Product Description
UNS S31254 (254 SMO) / 1.4547 / F44 is a premium 6% molybdenum super austenitic stainless steel designed for exceptionally corrosive environments. This high-performance alloy combines moderate mechanical strength (typically over 300 MPa yield strength) with outstanding ductility and superior corrosion resistance in aggressive media, particularly seawater and chloride-containing environments.
With its high content of chromium (19.5-20.5%), nickel (17.5-18.5%), molybdenum (6.0-7.0%), and nitrogen (0.18-0.25%), this grade achieves a Pitting Resistance Equivalent (PREn) value of 42-44, ensuring exceptional resistance to pitting corrosion and crevice corrosion. The alloy’s very low carbon content (max 0.020%) minimizes the risk of carbide precipitation during heating or welding processes.
This super austenitic stainless steel grade offers substantial improvements in corrosion resistance compared to conventional 300-series stainless steels, making it an ideal choice for applications where standard austenitic stainless steels would face premature failure. With corrosion resistance comparable to super duplex stainless steel but with the superior formability of austenitic grades, UNS S31254 provides an excellent balance of properties for demanding applications.
Applications
UNS S31254 (254 SMO) / 1.4547 / F44 super austenitic stainless steel is specifically developed for applications involving high chloride environments where traditional stainless steels would suffer from localized corrosion. Its exceptional corrosion resistance makes it particularly suitable for:
- Seawater cooling systems and marine equipment
- Petroleum production and processing equipment
- Saltwater handling systems
- Pulp mill bleach plants and bleach systems
- Tall oil distillation columns
- Desalination equipment and systems
- Food processing equipment exposed to cleaning chemicals
- Chemical processing equipment in chloride-containing environments
- Flue gas desulfurization scrubbers
- Offshore oil and gas production equipment
- Heat exchangers handling aggressive media
- Components exposed to brackish water
This alloy has proven to be a cost-effective alternative to high-nickel alloys and titanium in certain applications, offering excellent performance at a more economical price point.
Standards
UNS S31254 (254 SMO) / 1.4547 / F44 conforms to the following international standards:
American Standards:
- UNS S31254
- ASTM A182 F44 (Forgings)
- ASTM A240 (Plate, Sheet, Strip)
- ASTM A276 (Bar and Shapes)
- ASTM A479 (Bar and Shapes for Bolting)
- ASTM A312 (Seamless and Welded Pipe)
- ASTM A249 (Welded Tube)
- ASTM A269 (Seamless Tube)
- ASME corresponding specifications
- NACE MR01-75 (latest revision) / ISO 15156
European Standards:
- EN 10088-3 1.4547 (Grade X1CrNiMoN20-18-7)
- EN 10088-2 (Flat Products)
- EN 10216-5 (Seamless Tubes)
- EN 10217-7 (Welded Tubes)
- NORSOK MDS R11 to R15, R17 & R18
Grade Designations and Chemical Composition
Grade Equivalents
| UNS | EN | ASTM | Other |
|---|---|---|---|
| S31254 | 1.4547 (X1CrNiMoN20-18-7) | F44 | 254 SMO |
Chemical Composition (weight %)
| Element | Min % | Max % |
|---|---|---|
| Carbon (C) | – | 0.020 |
| Chromium (Cr) | 19.50 | 20.50 |
| Nickel (Ni) | 17.50 | 18.50 |
| Molybdenum (Mo) | 6.00 | 7.00 |
| Nitrogen (N) | 0.18 | 0.25 |
| Copper (Cu) | 0.50 | 1.00 |
| Manganese (Mn) | – | 1.00 |
| Silicon (Si) | – | 0.70 |
| Phosphorus (P) | – | 0.030 |
| Sulfur (S) | – | 0.010 |
| Iron (Fe) | Balance | Balance |
PREn (Pitting Resistance Equivalent) = %Cr + 3.3×%Mo + 16×%N = 42-44
Mechanical Properties
UNS S31254 (254 SMO) / 1.4547 / F44 offers an excellent combination of strength, ductility, and toughness. These properties make it suitable for demanding applications where both mechanical performance and corrosion resistance are required.
