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431 Stainless Steel Round Bar | ASTM A276 / UNS S43100 / EN 1.4057
High-Strength Martensitic Stainless Steel Round Bar for Shafts, Pumps & Precision Components
Xi'an Dongmeng Group Co., Ltd. is a professional manufacturer and exporter supplying 431 stainless steel round bars (UNS S43100) for global industrial distributors, equipment manufacturers, machining companies and engineering contractors.
Grade 431 is a nickel-containing martensitic stainless steel designed for applications requiring high mechanical strength, good toughness and improved corrosion resistance compared with conventional lower-chromium martensitic grades.
Commonly specified as AISI 431 / UNS S43100, this material is closely related to EN 1.4057 / X17CrNi16-2. However, their chemical composition limits and applicable product requirements are not identical, so the governing standard must be confirmed before ordering.
431 stainless steel round bars are frequently selected for pump shafts, marine equipment components, valve stems, mechanical transmission parts, industrial fasteners and precision-machined components.
We support inquiries for hot-finished, heat-treated, peeled, turned, ground and polished round bars, with customized cutting and inspection arrangements according to project requirements.
Available Procurement Services
Request 431 Stainless Steel Round Bar Quotation
Submit Drawings for Size and Tolerance Review
Confirm Heat Treatment and Mechanical Properties
Request Material Test Certificates and Inspection Details
What Is 431 Stainless Steel?
431 stainless steel is a heat-treatable martensitic stainless steel containing approximately 15–17% chromium and 1.25–2.50% nickel under the ASTM Type 431 composition specification.
Unlike conventional austenitic stainless steels such as 304 and 316, Grade 431 can be hardened through austenitizing, quenching and tempering.
The chromium content contributes to corrosion resistance, while the nickel addition helps produce a useful combination of strength and toughness after heat treatment.
Key Characteristics
High Mechanical Strength
431 stainless steel can achieve significantly higher tensile strength than annealed 304 or 316 stainless steel through appropriate heat treatment.
Improved Corrosion Resistance
Compared with common 12–13% chromium martensitic stainless steels, Grade 431 generally offers improved corrosion resistance in suitable environments.
Heat-Treatable Structure
The material can be supplied in different conditions to balance tensile strength, hardness, ductility and impact toughness.
Good Shaft Material
Its combination of mechanical strength, toughness and corrosion resistance makes 431 a candidate for pump shafts, transmission shafts and rotating equipment components.
Magnetic Properties
Grade 431 is generally magnetic because of its martensitic microstructure.
Important Selection Limitation
431 stainless steel should not automatically be selected for continuous seawater immersion, aggressive chloride environments or highly corrosive chemical processing applications.
Material selection must consider operating temperature, stress, exposure conditions, surface finish and the potential for pitting, crevice corrosion and stress-corrosion cracking.
431 Stainless Steel Chemical Composition
ASTM Type 431 / UNS S43100 Chemical Composition
| Element | Symbol | Composition (%) |
|---|---|---|
| Carbon | C | ≤0.20 |
| Chromium | Cr | 15.00–17.00 |
| Nickel | Ni | 1.25–2.50 |
| Manganese | Mn | ≤1.00 |
| Silicon | Si | ≤1.00 |
| Phosphorus | P | ≤0.040 |
| Sulfur | S | ≤0.030 |
| Iron | Fe | Balance |
EN 1.4057 / X17CrNi16-2 Composition Differences
| Element | EN 1.4057 / X17CrNi16-2 |
|---|---|
| Carbon | 0.12–0.22% |
| Chromium | 15.00–17.00% |
| Nickel | 1.50–2.50% |
Although ASTM 431 and EN 1.4057 are closely related, an individual heat must be checked against the specified standard before dual compliance is claimed.
Procurement Recommendation: Request a heat-specific chemical analysis report and confirm whether the material must comply with ASTM A276, EN 10088-3 or both standards.
Mechanical Properties of 431 Stainless Steel
The mechanical properties of 431 stainless steel depend strongly on heat-treatment condition, product diameter and the governing specification.
