Unifit Fastener is the leading manufacturer and supplier of stainless steel SMO 254 fasteners with extreme corrosion resistance and high-performance standards to the industries where such high standards are paramount. These fasteners are manufactured using UNS S31254 austenitic stainless steel, which provides good service under severe conditions with chloride conditions like seawater systems, offshore oil and gas, desalination plants, pulp and paper processing and chemical industries, which cannot be effectively utilised with other types of stainless steel.
The 254 SMO fasteners composition contains a high content of molybdenum and nitrogen that gives it excellent protection against pitting and crevice corrosion. The fasteners are robust and can withstand high temperatures and pressure working environments; therefore, they can be used in complex and demanding assemblies. On the one hand, they are created by means of hot and cold working, and they are then refined with precision finishing to obtain correct sizes and surface smoothness.
Having decades of industry experience, high-quality equipment, and strong quality assurance, Unifit Fastener uses all the fasteners, which meet the international standards, including ASTM, ASME, and DIN. It is our good metallurgical base, global delivery capacity, and the capability of supplying standard or custom-designed fasteners that put us as a reliable partner in an engineering project. All the products provide reliability, extended service life and stability in values across varying applications.
Stainless Steel SMO 254 fasteners are fastening components including bolts, nuts, screws, studs and washers manufactured from SMO 254 (UNS S31254), a high-alloy austenitic stainless steel developed for maximum corrosion resistance in highly aggressive chloride-bearing environments. This alloy contains approximately 20% chromium, 18% nickel, 6% molybdenum and nitrogen, giving it superior resistance to pitting and crevice corrosion compared to standard grades like 316L or 904L.
These fasteners are widely used where mechanical strength must be paired with exceptional resistance to seawater, acidic solutions, and halide-rich conditions. They maintain structural integrity under high temperatures and pressures, making them indispensable for critical infrastructure in marine engineering, petrochemicals, desalination systems and industrial fluid handling.
254 SMO fasteners are available in various forms to meet different mechanical and environmental requirements. From bolts and nuts for heavy-duty structures to washers and screws for precision assembly, each type serves a specific purpose. The table below highlights the main Stainless Steel SMO 254 fastener types, key features, and common applications for quick reference.
When selecting 254 SMO fasteners, understanding their specifications is crucial to ensuring the right fit for your application. At Unifit Fastener, we supply SMO 254 fasteners that strictly adhere to international standards, ensuring consistent quality, durability and performance across demanding industries.
| Specification Parameter | Details |
|---|---|
| Material Grade | Stainless Steel SMO® 254 (UNS S31254) |
| Standards | ASTM A193 / ASTM A194, DIN, ISO, BS, ANSI |
| Diameter Range | M1.6 to M100 or as per customer requirement |
| Length | Up to 5 meters (custom lengths available) |
| Thread Type | Metric, UNC, UNF, BSW, Acme, custom threads |
| Finish / Coating | Plain, Hot Dip Galvanized, Zinc Plated, PTFE Coated |
| Corrosion Resistance | Exceptional resistance to pitting, crevice, and chloride stress corrosion cracking |
| Temperature Range | Suitable for cryogenic to high-temperature service |
| Manufacturing Process | Forged, Machined, and Heat-Treated |
254 SMO fasteners (UNS S31254) fasteners are recognized internationally under various standards and designations. Knowing their equivalents helps engineers, procurement teams and manufacturers ensure material compatibility across different regions and industries.
| Standard / Specification | Equivalent Grade / Designation |
|---|---|
| UNS | S31254 |
| EN/DIN | 1.4547 |
| ASTM / ASME | A182 F44, A240, A276, A479 |
| JIS | SUS 312L |
| AFNOR | Z1CNDU25-20Az |
| ISO | X1CrNiMoN20-18-7 |
The chemical composition of Stainless Steel SMO 254 (UNS S31254) is what gives these fasteners their exceptional resistance to pitting, crevice corrosion, and chloride-induced stress cracking. Here’s the complete breakdown:
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.020 |
| Manganese (Mn) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.010 |
| Silicon (Si) | ≤ 0.80 |
| Chromium (Cr) | 19.5 – 20.5 |
| Nickel (Ni) | 17.5 – 18.5 |
| Molybdenum (Mo) | 6.0 – 6.5 |
| Nitrogen (N) | 0.18 – 0.22 |
| Iron (Fe) | Balance |
The combination of high molybdenum and nitrogen content gives SMO® 254 fasteners superior mechanical strength and outstanding performance in marine and chemical processing industries where conventional stainless steels fail.
