440C Stainless Steel
440C is a high-carbon martensitic stainless steel built for one goal: maximum hardness and wear resistance. It is widely selected for cutting edges, bearing parts, and precision components where edge life and surface durability matter.
440C is heat treatable and magnetic. Final performance depends on heat treatment control, section size, and surface finishing. If you have a target hardness, share it in the RFQ.
Hardness after heat treatment
Up to about 58–62 HRC
Often chosen when you need long edge life and high wear resistance.
High carbon design
C ~0.95–1.20%
Supports higher hardness, with a trade-off in toughness.
Corrosion performance
Good in mild service
Best in fresh water and low-chloride exposure.
Magnetic behavior
Magnetic in all conditions
Common for martensitic stainless steels.
440C is used when the part must stay sharp, resist abrasion, or hold size after heat treatment. It is not the first choice for heavy impact, but it performs strongly in wear-driven service.
- Cutting tools: premium kitchen knives, industrial blades, shears, scissors
- Bearings: bearing races, rolling elements, precision bearing parts
- Medical tools: selected surgical and dental components that need hardness and clean surfaces
- Wear parts: high-wear machine components, gauges, measuring parts
- Mechanical hardware: seals, valve parts, and wear-prone pins
440C is often shown under different standards on drawings and purchase documents. For a clean order, confirm the target standard, delivery condition, and inspection scope.
| System | Designation | Note |
|---|---|---|
| AISI / ASTM | 440C | Common name in many RFQs |
| UNS | S44004 | Used in specification cross-reference |
| EN | 1.4125 | European grade number |
| DIN | X105CrMo17 | Name format used in Europe |
| JIS | SUS440C | Common ordering name in Asia |
| GB | 9Cr18Mo | Often seen on Chinese mill certificates |
- Maximum hardness: one of the hardest commonly supplied stainless grades after heat treatment.
- High wear resistance: strong performance in sliding wear and edge wear.
- Edge retention: holds sharpness longer, but needs more effort to sharpen.
- Dimensional stability: stable for precision parts when heat treatment is controlled.
- Magnetic: magnetic in annealed and hardened conditions.
Limits vary slightly by standard. Use your Mill Test Certificate as the final check for the delivered heat.
| Standard | C | Cr | Mn | Si | P | S | Mo | Fe |
|---|---|---|---|---|---|---|---|---|
| ASTM (UNS S44004 / 440C) | 0.95–1.20 | 16.0–18.0 | ≤ 1.0 | ≤ 1.0 | ≤ 0.04 | ≤ 0.03 | 0.40–0.75 | Balance |
| EN (1.4125 / X105CrMo17) | 1.00–1.20 | 16.0–18.0 | ≤ 1.0 | ≤ 1.0 | ≤ 0.04 | ≤ 0.03 | 0.40–0.80 | Balance |
| GB (9Cr18Mo) | 0.95–1.20 | 16.0–18.0 | ≤ 1.0 | ≤ 1.0 | ≤ 0.035 | ≤ 0.03 | 0.60–0.80 | Balance |
Properties depend on product form, thickness, and heat treatment. Confirm acceptance values by the governing specification.
| Condition | Tensile | Yield (0.2%) | Elongation | Hardness |
|---|---|---|---|---|
| Annealed (typical) | ~760–830 MPa | ~450 MPa | ~10–12% | ≤ 223 HBW |
| Hardened & tempered | Varies by cycle | Varies by cycle | Varies by cycle | Up to ~58–62 HRC |
440C performs well in fresh water, humid indoor air, steam, and many mild service environments. Because carbon is high, corrosion resistance is usually lower than 440A and 440B.
For heat exposure, 440C can resist oxidation up to about 760°C in short exposure. For stable service, it is commonly kept below about 300°C for continuous operation.
440C can be supplied in common stainless product forms. Availability depends on tolerance, straightness, surface finish, and inspection scope. Share your sizes and end use for the best supply route.
| Form | Typical size range | Notes |
|---|---|---|
| Sheet (cold rolled) | 0.3–6.0 mm, width 1000–2000 mm | Used for parts needing cutting, grinding, or polishing |
| Plate (hot rolled) | 3–100 mm, width 1000–2000 mm | Machining stock for high-wear components |
| Coil (cold rolled) | 0.3–6.0 mm, width 1000–2000 mm | Slitting and cut-to-length available |
| Coil (hot rolled) | 3–14 mm, width 1000–2000 mm | For heavier coil supply routes |
| Strip | 0.3–10 mm, width 7–600 mm | Often used for precision parts and blades |
| Seamless pipe | OD ≤ 610 mm, WT 1–100 mm | Confirm straightness and NDT if required |
| Welded pipe | OD 6–3000 mm, WT 1–100 mm | Define weld type and surface requirements |
| Round bar | Diameter 1–200 mm, length 100–12000 mm | Common for bearings, shafts, and machined parts |
| Flat bar / shapes | Flat width 20–800 mm, thickness 3–60 mm | Channels and beams are available by request |
- Machining: 440C can be difficult to machine. Machine in annealed condition when possible.
- Tooling: use rigid setups, carbide tools, and steady feeds.
- Cutting speed: lower speeds can help control heat and tool wear.
- Coolant: use sufficient coolant for stable surface finish.
- Grinding: strong grindability for sharp edges and precision surfaces.
The ranges below are common references. The right cycle depends on section size and your target hardness.
| Step | Typical range | Purpose |
|---|---|---|
| Anneal | 840–900°C | Softens for machining and reduces stress |
| Harden | 1010–1070°C, air or oil quench | Builds hardness and wear resistance |
| Temper | 150–370°C | Balances hardness with toughness |
These grades share a similar base, but they serve different priorities. 440C focuses on maximum hardness. 440A focuses on corrosion margin.
| Property | 440A | 440B | 440C |
|---|---|---|---|
| Carbon | Lower | Medium | High |
| Hardness potential | ~54–58 HRC | ~56–60 HRC | ~58–62 HRC |
| Corrosion resistance | Best | Medium | Lower |
| Wear resistance | Good | Better | Best |
| Toughness | Better | Medium | Lower |
| Sharpening | Easier | Medium | Harder |
Before ordering, align key points so the delivered material matches your application.
- Grade identity: 440C / S44004 / 1.4125 / SUS440C / 9Cr18Mo
- Hardness target: HRC requirement and acceptable range
- Delivery condition: annealed, QT, or heat-treated by supplier
- Tolerances: thickness/OD/WT, straightness, and flatness
- Surface finish: bright, mirror, satin, or grinding allowance
- Certification: inspection scope and EN 10204 3.1 if needed
Use these tools to confirm equivalents, check hardness, and prepare a clear RFQ.
What hardness can 440C reach?
With proper hardening and tempering, 440C often reaches about 58–62 HRC. The exact result depends on section size and the heat treatment cycle.
Is 440C stainless steel magnetic?
Yes. 440C is a martensitic stainless steel and is magnetic in annealed and hardened conditions.
Does 440C have good corrosion resistance?
It performs well in fresh water and mild service, but it is less forgiving than 440A or 440B. If chloride exposure is high, consider 316L or duplex grades.
Can 440C be welded?
Welding is usually not recommended due to cracking risk from high carbon. If welding is unavoidable, controlled procedures are required.
What information helps you quote faster?
Standard, product form, size range, surface finish, tolerance, quantity, required tests, packing request, and destination port.