431 Stainless Steel
A Cr-Ni martensitic stainless steel, strong and relatively corrosion resistant
Typical values for the temper in the title
431 contains more chromium (15–17%) and added nickel (1.25–2.50%). The nickel keeps the structure martensitic despite the high chromium, so it combines high strength after hardening (860–1035 MPa tensile and more) with the best corrosion resistance among martensitic stainless steels.
It is used for pump and propeller shafts, high-strength bolts, and aerospace and marine parts.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 860–1035 MPa | |
| Yield strength Rp0.2 | 655–760 MPa | |
| Elongation A | 15% | |
| Hardness | 260–310 HB | |
| Modulus of elasticity E | 200 GPa | |
| Density ρ | 7.70 g/cm³ | |
| Machinability | 45% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Cr chromium | 15.0–17.0 | corrosion resistance |
| Ni nickel | 1.25–2.50 | keeps the structure martensitic with high chromium, and improves toughness |
| C carbon | max 0.20 | allows hardening |
| Mn manganese | max 1.00 | |
| Si silicon | max 1.00 | |
| Fe iron | balance |
Ranges per ASTM A276 and A240, and producer data (ATI). For purchasing, rely on the standard in the order.
Conditions and heat treatment
Martensitic stainless is hardened like steel: heating to the austenite range (usually 925–1070 °C), rapid cooling, then tempering. The tempering temperature sets the balance between hardness and toughness.
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed | for machining | delivery condition |
| Hardened and tempered (H&T) | 860–1035 MPa tensile and more | shafts and bolts |
| Tempering in the intermediate range | tempering around 400–580 °C lowers toughness and corrosion resistance, so it is avoided |
Applications
- Pump and propeller shafts
- High-strength bolts
- Aerospace parts
- Marine equipment
- Valve parts
Fabrication
Heat treatment
Hardened and tempered. For good toughness, temper high, above the intermediate range.
Machining
Reasonable annealed, harder when hardened.
Welding
Difficult: preheat and post-weld heat treatment are needed.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 410 | 480–830 / 275–620 MPa | Medium — Preheat | cheaper, and less resistant · material page |
| 17-4 PH (630) | 930–1310 / 725–1170 MPa | Excellent | stronger and easier to heat treat · material page |
| 316 / 316L | 485–620 / 170–310 MPa | Excellent — ER316L | more corrosion resistant, but weak · material page |
Common mistakes
Tempering in the intermediate range
Toughness drops. Temper above the range.
Expecting the resistance of 316
431 can also pit in stagnant seawater.
Replacing 431 with 17-4PH without calculation
Strength and properties differ. Check.
Equivalents, standards and supply
| EN | 1.4057 |
|---|---|
| DIN | X17CrNi16-2 |
| JIS | SUS431 |
| Standards | ASTM A276 / AMS 5628 |
| Forms | rod · forging |
| Producers | Carpenter · Böhler · Villares |
Learn more
Values are typical and for comparison only. For design, rely on the standard and on the mill certificate. Sources: ASTM A240, ASTM A276 and EN 10088 (composition), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026