Key Features:
Achieving top-tier corrosion resistance among all stainless steels through extremely high molybdenum, nitrogen, and copper content, especially exhibiting near-perfect resistance to chloride pitting and crevice corrosion.
Simply put, 254SMo is the "king of corrosion resistance among stainless steels," specifically designed for extreme corrosive environments that ordinary stainless steels (including 316L and 317L) and even duplex stainless steels cannot withstand.
Chemical Composition and Design Logic:
Ultra-High Molybdenum Content: A core element, with a content as high as 6%. Molybdenum is the most effective element against chloride pitting and crevice corrosion, and its content directly determines the material's corrosion resistance level.
High Chromium and High Nickel: Chromium (~20%) provides basic corrosion resistance, while nickel (~18%) stabilizes the austenitic structure and enhances resistance to reducing acids.
Key Strengthening Elements:
High Nitrogen: Approximately 0.2% nitrogen is added. Nitrogen is a powerful austenite forming agent and solid solution strengthening element, significantly increasing strength (its yield strength is twice that of 316L) and significantly improving resistance to pitting corrosion (synergistically with molybdenum).
Copper: Approximately 0.7% copper is added. The addition of copper greatly improves resistance to uniform corrosion in non-oxidizing acids such as sulfuric acid and phosphoric acid.
Extremely Low Carbon: Extremely low carbon content (≤0.02%) ensures excellent weldability and resistance to intergranular corrosion.
Key Performance Indicators:
Amazing Resistance to Localized Corrosion:
Extremely high pitting corrosion equivalent. Calculation formula: PREN = %Cr + 3.3×%Mo + 16×%N. The PREN value of 254SMo is > 43, far exceeding 316L (~25) and duplex steel 2205 (~35), and approaching that of some nickel-based alloys.
This means that it is virtually free from pitting and crevice corrosion in environments such as seawater, brine, and chlorine-containing bleach.
Excellent resistance to uniform corrosion:
Exhibits excellent performance in sulfuric acid, phosphoric acid, and organic acids over a wide range of concentrations and temperatures. Demonstrates strong resistance to acidic chloride solutions (such as wet chlorine and hypochlorite).
High strength: Thanks to nitrogen strengthening, its yield strength can reach over 300 MPa, comparable to duplex steel and far exceeding that of ordinary austenitic stainless steel.
Good weldability and formability: Despite its high alloy content, it retains good austenitic steel machinability.
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