53 Brass

Brass, like bronze, is a copper alloy but has a primary alloying element of zinc instead of tin. Zinc alloying of copper to produce brass had been around since the discovery of bronze. However, it was not as easy to produce brass and therefore was not as commonly used.

Over the last few centuries, the alloying of copper-tin and copper-zinc with other elements has become so nearly alike, and the results so similar, that today there are very few functional differences between bronze and brass. Generally, whatever you can be accomplished with a particular bronze alloy can be accomplished with some other kind of brass alloy and vice versa. However, there is one significant difference worth mentioning. Brass, when polished, looks like gold but bronze does not polish as nicely. So, brass has more decorative uses than bronze and – throughout history – has been used this way.

The two primary brasses of interest are those called by their color because the hue of the metals distinguishes it from its siblings. Red brass contains has less zinc (more copper) and yellow brass contains more zinc (less copper). It is not uncommon for the seasoned machinist to request this copper alloy simply by stating its color: “Red Brass” or “Yellow Brass”

C36000

• Primary alloy Lead
• Machinability the best of the brass family
  

  

• Weldability soldering and brazing
• Applications screw machine products
• Comments the most free machining of all metals. The standard by which all brass machinability is judged.

C35300

• Primary alloy lead
• Machinability almost as good as C3600
• Weldability soldering and brazing
• Applications screw machine products, hose fittings, lock parts.
• Comments less free machining than C3600 but more formable for forgings, cold heading, etc.

C35300

• Primary alloy iron
  

  

• Machinability poor for brass
• Weldability soldering and brazing
• Applications electrical hardware, fasteners, fittings
• Comments a cold form brass that is machined after heading.

Copper alloys are designated by UNS as CXXXXX as shown:

Brass (left) is an alloy of Copper and Zinc (5 to 45%), it increases strength and hardness but is less resistant to stress corrosion cracking.

Bronze is an alloy of copper and tin. It is more expensive than brass, but its corrosion resistance, strength, and fatigue resistance is better.

The UNS designation system is straightforward. The copper designator is the letter C followed by five digits.

The Key to the UNS Copper Numbering System

There are many more brasses and bronzes but the above listed should serve the machinist’s needs well enough. One important thing to remember is C2, C3, and C4 is brass. C5 and C6 is bronze.

Derived from The Virtual Machine Shop at http://www.jjjtrain.com/vms/eng_metal_stds/eng_metal_stds_07.html retrieved from the Wayback Machine 16 January 2024.