Brass Knowledge

What is brass :

Brass is any alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.

In comparison, bronze is principally an alloy of copper and tin.

Despite this distinction, some types of brasses are called bronzes. Brass is a substitutional alloy. It is used for decoration for its bright gold-like appearance; for applications where low friction is required such as locks, gears, bearings, ammunition, and valves; for plumbing and electrical applications..

Brass has a muted yellow color, somewhat similar to gold.

Brass has likely been known to humans since prehistoric times, even before zinc itself was discovered. It was produced by melting copper together with calamine, a zinc ore. In the German village of Breinigerberg, an ancient Roman settlement was discovered where a calamine ore mine existed. During the melting process, the zinc is extracted from the calamine and mixes with the copper. Pure zinc, on the other hand, has too low a boiling point to have been produced by ancient metalworking techniques. The many references to 'brass' appearing throughout the King James Bible are thought to signify another bronze alloy, or copper, rather than the strict modern definition of 'brass'

 Top  

Commercial Compositions :

There are around 370 commercial compositions for copper alloys. The most common grade tends to be C12200 - the standard water tube grade of copper.World consumption of copper and copper alloys now exceeds 18 million tonnes per annum.

 Top  

Types of Brass : :

  • Admiralty brass contains 30% zinc and 1% tin which inhibits dezincification in most environments.
  • Alpha brasses (Prince's metal), with less than 35% zinc, are malleable, can be worked cold, and are used in pressing, forging, or similar applications. They contain only one phase, with face-centered cubic crystal structure.
  • Alpha-beta brass (Muntz metal), also called duplex brass, is 35-45% zinc and is suited for hot working. It contains both a and ' phase; the '-phase is body-centered cubic and is harder and spaner than a. Alpha-beta brasses are usually worked hot.
  • Aluminium brass contains aluminium, which improves its corrosion resistance. Used in Euro coins (Nordic gold).
  • Arsenical brass contains an addition of arsenic and frequently aluminium and is used for boiler fireboxes.
  • Beta brasses, with 45-50% zinc content, can only be worked hot, and are harder, spaner, and suitable for casting.
  • Cartridge brass is a 30% zinc brass with good cold working properties.
  • Common brass, or rivet brass, is a 37% zinc brass, cheap and standard for cold working.
  • DZR brass is Dezincification resistant Brass with a small percentage of Arsenic.
  • Gilding metal is the softest type of brass commonly available. An alloy of 95% copper and 5% zinc, gilding metal is typically used for ammunition components.
  • High brass, contains 65% copper and 35% zinc, has a high tensile strength and is used for springs, screws, rivets.
  • Leaded brass is an alpha-beta brass with an addition of lead. It has excellent machinability.
  • Low brass is a copper-zinc alloy containing 20% zinc with a light golden color, excellent ductility and is used for flexible metal hoses and metal bellows.
  • Naval brass, similar to admiralty brass, is a 40% zinc brass and 1% tin.
  • Red brass, while not technically brass, is an American term for CuZnSn alloy known as gunmetal.
  • Rich low brass contains 85% copper 15% zinc often used in jewelry applications.
  • White brass contains more than 50% zinc and is too brittle for general use.
  • Yellow brass is an American term for 33% zinc brass.

 Top  

Brass Classes :

Brasses are divided into two classes. These are :

  • The alpha alloys, with less than 37% Zinc. These alloys are ductile and can be cold worked.
  • The alpha/beta or duplex alloys with 37-45% Zinc. These alloys have limited cold ductility and are typically harder and stronger.

 Top  

Important Properties of Brass :

Excellent Machinability

  • Sets the standard by which other materials are judged
  • Slight reduction in ductility when lead is present

Brass has excellent machinability and is the material by which all other materials are judged, however this can be improved even further by the addition of 3% lead to give free cutting high speed machining brasses. The addition of lead however gives a slight reduction in ductility.

 Top  

Brass Families :

There are three main families of wrought alloy brasses :

  • Copper-Zinc alloys
  • Copper-Zinc-Lead alloys (Leaded brasses)
  • Copper-Zinc-Tin alloys (Tin brasses)

Cast brass alloys can be broken into four main families :

  • Copper-Tin-Zinc alloys (red, semi-red and yellow brasses)
  • Manganese Bronze alloys (high strength yellow brasses) and Leaded Manganese Bronze alloys (leaded high strength yellow brasses)
  • Copper-Zinc-Silicon alloys (Silicon brasses and bronzes)
  • Cast Copper-Bismuth and Copper-Bismuth-Selenium alloys.

 Top  

Comparisons of Machinability :

Metal BS Number Specification Designation Metal Removal Rate CM.Min
Brass(4% Lead) EN12164 CW609N 133
Aluminium 4300Pt.5 2001 80
Aluminium 1474 6082 44
Mild Steel 970 Pt. 3 230M07 36
Stainless Steel 970 Pt.3 304S15 6

Table comparing the machinability of brass with other common metals.