For European Grade 1.4057, two commonly referenced quenched-and-tempered conditions are:
+QT800: Lower strength with greater ductility potential.
+QT900: Higher minimum strength with different toughness and elongation requirements.
EN 1.4057 Mechanical Properties - Quenched and Tempered
The following values are established reference requirements for EN 10088-3 long products in the specified diameter ranges. Confirm the applicable standard edition and product delivery condition when ordering.
| Property | +QT800 ≤60 mm | +QT800 >60–160 mm | +QT900 ≤60 mm | +QT900 >60–160 mm |
|---|---|---|---|---|
| Tensile Strength Rm (MPa) | 800–950 | 800–950 | 900–1050 | 900–1050 |
| 0.2% Proof Strength Rp0.2 (MPa), Min. | 600 | 600 | 700 | 700 |
| Elongation A5 (%), Min. | 14 | 12 | 12 | 10 |
| Charpy V Impact Energy (J), Min.* | 25 | 20 | 16 | 15 |
Impact values are longitudinal reference values under the cited long-product data specification. Test temperature, specimen orientation and acceptance requirements must be verified against the purchase specification.
Important Mechanical Property Notes
+QT800 and +QT900 are European delivery conditions and should not automatically be treated as equivalent to ASTM Condition T.
For diameters above 160 mm, mechanical property requirements and test locations should be agreed upon with the manufacturer.
Actual mechanical properties must be confirmed by product testing when certification is required.
Hardness and tensile strength must not be assumed to be interchangeable acceptance criteria.
431 Stainless Steel Hardness and Heat Treatment
431 stainless steel can be strengthened by heat treatment. The final hardness depends on the austenitizing temperature, cooling conditions, tempering temperature and section size.
Heat Treatment Reference
| Process | Typical Temperature | Purpose |
|---|---|---|
| Soft Annealing | 680–800°C | Reduce hardness and facilitate machining |
| Austenitizing | Approximately 950–1060°C | Prepare the structure for martensitic hardening |
| Quenching | Air / Oil / Controlled Medium | Develop martensitic structure |
| Tempering | According to target properties | Balance strength, toughness and ductility |
| +QT800 | Specified heat-treatment cycle | Meet +QT800 mechanical requirements |
| +QT900 | Specified heat-treatment cycle | Meet +QT900 mechanical requirements |
These temperatures are technical reference ranges, not a universal production procedure. Actual cycles must account for material chemistry, diameter, equipment and component geometry.
Which Condition Should You Choose?
Choose +QT800 when:
Moderate-to-high strength is required.
Greater ductility or toughness is important.
Components experience combined mechanical loading.
The project specification calls for +QT800 properties.
Choose +QT900 when:
Higher minimum yield and tensile strengths are required.
Shaft and mechanical component designs require greater strength.
The specified elongation and impact requirements remain acceptable.
The engineering specification identifies +QT900 as the required condition.
Temper Embrittlement Warning
431 stainless steel can experience reduced impact toughness when exposed to certain intermediate tempering temperatures.
Tempering in the approximate 425–600°C range requires particular caution because of potential embrittlement effects.
The final heat-treatment schedule should be selected and validated against the required mechanical properties.
Procurement Tip: Always specify the required heat-treatment condition, tensile strength, proof strength, hardness and impact requirements rather than ordering simply by material grade.
431 Stainless Steel Round Bar Sizes
431 stainless steel round bars are available for inquiry in metric and imperial dimensions.
Availability depends on material specification, manufacturing process, heat treatment and order quantity.
| Parameter | Typical Ordering Options |
|---|---|
| Diameter | 1.6–254 mm / 1/16–10 in |
| Common Metric Lengths | 3000 mm / 6000 mm |
| Common Imperial Lengths | 12 ft / 20 ft |
| Custom Length | According to drawings |
| Cut-to-Length | Subject to processing capability |
| Surface | Hot Finished / Peeled / Ground / Polished |
| Diameter Tolerance | According to applicable standard or agreed drawing |
| Straightness | According to purchase requirements |
| End Preparation | Saw Cut / Deburred / Machined as specified |
Common 431 Stainless Steel Round Bar Size and Weight Chart
The following weights are theoretical estimates calculated using a density of approximately 7.80 g/cm³.
