Duplex steel lap joint stub ends are used for removable lap joint connections in high-salt, high-chloride, strong acid and alkali, and high-temperature and high-pressure pipelines. We offer two structural types: LP long type and SP short type, matched with three manufacturing processes: integrally stamped, precision-turned from seamless pipe, and rolled from plate for large diameters, with specifications covering DN15 to DN3000. Materials cover 2101/2304 lean duplex, 2205 standard duplex, and 2507/S32760 super duplex steel, manufactured according to GB/T12459, ASME B16.9, and MSS SP43 standards. One end of the product is a butt-weld bevel, which can be homogeneously fusion-welded with duplex steel pipes; the other end is a dense and flat lap joint sealing surface, which, paired with a loose flange, can rotate freely for alignment, facilitating construction connection and later maintenance. The industry commonly uses the "duplex steel stub end + carbon steel loose flange" solution to control engineering costs while ensuring corrosion resistance and pressure resistance.
Overview
The duplex steel lap joint stub end is a pipe lap joint fitting used in high-pressure, high-chloride-ion, and strong acid-base corrosion working conditions. One end is a standard butt-weld bevel, which can be homogeneously welded with duplex steel pipes; the other end is formed by hot pressing or CNC precision turning to create a dense and flat lap sealing surface, which, when paired with a loose flange, can rotate 360° freely for alignment. This structure mainly solves problems such as misalignment during construction of high-pressure corrosive pipelines, difficulty of installation in confined spaces, and cumbersome disassembly and assembly during later maintenance. We provide two standard structures: LP long type and SP short type. Materials cover 2101/2304 lean duplex, 2205 standard duplex, and 2507/S32760 super duplex steel. They are manufactured according to GB/T12459, ASME B16.9, and MSS SP43 standards, with specifications from DN15 to DN3000.
Key Features
The metallographic structure of duplex steel consists of two phases, ferrite and austenite. Its strength is about twice that of ordinary austenitic stainless steel, making it suitable for high-pressure, heavy-load pipelines. In terms of corrosion resistance, it has strong resistance to chloride ion pitting corrosion, crevice corrosion, and stress corrosion cracking, and can be used in highly corrosive media environments such as coastal salt spray, desulfurization slurry, and brine. It has good thermal stability and a low coefficient of linear expansion, is not easily deformed under alternating hot and cold working conditions, and the sealing surface can remain stable. The welding end is a butt-weld bevel. After homogeneous welding with duplex steel pipes, the weld structure is uniform, with no hidden risk of intergranular corrosion. For buyers, the industry-commonly used combination of "duplex steel stub end + carbon steel loose flange" can reduce overall project cost while ensuring corrosion resistance and pressure resistance under extreme working conditions.
Applications
For marine and maritime applications, it is suitable for offshore platform process pipelines, ship corrosion pipe networks, coastal power plant outdoor salt spray pipe networks, and seawater extraction and transportation pipelines, and can withstand long-term seawater immersion and chloride ion erosion. For power and environmental protection applications, it is used in thermal power plant desulfurization and denitrification slurry pipelines, dust removal corrosion pipe networks, and high-salinity wastewater transportation systems, resisting acid-base slurry erosion and corrosion. For petrochemical and chemical applications, it is used in fine chemical strong acid and strong alkali media, brine and salt chemical engineering, petroleum refining corrosion branch lines, and high-pressure reactor external connection pipe networks, resisting medium permeation and stress cracking. For special industrial applications, it is suitable for papermaking black liquor pipe networks, heat exchange high-pressure corrosion pipelines, and industrial circulating water systems in high-salinity areas. 2205 material is suitable for moderately strong corrosion working conditions, while 2507 super duplex steel can handle more severe working conditions such as deep sea, high-concentration acids and bases, and high-pressure heavy loads.
Specifications
In terms of materials, we provide a full range of choices: 2101/2304 lean duplex, 2205 standard duplex, and 2507/S32760 super duplex steel. Structurally, they are divided into LP long type and SP short type. LP long type is suitable for high-temperature and high-pressure main process pipelines, while SP short type is suitable for installation positions with limited space. Manufacturing processes include integrated stamping, seamless pipe precision turning, and large-diameter plate rolling. Diameters cover DN15 to DN3000. The implemented standards are GB/T12459, ASME B16.9, and MSS SP43. For customization, we can undertake non-standard diameters, non-conventional straight pipe lengths, widened and thickened high-pressure flanged sealing surfaces, ultra-thick pressure-bearing wall thicknesses, as well as process requirements such as internal and external mirror polishing, precision zero-tolerance turning, solution strengthening, and non-magnetic treatment. Please contact us to confirm specific specifications and parameters.
