440C Stainless Steel
A 17% chromium martensitic stainless steel with very high carbon
Typical values for the temper in the title
440C contains about 17% chromium and 0.95–1.20% carbon. The high carbon forms hard martensite and carbides after hardening, so it reaches a hardness of 58–60 HRC.
It is the hardest standard stainless steel and the classic choice for stainless bearings, wear-resistant valve parts and quality knives. The cost: low toughness, and lower corrosion resistance than 304.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 760–1900 MPa | |
| Yield strength Rp0.2 | 450–1860 MPa | |
| Elongation A | 14% | |
| Hardness | 269 → HRC 58-60 | |
| Modulus of elasticity E | 200 GPa | |
| Density ρ | 7.65 g/cm³ | |
| Machinability | 50% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Cr chromium | 16.0–18.0 | corrosion resistance |
| C carbon | 0.95–1.20 | hardness and carbides |
| Mo molybdenum | max 0.75 | |
| 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 | soft, for machining | delivery condition |
| Hardened, tempered at 150–370 °C | 58–60 HRC | bearings, knives, wear parts |
Applications
- Stainless bearings
- Valve parts and seats
- Quality knives
- Tools and wear parts
- Nozzles
Fabrication
Heat treatment
Hardened in oil or air, and tempered low (150–370 °C). Temper immediately after hardening.
Machining
Machine annealed, and grind after hardening.
Welding
Not suited to welding.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| 440A | 725–1790 / 415–1650 MPa | Difficult | less carbon: tougher and more resistant · material page |
| 420 | 586–1900 / 414–1650 MPa | Difficult — Preheat 200C | cheaper, lower hardness · material page |
| 17-4 PH (630) | 930–1310 / 725–1170 MPa | Excellent | stronger and more resistant, but not as hard · material page |
Common mistakes
Choosing 440C for a shock-loaded part
Toughness is low. For such a part, 431 or 17-4PH.
Leaving time between hardening and tempering
The part may crack. Temper immediately.
Welding
The high carbon causes cracking.
Equivalents, standards and supply
| EN | 1.4125 |
|---|---|
| DIN | X105CrMo17 |
| JIS | SUS440C |
| Standards | ASTM A240 / AMS 5630 |
| Forms | rod · plate |
| Producers | Carpenter · Böhler N695 · Sandvik · Valbruna |
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