Understanding Duplex Stainless Steel: UNS S31803 and S32750 Applications

Physical Properties

Tensile Strength: 620–850 MPa

Nearly double the strength of regular austenitic stainless steels such as 304 and 316. This enhanced strength allows the material to endure high-pressure conditions while decreasing the requirement for additional wall thickness — directly reducing material cost without sacrificing structural performance.

Mechanical Properties

Yield Strength: ~2× That of 304 / 316

The ferritic-austenitic microstructure enables thinner cross-sections in structural designs while sustaining structural components under load. The alloy exhibits outstanding resistance against three types of corrosion — enabling reliable operation in essential environments including operations with high chloride concentrations where austenitic steels are prone to stress corrosion cracking (SCC).

SCC Resistance

Superior Stress Corrosion Cracking Resistance

The duplex microstructure provides outstanding protection against stress corrosion cracking (SCC) which frequently occurs in environments containing chloride. These properties support sustainable practices because they decrease the need for equipment repairs and maintenance activities — resulting in longer operational periods and better system performance in process-critical settings.

Applications: Oil and gas extraction, desalination plants, chemical processing equipment.

Advantage: Maintains mechanical properties across environments featuring high thermal gradients, corrosive media, and variable mechanical stress.

Comparison 01

Corrosion Resistance

The higher chromium and molybdenum and nitrogen content of UNS S32750 establishes better pitting and crevice corrosion protection in chloride environments which include seawater and chemical processing facilities. The material protects against aggressive chloride exposure because its Critical Pitting Temperature (CPT) exceeds 50°C (122°F). UNS S31803 protects against corrosion at a high level which suits moderate corrosive environments, thus enabling industrial operations to run with reduced expenses while still achieving dependable protection.

Comparison 02

Strength and Durability

Both grades achieve their exceptional mechanical strength and durability through their dual-phase austenite-ferrite microstructure. UNS S32750 achieves a tensile strength range of 795–1000 MPa, exceeding standard austenitic grades such as 316L. The material strength allows construction to use thinner parts which results in both financial and material savings. The durability assessment shows that UNS S32750 outperforms S31803 in all three categories of stress corrosion cracking resistance and fatigue failure resistance and wear resistance which researchers and industrial testing confirmed through their testing process in offshore and chemical processing environments.

Comparison 03

Cost and Availability

Duplex stainless steel prices range approximately from $3,500 to $4,500 per metric ton, varying by grade and supplier. The cost-to-performance ratio of duplex grades is favorable compared to traditional austenitic grades because they use less nickel and their production methods are more efficient. Major global producers including Outokumpu Sandvik and Alleima maintain continuous supply chains which operate throughout Europe North America and Asia. Custom alloy compositions or specialized certification requirements will increase lead times which makes supplier evaluation and advanced planning essential for cost-efficient procurement.

Application 01

Oil & Gas Industry

Duplex stainless steel UNS S31803 is widely employed in the oil and gas sector because it has exceptional chloride stress corrosion cracking resistance combined with high mechanical strength. The material serves essential functions in three primary areas: pipelines, subsea equipment, and pressure vessels — because these areas frequently experience direct contact with highly corrosive seawater and aggressive chemical substances. Operators who use UNS S31803 decrease equipment failure risks while boosting operational efficiency through optimized maintenance practices, which extend equipment lifespan and reduce operational costs in this demanding industry.

• High-pressure pipelines and subsea transmission systems
• Pressure vessels and process separators in upstream operations
• Wellhead equipment and manifolds exposed to corrosive fluids

Application 02

Marine Applications

UNS S31803 provides superior mechanical strength combined with corrosion resistance protection for demanding marine environments. Its dual-phase microstructure produces excellent protection against pitting, crevice corrosion, and stress corrosion cracking in high-chloride environments. The material serves as an essential solution for critical marine functions because it protects subsea pipelines, structural components, and equipment in contact with seawater. Marine operations using UNS S31803 meet industry standards while enhancing operational efficiency and decreasing material loss in environments which contain highly corrosive substances.

• Subsea pipelines and structural support components
• Offshore platform structural members and seawater systems
• Desalination plant intake and brine discharge piping

Application 03

Chemical Processing

The chemical processing sector is increasingly adopting UNS S31803 duplex stainless steel for its superior ability to resist multiple corrosive materials which include acids and alkalis and chlorides. The material displays its best performance in operational environments which subject equipment to severe chemical exposure while maintaining variable temperature conditions. The material demonstrates excellent performance when it operates under high-pressure and high-temperature reactor systems because it combines high strength-to-weight ratio with exceptional thermal stability that enables it to endure high operational pressures while protecting against thermal fatigue. Industry research and practical field testing have proven the material’s ability to function in these extreme conditions which establish its status as an essential component for chemical processing systems.

