440C Stainless Steel (UNS S44004)
The hardest stainless steel: about 1 percent carbon and 17 percent chromium, heat treatable to 58 to 60 HRC, for bearings, valve balls and seats, and wear-resistant machined parts.
What 440C Stainless is.
Type 440C carries 0.95 to 1.20 percent carbon and 16 to 18 percent chromium, which lets it harden to about 60 HRC while remaining stainless in mild environments. It is used where a part must resist wear and hold an edge or a seat: bearing races and balls, valve balls and seats, pump wear rings, nozzles and cutting tools. Toughness is low at full hardness, so it is not a bolting material.
We machine 440C components from certified A276 bar in the annealed condition and harden and temper them to the specified hardness, with grinding after heat treatment where the drawing needs it.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | 0.95 | 1.20 |
| Manganese | Mn | — | 1.00 |
| Phosphorus | P | — | 0.040 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 16.0 | 18.0 |
| Molybdenum | Mo | — | 0.75 |
Values per ASTM A276/A276M-17 Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Condition and nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| Condition A (annealed), hot finished — all | — | — | — | — | 269 HBW max |
| Condition A (annealed), cold finished — all | — | — | — | — | 285 HBW max |
Values per ASTM A276/A276M-17 Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. A276 controls 440C bar by annealed hardness; hardened properties are to the drawing.
Specifications that apply.
How 440C Stainless ships from Houston.
- Hex and heavy hex bolts and cap screws
- Full-thread studs and threaded rod
- Socket head cap and set screws
- Hex, jam and lock nuts
- Washers and spacers
- Machined components from certified bar
440C Stainless fasteners we make.
Every item is manufactured to your drawing or standard in 440C Stainless, imperial or metric, with an EN 10204 3.1 certificate.
What is 440C stainless steel?
440C is the high-carbon end of the martensitic stainless family. Its carbon content, over 1 percent, forms a large volume of hard chromium carbides and lets the matrix harden fully, so the alloy reaches about 60 HRC, the highest of any standard stainless. Corrosion resistance is moderate and depends on a good temper and finish, and toughness at full hardness is low, so 440C is a wear-part material rather than a fastener steel.
Working with 440C
- Machine in the annealed condition and finish grind after hardening; the alloy moves slightly in heat treatment.
- Specify the hardness range on the drawing; 58 to 60 HRC is typical for seats and bearings.
- A sub-zero treatment after quenching improves dimensional stability in precision parts.
- For a bolt or stud that must be hard and corrosion resistant, use 431 or 17-4 PH instead.
Testing, certification and marking
- Hardness tested after heat treatment on every lot
- Manufacturer's identification and heat number on every piece where size allows
- EN 10204 3.1 material test report with heat number and chemistry
- Dimensional inspection report on ground parts on request
410 Stainless Steel (UNS S41000)
The basic hardenable stainless: 12 percent chromium, heat treatable to 120 ksi and beyond, magnetic, and corrosion resistant in mild atmospheres — for valve trim, pump parts and high-strength stainless bolts.
ASTM A276 bar · ASTM F593 bolts431 Stainless Steel (UNS S43100)
The strongest and most corrosion resistant of the common martensitic grades: 16 percent chromium with nickel, heat treatable to 220 ksi bolts, for marine shafts, pump parts and high-strength stainless fasteners.
ASTM A1082 bolting · ASTM A564 bar17-4 PH Stainless (Type 630, UNS S17400)
The high-strength stainless — up to 190 ksi in H900, or 115 to 135 ksi with real toughness in the H1150 conditions — for pump shafts, valve stems, subsea and aerospace fasteners.