Mild Steel Pipe vs. Ductile Iron Pipe

In pipeline engineering, mild steel pipe and ductile iron pipe are two common materials, which have significant differences in material composition, strength, corrosion resistance and service life. This article will compare the two in detail to help choose the most suitable pipeline material.

Mild steel vs. Ductile iron

1. Mild steel

2. Ductile iron

Common standards: ISO 2531, EN 545, EN 598, AWWA C151, GB/T 13295.

Ductile iron pipe vs Mild steel pipe: Material composition

Mild steel pipe is made of steel with a carbon content between 0.05% and 0.25%. It is a carbon steel pipe with high toughness and plasticity. Due to its low carbon content and excellent welding performance, it is suitable for engineering scenarios that require high-strength connections.

The material of ductile iron pipe is cast iron, which is formed by adding elements such as nickel and vanadium to form ductile iron, thereby improving the strength and toughness of the material. Its unique structure makes it have both the corrosion resistance of cast iron and the strength of steel.

Ductile iron pipe vs Mild steel pipe: Strength

The strength of mild steel pipe is higher than that of ductile iron pipe, mainly reflected in tensile strength and bending strength. Mild steel pipe is often used in engineering occasions with high pressure, such as transporting oil and natural gas, for OCTG pipe and casing pipe, etc.

Although the strength of ductile iron pipes is not as good as that of mild steel pipes, they have excellent pressure resistance and good impact resistance, making them suitable for municipal water supply, drainage systems, and low-pressure gas transportation.

Ductile iron pipe vs Mild steel pipe: Corrosion resistance

Mild steel pipes have poor corrosion resistance and are easily corroded and oxidized in humid or chemically corrosive environments. Therefore, when using mild steel pipes, additional anti-corrosion measures such as coating or galvanizing are usually required.

Ductile iron pipes have good corrosion resistance and can resist erosion by soil, moisture, and chemicals, making them particularly suitable for use in engineering occasions such as high-speed railway subgrades.

Ductile iron pipe vs Mild steel pipe: Service life

The service life of mild steel pipes is about 20 years. If the environment is highly corrosive and no effective anti-corrosion measures are taken, their service life may be greatly shortened.

The service life of ductile iron pipes can reach more than 40 years, and their long life makes them an ideal choice for municipal engineering and infrastructure construction.

How to distinguish between mild steel pipes and ductile iron pipes

1. By Appearance

Mild steel has a smoother surface, uniform color, and finer grains, while ductile iron has a rougher surface and may contain graphite spots.

2. By Hardness Testing

Mild steel has a lower hardness, generally below HRB80, while ductile iron has a higher hardness, usually above HB170, and some can even reach above HB300.

3. By Application

Mild steel is mainly used to manufacture some light mechanical parts, while ductile iron is usually used to manufacture some heavy or stress-bearing parts.

Ductile iron pipes vs. Mild steel pipes: Selection recommendations

1. Typical Scenarios for Choosing Mild Steel Pipes

Oil, natural gas, and high-pressure steam pipelines

Industrial fluid transportation

Piping systems requiring welding or customization

High mechanical stress or earthquake-prone areas

2. Typical Scenarios for Choosing Ductile Iron Pipes

Municipal water supply and drainage networks

Underground buried projects

Projects requiring long-term operation and low maintenance

Medium and low-pressure transmission systems

Summary

In summary, mild steel pipes and ductile iron pipes have their own advantages and disadvantages, and should be selected according to the needs of specific projects. In practical applications, it is necessary to fully consider factors such as material strength, corrosion resistance, and service life, and to carry out reasonable design and use.

Read more: Difference between mild steel pipe and carbon steel pipe or Mild steel pipe VS. Carbon steel pipe