-40°C Ductile Iron Castings Reliable Way for Extreme Temperature

When it comes to working with ductile iron, especially the kind that performs well in low temperatures, every detail in the casting process matters.

At Luoyang Fonyo Heavy Industries Co., Ltd., we produce -40°C low-temperature ductile iron parts such as motor bases，Large Wind Turbine Generator Shell and gearbox housings for railway and industrial use. Over the years, our engineers have learned that keeping ductile iron tough and reliable in cold environments requires both science and experience.

Let’s look at what we always pay attention to during casting.

1. The Right Material Composition for ductile iron castings

Low-temperature ductile iron starts with the right chemical balance.

We carefully control carbon, silicon, and magnesium levels to ensure stable graphite formation. The addition of nickel (Ni) or copper (Cu) helps the material stay ductile even at -40°C.

We also keep sulfur and phosphorus very low — because even a small amount can make the casting brittle in cold conditions.

In short, clean and balanced composition is the foundation for strong ductile iron.

2. Proper Spheroidization and Inoculation of ductile iron castings

To make the iron truly “ductile,” graphite must form as smooth, round spheres inside the metal. That’s why we control the magnesium treatment and add the inoculant at just the right time. Although this step may sound small, but it greatly affects how the casting behaves later. Our engineers always check the melt temperature and timing to make sure the spheroidization stays effective.

3. Controlled Pouring and Cooling

Temperature control is critical during casting.

We usually pour low-temperature ductile iron at a slightly higher temperature than regular grades, to keep the metal flow smooth and uniform.

Then we manage cooling carefully — not too fast, to avoid white iron layers, and not too slow, to keep the structure even.

In some cases, we use preheated molds or cover sand to ensure the cooling rate stays just right.

4. Heat Treatment for Stability of ductile iron castings

After casting, the parts often undergo annealing to remove internal stress and make the microstructure more uniform. For critical applications like railway gearbox housings, we may also use isothermal heat treatment to achieve both strength and flexibility.

The result is a fine balance, so the casting remains strong but still ductile even in freezing weather.

5. Microstructure and Quality Testing

We don’t just stop at the process — every batch of ductile iron castings goes through microstructure inspection and low-temperature impact testing.

Under the microscope, then we expect to see uniform, round graphite nodules in a mostly ferritic matrix.

This combination gives our -40°C motor bases and gearbox housings their reliable toughness and long life.

6. Real-World Application: -40°C Motor Bases and Gearboxes

Our low-temperature ductile iron motor bases and gearboxes are designed to work in extreme environments, such as cold railway regions or northern industrial zones.

So they perform steadily even when the temperature drops below freezing.

This reliability comes from every small control we make in composition, casting, and heat treatment.

7. Provider

Casting low-temperature ductile iron is not just about pouring metal — it’s about understanding how each factor affects the final performance.

At Fonyo Heavy Industries Co., Ltd., we focus on every stage. From alloy design to microstructure testing, we want to ensure our castings remain safe, tough, and stable even at -40°C.

So if you are looking for custom ductile iron castings for cold environments, feel free to reach out to us. Please visit our website www.railwaypart.com to get more information. We’ll be glad to share our experience and help you find the most reliable solution for your project.