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E: enquiry@qilumetal.com
No. 18 Xiangfu Middle Road,Yuhua District, Changsha City
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Grade: AISI 431
Equivalent Steel: EN X17CrNi16-2/1.4057, GB 17Cr16Ni2, JIS SUS431, GOST 20X17H2
The chemical composition of AISI 431 stainless steel is precisely balanced to achieve a combination of high strength, good toughness, and moderate corrosion resistance. Chromium content is maintained between 15.00% and 17.00%, providing the material with fundamental corrosion resistance in atmospheric, fresh water, and mild chemical environments. Nickel, ranging from 1.25% to 2.50%, significantly enhances impact toughness and improves resistance to stress corrosion cracking—a key differentiator from common martensitic grades such as 410. Carbon is strictly limited to a maximum of 0.20%, enabling substantial hardness development through heat treatment while preserving weldability and ductility.
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431
Qilu
AISI 431 (UNS S43100) is a heat-treatable martensitic stainless steel optimized with a 15-17% chromium content for corrosion resistance and 1.25-2.50% nickel for enhanced toughness and ductility—two key alloying elements that set it apart from low-nickel martensitic grades like 410 and 420. Its martensitic crystalline structure enables dramatic strength improvements through quenching and tempering, a capability absent in non-heat-treatable austenitic stainless steels such as 304 and 316.
This grade maintains consistent mechanical performance in temperatures ranging from -40°C to 400°C , with exceptional stability in high-heat, high-stress operating conditions. AISI 431 is supplied in a variety of industrial forms, including hot-rolled bars, forged plates, and custom-machined components, all with precision surface finishes and dimensional tolerances to meet the strictest engineering requirements. It is the preferred material for applications where both mechanical durability and corrosion resistance are non-negotiable.
AISI 431 is standardized across all major international steel systems, with direct grade equivalents for seamless supply chain integration:
Country | USA | EN | China | Japan | Russia |
Standard | ASTM A276/276M | EN10088-3 | GB/T1220 | JIS G4303 | GOST 5632-76 |
Grade | 431 | 1.4057/ X17CrNi16-2 | 17Cr16Ni2 | SUS431 | 20X17H2 |
The chemical composition of AISI 431 and its global equivalents is optimized for corrosion resistance, strength, and processability, with strict limits on impurities to prevent brittleness and structural failure. Minor differences in elemental ranges reflect regional standardization requirements, while the core Cr-Ni alloy ratio is preserved for consistent performance.
Grade | C | Si | Mn | P | S | Cr | Ni |
431 | 0.20Max | 1.00Max | 1.00Max | 0.040Max | 0.030Max | 15.00-17.00 | 1.25-2.50 |
1.4057/ X17CrNi16-2 | 0.12-0.22 | 1.00Max | 1.50Max | 0.040Max | 0.030Max | 15.00-17.00 | 1.50-2.50 |
17Cr16Ni2 | 0.12-0.22 | 1.00Max | 1.50Max | 0.040Max | 0.030Max | 15.00-17.00 | 1.50-2.50 |
SUS431 | 0.20Max | 1.00Max | 1.00Max | 0.040Max | 0.030Max | 15.00-17.00 | 1.25-2.50 |
20X17H2 | 0.17-0.25 | 0.80Max | 0.80Max | 0.035Max | 0.025Max | 16.00-18.00 | 1.50-2.50 |
AISI 431’s mechanical properties are highly customizable via quenching and tempering (QT) and annealing, with regional standards defining grade-specific minimum performance metrics. High-temperature stability is a key advantage, with retained proof strength at temperatures up to 400°C, making it suitable for high-heat industrial environments.
Grade | Tensile strength | Yield strength | Alongation | Area of reduction | Impact value at RT/J | Hardness |
17Cr16Ni2 | 900-1050Mpa | 700Mpa Min | 12% Min | 45% Min | 25J Min | HBW295Max (Annealing) |
800-950Mpa | 600Mpa Min | 14% Min | 45% Min | 25J Min | ||
SUS431 | 780Mpa Min | 590Mpa Min | 15% Min | 40% Min | 39J Min | HBW229Max |
A=Annealed; QT=Quenched and Tempered; L=Longitudinal; Tr=Transverse
Steel grade | Size range | HT condition | Tensile strength | Yield strength | Alongation | Impact value at RT/J | Hardness /HBW | ||
L | Tr | L | Tr | ||||||
X17CrNi16-2/1.4057 | A | 950 Mpa Max | / | / | / | / | / | 295Max | |
d≤60 | QT 800 | 800-950 Mpa | 600 Mpa Min | 14% Min | / | 25J Min | / | / | |
60＜d≤160 | 12% Min | / | 20J Min | / | / | ||||
d≤60 | QT 900 | 900-1050 Mpa | 700 Mpa Min | 12% Min | / | 20J Min | / | / | |
60＜d≤160 | 10% Min | / | 15J Min | / | / | ||||
Retained structural strength at elevated temperatures is critical for high-heat applications such as gas turbines, engine components, and industrial furnaces.
