Views: 1 Author: Site Editor Publish Time: 2026-06-03 Origin: Site
Recently, our company successfully delivered a batch of UNS 31803 duplex stainless steel butt-weld fittings to a long-term Italian customer. This customer regularly purchases stainless steel fittings, flanges, and other pressure piping components from us every year. Through years of cooperation, a high level of trust and mutual understanding has been established between both parties.
This order of UNS 31803 duplex stainless steel butt-weld fittings is intended for use in an important marine engineering project as critical components. Therefore, the customer imposed extremely strict requirements on the products, covering aspects such as material chemical composition, mechanical properties, dimensional tolerances, surface quality, and packaging methods.
Leveraging years of technical experience and a comprehensive quality control system, our company strictly controlled every production process to ensure that the products fully complied with the customer's technical specifications. The entire order execution went smoothly and efficiently, and production and delivery were completed on schedule.
Item | Description of Goods | Material | Qty | Unit |
10 | Curva SS 45° LR Ø88,9 Sp.5,49 | UNS S31803 | 20 | PCS |
11 | Curva SS 90° LR Ø88,9 Sp.5,49 | UNS S31803 | 40 | PCS |
12 | Curva SS 90° LR Ø114,3 Sp.3,05 | UNS S31803 | 25 | PCS |
13 | Curva SS 90° LR Ø219,1 Sp.3,76 | UNS S31803 | 28 | PCS |
14 | Curva SS 90° LR Ø273 Sp.4,19 | UNS S31803 | 20 | PCS |
15 | Tee SS Ø219,1 Sp.3,76 | UNS S31803 | 18 | PCS |
16 | Tee SS ridotto Ø219,1x114,3 Sch10S | UNS S31803 | 43 | PCS |
17 | Tee SS ridotto Ø273x219,1 Sch10S | UNS S31803 | 25 | PCS |
18 | Cap SS Ø219,1 Sp.3,76 | UNS S31803 | 32 | PCS |
19 | Cap SS Ø273 Sp.4,19 | UNS S31803 | 27 | PCS |
20 | TOTAL | 278 |
The end customer was very satisfied with the goods upon receipt, further solidifying our long-term and stable cooperative relationship. Our company will continue to focus on quality and provide reliable pressure piping component products to customers worldwide.
UNS S31803 duplex stainless steel butt-weld fittings are a type of welded pipe connector made from duplex stainless steel. They offer excellent corrosion resistance and mechanical properties and are widely used in harsh environments such as chemical plants, marine applications, oil and gas, papermaking, and desalination. UNS S31803 is an American standard duplex steel with excellent corrosion resistance and high strength, and particularly good resistance to localized corrosion. It is widely used as a material for chemical equipment. Compared with 316L and 317L austenitic stainless steels, S31803 has superior resistance to pitting and crevice corrosion. It also has high corrosion resistance, lower thermal expansion coefficient, and higher thermal conductivity than austenitic steels.
Duplex stainless steel is a special stainless steel consisting of approximately 50% ferrite phase and 50% austenite phase. This unique dual-phase structure gives it both the high strength of ferritic stainless steel and the good toughness of austenitic stainless steel, achieving a balance between strength and corrosion resistance.
Since its development in the 1930s, duplex stainless steel has become the material of choice for harsh corrosive environments in industries such as oil and gas, marine engineering, and chemicals, thanks to its excellent overall performance.
UNS S31803 is the most widely used representative grade of duplex stainless steel, commonly known in the industry as 2205 duplex stainless steel. Its key characteristics are as follows:
Feature | Description |
Duplex Structure | ~50% ferrite + ~50% austenite, combining the advantages of both structures |
High Strength | Yield strength is more than twice that of 316L austenitic stainless steel |
Excellent Corrosion Resistance | Significantly better resistance to pitting, crevice corrosion, and chloride stress corrosion cracking than 316L |
Good Weldability | Nitrogen-enhanced, improving corrosion resistance under welding conditions |
Cost Advantage | Lower nickel content (4.5–6.5%), much lower cost than nickel-based alloys |
PREN value (Pitting Resistance Equivalent Number): 32–33, between 316L and 6% Mo super-austenitic stainless steel.
Chemical Composition
| CHEMICAL | C | Mn | P | S | Si | Ni | Cr | Mo | N |
| ASTM A815 UNS 31803 | 0.03 max | 2.0 max | 0.030 max | 0.020 max | 1.0 max | 4.5-6.5 | 21.0-23.0 | 2.5-3.5 | 0.08-0.20 |
UNS S32205 is a very similar upgraded grade to S31803, with composition controlled to the upper limit of S31803 specifications, providing even better corrosion resistance. The two grades can be dual-certified.
Mechanical Properties
| MATERIAL | T.S (MPA) | Y.S (MPA) | EL % | HARDNESS |
| UNS S31803 | 620 min | 450 min | 20 min | 290 max |
Significance of strength advantage: Because the yield strength is more than double that of 316L, for components designed for the same load, wall thickness can be significantly reduced, thereby lowering equipment weight and raw material costs.
UNS S31803 duplex stainless steel butt-weld fittings are widely used in the following fields:
Industry | Specific Applications |
Marine Engineering | Offshore oil platforms, submarine pipelines, seawater desalination, marine platform structures |
Oil & Gas | Oil and gas transmission pipelines, refinery equipment, wellhead devices |
Petrochemicals & Chemicals | Chemical equipment, reactors, heat exchangers, conveying pipelines |
Pulp & Paper Industry | Digesters, bleaching equipment |
Pharmaceuticals & Food | Pharmaceutical equipment, food processing equipment |
Environmental Protection & Energy | Flue gas desulfurization, fertilizer industry, urea industry |
High-Strength Structures | Bridges, building structures, pressure vessels |
Typical service conditions: Chloride-containing environments, neutral chloride environments, seawater contact environments, oxidizing and acidic solution environments.
According to ASME B16.9, butt-weld fittings can be classified into the following types:
Type | Abbreviation | Description |
45° Elbow | 45EL / LR | Long radius |
3D | R=3D | |
90° Elbow | 90EL / LR | Long radius |
90EL / SR | Short radius | |
3D | R=3D | |
180° Elbow | 180EL / LR | Long radius |
180EL / SR | Short radius | |
Reducer | CONC REDUCER | Concentric reducer |
ECC REDUCER | Eccentric reducer | |
Tee | EQUAL TEE | Straight tee |
RED TEE | Reducing tee | |
Cross | EQUAL CROSS | Straight cross |
RED CROSS | Reducing cross | |
Cap | CAP | Sealing of Pipe End |
Stub End | STUB END | Used with lap joint flanges |
Size range: DN15 to DN1200 (NPS 1/2" to NPS 48")
Seamless fittings: manufactured from duplex stainless steel seamless pipes
Welded fittings: manufactured from duplex stainless steel plates or longitudinally welded pipes
Production standards: Available in American standards (ANSI), Chinese standards (GB), chemical industry standards (HG), Japanese standards (JIS), German standards (DIN), etc.
