What is 1.4057 Stainless Steel?
Jan 14, 2026
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1.4057 stainless steel, commonly known as 431 or UNS S43100, is a martensitic stainless steel with high strength, good corrosion resistance, and excellent toughness. Its higher chromium content compared to other martensitic grades provides better corrosion resistance, and its composition allows for hardening through heat treatment. This makes it suitable for high-strength structural components, fasteners, and parts exposed to mildly corrosive environments.
This high-strength martensitic grade is standardized under key international systems.
| Standard | Equivalent Grade |
|---|---|
| EN (Europe) | 1.4057 |
| ASTM/AISI (USA) | 431, UNS S43100 |
| JIS (Japan) | SUS431 |
| KS (Korea) | STS431 |
Its composition includes chromium for corrosion resistance and nickel for toughness and hardenability.
| Element | C | Si | Mn | P | S | Cr | Ni |
|---|---|---|---|---|---|---|---|
| Content (%) | 0.12 - 0.20 | ≤ 1.0 | ≤ 1.0 | ≤ 0.04 | ≤ 0.03 | 15.0 - 17.0 | 1.5 - 2.5 |
It can achieve a good balance of strength and toughness through heat treatment.
| Condition | Yield Strength (Rp0.2) | Tensile Strength (Rm) | Elongation (A) | Hardness (HRC) |
|---|---|---|---|---|
| Annealed | ~ 550 MPa | ~ 740 MPa | ~ 20% | ~ 25 HRC |
| Hardened & Tempered | ≥ 690 MPa | ≥ 860 MPa | ≥ 15% | 30 - 40 HRC |
Key Characteristics and Applications of 1.4057 / 431
High Strength and Good Toughness: Offers a favorable combination of strength and impact resistance, especially in the hardened and tempered condition.
Better Corrosion Resistance: Higher chromium content provides better corrosion resistance than many other martensitic grades like 410 or 420, though still not equivalent to austenitic grades.
Magnetic and Hardenable: Strongly magnetic and responds well to heat treatment for hardening.
Primary Applications:
Aerospace and Defense: High-strength fasteners, landing gear components, and structural parts.
Oil and Gas Industry: Valve stems, pump shafts, and downhole tools requiring strength and moderate corrosion resistance.
Marine Equipment: Shafts, propeller fittings, and hardware for marine environments.
General Engineering: High-stress components like gears, bolts, and rollers.
How does 431 (1.4057) compare to 420 (1.4021) stainless steel?
Grade 431 contains more chromium and includes nickel, giving it better corrosion resistance and significantly higher toughness than 420. While 420 is typically used for cutlery and wear-resistant parts where high hardness is the priority, 431 is chosen for structural and high-stress applications where a combination of strength, toughness, and moderate corrosion resistance is required. 431 generally achieves lower maximum hardness but much better impact resistance.
What are the heat treatment recommendations for 431 stainless steel?
For optimum properties, 431 is typically hardened by austenitizing at 980-1050°C followed by oil quenching. It is then tempered at temperatures between 540-660°C to achieve the desired balance of strength and toughness. Higher tempering temperatures increase toughness and ductility while reducing hardness and strength. Care must be taken to avoid tempering in the range of 370-540°C to prevent tempered martensite embrittlement.
Looking for a Reliable Supplier of 1.4057 / 431 Stainless Steel?
GNEE Steel supplies high-strength 431 (1.4057) stainless steel in bar, plate, and forging forms, available in annealed or heat-treated conditions to meet demanding mechanical requirements. We provide full material certification and processing support. If you have any requirements, please feel free to contact us.
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