• High-pressure reactors and process vessels in acid service
• Heat exchangers and cooling systems in aggressive chemical environments
• Scrubbers, columns, and storage tanks in chemical plants

Application 04

Heat Exchangers & Infrastructure

All worldwide infrastructure projects now give their main focus to sustainable materials which deliver enduring performance capabilities. UNS S31803 and S32750 both function as common materials for heat exchangers and pressure vessels because they provide exceptional protection against corrosion while withstanding extreme mechanical forces. Industries now show more interest in lifecycle cost assessment which duplex stainless steel materials deliver through their extended lifespan and lower upkeep needs. The material serves as an essential component in contemporary infrastructure development efforts because it can withstand both high temperature and high pressure extreme weather conditions while maintaining strength across extensive operational periods.

• Shell-and-tube and plate heat exchangers in process industries
• Pressure vessels and storage systems in power and energy sectors
• Water treatment and desalination infrastructure globally

What are the primary applications of UNS S31803 duplex stainless steel?

Industries that need high-strength metal and corrosion-resistant material properties extensively use UNS S31803 material throughout their operations. The grade which engineers specify as duplex 2205 or 1.4462 provides effective protection against chloride pitting and crevice corrosion in industrial applications. The ferritic-austenitic microstructure of this duplex stainless steel delivers users balanced mechanical and corrosion properties which standard austenitic grades fail to provide. Stockists and distributors supply this material in a wide range of sizes and product forms to meet fabrication needs. The material serves as an economical alternative to higher-alloyed stainless steels for applications which must perform under challenging operational conditions.

How does UNS S31803 compare to other stainless grades in chemical and physical properties?

The combination of 22% chromium and 5-6% nickel plus molybdenum and nitrogen in duplex UNS S31803 creates a material with better corrosion resistance than standard austenitic steels. The material achieves superior yield strength which generally reaches twice the strength of 304 and 316 stainless steel, making it suitable for designs that need to minimize weight without sacrificing structural integrity. The material protects against sulfide stress corrosion cracking and chloride pitting which makes it essential for applications in marine and chemical industrial environments. The different environmental performance characteristics of UNS S31803 and S32750 stem from their separate compositional variations despite both materials exhibiting strong strength and corrosion protection. Stockist availability and ASTM specification compliance control the selection process for these duplex options.

What are the corrosion resistance characteristics of 2205 duplex stainless steel?

The alloy 2205 duplex stainless steel — identified as UNS S31803 and 1.4462 — achieves exceptional protection against general corrosion and chloride pitting and crevice corrosion in environments containing chloride ions. The combination of duplex microstructure and molybdenum content provides better defense against chloride pitting and crevice corrosion compared to most austenitic steel grades. The steel demonstrates excellent performance in environments that pose sulfide stress corrosion dangers, making it appropriate for use in both oil and gas operations and pulp and paper manufacturing processes. The operators need to avoid extended periods in the temperature range which results in sigma phase development because proper fabrication and heat treatment methods protect corrosion resistance. Users should acquire 2205 from reliable stockists or distributors who can confirm products meet high quality standards and applicable specifications.

Can UNS S31803 be welded easily, and what should fabricators consider?

Duplex steel S31803 can be welded with common techniques such as TIG, MIG, and SMAW — but operators must control heat input during welding to achieve proper ferrite-austenite balance and prevent sigma phase development. Welders must be qualified according to applicable ASTM standards and must understand how to select suitable filler metals; proper welding parameters generally eliminate any need for pre-weld and post-weld heat treatments. The use of compatible duplex filler metals enables maintenance of corrosion resistance and mechanical properties through the entire joint structure. Fabrication shops should also consider potential distortion and select appropriate sizes and annealed condition material from a trusted stockist. The combination of proper inspection methods and non-destructive testing leads to the creation of high-quality welds which meet standards for pressure equipment and structural components.

What is the recommended heat treatment and anneal practice for duplex UNS S31803?

The standard supply condition of duplex UNS S31803 includes an annealed state — achieved through solution annealing at 1020–1100°C followed by immediate quenching. This thermal treatment restores the duplex microstructure and reduces the presence of sigma intermetallic phases that create toughness deficiencies and corrosion protection failures. Operators must protect parts from heat treatment damage through proper handling methods which prevent material sensitization and stop exposure to temperatures that cause brittle phase precipitation. The welding process requires operators to control localized heating across large manufactured components — resulting in material degradation concerns that create the need for post-weld heating management or repair work. Many fabricators rely on material certifications from a stockist or distributor confirming annealed condition and compliance with ASTM specifications before proceeding with fabrication.

What mechanical properties does duplex S31803 offer for structural applications?

Duplex S31803 displays superior mechanical strength because its yield strength achieves 400 MPa and reaches 550 MPa while its tensile strength meets 700 MPa. The high-strength profile enables designers to create structural and pressure vessel components through thinner sections which result in products that maintain their impact resistance across the correct heat treatment conditions. The combined ferritic and austenitic microstructure provides adequate fatigue resistance under repetitive stress conditions. Engineers consider this duplex grade as the ideal choice for projects which require both extensive temperature control and advanced strength and corrosion protection. Stockists provide material availability in multiple sizes which enables designers to develop a range of fabrication configurations that meet specific project requirements.