| Diameter (mm) | Approx. Diameter (inch) | Theoretical Weight (kg/m) |
|---|---|---|
| 10 | 0.394 | 0.613 |
| 12 | 0.472 | 0.882 |
| 16 | 0.630 | 1.568 |
| 20 | 0.787 | 2.450 |
| 25 | 0.984 | 3.829 |
| 30 | 1.181 | 5.513 |
| 40 | 1.575 | 9.802 |
| 50 | 1.969 | 15.315 |
| 60 | 2.362 | 22.054 |
| 80 | 3.150 | 39.207 |
| 100 | 3.937 | 61.261 |
Round Bar Weight Calculation
Theoretical Weight (kg/m) = Diameter² (mm²) × 0.006126
This formula assumes a density of approximately 7.80 g/cm³.
Actual shipping weights may differ because of dimensional tolerances, surface processing and cutting allowances.
Surface Finish and Precision Tolerance Options
The surface condition of 431 stainless steel round bar affects machining allowance, dimensional accuracy, component performance and processing cost.
Hot-Finished Round Bar
Suitable for applications where additional machining or turning will be performed.
Typical characteristics include a mill-finished surface and larger machining allowances.
Peeled or Turned Round Bar
The outer surface is mechanically processed to remove scale and improve dimensional consistency.
This condition is often selected as a starting material for machined shafts and industrial components.
Centerless-Ground Round Bar
Centerless grinding provides improved diameter control and surface finish.
It is suitable for applications requiring more consistent bar dimensions before precision machining.
Polished Round Bar
Polishing improves the surface appearance and can help reduce surface irregularities.
The required surface roughness should be stated when the bar will be used in sealing, sliding or other critical mechanical applications.
Diameter Tolerance Requirements
For ASTM stainless steel bars, general dimensional requirements may be specified through ASTM A484/A484M.
Precision diameter tolerances such as h9, h8 or h7 may be requested where supported by the manufacturing process.
These tolerance grades are not automatically included with ASTM A276 material certification.
The customer should specify:
Nominal diameter
Permitted diameter tolerance
Required straightness
Surface roughness
Bar length and cutting tolerance
Inspection and measurement method
Engineering Note: For finished pump shafts, piston rods and bearing locations, verify whether the project requires ground bar stock or fully machined components.
Physical Properties of 431 Stainless Steel
| Property | Typical Reference Value |
|---|---|
| Density | Approximately 7.80 g/cm³ |
| Elastic Modulus | Approximately 200 GPa |
| Thermal Conductivity | Approximately 20–25 W/m·K near ambient temperature |
| Specific Heat Capacity | Approximately 460 J/kg·K |
| Thermal Expansion Coefficient | Approximately 10–11 × 10⁻⁶/K near ambient temperature |
| Magnetic Behavior | Magnetic |
| Microstructure | Primarily martensitic after hardening |
Values are approximate and may vary with temperature, composition and heat-treatment condition.
Corrosion Resistance of 431 Stainless Steel
431 stainless steel offers relatively good corrosion resistance among conventional martensitic stainless steels.
Its chromium and nickel content contributes to resistance against atmospheric corrosion, freshwater exposure and certain mildly corrosive environments.
However, corrosion performance depends on surface condition, heat treatment, environmental chemistry and design details.
Atmospheric Environments
Grade 431 can provide good resistance in many industrial atmospheric applications when the surface is properly processed and maintained.
Freshwater Applications
431 is often considered for pump shafts and mechanical components operating in freshwater environments.
The suitability of the material depends on water chemistry, chloride concentration, temperature and the presence of deposits or crevices.
Marine Environments
431 stainless steel has applications in selected marine equipment, but it is generally not recommended for prolonged direct seawater immersion without specific corrosion validation.
Chloride-Containing Environments
Pitting, crevice corrosion and stress-corrosion cracking may become concerns under aggressive chloride exposure.
