The Difference between Ductile Iron and Gray Iron

Continuous casting of ductile and gray iron dominates the industry in terms of low material cost, high machinability, and high performance. Both metals are used for a wide range of applications, including construction equipment, pipe fittings, oil field machinery, and even transportation services.

Contact us to discuss your requirements of ductile iron vs gray iron. Our experienced sales team can help you identify the options that best suit your needs.

Each metal has its own advantage due to the differences in carbon levels and is used for different applications according to its strengths.

Gray Iron/Ductile Iron Comparison

Contact continuous cast iron suppliers for gray and ductile iron raw stock.

1. Gray iron’s tensile strength ranges from 20,000 psi – 60,000 psi, whereas ductile iron ranges from 65,000 psi – 80,000 psi and can be heat treated to 100,000 psi
2. Ductile iron has lower thermal conductivity so it can insulate better than gray iron
3. Ductile iron is more tailored for engineering applications
4. Graphite in ductile iron is nodular and flaked in gray iron—meaning ductile iron is stronger and contains higher ductility
5. Gray iron dampens vibration better than ductile iron

fast Quote

More details about Versa-Bar gray and ductile iron

Gray and ductile iron, both superior alternatives to steel, each present a different makeup and suitability in the CNC machining industry.

Gray Iron

American Iron has the best replacement for steel in the form of V-2 Class 40 Versa-Bar continuous cast gray iron. During solidification, rod-like graphite flakes precipitate into the composition, outlining the difference between gray and ductile iron. Producers utilize grey continuous cast iron for its high density and strength, but its popularity comes from its low cost. Continuous cast gray iron combines affordable prices with quality lightweight metal to create a material ideal for applications such as vibration damping and use in manufacturing equipment frames. Gray iron is also applied in:

• Construction equipment
• Valves and fittings
• Compressors and pumps
• Diesel engine parts
• Transportation system components

Gray iron is often mistakenly described as cheap and dirty metal. Still, its high cutting speeds, superior damping ability, durability, and unique metallurgical makeup make it popular. Part of the gray iron’s success comes from its ability to be easily machined and is used where strength is not a critical requirement, like maintenance hole covers and counterweights. Gray iron is considerably stronger than steel and costs less. You’ll save money in the short AND long run. Consider gray iron the immediate steel replacement. Ductile iron is the next step up.

Ductile iron

Ductile iron offers numerous machining advantages over gray iron.

The company is the world’s best oem iron casting supplier supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Ductile continuous cast iron has made its name in the machining industry from its high tensile strength and flexibility. Its flexibility makes it great for being shaped into wires and other applications that require a level of elasticity. Instead of rod-like flakes, the ductile iron bar is composed of graphite nodules making it flexible during solidification. This type of iron is often used in areas that require the ability to elongate under tension. It is most often used in:

• Couplings
• Machine frames
• Hydraulic valves
• Pumps
• Gearboxes

The many advantageous features of continuous cast ductile iron make it the perfect alternative to steel. American Iron offers two high-quality ductile iron grades, V-3 and V-4. The distinctive metallurgic composition of V-3 65-45-12 iron makes it the easiest to machine out of the three grades of continuously cast metal. V-4 80-55-06 ductile iron is stronger than V-3 and is a popular choice for automobile parts and hydraulic cylinders. Ductile iron is not only more versatile than steel but costs significantly less. Buying Versa-Bar continuous cast ductile iron from American Iron means savings on every project.

fast Quote

American Iron delivers raw stock and custom iron components

Ductile iron stock is available for sale as a raw material for you to process and finish on your own, or we can finish and machine it into custom continuous cast iron components based on your requirements at our state-of-the-art CNC facility in Waukesha. It’s up to you. We provide you with high-quality ductile iron in whatever form you desire.

Contact American Iron for continuous cast iron supply, custom metal components, and raw gray and ductile iron stock.

One thing I've run into in machining castings is gray iron is very nice to machine, ductile can be mean. Having worked at Moline iron foundry where we cast ductile, malleable, and gray irons we had to turn test bars from every melt to test the tensile strength. Never had a problem turning the gray bars but the ductile -- wow, if you found a hard spot, toss the sucker in the garbage. It would tear up a carbide insert faster than you could shut the feed off and send our poor South Bend lathe jumping across the floor. Milling was the same story. Not even a carbide endmill would last once you hit a hard spot in a ductile iron casting. Gray iron filled the cavities better and gave better detail than ductile. And the hot ductile casting was easy to tell from others - spit on it and you could smell the sulphur. Had more problems with gas holes in ductile castings, venting and gating were a trial and error process on the molds.

The main difference between gray, malleable, and ductile is the graphite.

Graphite is a practically pure form of free carbon in the iron.

Gray iron contains graphite in thin flat flakes that are distributed though a matrix of pearlite and some ferrite. These flakes are responsible for giving gray iron its excellent machinability and vibration damping qualities but also to limiting its mechanical properties. A 40 class gray iron has 40,000 psi tensile strength, 80 class has 80,000 psi.

Malleable iron has nodular graphite distributed through a ferritic matrix. These nodules have less effect on the mechanical properties than do the flakes of gray iron. The nodules are composed of an aggregate of fine flakes.

Ductile iron has graphite in the form of spheroids which are single polycrystaline particles. This structure is obtained by adding magnesium (nickel-magnesium alloy containing 50-80% nickel) in the ladle just before pouring. Tensile strengths above 150,000 psi have been achieved for ductile iron.

Thanks to my metallurgy text book.

Steve

Want more information on pump body casting? Feel free to contact us.