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UNS S31254 Screw
QS Fastener: UNS S31254 Screw
Name: UNS S31254 Screw
Material: 254SMO
Size: 5/16 to 4 inch
Length: 30 to 3000 mm
Standard: ANSI, DIN
Product Grade: A
Tensile Strength(Rm): 650 N/mm²
Elongation: 35%
Feature: Excellent Resistance to Spot Corrosion and Crevice Corrosion.
Application: For Petroleum and petrochemical equipment, etc.
Material: 254SMO
Size: 5/16 to 4 inch
Length: 30 to 3000 mm
Standard: ANSI, DIN
Product Grade: A
Tensile Strength(Rm): 650 N/mm²
Elongation: 35%
Feature: Excellent Resistance to Spot Corrosion and Crevice Corrosion.
Application: For Petroleum and petrochemical equipment, etc.
Quantity
The UNS S31254 Screw is manufactured from the high-performance material 254SMO, with size ranges from 5/16 to 4 inches and lengths from 30 to 3000 mm. It complies with ANSI and DIN standards and is classified as Grade A. With a tensile strength exceeding 650 N/mm² and an elongation rate of 35%, it offers exceptional resistance to pitting and crevice corrosion, making it particularly suitable for harsh environments such as oil and petrochemical equipment. Choosing the **UNS S31254 Screw** means opting for a reliable, durable, and high-performance fastening solution that ensures your equipment maintains excellent performance under extreme conditions.
Detailed Analysis of 254 SMO Corrosion Resistance
1. Critical Pitting Temperature (CPT): 80°C
The Critical Pitting Temperature (CPT) is a key indicator of a material's resistance to pitting corrosion in chloride-containing environments. The CPT value of 254 SMO is 80°C, far exceeding that of ordinary stainless steels (e.g., 316L has a CPT of approximately 25°C). This characteristic ensures that the UNS S31254 Screw maintains excellent corrosion resistance even in high-temperature chloride-containing media.
1. Critical Pitting Temperature (CPT): 80°C
The Critical Pitting Temperature (CPT) is a key indicator of a material's resistance to pitting corrosion in chloride-containing environments. The CPT value of 254 SMO is 80°C, far exceeding that of ordinary stainless steels (e.g., 316L has a CPT of approximately 25°C). This characteristic ensures that the UNS S31254 Screw maintains excellent corrosion resistance even in high-temperature chloride-containing media.
- In seawater desalination equipment, where operating temperatures typically range from 60°C to 80°C, the UNS S31254 Screw effectively resists chloride-induced corrosion in high-temperature seawater, preventing pitting.
- In the petrochemical industry, acidic media and chloride-containing process fluids often operate at high temperatures. The high CPT value of the UNS S31254 Screw ensures long-term stable operation of equipment, avoiding leaks or failures caused by pitting.
- According to ASTM G48 standard tests, 254 SMO shows no pitting in 6% FeCl3 solution at 80°C, while 316L begins to exhibit pitting at 25°C.
2. Critical Crevice Corrosion Temperature (CCT): 60°C
The Critical Crevice Corrosion Temperature (CCT) is a crucial parameter for measuring a material's resistance to corrosion in crevice environments. The CCT value of 254 SMO is 60°C, significantly higher than that of ordinary stainless steels (e.g., 316L has a CCT of approximately 10°C). This characteristic ensures that the UNS S31254 Screw maintains excellent corrosion resistance even in complex crevice structures, such as flange and threaded connections.
The Critical Crevice Corrosion Temperature (CCT) is a crucial parameter for measuring a material's resistance to corrosion in crevice environments. The CCT value of 254 SMO is 60°C, significantly higher than that of ordinary stainless steels (e.g., 316L has a CCT of approximately 10°C). This characteristic ensures that the UNS S31254 Screw maintains excellent corrosion resistance even in complex crevice structures, such as flange and threaded connections.
- In marine engineering, seawater media and complex equipment structures are prone to crevice corrosion. The UNS S31254 Screw effectively resists crevice corrosion in environments below 60°C, extending equipment service life.