For demanding chloride environments, designers should evaluate alternative grades such as 316L, duplex 2205 or higher-alloy materials.
Chemical Processing Applications
The material may be considered for selected pump and valve components, but its compatibility with acids, alkalis and process chemicals must be evaluated individually.
Important: Corrosion resistance cannot be guaranteed by stainless steel grade designation alone.
Machining and Welding Characteristics
Machining
431 stainless steel can be machined using suitable tooling, cutting parameters and coolant systems.
Machinability depends strongly on material hardness.
Annealed or lower-hardness material is generally easier to machine than high-hardness quenched-and-tempered material.
For precision shaft production, machining allowances and final grinding requirements should be considered when ordering raw bar stock.
Welding
Welding 431 stainless steel requires careful procedure development because its high hardenability increases susceptibility to cracking.
Preheating, suitable filler metal selection, controlled cooling and post-weld heat treatment may be necessary.
Weld procedure qualification should consider component thickness, restraint, required mechanical properties and service environment.
431 should not be treated as having the same welding characteristics as austenitic 304 or 316L stainless steel.
Forming
Cold forming of hardened 431 stainless steel is more difficult because of its high strength and reduced ductility.
Complex deformation operations should be evaluated in relation to the delivery condition.
Industrial Applications of 431 Stainless Steel Round Bar
Pump Shafts
431 stainless steel round bars are used to manufacture selected industrial pump shafts requiring strength, toughness and moderate corrosion resistance.
Typical design considerations include shaft diameter, torsional loading, fatigue performance, straightness and surface finish.
Marine Equipment Components
431 may be used in selected marine mechanical components where the operating environment has been assessed.
For components exposed to continuous seawater immersion, corrosion-resistant alternatives should be evaluated.
Valve Stems and Valve Components
431 stainless steel is used for machined valve components requiring mechanical strength and resistance to suitable service environments.
The exact material condition should match the valve design, operating temperature and process fluid.
Industrial Machinery Shafts
Suitable applications include transmission shafts, spindles, rotating components and precision-machined mechanical parts.
Fasteners and Mechanical Components
431 can be considered for certain high-strength bolts, nuts and other machined components when appropriate product standards and mechanical requirements are specified.
Paper and Processing Equipment
The grade may be used for industrial spindles, machine components and processing equipment requiring a combination of strength and corrosion resistance.
431 vs 410 vs 420 vs 304 vs 17-4 PH Stainless Steel
| Grade | Material Structure | Main Advantage | Typical Selection |
|---|---|---|---|
| 410 | Martensitic | Heat treatability and moderate corrosion resistance | General mechanical components |
| 420 | Martensitic | Higher hardness potential in selected compositions | Wear-resistant parts and tools |
| 431 | Martensitic | High strength, toughness and relatively good corrosion resistance | Shafts, pumps and mechanical components |
| 304 | Austenitic | General corrosion resistance and fabrication properties | General processing equipment |
| 316L | Austenitic | Improved resistance to many chloride-containing environments compared with 304 | Chemical and marine-related equipment |
| 17-4 PH | Precipitation Hardening | High strength with selectable aging conditions | Shafts and high-strength engineered components |
When Should You Choose 431 Instead of 410?
431 is worth considering when improved corrosion resistance and a stronger combination of mechanical properties are required.
When Should You Choose 431 Instead of 304?
431 may be more suitable when the component requires higher achievable strength and heat-treatment capability.
304 is often preferable for general corrosion resistance, welding and fabrication.
When Should You Choose 17-4 PH Instead of 431?
17-4 PH may be preferred when the design requires precipitation-hardening characteristics, controlled aging conditions or a different balance of strength and dimensional stability.
Final selection should be based on verified mechanical and corrosion performance rather than grade names alone.