Steel garde | HT condition | Minimum 0.2% proof strength at a temperature of: | ||||||
100℃ | 150℃ | 200℃ | 250℃ | 300℃ | 350℃ | 400℃ | ||
X17CrNi16-2/1.4057 | QT 800 | Mpa or N/mm2 | ||||||
515 | 495 | 475 | 460 | 440 | 405 | 355 | ||
Minimum 0.2% proof strength at a temperature of: | ||||||||
QT 900 | 100℃ | 150℃ | 200℃ | 250℃ | 300℃ | 350℃ | 400℃ | |
Mpa or N/mm2 | ||||||||
565 | 525 | 505 | 490 | 470 | 430 | 375 | ||
We provide a certified material test report (MTR) for all AISI 431 products, including:
Batch/lot number, heat number, and product dimensions
Full chemical composition analysis (per ASTM/EN/GB/T/JIS/GOST)
Mechanical property test results (tensile, yield, elongation, impact, hardness)
Heat treatment process and parameters
Ultrasonic testing results
Compliance with international standard specifications
AISI 431 is available in a comprehensive range of industrial forms and dimensions, with custom manufacturing options for unique engineering designs. All products adhere to strict dimensional and straightness tolerances for precision component production:
Product type | Size range | Length |
Hot rolled bar | Φ10-Φ130mm | 5000-7000mm |
Hot forged bar | Φ140-Φ600mm | 2000-5800mm |
Hot rolled plate/sheet | T:2-60mm; W:310-810mm | 6000-12000mm |
Hot forged plate | T:70-250mm; W:310-810mm | 2000-5800mm |
Hot Forged block | T: 260-500mm; W: 300-1000mm | 2000-5800mm |
Surface Finish | Turned | Milled | Grinding(Best) | Polished(Best) | Peeled(Best) | Black Forged | Black Rolled |
Tolerance | +0/+3mm | +0/+3mm | +0/+0.05mm | +0/+0.05mm | +0/+0.1mm | +0/+5mm | +0/+1mm |
Straighness | 1mm/1000mm max. | 3mm/1000mm max. | |||||
Hot Rolled Bar Stock Diameter: 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 120, 130, 140, 150, 160, 170, 180, 190mm
Hot Forged Bar Stock Diameter: 200, 210, 220, 230, 240, 250, 260,270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400mm
For real-time stock availability and custom size inquiries, contact our sales team directly.
AISI 431 delivers the highest corrosion resistance among all 400-series martensitic stainless steels , outperforming 410, 420, and 440 grades in atmospheric, freshwater, and mild chemical environments. It resists oxidation from nitric acid, most organic acids, and petroleum hydrocarbons , making it suitable for petrochemical and industrial fluid handling applications.
While its corrosion resistance is lower than austenitic grades like 304 and 316, AISI 431’s performance can be further enhanced through passivation treatment—a surface process that reinforces the chromium oxide protective layer . It offers better saltwater corrosion resistance than standard carbon steels, making it a cost-effective choice for marine mild-corrosion applications.
All AISI 431 bars and forgings undergo ultrasonic non-destructive testing (NDT) to ensure zero internal defects (cracks, inclusions, porosity) for high-stress applications. Testing complies with international standards:
EN 10228-3 Class III: For general industrial components
Sep 1921-84 D/D: For critical high-performance parts (automotive, energy, marine)
Qilu Steel uses advanced steel making and forging processes to ensure the purity, uniformity, and structural integrity of AISI 431, eliminating internal defects and enhancing mechanical performance.
EF+LF+VD (Electric Furnace + Ladle Furnace + Vacuum Degassing)
EAF+LF+VD (Electric Arc Furnace + Ladle Furnace + Vacuum Degassing)
EF+LF+VD+ESR (Electric Furnace + Ladle Furnace + Vacuum Degassing + Electro-slag Remelting)
EAF+LF+VD+ESR (Electric Arc Furnace + Ladle Furnace + Vacuum Degassing + Electro-slag Remelting)
ESR process is recommended for critical components requiring ultra-high purity and uniformity.
Forging Temperature: 800-1100℃ (optimal for structural uniformity)
Cooling: Slow cooling (air/lime/ash) to prevent thermal stress and cracking
Post-Forging: Immediate stress relief annealing to restore ductility for further processing
AISI 431’s martensitic structure enables full customization of mechanical properties via annealing (softening) and quenching/tempering (hardening/strengthening). Proper heat treatment is critical to maximizing strength, toughness, and corrosion resistance for specific applications.
