431 Stainless Steel is a hardenable martensitic stainless steel that combines high tensile and torsional strength with good corrosion resistance. Thanks to its excellent resistance to salt water, it is particularly suitable for marine applications such as drive shafts, pumps and valves.
It is easily machinable in the annealed condition, but weldability is difficult due to the risk of cracking, making preheating necessary to improve welding performance.

Reference standards:

• ASTM A276 / A314 / A479
• ASTM A182 (forgings)
• AMS 5628
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Chemical composition (%)

Element Min (%) Max (%)
Carbon (C) – 0.20
Manganese (Mn) – 1.00
Silicon (Si) – 1.00
Phosphorus (P) – 0.04
Sulphur (S) – 0.03
Chromium (Cr) 15.00 17.00
Nickel (Ni) 1.25 2.50
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Mechanical Properties (condition T)

Property Value
Tensile Strength (UTS) 850–1000 MPa
Yield Strength (Proof Stress) ≥665 MPa
Elongation (A5) ≥12%
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Physical properties

Property Value
Density 7.80 g/cm³
Modulus of elasticity 200 GPa
Thermal Conductivity (100°C) 20.2 W/m·K
Electrical Resistivity 720 nΩ·m
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Key Features

• High mechanical strength (especially tensile and torsional).
• Good corrosion resistance similar to 304 stainless steel.
• Excellent resistance to salt water, ideal for marine applications.
• Difficult to weld, preheating recommended.
• Easy machinability in the annealed condition.
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Available forms

• Round bars
• Plates
• Sheets
• Tubes
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Industrial applications

Thanks to its combination of mechanical strength and corrosion resistance, 431 is used in:
• Marine systems: Propeller shafts, pumps, outboard motors.
• Aerospace industry: Structural components subject to high stress.
• Valves and valve stems: In corrosive environments.
• Axles: For industrial and marine vehicles.