Piping materials: carbon steel VS cast iron

Carbon steel and cast iron are two common pipe materials, which have their own characteristics in terms of performance and use. The two materials of cast iron and carbon steel are compared in several aspects:

1. Definitions

Carbon steel material: Carbon steel is a carbon content of 0.0218%~2.11% with iron and carbon as the main components of the alloy, in addition to generally contains a small amount of silicon, manganese, sulfur, phosphorus and other elements. Generally, the higher the carbon content of carbon steel, the greater the hardness, the higher the strength, but the plasticity is reduced. According to the different carbon content, carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel. Among them, low carbon steel (carbon content below 0.2%) is the most commonly used type in pipelines.

Cast iron material: Cast iron is a high carbon content of iron-carbon alloy, in addition to carbon, cast iron also contains 1% to 3% silicon, as well as manganese, phosphorus, sulfur and other elements. Silicon is the main element that affects the microstructure and properties of cast iron. Cast iron can be divided into gray cast iron, ductile cast iron and so on according to the different shapes of graphite.

2. Performance comparison

(1) Mechanical properties
Carbon steel material: the strength of carbon steel is relatively high tensile strength is usually 350~650 MPa, and with the increase of carbon content, the strength of carbon steel will also increase, commonly used low carbon steel has excellent toughness and ductility, good wear resistance.

Cast iron materials: The performance of cast iron varies greatly due to different categories, some are very brittle, the use value is small, and some have good performance, which is not much worse than tempered steel (such as ductile iron).

(2) Corrosion resistance

Carbon steel material: The steel pipe made of carbon steel as the pipe material is prone to oxidative corrosion, and the corrosion resistance needs to be enhanced by external coating, galvanizing and other anti-corrosion measures. It performs well in high temperature and high pressure environments, and requires anti-corrosion treatment for long-term use.

Cast iron materials: Steel pipes made of cast iron as pipe materials have good natural corrosion resistance, especially at room temperature. Among them, the corrosion resistance of ductile iron is better than that of gray cast iron, but it can not be used in areas containing acidic media.

(3) Pressure resistance

Carbon steel material: has excellent pressure resistance, suitable for high pressure pipeline system, widely used in oil, gas and industrial boiler pipelines.

Cast iron material: pressure resistance is weak, generally used for low-pressure water transmission needs. Ductile iron pipe has high pressure resistance and can partially replace carbon steel pipe.

3. Application area

Carbon steel pipeline: commonly used in industrial pipelines, building structure pipelines, oil and gas pipelines and other high-pressure, high-temperature complex environment.
Cast iron pipes: often used in water supply, drainage, sewage treatment, underground engineering and other room temperature, low pressure. Strong corrosion resistance environment.

In summary, carbon steel materials and cast iron materials in the performance, use and other aspects of there are no small differences, in the selection of materials, should be combined with the needs and use of the scene to choose a reasonable material.

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