431 stainless steel vs 440C: Hardness and Wear Resistance
Jul 13, 2026
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When selecting stainless steel for high-wear, high-strength, and precision mechanical applications, buyers often compare 431 and 440C grades. Both are martensitic stainless steels; understanding the differences in hardness and wear resistance between 431 and 440C helps engineers choose the most suitable material for shafts, bearings, cutting tools, molds, and various industrial components.
What is the hardness of 431 stainless steel bar?
Tempering within the 370°C to 570°C range should generally be avoided, as it significantly reduces the material's impact toughness.
The hardness of 431 stainless steel bars depends largely on the heat treatment process. Tempering within the 370°C to 570°C range should generally be avoided, as it significantly reduces the material's impact toughness. In the annealed condition, the maximum hardness is approximately 331 HBW; after quenching and tempering, the hardness typically reaches 40–50 HRC (or 360–480 HBW).
Hardness details by condition:
Annealed condition (as-delivered): Max. 331 HBW (approx. 35 HRC);
T condition (quenched and tempered): Approx. 248–302 HBW or 25–30 HRC;
H condition (fully quenched): 40–50 HRC (approx. 380–480 HBW).
What is the hardness of 440C stainless steel round bar?
The hardness of 440C stainless steel round bar depends on its heat treatment. In the annealed condition, it has a Brinell hardness of around 223–269 HB (approx. 29–31 HRC). When properly hardened and tempered, it reaches a Rockwell hardness of 58 to 60 HRC (and can sometimes hit up to 65 HRC), making it the hardest of all standard stainless steel alloys.
431 vs 440C Stainless Steel:Chemical Composition
| Element | AISI 431 | AISI 440C |
| Carbon (C) | 0.12 – 0.22 | 0.95 – 1.20 |
| Chromium (Cr) | 15.00 – 17.00 | 16.00 – 18.00 |
| Nickel (Ni) | 1.50 – 2.50 | - |
| Manganese (Mn) |
≤ 1.00 |
≤ 1.00 |
| Silicon (Si) |
≤ 1.00 |
≤ 1.00 |
| Molybdenum (Mo) | - | 0.75 (Typical) |
431 vs 440C Stainless Steel: Mechanical Properties (After Heat Treatment)
| Property | AISI 431 (Q&T) | AISI 440C (Hardened) |
| Hardness (Rockwell) | 30 – 40 HRC | 58 – 62 HRC |
| Tensile Strength | 850 – 1000 MPa | 1800 – 2000 MPa |
| Yield Strength | 650 – 800 MPa | 1300 – 1500 MPa |
| Elongation |
≥ 15% |
≈ 2% |
431 vs 440C Stainless Steel:Heat Treatment Specifications
| Process | AISI 431 | AISI 440C |
| Annealing | 680 – 800°C (Slow cool) | 840 – 900°C (Slow cool) |
| Hardening (Quench) | 950 – 1050°C (Oil/Air) | 1010 – 1070°C (Oil/Air) |
| Tempering | 550 – 650°C (For toughness) | 150 – 200°C (To maintain hardness) |
| Cold Treatment | Usually not required | Recommended (Sub-zero) for stability |
Is 431 stainless steel stronger than 440C?
440C is significantly harder and more wear-resistant than 431 stainless steel. 440C contains higher carbon (up to 1.20%), enabling it to reach 58--62 HRC after heat treatment, making it ideal for knife edges and bearings. Conversely, 431 has lower carbon and achieves 40--48 HRC, but provides better corrosion resistance and toughness.
431 vs. 440C Stainless Steel: Corrosion Resistance
The corrosion resistance of 431 stainless steel is generally superior to that of 440C. Containing approximately 15%–17% chromium (Cr) and 1.25%–2.50% nickel (Ni), 431 performs well in atmospheric, fresh water, and mild marine environments. Although 440C contains 16%–18% chromium, its high carbon content (0.95%–1.20%) leads to the formation of chromium carbides, which slightly reduces its corrosion resistance.
431 vs. 440C Stainless Steel: Machinability
Both 431 and 440C are hardenable martensitic stainless steels, but 431 offers significantly better machinability. 431 has a machinability rating of approximately 48%, whereas 440C is difficult to machine and causes severe tool wear, typically resulting in a rating of only 20% to 25%. 431 offers a cost advantage when machining parts with complex shapes, while 440C is generally selected when superior wear resistance is the primary requirement.
431 vs. 440C Stainless Steel: How to Choose?
431: Commonly used for structural components subject to high stress that also require corrosion resistance, such as marine hardware, pump shafts, valve stems, bolts, and aerospace components.
440C: Used almost exclusively in applications requiring exceptional wear and friction resistance. Common applications include ball bearings, valve seats, surgical instruments, and high-end, heavy-duty knife blades.
ASTM A276 431 / 440C Stainless Steel Bar Manufacturers
| Product Form | Size Range (Diameter/Width) | Length | Standard Tolerances |
| Round Bar (Cold Drawn) | 2.0 mm – 50.0 mm | 3m / 6m | ISO h8, h9, h10, h11 |
| Round Bar (Centerless Ground) | 5.0 mm – 100.0 mm | 3m / 6m | ISO h8, h9 (Precision) |
| Round Bar (Hot Rolled/Peeled) | 20.0 mm – 300.0 mm | 4m – 6m | ASTM A484 |
| Square Bar | 10 mm – 150 mm | 3m – 6m | Hot Rolled / Cold Drawn |
| Hexagonal Bar | 5.0 mm – 75.0 mm | 3m – 4m | Cold Drawn |
| Flat Bar | (T) 3 – 60mm×(W) 20 – 200mm | 3m – 6m | HRAP (Pickled) |
Supply Conditions (Heat Treatment)
| Grade | Condition | Description | Hardness Requirement |
| 431 | Condition A | Annealed |
≤ 285 HBW |
| 431 | Condition T | Intermediate Temper (Q&T) | 248 – 302 HBW (Typical) |
| 431 | Condition H | Hardened & Tempered | 285 – 341 HBW (Typical) |
| 440C | Condition A | Annealed (Soft for Machining) |
≤ 269 HBW |
| 440C | Hardened* | User Heat Treated (Quench + Temper) | 58 – 62 HRC (After HT) |
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