1. Manufacturing Process Comparison
- Forged Steel Valves: Utilizing a forging process, the metal blank undergoes plastic deformation under high temperature and high pressure, eliminating weld defects and resulting in a dense internal structure free of pores or looseness.
- Cast Steel Valves: Utilizing a casting process, liquid metal is poured into a mold to form the valve. These valves are suitable for complex shapes and large workpieces, but may introduce defects such as sand holes.
2. Performance Comparison
- Strength and Toughness:
Forged steel valves offer higher mechanical strength and can withstand ultra-high pressures exceeding 42 MPa (e.g., A105 carbon steel forgings). They also possess superior toughness and impact resistance compared to cast steel.
Cast steel valves are relatively weak (commonly used in PN16-PN40 grades) and are susceptible to low-temperature brittleness, requiring special handling at temperatures below -29°C.
- Sealing and Leakage Risk:
Forged steel valves offer excellent leak resistance (e.g., bellows design achieves zero leakage), are free of sand holes, and are suitable for use with toxic or flammable media. Cast steel valves are prone to forming sand holes during the casting process, resulting in weak sealing and requiring regular maintenance in medium- and low-pressure environments.
- Temperature and Pressure Range:
Forged steel valves offer a wide temperature range (-196°C to 650°C) and high-pressure ratings up to PN320 or 3500LB, making them suitable for extreme operating conditions.
Cast steel valves are suitable for medium-temperature and medium-pressure applications (-29°C to 180°C), with pressure ratings typically below PN40. They are low-cost but have limited pressure resistance.
3. Application Comparison
Forged steel valves are primarily used in demanding high-pressure and high-temperature environments, such as petrochemicals (oil and gas transportation), LNG storage and transportation (-196°C liquid nitrogen), or pharmaceutical sterile systems requiring zero leakage.
Cast steel valves are more suitable for medium- and low-pressure, ambient-temperature applications, such as urban heating pipelines and general industrial fluid systems, and offer a high cost-effectiveness.
4. Key Selection Factors
Size Limitations: Forged steel valves typically have a diameter of DN50 or less (for small to medium-sized valves), while cast steel valves can cover large or unusually shaped structures.
Cost and Maintenance: Forged steel valves have a higher initial investment but a longer lifespan (lower maintenance). Cast steel valves have a lower initial cost but require frequent inspection to prevent leaks.
