AISI 431 Stainless Steel Plate | A240 Type 431 | UNS S43100
What is AISI 431 Stainless Steel?
As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 431 Stainless Steel Plate.
AISI 431 is widely known and searched under many different names and designations, including AISI 431, ASTM A240 Type 431, ASME SA240 Type 431, UNS S43100, 431 stainless steel, 431 stainless steel plate, SUS431, 1.4057, X17CrNi16-2, 1Cr17Ni2 and 14Cr17Ni2. All these names refer to the same nickel-bearing 15–17% chromium martensitic stainless steel.
AISI 431 contains higher chromium than A240 410 plus 1.25–2.50% nickel. Nickel improves hardenability and toughness after quench and temper. Higher chromium improves corrosion resistance versus 410 and 414. The grade remains magnetic and can be heat treated to high tensile strength.
Typical uses include pump shafts, boat shafts, marine fittings, aircraft fittings, valve stems, fasteners and other high-strength parts that need better corrosion resistance than 12% Cr martensitics. In the annealed condition AISI 431 can also be supplied as plate for later fabrication and heat treatment.
SHH STEEL supplies AISI 431 as true China steel mill-Direct Supply, sourcing directly from major Chinese stainless steel mills. This model delivers competitive mill pricing, consistent quality, complete heat traceability and reliable delivery.
AISI 431 is frequently compared with A240 410, A240 410S, A240 430, A240 429, a240 304 and a240 316l. SHH STEEL provides technical support to help customers choose the most appropriate grade.
Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Grade | AISI 431 / A240 Type 431 / UNS S43100 | Confirmed |
| Related Standards | ASTM A240, ASTM A276, JIS SUS431, EN 1.4057 | Available |
| Product Form | Plate, Sheet, and heat-treatable flat products | Available |
| Delivery Condition | Annealed (hardened + tempered on request) | Standard annealed |
| Thickness Range | 1 mm – 80 mm (thicker available on request) | Custom sizes supported |
| Width | Up to 1500–2000 mm | Available |
| Length | Up to 6000–12000 mm or cut-to-length | Available |
| Surface Finish | No.1, 2B, peeled / ground as specified | Available |
| Certification | EN 10204 3.1 / Mill Test Certificate | Available |
SHH STEEL can supply dual-certified ASTM A240 / ASME SA240 Type 431 material when required by the project.
Chemical Composition
Typical Chemical Composition of AISI 431 (UNS S43100):
| Element | Content (%) |
|---|---|
| Carbon (C) | ≤ 0.20 |
| Silicon (Si) | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 |
| Chromium (Cr) | 15.00 – 17.00 |
| Nickel (Ni) | 1.25 – 2.50 |
| Iron (Fe) | Balance |
The defining features of AISI 431 are 15–17% chromium plus 1.25–2.50% nickel. Higher chromium improves corrosion resistance versus 410. Nickel improves toughness and hardenability after heat treatment. Carbon is high enough to form martensite. SHH STEEL carefully controls Cr and Ni so heat-treated properties stay consistent.
Mechanical Properties
Annealed Condition (typical values)
| Property | Value |
|---|---|
| Tensile Strength | ≥ 550–750 MPa depending on condition |
| Yield Strength (0.2%) | High after QT |
| Elongation | Useful in annealed condition |
| Hardness | Soft annealed for machining |
After quench and temper, AISI 431 can reach tensile strengths around 850–1050 MPa or higher, depending on tempering temperature. It is one of the highest-strength common martensitic stainless grades. SHH STEEL normally supplies plate in the annealed condition unless a hardened-and-tempered condition is specified.
Physical Properties
Density is approximately 7.70–7.75 g/cm³. Melting range is approximately 1450–1510°C. The grade is magnetic in all common heat-treated conditions.
Material Comparison
| Grade | UNS | Cr (%) | Ni (%) | Hardenable | Typical Preference |
|---|---|---|---|---|---|
| AISI 410 | S41000 | 11.5–13.5 | ≤ 0.75 | Yes | General 12% Cr wear / valves |
| AISI 414 | S41400 | 11.5–13.5 | 1.25–2.50 | Yes | Tougher 12% Cr martensitic |
| AISI 431 | S43100 | 15.0–17.0 | 1.25–2.50 | Yes | High-strength shafts / marine fittings |
| AISI 410S | S41008 | 11.5–13.5 | ≤ 0.60 | Limited | Welded 12% Cr constructions |
| AISI 430 | S43000 | 16.0–18.0 | ≤ 0.75 | No | Appliances and ferritic plate |
| AISI 304 | S30400 | 18–20 | 8–10.5 | No | General corrosion resistance |
AISI 431 is selected when high strength after heat treatment and better corrosion resistance than 410/414 are both required. It is not a substitute for a240 304 or a240 316l in highly corrosive chloride service. For welded soft plate, SHH STEEL recommends A240 410S or 430.
Corrosion Resistance
AISI 431 offers better corrosion resistance than 410 and 414 because of higher chromium and nickel. It performs well in mild atmospheres, fresh water, steam and many marine-atmosphere fittings when properly heat treated and passivated.
It is still a martensitic grade and is not equivalent to 304 or 316L in seawater immersion or strong acids. Best corrosion performance is obtained after heat treatment with a clean, passive surface. For indoor decorative plate, A240 430 is usually more economical.
Weldability
AISI 431 has limited weldability because it can air-harden in the heat-affected zone. Preheat and post-weld heat treatment are often required, especially on thicker sections.