Applicable Standards and Material Designations
| Standard | Material / Scope |
|---|---|
| ASTM A276 / A276M | Stainless Steel Bars and Shapes |
| ASTM A479 / A479M | Stainless Steel Bars and Shapes for Boilers and Other Pressure Vessels |
| ASTM A484 / A484M | General Requirements for Stainless Steel Bars, Billets, Shapes and Forgings |
| EN 10088-3 | Corrosion-Resistant Stainless Steel Long Products |
| EN 10204 | Metallic Product Inspection Documents |
| JIS G4303 | Stainless Steel Bars |
| UNS | S43100 |
| EN Material Number | 1.4057 |
| EN Material Name | X17CrNi16-2 |
| AISI / Type | 431 |
| JIS Reference | SUS431 |
Important Standard Selection Note
ASTM A276 and ASTM A479 are different product specifications and must not be assumed interchangeable.
ASTM A479 applies to bars and shapes intended for boiler and pressure-vessel applications.
Compliance with ASTM A479 does not automatically establish the suitability of a particular 431 component for pressure-containing service.
Engineering design requirements, applicable construction codes, material conditions and certification requirements must be verified separately.
Inspection and Quality Assurance
Xi'an Dongmeng Group Co., Ltd. supports material specification review, inspection coordination and quality documentation according to agreed purchasing requirements.
Chemical Composition Verification
Chemical composition can be verified through heat analysis reports or approved testing methods.
Positive Material Identification (PMI) may be requested to confirm principal alloying elements.
PMI alone is not sufficient to verify all chemical requirements, particularly carbon content.
Mechanical Testing
Depending on the product standard and order requirements:
Tensile strength testing
Yield or proof strength testing
Elongation testing
Hardness testing
Impact testing where specified
Dimensional Inspection
Inspection may include:
Outside diameter
Length
Straightness
Surface condition
Machining allowances
Diameter tolerance
Surface roughness where specified
Non-Destructive Testing
Ultrasonic testing or other appropriate NDT methods can be discussed for critical applications.
The inspection method, examination coverage and acceptance criteria must be agreed upon before production.
Material Traceability
For projects requiring traceability, material heat numbers can be linked to the corresponding inspection documentation.
Material Test Certificates
EN 10204 Type 3.1 inspection certificates and third-party inspection arrangements may be requested.
Certificate type and documentation requirements should be confirmed before order placement.
Manufacturing, Processing and Delivery Options
Available Processing Services for Inquiry
Cut-to-Length
Round bars can be quoted in specified lengths with agreed cutting tolerances.
Turning and Peeling
Surface preparation can be considered for applications requiring machining allowances or improved surface condition.
Grinding and Polishing
Precision-ground and polished bar options can be discussed according to diameter, tolerance and surface requirements.
Heat-Treatment Coordination
Annealed or quenched-and-tempered conditions can be evaluated against required mechanical properties.
Custom Machining
Drawing-based processing requests can be reviewed for shaft blanks and other mechanical components.
Production and Delivery Planning
Production lead time depends on:
Required grade and specification
Diameter and length
Quantity
Heat-treatment condition
Surface finish
Inspection requirements
Processing complexity
Availability, minimum order quantity and delivery schedules are confirmed during quotation.
packaging and International Shipping
431 stainless steel round bars can be prepared for international shipment using packaging appropriate to material condition, dimensions and transport requirements.
Common Packaging Options
Protective wrapping
Secure steel bundling
Wooden pallets
Export wooden cases
Moisture protection
End protection for processed bars
Heat-number and identification labels
Export Documentation
Depending on the transaction and destination, documentation may include:
Commercial Invoice
Packing List
Material Test Certificate
Certificate of Origin where applicable
Inspection Report where specified
Shipping Documentation
Packaging requirements should be included in the purchase order.
Why Choose Xi'an Dongmeng Group Co., Ltd.?
Grade and Standard Selection Support
We assist international buyers in identifying the required material designation, product standard and heat-treatment condition before quotation.
Industrial Procurement Focus
Our stainless steel product offerings support manufacturers, distributors, machining companies and engineering projects.
Customized Processing Options
Customers can submit drawings and technical requirements for cutting, finishing and machining feasibility review.
Inspection and Documentation
Material inspection, traceability and certification requirements can be coordinated according to agreed order specifications.
