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There is a significant positive correlation between the material grade and cost of duplex steel flanges, which is reflected in the following aspects:
1. Alloying element content determines the grade difference and cost base
The material grade of duplex steels is mainly classified according to its alloying element (e.g. chromium, nickel, molybdenum, nitrogen, etc.) content and performance, and the higher the grade, the higher the proportion of rare alloying elements is usually contained in the material. For example, ** low-grade duplex steel (such as S32304) contains only about 23% chromium, 4% nickel, the alloy composition is simple, the smelting process is relatively easy, the production cost is low; and high-grade duplex steel (such as S32750, S32760) ** need to add more than 10% of nickel, more than 3% of molybdenum and nitrogen, these alloying raw materials are expensive, and the smelting process needs to be precise control of the proportion of composition and heat treatment process (such as solid solution treatment temperature, heat treatment temperature and nitrogen). These alloys are expensive raw materials, and the smelting process requires precise control of the composition ratio and heat treatment process (such as solid solution treatment temperature, cooling rate), resulting in a significant increase in production difficulties and energy consumption, directly pushing up the cost of materials.
2. Increased performance requirements lead to process complexity and cost increases
High-grade duplex steels need to meet more stringent performance indicators (such as high strength, high corrosion resistance, stress corrosion cracking resistance), which puts forward higher requirements for the production process. Example:

Smelting process: High-grade materials may require high-precision processes such as vacuum melting and electroslag remelting to reduce impurities and segregation, and the process cost is 30%~50% higher than normal steelmaking.
Processing Difficulty: High alloy content improves the hardness and strength of the material, which requires the use of special tools, higher power machine tools and low cutting efficiency, and the processing cost can be 20%~40% higher than that of low-grade materials.
Testing cost: High-grade flanges need to pass more stringent non-destructive testing (such as ultrasonic flaw detection, magnetic particle testing), mechanical properties testing (such as impact test, intergranular corrosion test), testing costs account for a higher proportion.
3. Special requirements of application scenarios further affect the cost
Different grades of duplex steel are suitable for different corrosive environments and pressure levels:

Low-grade materials (e.g. S32101) are commonly used in general chemical industry, water treatment and other mild corrosion scenarios, the market demand is high, and large-scale production can reduce unit costs.
High-grade materials (e.g. S32750) are mostly used in highly corrosive, high-pressure environments such as offshore engineering, petroleum refining, etc. Such scenarios require extremely high reliability of flanges, which often require customized production and small order batches, resulting in higher marginal costs. In addition, high-grade materials may need to comply with international standards (e.g. ASME, EN) or special certifications (e.g. NACE corrosion-resistant certification), and certification fees and compliance costs will also increase the overall cost.
4. Indirect impact of market supply and demand on costs
High-grade duplex steels, due to their high technical threshold and concentrated global production capacity, may be in short supply when demand surges in specific industries (e.g., deep-sea oil and gas development), resulting in a significant price increase. In contrast, low-grade materials have sufficient production capacity and intense market competition, resulting in relatively stable prices. For example, during the recovery period of the oil and gas industry, the price of S32750 flanges may increase by 50% to 80% compared with the off-season, while the price fluctuation of S32304 flanges is usually less than 20%.
To summarize
The material grade of duplex steel flanges is essentially the result of a “performance - cost” balance: the higher the grade, the higher the cost of the alloy, the difficulty of the process, the higher the testing requirements and the scarcity in the market, which ultimately translates into a higher selling price. Users need to choose the most cost-effective material grade under the premise of performance according to the corrosion level, pressure and temperature parameters, service life requirements and budget of the specific application, so as to avoid cost wastage due to over-pursuit of high performance or safety hazards caused by insufficient grade.