Matching 431 or appropriate martensitic fillers are used when welding is unavoidable. If extensive welding is the main fabrication method, SHH STEEL recommends A240 410S or an austenitic grade.
Heat Treatment
AISI 431 is normally supplied in the annealed condition by SHH STEEL and can be hardened by quench and temper.
Typical hardening is performed from about 980–1065°C, followed by oil or air cooling and tempering to the required strength and toughness. Nickel helps retain toughness at high strength. SHH STEEL can supply annealed plate or discuss hardened-and-tempered supply when the drawing requires it.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | AISI 431 No.1 / A240 431 No.1 – industrial plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | AISI 431 2B – thinner plate and sheet |
| Peeled / Ground | Machined or precision ground | AISI 431 ground – shafts and pump parts |
SHH STEEL regularly supplies AISI 431 in No.1, 2B and ground finishes.
Tolerances
Dimensional tolerances for AISI 431 Stainless Steel Plate supplied by SHH STEEL generally conform to ASTM A480 practices.
Typical available size range is thickness 1 mm – 80 mm, width up to 1500–2000 mm, and length up to 6000–12000 mm or cut-to-length. SHH STEEL provides precise dimensional control and can support tighter tolerances when required.
Equivalent Material Grades
| Grade / Designation | Standard / Region | Notes |
|---|---|---|
| AISI 431 | AISI | Main commercial keyword |
| A240 Type 431 | ASTM A240 / ASME SA240 | Plate specification |
| UNS S43100 | Unified Numbering System | Primary UNS designation |
| 1.4057 / X17CrNi16-2 | EN (Europe) | European equivalent |
| SUS431 | JIS (Japan) | Japanese equivalent |
| 1Cr17Ni2 / 14Cr17Ni2 | GB/T (China) | Chinese equivalents |
| Related 410 / 414 | Multiple | Lower-Cr martensitic variants |
Related grades for comparison include A240 410, A240 410S, A240 430, A240 429, a240 304 and a240 316l.
Applications
AISI 431 is selected for high-strength martensitic parts that need better corrosion resistance than 410. Typical applications of AISI 431 include:
| Industry / Sector | Typical Components / Equipment (with keywords) |
|---|---|
| Marine | AISI 431 boat shafts, propeller shafts and marine fittings |
| Pumps & Valves | AISI 431 pump shafts, stems and high-strength wear parts |
| Aerospace / Aircraft | AISI 431 fittings and heat-treated structural parts |
| Fasteners | AISI 431 high-strength bolts, studs and pins |
| General Engineering | AISI 431 shafts, axles and machined components |
| Industrial Equipment | A240 Type 431 No.1 plate for subsequent hardening |
SHH STEEL supplies AISI 431 for these high-strength applications with consistent quality. For related industry solutions, see our marine industry, equipment manufacturing and machinery industry pages. Supporting services include steel cutting services, cnc steel machining services and worldwide shipping service.
Why Choose SHH STEEL
SHH STEEL is a China steel mill-Direct Supply specializing in stainless steel plate and heat-treatable grades. By working directly with major Chinese stainless steel mills, SHH STEEL supplies AISI 431 with the following advantages:
- Genuine China steel mill-Direct Supply pricing
- Consistent quality and complete heat traceability
- Full Mill Test Certificates (EN 10204 3.1)
- Ni-bearing AISI 431 material optimized for high strength plus improved corrosion resistance
- Flexible dimensions and finishes (including AISI 431 No.1, AISI 431 2B and AISI 431 ground)
- Technical support for selection among AISI 410, 414, 431 and 304
- Value-added services including steel cutting services, cnc steel machining services and worldwide shipping service
For more information about our company and full product range, please visit China steel Mill Agent-SHH STEEL.
FAQ
- What are the other common names for AISI 431?AISI 431 is also known as ASTM A240 Type 431, UNS S43100, SUS431, 1.4057, X17CrNi16-2, 1Cr17Ni2 and 14Cr17Ni2. SHH STEEL can certify the required designation.
- What is the difference between AISI 431 and AISI 410?AISI 431 has higher chromium (15–17%) and 1.25–2.50% nickel, so it offers better corrosion resistance and high strength after heat treatment. SHH STEEL recommends 431 for shafts and marine fittings.
- Can AISI 431 be hardened?Yes. It is a martensitic grade designed for quench and temper. SHH STEEL normally supplies annealed plate unless a hardened condition is specified.
- Is AISI 431 magnetic?Yes. It is magnetic in both the annealed and hardened conditions
- What is the density of AISI 431?Approximately 7.70–7.75 g/cm³. SHH STEEL provides mill certificates confirming chemistry and mechanical properties.
- Can AISI 431 replace 316L in seawater?Not for continuous seawater immersion. 431 is used for marine fittings and shafts with proper design and maintenance. SHH STEEL recommends 316L for highly corrosive chloride service.
- Does SHH STEEL supply dual-certified ASTM A240 Type 431 / AISI 431 material?Yes, SHH STEEL commonly supplies dual-certified material upon request.
Conclusion
AISI 431 Stainless Steel Plate is a nickel-bearing 15–17% chromium martensitic grade designed for high strength after heat treatment and better corrosion resistance than 410 or 414. It is a practical choice for pump shafts, boat shafts, marine fittings, aircraft fittings and other high-strength 400-series parts.
As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 431 Stainless Steel Plate with competitive pricing, full certification and complete technical support.
Contact SHH STEEL today for stock availability, heat-treatment condition, surface finish options (including AISI 431 No.1, AISI 431 2B and AISI 431 ground), or a competitive quotation.
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