| Property | Sheet & Strip | Plate |
|---|---|---|
| Tensile Strength (min) | 100 ksi (690 MPa) | 95 ksi (655 MPa) |
| 0.2% Yield Strength (min) | 45 ksi (310 MPa) | 45 ksi (310 MPa) |
| Elongation (min) | 35% in 50mm | 35% in 50mm |
| Hardness (max) | 223 HB / 96 HRB | 223 HB / 96 HRB |
| Impact Strength | 100 J (74 ft-lb) | 100 J (74 ft-lb) |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.0 kg/dm³ |
| Modulus of Elasticity at 20°C | 195 GPa |
| Mean Coefficient of Thermal Expansion (20-100°C) | 16.5 × 10⁻⁶ K⁻¹ |
| Thermal Conductivity at 20°C | 14 W·m⁻¹·K⁻¹ |
| Specific Thermal Capacity at 20°C | 500 J·kg⁻¹·K⁻¹ |
| Electrical Resistivity at 20°C | 0.85 Ω·mm²·m⁻¹ |
| Magnetisable | No (except when cold worked) |
Available Dimensions
FUSHUN METAL offers UNS S31254 (254 SMO) / 1.4547 / F44 in a wide range of product forms and dimensions:
Sheet & Coil
Thickness: 0.5mm to 6.0mm
Width: 500mm to 2000mm
Length: Up to 6000mm or coil form
Plate
Thickness: 6.0mm to 100mm
Width: 1000mm to 3000mm
Length: 2000mm to 12000mm
Round Bar
Diameter: 6mm to 300mm
Length: Up to 6000mm
Flat Bar
Thickness: 5mm to 100mm
Width: 10mm to 300mm
Length: Up to 6000mm
Pipe & Tube
Outside Diameter: 6mm to 325mm
Wall Thickness: 0.5mm to 20mm
Length: Up to 12000mm
Forgings
Custom dimensions available upon request
Flanges
According to standard specifications or custom requirements
Fabrication Information
Corrosion Resistance
UNS S31254 (254 SMO) / 1.4547 / F44 offers exceptional resistance to various forms of corrosion:
- Excellent resistance to pitting and crevice corrosion due to its high chromium, molybdenum, and nitrogen content
- Outstanding resistance to stress corrosion cracking
- Superior resistance to uniform corrosion in oxidizing and reducing acids
- Excellent resistance to corrosion fatigue
- The very low carbon content minimizes the risk of carbide precipitation during heating
- Performs exceptionally well in seawater and can be exposed to it for prolonged periods without suffering from crevice corrosion
Weldability
UNS S31254 (254 SMO) / 1.4547 / F44 possesses good weldability with the following considerations:
- Welding should be performed without pre-heating
- No post-weld heat treatment is required when welding is correctly performed
- Low thermal conductivity and high thermal expansion necessitate careful control to minimize distortion of welded joints
- Welding without filler metal should be avoided as it results in poor strength properties
- Overalloyed filler metals are recommended to ensure adequate corrosion resistance in the weld area
Machinability
Machining UNS S31254 (254 SMO) / 1.4547 / F44 presents certain challenges:
- High work hardening rate combined with low sulfur content makes it relatively difficult to machine
- Best results are achieved with slow speeds, sharp tools, positive feeds, powerful machine tools, and ample lubrication
- Cutting tools should be kept engaged with the workpiece and interrupted cuts should be avoided
Why Choose FUSHUN METAL for UNS S31254 / 1.4547 / F44 Products
When your application demands the exceptional corrosion resistance and durability of UNS S31254 (254 SMO) / 1.4547 / F44 super austenitic stainless steel, FUSHUN METAL stands as your trusted supply partner:
- Comprehensive inventory of UNS S31254 / 1.4547 / F44 in various product forms including sheet, plate, bar, pipe, tube, and forgings
- Premium quality materials sourced from approved mills with full material certification and traceability
- In-house processing capabilities including cutting, beveling, and custom fabrication
- Strict quality control procedures ensuring all products meet the specified standards
- Technical expertise to assist with material selection and application guidance
- Competitive pricing and reliable delivery schedules
- Experience serving industries that depend on high-performance corrosion-resistant alloys
For applications where standard austenitic stainless steels would face premature failure due to chloride-induced corrosion, our UNS S31254 / 1.4547 / F44 super austenitic stainless steel provides the ideal solution. Contact our sales team today for a detailed quotation and product information tailored to your specific requirements. Our technical advisors are ready to assist with your material selection to ensure the optimal performance and longevity of your critical equipment.