SMO 254 (UNS S31254) fasteners exhibit a remarkable combination of mechanical attributes, including exceptional tensile and yield strength, high elongation, and impressive impact resistance. Below is the table outlining the key mechanical properties of Stainless Steel SMO 254 fasteners:
| Property | Typical Value |
|---|---|
| Tensile Strength | ≥ 650 MPa |
| Yield Strength (0.2% Proof) | ≥ 300 MPa |
| Elongation | ≥ 35% |
| Hardness (Brinell) | ≤ 223 HB |
| Impact Toughness (Charpy V-notch) | High (Even at sub-zero temperatures) |
| Modulus of Elasticity | ~ 195 GPa |
At Unifit Fastener, we offer SMO 254 fasteners in a wide range of standard and customized sizes to suit diverse industrial applications. The following size charts will help you select the right fastener type for your project requirements:
SMO 254 bolts and screws are available in both metric and imperial sizes, with various thread types (UNC, UNF, Metric Coarse, Metric Fine) for superior fastening in marine, chemical, and offshore applications.
| Parameter | Metric | Imperial |
|---|---|---|
| Size Range | M3 – M64 | 3/16” – 2 ½” |
| Length Range | 6 mm – 500 mm | ¼” – 20” |
| Thread Types | UNC, UNF, Metric Coarse, Metric Fine | UNC, UNF, Metric Coarse, Metric Fine |
Designed to complement SMO 254 bolts and studs, these nuts are ideal for high-load and corrosive service environments.
| Parameter | Metric | Imperial |
|---|---|---|
| Size Range | M3 – M64 | 3/16” – 2 ½” |
| Types Available | Hex Nuts, Heavy Hex Nuts, Lock Nuts | Hex Nuts, Heavy Hex Nuts, Lock Nuts |
SMO 254 washers are used to evenly distribute the load of threaded fasteners and protect surfaces from damage.
| Parameter | Metric | Imperial |
|---|---|---|
| Outer Diameter (OD) | 3 mm – 100 mm | 1/8” – 4” |
| Types Available | Flat, Spring, Fender, Belleville | Flat, Spring, Fender, Belleville |
Available in multiple threading options to match application needs:
| Thread Type | Description |
|---|---|
| UNC | Unified Coarse Thread – standard general-purpose thread |
| UNF | Unified Fine Thread – higher tensile stress area and better grip |
| Metric Coarse | Standard metric thread for general applications |
| Metric Fine | Higher precision and greater tensile stress capacity |
Stainless Steel SMO 254 fasteners are the go-to solution for industries where maximum corrosion resistance and superior mechanical performance are non-negotiable. With a Pitting Resistance Equivalent Number (PREN) exceeding 42, they offer exceptional defense against pitting and crevice corrosion in highly aggressive, chloride-rich environments such as seawater, brine and harsh process chemicals. Their advanced alloy composition - rich in molybdenum and nitrogen ensures stable performance where conventional stainless steels are prone to rapid degradation, preventing costly downtime, safety hazards and premature replacements.
Beyond corrosion resistance, SMO 254 fasteners deliver a rare combination of high tensile strength, excellent ductility and outstanding impact toughness even in sub-zero conditions. This enables them to handle fluctuating loads, vibration and severe thermal cycling without compromising integrity. Their proven reliability makes them the first choice for engineers and project managers who demand longevity, operational safety and uncompromising performance in mission-critical applications.
SS SMO 254 fasteners are specifically chosen for environments where standard stainless steels fail prematurely, offering unmatched corrosion resistance in high-salinity, high-chloride and chemical-laden conditions. They ensure mechanical integrity in mission-critical assemblies even under thermal cycling, vibration and continuous exposure to aggressive media.
The price of SMO 254 fasteners depends on several factors such as size, type, coating/finish, manufacturing standards and order volume. Being a high-alloy austenitic stainless steel with exceptional corrosion resistance SMO 254 typically falls in a higher price bracket compared to standard stainless grades like 304 or 316. However, its durability in aggressive environments often results in lower lifecycle costs by minimizing replacements and maintenance.
When sourcing SMO 254 fasteners, pricing considerations generally depend on:
For large-scale projects or specialized applications, it’s advisable to request quotations from multiple suppliers, verify material test certificates (MTC) and compare based on both price and quality assurance.
At Unifit Fastener, we specialize in manufacturing and supplying premium-grade Stainless Steel SMO 254 fasteners that meet the highest industry standards. With years of expertise and advanced production capabilities, we ensure every fastener delivers exceptional strength, precise dimensions and consistent corrosion resistance essential for critical applications.
Our fasteners undergo rigorous quality control processes, including chemical composition analysis, mechanical testing, and dimensional inspections, ensuring compliance with ASTM B479, ASME SB479 and international standards. Serving sectors like offshore, petrochemical, desalination, and heavy engineering, we are committed to timely delivery, technical support and customized solutions that align perfectly with your project requirements. Partner with us for reliable, long-lasting fastening solutions backed by technical excellence and trusted global supply chains.
Request QuoteSMO® 254 offers superior corrosion resistance especially against pitting and crevice corrosion in chloride-rich environments along with higher tensile strength and toughness compared to grades like 304 and 316.
They maintain good mechanical properties and corrosion resistance at moderately elevated temperatures but are typically used in environments up to about 2100°F (1149°C).
Yes, manufacturers typically offer custom sizing, threading, and finishes such as passivation or coating to meet specific project needs.
No, SMO 254 is austenitic and non-magnetic, suitable for applications sensitive to magnetic interference.
Request material test certificates (MTC), mechanical and chemical analysis reports and check compliance with international standards from your supplier.