420 stainless steel is a high-carbon martensitic stainless steel, known for:
• Excellent hardenability (up to 50 HRC Rockwell).
• Good corrosion resistance once hardened and polished.
• Excellent ductility in the annealed state.
Derived from 410, but with higher carbon content for better

Mechanical Properties

after hardening. It is frequently used for cutlery, surgical blades, valves, and applications requiring high hardness.
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Chemical Composition (%)

Element Min (%) Max (%)
Carbon (C) 0.15 –
Manganese (Mn) – 1.00
Silicon (Si) – 1.00
Phosphorus (P) – 0.040
Sulfur (S) – 0.030
Chromium (Cr) 12.00 14.00
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Mechanical Properties

(typical values)
Condition Tensile strength (MPa) Yield strength (MPa) Elongation (%) Hardness (HB)
Annealed 655 345 25 ≤255
Tempering 204°C 1600 1360 12 444
Tempering 316°C 1580 1365 14 444
Tempering 427°C 1620 1420 10 461*
Tempering 538°C 1305 1095 15 375
Tempering 593°C 1035 810 18 302
Tempering 650°C 895 680 20 262
(*) Avoid the 425–600°C tempering range due to risk of low impact resistance.
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Physical Properties

(annealed condition)
Property Value
Density 7,700 kg/m³
Modulus of elasticity 200 GPa
Coefficient of thermal expansion (0–100°C) 10.3 µm/m/°C
Thermal conductivity (100°C) 24.9 W/m·K
Specific heat 460 J/kg·K
Electrical resistivity 550 nΩ·m
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Heat Treatments

• Full annealing: 840–900°C with slow cooling to 600°C, then air.
• Process annealing: 735–785°C with air cooling.
• Hardening: 980–1035°C, oil or air quench.
• Tempering: 150–370°C to achieve various combinations of hardness and ductility.
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Key Features

• Maximum hardness among 12% chromium stainless grades.
• Sufficient corrosion resistance for cutlery and surgical instruments.
• Limited corrosion resistance compared to austenitic stainless steels (e.g., 304, 316).
• Not recommended for high temperatures exceeding the tempering range.
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Available Formats

• Bars (most common form)
• Plates
• Sheets
• Forgings
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Industrial Applications

• Cutlery: Knife blades and cutting tools.
• Surgical instrumentation: Blades and medical instruments.
• Mechanical components: Valves, valve needles.
• Industrial shears and blades.