Material Property Comparison
Carbon steel has a carbon content of 0.02% to 2.11% and is primarily composed of iron and carbon. Steel ingots are formed through pressure processes such as rolling and forging. They offer excellent overall performance, with a balance of strength, ductility, and toughness, good weldability, and machinability, but relatively poor corrosion resistance.
Cast steel has a carbon content of 0.15% to 0.6% and is low in impurities. They are cast from molten steel and require heat treatment to improve properties. They offer high strength, good toughness, and impact resistance. Alloying (such as adding chromium or nickel) can enhance corrosion resistance and high-temperature resistance.
Key Performance Differences
1. Mechanical Properties
Strength and Toughness
Carbon steel: Tensile strength increases with increasing carbon content (e.g., Q235 steel has a tensile strength of approximately 370 to 500 MPa, while 45 steel can reach over 600 MPa). They also have good ductility and toughness, allowing them to withstand some deformation.
Cast steel: Its tensile strength is typically 450-800 MPa, and its toughness is significantly superior to cast iron (for example, ZG230-450 cast steel has an elongation of up to 22%), making it suitable for bearing dynamic loads.
2. Corrosion Resistance
Carbon steel: It is prone to rust and corrodes rapidly in humid, acidic, and alkaline environments, requiring additional anti-corrosion treatment (such as electroplating or epoxy coating).
Cast steel: The corrosion resistance of ordinary cast steel is similar to that of carbon steel, but stainless steel cast steel (such as CF8 and CF3M) can be created by adding alloying elements (such as Cr and Ni), significantly improving its corrosion resistance.
3. High-Temperature Resistance
Carbon steel: The long-term operating temperature of ordinary carbon steel is ≤450°C. At high temperatures, its strength decreases significantly, so heat-resistant steel (such as 15CrMo) is required.
Cast steel: Alloying can provide high-temperature resistance (for example, ZG1Cr18Ni9Ti stainless steel cast steel can withstand temperatures exceeding 800°C), making it suitable for use with high-temperature media (such as steam and hot oil).
4. Processability
Carbon steel: Offers excellent forging, welding, and cutting properties, making it easy to process into various shapes (such as flanges and threaded connections) and suitable for applications requiring frequent assembly and disassembly.
Cast steel: The casting process is more complex than cast iron (requiring controlled casting temperature and cooling rate), but heat treatment (such as normalizing and tempering) can improve performance, and weldability is superior to cast iron.
Application Comparison
1. Carbon Steel Valves
Applicable Applications:
Medium- and high-pressure pipelines (e.g., PN ≤ 16 MPa), media such as air, steam, oil, and gas, that must withstand certain pressures and vibrations (e.g., industrial pipelines and thermal systems).
Typical Valves: Ball valves, butterfly valves, and safety valves (e.g., valves made of Q235 and 20# steel).
Advantages: High strength, balanced overall performance, and moderate processing costs.
Disadvantages: Inadequate corrosion resistance, requiring regular corrosion protection.
2. Cast Steel Valves
Applicable Applications:
High pressure, high temperature, high shock, or complex operating conditions (e.g., pressure PN ≥ 25 MPa, temperature ≥ 450°C), or applications requiring corrosion resistance (e.g., stainless steel cast steel).
Typical Valves: Power plant valves (e.g., gate valves, globe valves), chemical valves (e.g., stainless steel ball valves), and offshore valves.
Advantages: High strength, good toughness, and adaptability to extreme environments through alloying.
Disadvantages: High cost and complex casting process.
Summary and Selection Recommendations
Carbon Steel: Medium and high pressure, conventional media. Balanced strength and toughness, easy processing, and high cost-effectiveness.
Cast Steel (Alloy): High pressure, high temperature, and corrosion. Alloying can improve strength, high temperature resistance, and corrosion resistance, making it suitable for complex operating conditions.
