Key Feature

The High-Hardness Martensitic Piping Grade. Elevated carbon content enables exceptional hardness (up to 55 HRC) and superior wear resistance for cutting and wear applications in pipe form.

The standard choice for specialized applications requiring maximum hardness and wear resistance in stainless steel pipe.

Common Designations

UNS S42000
AISI 420
ASTM A268 TP420 (Seamless Ferritic/Martensitic)
EN 1.4021, X20Cr13
JIS SUS420

Multiple sub-grades exist: 420A (lower carbon), 420B, 420C (higher carbon).

Chemical Composition (Typical wt.%)

C: 0.15 - 0.40Cr: 12.0 - 14.0
Mn: ≤ 1.00
Si: ≤ 1.00
P: ≤ 0.040
S: ≤ 0.030

Carbon range defines capability: 0.15-0.30% for general applications; 0.30-0.40% for maximum hardness.

Mechanical Properties (Annealed)

Tensile Strength: ≥ 500 MPa
Yield Strength: ≥ 345 MPa
Elongation: ≥ 15%
Hardness: ≤ 223 HB

Higher strength in annealed condition compared to 410 due to higher carbon.

Mechanical Properties (Hardened & Tempered)

Tensile Strength: Up to 1600 MPa
Yield Strength: Up to 1350 MPa
Hardness: Up to 55 HRCElongation: Reduced to 5-10%

Maximum hardness achievable depends on carbon content and heat treatment precision.

Physical Properties

Density: 7.70 g/cm³
Melting Range: 1450 - 1510 °C
Thermal Conductivity: 24.9 W/m·K (100°C)
Strongly magnetic

Similar density to 410; always magnetic due to martensitic structure.

Heat Treatment Capability

Austenitizing: 980-1065°C
Quenching: Oil or air
Tempering Range: 150-370°C (for high hardness)
Annealing: 735-785°C, slow cool

Critical: Must be tempered immediately after quenching to prevent cracking.

Pressure Ratings

Limited pressure applicationsPrimarily mechanical/structural useConsult manufacturer for specific ratings

Generally not used for pressure piping; mainly for mechanical components.

Corrosion Resistance

Moderate resistance to water, atmosphere, and mild chemicals. Not for marine or harsh chemical environments.

Better than tool steels but inferior to 304/316; requires proper passivation.

Welding Characteristics

Very difficult to weldHigh risk of crackingPre-heat and Post-heat treatment essentialMatching filler metals critical

Generally avoided for welded pipe; preferred as seamless for machining applications.

Key Standards

ASTM A268 TP420: General Service Pipe
ASTM A731/A731M: Seamless Pipe
AMS 5616 (Aerospace)
EN 10216-5: Seamless Pressure Tubes
Custom specifications common

Often supplied to custom requirements rather than standard pipe specifications.

Common Applications

• Cutlery & Tool Manufacturing: Knife barrels, scissor tubes, tool bodies
• Surgical Instruments: Scalpel handles, instrument bodies, dental tool components
• Industrial Blades: Paper cutter tubes, textile blade shafts, cutting system components
• Mold Components: Plastic injection mold cores, insert housings
• Mechanical Parts: Wear sleeves, bearing housings, valve guide tubes
• Food Processing: Cutting blade housings, slicer components
• Defense/Military: Bayonet sheaths, specialized weapon components

Specifically designed where hardness and wear resistance are paramount in tubular form.