Purchasing & Delivery
Regarding minimum order quantity, for DN15–DN300 conventional stamped and pipe-made stock specifications, the MOQ for mainstream 2205 duplex steel material is as low as 1 piece, and we support sample submission for inspection and special project replacement parts; for bulk centralized procurement and foreign trade distribution, please contact us to confirm tiered minimum order plans. Regarding delivery, we regularly stock 2205 and 2507 material pipe blanks and plates. For DN15–DN300 conventional stock specifications, after order confirmation, solution treatment and passivation, high-pressure precision inspection, protective packaging, and shipment are completed within 48 hours. Packaging uses foreign-trade-grade protection: each piece is fully enclosed and wrapped independently in PE film, the sealing surface is covered with thickened anti-scratch protective film, and the welding bevel is fitted with a plastic anti-collision protective ring; small pieces are packed in thickened moisture-proof cartons with desiccant, and medium and large diameters are wrapped on the outer layer with pearl cotton and waterproof stretch film; full-container orders use fumigation-free solid wood pallets and high-strength steel straps for fastening, suitable for ocean shipping. Customized English shipping marks, customer LOGO, and batch numbers are supported.
Service & Support
In the pre-sales stage, our technical team can assist with selection for extreme corrosion working conditions, special material matching, high-pressure grade adaptation, flange matching, and installation protection guidance. In the after-sales stage, we provide duplex steel welding process guidance, passivation layer protection, and high-pressure pipe network operation and maintenance Q&A, full-process logistics tracking for orders, and assistance for overseas customers with rapid customs clearance. Before leaving the factory, products undergo multiple quality inspections such as alloy spectrum verification, solution treatment and passivation testing, precision dimensional re-inspection, end-face flatness inspection, high-pressure hydrostatic pressure testing, and non-destructive testing. The warranty period is 18 months, with 7×24-hour after-sales response. In the event of factory production quality defects, free returns and exchanges and free replacement shipments are supported. Welcome to contact us to confirm specific service terms.
FAQ
What is the difference between duplex steel lap joint stub ends and ordinary stainless steel pipe fittings?
Duplex steel has a ferritic + austenitic dual-phase structure, with strength about twice that of ordinary austenitic stainless steel, and its resistance to chloride pitting corrosion and stress corrosion is significantly better than 304 and 316L. It is mainly used in extreme corrosion and high-pressure working conditions that carbon steel and ordinary stainless steel cannot handle, such as seawater pipeline networks, desulfurization slurry pipelines, and brine systems.
How to choose between the two materials 2205 and 2507?
2205 standard duplex steel is suitable for moderate salt corrosion, desulfurization, and conventional chemical strong-corrosion working conditions, and is a widely used general-purpose choice. 2507 super duplex steel has higher corrosion resistance and strength, and is suitable for more severe working conditions such as deep sea, high-concentration acids and alkalis, and high-pressure heavy loads. For specific selection, you can contact us, and we will assist in confirming based on the medium, temperature, and pressure parameters.
Can duplex steel flanged short ends be used in seawater pipeline networks?
Yes. Duplex steel has strong resistance to chloride pitting corrosion in seawater, and is suitable for seawater pipeline network scenarios such as seawater desalination, offshore platforms, and coastal power plants. For material selection and wall thickness design under long-term immersion working conditions, you are welcome to contact us to confirm based on project parameters.
What is the difference between LP long type and SP short type, and how to choose?
The LP long type flanged short end is longer in length, suitable for high-temperature and high-pressure main process pipelines, and can better protect the sealing surface and adapt to pipeline thermal expansion and contraction. The SP short type has a compact structure and is suitable for locations with limited installation space. Both structures can be used for lap joint flange connection; for specific selection, please contact us to confirm.
What are the minimum order quantity and delivery time?
DN15–DN300 conventional stamped and tubular in-stock specifications, MOQ for mainstream 2205 material is as low as 1 piece, supporting sample submission for inspection and engineering replacement parts. For conventional in-stock specifications, quality inspection, packaging, and shipping are completed within 48 hours after order confirmation. For the lead time of non-standard customized and bulk orders, please contact us to confirm according to specifications and quantity.
