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Weldability
Grade 1.4057 is weldable in both the annealed and quenched-tempered conditions, but welding requires precautions. The material should be preheated—typically to 200–300°C—to reduce residual stresses and minimize cracking risk. During welding it is important to prevent cooling below 200°C. Suitable processes include TIG and MAG welding; avoid gases containing hydrogen or nitrogen as they can detrimentally affect mechanical properties. Post-weld tempering is required to restore mechanical and corrosion performance, and temper colors must be removed after tempering.
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Machinability
Machinability of 1.4057 is comparable to other martensitic stainless steels and is generally rated from average to poor, depending on hardness and strength. These factors can increase tool wear and affect surface finish. Carbide tooling and controlled cooling are essential for reliable machining.
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Forgeability
AISI 431 can be forged. Recommended practice is slow heating to about 850°C followed by rapid heating to 1150–1200°C. Forging is typically performed between 950–1200°C, followed by slow, controlled cooling to avoid residual stresses. Further heat treatments are possible after forging.
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Magnetism
Due to its martensitic structure, this alloy is magnetic, which can be advantageous where couplings or sensor feedback are required.
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Corrosion resistance
1.4057 generally offers good corrosion resistance compared to other martensitic stainless steels, particularly in fresh water and mild acidic environments. Best resistance is achieved on a clean metallic surface. The material is, however, susceptible to intergranular corrosion because of chromium carbide precipitation and associated chromium depletion.