- In the chemical industry, flange connections in reactors and piping systems are often high-risk areas for crevice corrosion. The high CCT value of the UNS S31254 Screw ensures the safety and reliability of these critical components.
- According to ASTM G48 standard tests, 254 SMO shows no crevice corrosion in 6% FeCl3 solution at 60°C, while 316L begins to exhibit crevice corrosion at 10°C.
3. Pitting Resistance Equivalent Number (PREN): >42
The Pitting Resistance Equivalent Number (PREN) is a comprehensive indicator of a material's resistance to pitting corrosion, calculated as:
PREN = %Cr + 3.3 × %Mo + 16 × %N
The Pitting Resistance Equivalent Number (PREN) is a comprehensive indicator of a material's resistance to pitting corrosion, calculated as:
PREN = %Cr + 3.3 × %Mo + 16 × %N
The PREN value of 254 SMO is >42, far exceeding that of ordinary stainless steels (e.g., 316L has a PREN of approximately 26, and 304 has a PREN of approximately 19). This characteristic ensures that the UNS S31254 Screw exhibits exceptional pitting resistance in chloride-containing media.
- PREN Value Comparison:
| Material | Chromium (Cr) | Molybdenum (Mo) | Nitrogen (N) | PREN Value |
| 254 SMO | 20% | 6.2% | 0.2% | >42 |
| 316L | 16.5% | 2.1% | 0.02% | 26 |
| 304 | 18% | 0% | 0.05% | 19 |
- In seawater environments, the high PREN value of the UNS S31254 Screw enables it to resist corrosion from high chloride concentrations, making it suitable for seawater desalination equipment, ship components, and offshore platforms.
- In the chemical industry, acidic media containing chlorides (e.g., hydrochloric acid, sulfuric acid) demand high pitting resistance. The PREN value of the UNS S31254 Screw ensures long-term stability of equipment in harsh environments.
- Laboratory tests show that 254 SMO exhibits an extremely low pitting rate (<0.001 mm/year) in 3.5% NaCl solution even at 50°C, while 316L has a pitting rate of up to 0.1 mm/year under the same conditions.
4. Comprehensive Corrosion Resistance
The corrosion resistance of the UNS S31254 Screw is not limited to pitting and crevice corrosion but also includes the following characteristics:
- Stress Corrosion Cracking (SCC): In chloride-containing and high-temperature environments, the UNS S31254 Screw exhibits excellent resistance to stress corrosion cracking, far surpassing ordinary stainless steels.
The corrosion resistance of the UNS S31254 Screw is not limited to pitting and crevice corrosion but also includes the following characteristics:
- Stress Corrosion Cracking (SCC): In chloride-containing and high-temperature environments, the UNS S31254 Screw exhibits excellent resistance to stress corrosion cracking, far surpassing ordinary stainless steels.
- Uniform Corrosion: In strong acids (e.g., sulfuric acid, hydrochloric acid) and strong alkalis (e.g., sodium hydroxide), the UNS S31254 Screw shows an extremely low uniform corrosion rate, ensuring long-term stable operation of equipment.
- In flue gas desulfurization (FGD) systems, the UNS S31254 Screw resists corrosion from sulfur-containing flue gas in high-temperature and high-humidity environments, extending equipment service life.
- In nuclear power plants, the high corrosion resistance of the UNS S31254 Screw makes it an ideal material for critical components, ensuring equipment safety in radioactive environments.
5. Summary
With its high CPT, CCT, and PREN values, 254 SMO demonstrates exceptional corrosion resistance in extreme corrosive environments. Whether in high-temperature chloride-containing media, complex crevice structures, or strong acid and alkali environments, the UNS S31254 Screw provides reliable solutions, ensuring long-term stable operation of equipment, reducing maintenance costs, and improving economic efficiency.
With its high CPT, CCT, and PREN values, 254 SMO demonstrates exceptional corrosion resistance in extreme corrosive environments. Whether in high-temperature chloride-containing media, complex crevice structures, or strong acid and alkali environments, the UNS S31254 Screw provides reliable solutions, ensuring long-term stable operation of equipment, reducing maintenance costs, and improving economic efficiency.
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