Temperature: 680-800℃ (furnace heating)
Cooling: Furnace cooling or air cooling (slow cooling to avoid martensite formation)
Result: Hardness ≤295HBW, improved ductility and machinability for blanks and forming operations
Quenching: Heat to 950-1050℃ (furnace), cool in oil/air (forms martensitic structure for maximum strength)
Tempering:
600-650℃ (air cooling) – Balanced strength and toughness (QT 800/QT 900)
750-800℃/650-700℃ (air cooling) – Enhanced ductility for high-impact applications
Result: Tensile strength 800-1050Mpa, hardness 229-295HBW, retained impact resistance
AISI 431’s unique combination of heat-treatable strength, moderate corrosion resistance, and toughness makes it indispensable across high-stress industrial sectors. Its ability to withstand extreme mechanical load, high temperatures, and mild corrosive environments positions it as a premium material for critical components:
The gold standard for high-performance automotive components under extreme engine and drivetrain stress: engine valves, turbocharger housings and rotors, transmission shafts, drive axles, and piston rods. Its high wear resistance and strength resist deformation under extreme engine pressures and temperature fluctuations.
Ideal for fluid handling and process equipment: valves, pump rotors, impellers, pipe fittings, and pressure vessel components. Resists corrosion from petroleum hydrocarbons, organic acids, and mild industrial chemicals .
Critical for high-temperature, high-stress energy infrastructure: gas turbine components, nuclear power fasteners, thermal power plant valve stems, and wind turbine drive shaft parts. Maintains structural integrity at temperatures up to 400°C .
Cost-effective solution for mild marine corrosion environments: propeller shafts, deck hardware, marine fasteners, and small boat drivetrain components. Outperforms carbon steel in saltwater and coastal atmospheric corrosion.
Used for durable, sterilizable medical devices: surgical tools, biopsy instruments, and temporary orthopedic implants. Combines biocompatibility with the toughness to withstand repeated high-temperature sterilization.
High-strength fasteners, aircraft landing gear components, machine tool shafts, and plastic mold frames. Its heat-treatable hardness and toughness make it suitable for precision engineering applications requiring both strength and dimensional stability.
One of the most common customer questions is how AISI 431 compares to other popular stainless steel grades—below is a detailed comparison of key performance and application differences to guide material selection:
| Aspect | AISI 431 | AISI 420 |
| Nickel Content | 1.25-2.50% (high) | ≤0.50% (low) |
| Toughness & Ductility | Excellent (high nickel) | Poor (brittle when hardened) |
| Corrosion Resistance | Superior (best in martensitic grades) | Moderate (only atmospheric) |
| Strength Balance | Strength + ductility (load-bearing) | Maximum hardness (wear-only) |
| Key Applications | Shafts, rotors, valves | Knives, cutlery, small wear parts |
AISI 431 outperforms 410 in all key performance metrics due to its higher nickel content:
410 has 0% nickel, leading to low toughness and ductility
431 offers 2-3x better impact resistance and corrosion resistance
410 is limited to low-stress, non-critical applications; 431 for high-stress load-bearing parts
| Aspect | AISI 431 | AISI 304 |
| Steel Type | Martensitic (magnetic) | Austenitic (non-magnetic) |
| Heat Treatability | Fully heat-treatable (strength customization) | Non-heat-treatable (fixed properties) |
| Strength | Ultra-high (up to 1300MPa after QT) | Moderate (505MPa tensile strength) |
| Corrosion Resistance | Moderate (martensitic leader) | Excellent (universal corrosion resistance) |
| Formability | Limited (work hardening) | Excellent (cold forming, deep drawing) |
| Cost | Mid-range | Mid-range (higher for special finishes) |
| Key Applications | High-stress mechanical parts | General-purpose, corrosion-prone applications |
| Aspect | AISI 431 | AISI 630 (17-4PH) |
| Hardening Method | Quenching + tempering (martensitic) | Precipitation hardening (age hardening) |
| Corrosion Resistance | Moderate | Superior (near austenitic grades) |
| Strength | High (900-1300MPa) | Ultra-high (1100-1400MPa) |
| Cost | Cost-effective | Premium (2-3x higher than 431) |
| Key Applications | Cost-sensitive high-stress parts | High-corrosion, high-stress aerospace/medical parts |
A1: Minor compositional (C/Si/Mn ranges) and mechanical property minimums reflect regional standardization, but all equivalents retain the core martensitic structure, 15.00-18.00% Cr, 1.25-2.50% Ni, and high-strength characteristics of AISI 431.
A2: Yes, but precautions are necessary due to its martensitic nature. Use low-hydrogen welding processes (e.g., GTAW with matching filler like AWS ER 431) and preheat to 200–300°C to avoid hydrogen cracking. Post-weld heat treatment (tempering) is recommended to restore ductility and relieve residual stresses.
A3: AISI 431 is a martensitic stainless steel hardened by carbon and nickel, offering high strength and moderate corrosion resistance. 17-4 PH is a precipitation-hardening stainless steel that achieves even higher strength through heat treatment and contains copper, providing superior corrosion resistance in many environments. AISI 431 is often more cost-effective for applications where extreme corrosion resistance is not required.
A4: We offer turned (bright), milled (scalped), centerless ground (tolerance ±0.05mm), and polished finishes. Custom surface roughness (Ra) requirements can be accommodated upon request.
Contact Us: We provide personalized material solutions, including custom heat treatment, surface finishing, and precision machining, to meet your unique industrial application requirements.
