small amounts of arsenic help to inhibit corrosion of the brass.

Tin is also used to increase corrosion resistance in certain brasses (e.g. C43500), particularly to decrease the effect of dezincification.

Manganese brass (C86300 and C675) can also be classified as a type of bronze and is a high strength alloy with good corrosion resistance and torsional properties.

Nickel has a long history of being alloyed with brass, probably because it produces a brilliant silver, corrosion resistant metal. 'Nickel silver' (ASTM B122) as these alloys are normally referred, in fact, contain no silver, but are comprised of copper, zinc, and nickel.

The British one pound coin is made from Nickel silver containing 70% copper, 24.5% zinc, and 5.5% nickel.

Finally, iron can also be alloyed in small quantities to increase strength and hardness of brass. Sometimes referred to as Aich's metal - a type of gun metal - such brasses have been used in marine applications.

The chart below summarizes common brass additives and the properties that they benefit.

Common Brass Alloy Elements and Properties Improved

ElementQuantityProperty Enhanced
Lead1-3%Machinability
Manganese
Aluminum
Silicon
Nickel
Iron
0.75-2.5%Yield strength up to 500MN/m2
Aluminum
Arsenic
Tin
0.4-1.5%Corrosion resistance, especially in sea water

Source: www.brass.org 

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