Choosing the Right Cast Iron for Precision Machining

Junying is going to explain how to select the metal for your machining project, focusing on properties, advantages and disadvantages of the metals.

Ferrous metals refer to those containing iron such as cast iron, steel, etc. If strength is the most important factor for your project, ferrous metals are your best option.

Ductile Cast Iron ASTM 536

Usually, ductile cast iron is used for cast iron pipe, which is used for water and sewer lines. Ductile iron is a kind of metal which is useful in a lot of automotive parts, especially strength should be better than that of aluminum. It can also be used in industrial field such as agricultural tractors, oil well pumps and Class 8 trucks. Nodular cast iron is applicable for hubs and structural parts like machine frames in wind power industry and is good for complex and large shapes and high loads. Ductile cast iron has great vibration dampening, so it is better than steel when it comes to manufacturing machine tools.

Advantages

• Ductile cast iron is more stronger than grey cast iron. Tensile strength of ductile cast iron is between 60,000 psi and 120,000 psi, while tensile strength of gray cast iron is from 20,000 to 60,000 psi.
• Ductile cast iron can be easily machined. Coolant is not required, because the graphite is a natural lubricant.
• Ductile cast iron can dissipate heat well.
• Ductile cast iron has great wear resistance because of the graphite.
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Disadvantages

• Ductile cast iron shows nodules.
• Ductile cast iron can make a mess because of the graphite.
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Gray cast iron (ASTM A247, ASTM A48 and SAE J431)

The graphite is in the shape of flakes in gray cast iron, which encourages cracking. For the flakes are stress risers. If your project attaches importance to durability and wear, gray cast iron may not be a good metal to choose.

Advantages

• Gray cast iron relatively costs lower.
• Gray cast iron usually contains silicon, which has great corrosion resistance.
• Gray cast iron has great wear resistance.
• Gray cast iron doesn’t require coolant as the graphite and can be easily machined.
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Disadvantages

• Gray cast iron can’t be rolled, forged or extruded due to its tendency to crack.
• Gray cast iron shows flake microstructure.
• Gray cast iron doesn’t have impact and shock resistance.
• Gray cast iron can make a mess because of the graphite.

About Junying 

Junying has rich experience in industrial parts manufacturing and our services include CNC machining, 3D printing, zinc alloy& aluminum alloy die-casting technology. We supply lab parts for many university laboratories.