 Top  

Brass Additives :

Adding Lead to a brass composition can result in a brass with the ability to be rapidly machined. It will also produce less tool wear. Adding Aluminium, Iron and Manganese to brass improves strength. Silicon additions improve wear resistance. Brasses are divided into two classes and three families.

 Top  

Brasses :

Brasses contain Zinc as the principal alloying element.

Other alloying elements may also be present to impart advantageous properties. These elements include Iron, Aluminium, Nickel and Silicon.

Brasses are most commonly characterised by their free machining grades by which machining standards are set for all other metals.

Brasses can also have high corrosion resistance and high tensile strength. Some brasses are also suited to hot forging.

 Top  

Conductivity :

Electrical

Brass Components
From a 13 Amp Plug

Thermal

Car Radiator

Radiators and Heat Exchangers

For many years, car radiators were made from copper finstock of excellent thermal conductivity, brass tubes and brass header and bottom tanks, all soldered together to give a long-lasting product with the advantage that it could be repaired if ever damaged.

With the development of the use of other materials to make some radiators, there was a need to review and improve the design to meet the competition. This has now been achieved with the use of copper finstock rolled to much thinner gauge in modern mills, tubing made from precision strip by either high-frequency welding or laser welding, and the use of either a zinc-based solder or a new brazing system that will permit operation at much higher temperatures. Special lacquers, electrophoretically applied, protect the finstock from corrosion caused by salted roads.

A new sealing method is used to join the heat exchanger to the header and bottom tanks. This has reduced initial cost and weight, while retaining the high heat-exchange efficiency of copper to permit the use of a smaller total heat exchange surface and smaller content of cooling water. The finished radiator is lighter than those made of other materials, both as made and when full of coolant.

13 Amp Plug

For economic production of these safety-critical items, brass is used to make the pins to ensure a long, trouble-free life. Brass does not corrode in service, has good strength, electrical conductivity and resistance to wear as well as being easy to extrude.

 Top  

Background :

Copper is the oldest metal used by man. It's use dates back to prehistoric times. Copper has been mined for more than 10,000 years with a Copper pendant found in current day Iraq being dated to 8700BC. By 5000BC Copper was being smelted from simple Copper Oxides.

Copper is found as native metal and in the minerals cuprite, malachite, azurite, chalcopyrite and bornite. It is also often a by-product of silver production. Sulphides, oxides and carbonates are the most important ores.

Copper and Copper alloys are some of the most versatile engineering materials available. The combination of physical properties such as strength, conductivity, corrosion resistance, machinability and ductility make copper suitable for a wide range of applications. These properties can be further enhanced with variations in composition and manufacturing methods.

 Top  

The Extrusion Process :

Direct Extrusion
Indirect Extrusion

  • In direct extrusion a ram forces the preheated brass billet through the die. This can be likened to squeezing toothpaste out of a tube. Using this method it is possible to extrude up to six lengths from one die.
  • Direct extrusion is usually used for the manufacture of profiled sections and hollow bar products.
  • Indirect extrusion is the reverse of direct extrusion, the die being forced on to the billet rather than the billet being forced through the die.

 Top  

Building Industry :

The largest end use for Copper is in the building industry. Within the building industry the use of copper based materials is broad. Construction industry related applications for copper include:

  • Roofing
  • Cladding
  • Rainwater systems
  • Heating systems
  • Water pipes and fittings
  • Oil and gas lines
  • Electrical wiring

The building industry is the largest single consumer of copper alloys. The following list is a breakdown of copper consumption by industry on an annual basis:

 

  • Building industry - 47%
  • Electronic products - 23%
  • Transportation - 10%
  • Consumer products - 11%
  • Industrial machinery - 9%

 Top  

Typical Extrusions :

Typical Extrusion

 Top  

Attractive Colours :

CuZn5    4-6%Zn
CuZn10   9-11%Zn
CuZn15   14-16%Zn
CuZn20   19-20%Zn
CuZn30   29-31%
CuZn33   32-34%Zn
CuZn36   34.5-36.5%Zn
CuZn37   36-38%Zn
CuZn40   39.5-41.5%Zn

In brasses, the red of copper is toned to a range of attractive yellow hues by the addition of varying amounts of zinc, ranging from the gold-like colours of the 95/5, 90/10, 85/15 and 80/20 alloys (appropriately called "gilding metals") through the more subtle variations in the 70/30, 2/1 and 64/36 series of brasses to the stronger yellow colour of the 60/40 alloy, formerly known as "yellow metal".

 Top  

Applications :

  • Power transmission lines
  • Architectural applications
  • Cooking utensils
  • Spark plugs
  • Electrical wiring, cables and busbars
  • High conductivity wires
  • Electrodes
  • Heat exchangers
  • Refrigeration tubing
  • Plumbing
  • Water-cooled copper crucibles

Top