International Export Support
We provide quotation and export coordination services for overseas industrial procurement requirements.
Request technical confirmation before placing an order to ensure that the selected grade, condition, size and inspection requirements match your application.
Frequently Asked Questions About 431 Stainless Steel Round Bar
Q1. What is 431 stainless steel?
431 is a nickel-containing martensitic stainless steel that can be hardened and tempered to obtain high mechanical strength, useful toughness and relatively good corrosion resistance.
Q2. Is AISI 431 the same as UNS S43100?
UNS S43100 is the commonly used UNS designation for ASTM Type 431 stainless steel.
The actual material must comply with the chemical composition and delivery requirements of the specified product standard.
Q3. Is EN 1.4057 equivalent to AISI 431?
EN 1.4057 / X17CrNi16-2 is closely related to AISI 431, but their chemical composition limits are not completely identical.
Dual compliance must be verified.
Q4. What is the hardness of 431 stainless steel?
Hardness depends on the heat-treatment condition. Annealed and quenched-and-tempered 431 stainless steel can have significantly different hardness values.
The required hardness range should be specified and verified by testing rather than assumed from the grade designation alone.
Q5. What is the difference between QT800 and QT900?
QT800 and QT900 are quenched-and-tempered conditions commonly used for EN 1.4057.
QT900 specifies higher minimum tensile and proof strengths, while QT800 generally provides greater ductility potential.
Q6. Is 431 stainless steel magnetic?
Yes. Grade 431 is generally magnetic because of its martensitic structure.
Q7. Is 431 stainless steel suitable for seawater?
431 may be suitable for selected marine components, but it is generally not recommended for prolonged direct seawater immersion without corrosion validation.
Q8. Can 431 stainless steel be welded?
Yes, but welding is difficult because of its high hardenability and cracking susceptibility.
Qualified welding procedures and suitable preheat and post-weld heat treatment may be required.
Q9. What are the common applications of 431 round bars?
Typical applications include pump shafts, industrial spindles, valve components, mechanical transmission parts and other high-strength machined components.
Q10. What is the difference between 431 and 304 stainless steel?
431 is a heat-treatable martensitic stainless steel, while 304 is an austenitic stainless steel.
431 offers higher achievable strength through heat treatment, while 304 generally provides better fabrication and welding characteristics.
Q11. Can 431 stainless steel round bars be supplied with MTC 3.1?
EN 10204 Type 3.1 inspection certification can be requested subject to order requirements and supplier confirmation.
Q12. What information is needed for a 431 stainless steel round bar quotation?
Provide the grade, standard, diameter, length, quantity, heat-treatment condition, surface finish, tolerances, mechanical requirements, inspection documents and delivery destination.
Request a Quote - 431 Stainless Steel Round Bar
Looking for ASTM A276 Type 431 / UNS S43100 stainless steel round bar for shafts, pumps, valves or precision-machined industrial components?
Xi'an Dongmeng Group Co., Ltd. supports international procurement inquiries for standard and customized stainless steel round bars.
Please Include the Following Information
Material Grade: AISI 431 / UNS S43100 / EN 1.4057
Product Standard: ASTM A276 / ASTM A479 / EN 10088-3 / JIS G4303
Required Diameter: mm or inches
Required Length: mm, meters or feet
Heat Treatment: Annealed / QT800 / QT900 / Other Specified Condition
Surface Finish: Hot Finished / Peeled / Turned / Ground / Polished
Required Tolerances: Diameter / Straightness / Surface Roughness
Inspection: MTC / PMI / UT / Tensile / Hardness / Third-Party Inspection
Quantity: Pieces / Total Weight
Delivery Destination: Country / Port / Delivery Terms
Contact Us
Xi'an Dongmeng Group Co., Ltd.
Office Information
Phone / WhatsApp: +86 157 6921 4734
Email: office@dongmjd.com
Address: Room 4107, Runfeng Building, Sanqiao New Street, Weiyang District, Xi'an City, Shaanxi Province, China.
Request a Quote | Submit Drawings | Confirm Material Condition | Request MTC
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