431 is a martensitic stainless with higher chromium and a nickel addition, which gives it better corrosion resistance than 410 or 420 while still hardening by quench and temper to high strength.
It is a standard choice for shafts, pump and valve components, fasteners and marine hardware that need both strength and salt exposure resistance.
Stocked as bar and billet, supplied annealed for machining or heat treated to the ordered condition.
Sizes and stock
- Round bar: through 6" DIA
- Forgings: available by request
Processing capabilities
- Shearing, waterjet, laser and saw cut blanks
- Centerless grinding, turning and polishing
- Penetrant dye and ultrasonic inspection, chemical assay and physical testing
Specifications
Material is released to the applicable specification with mill test reports and, on request, independent lab verification.
Why engineers specify 431
- Highest corrosion resistance among common martensitic stainless grades
- High strength and toughness after quench and temper
- Good performance in marine and mildly corrosive service
- Readily machined in the annealed condition
Nominal chemistry
Percent by weight, nominal composition per the governing specification. The mill test report for your heat is the controlling document.
Typical mechanical properties
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Annealed | ~120 ksi | ~95 ksi | ~20% | - |
| Q&T 1100F | ~145 ksi | ~115 ksi | ~15% | ~32 HRC |
Typical published values for reference only, not for design. Properties vary with section size, product form and processing. Order to the specification and condition your drawing requires.
Typical applications
- Pump and valve shafts
- Marine fittings and fasteners
- Aerospace bolts
- Machined hardware in corrosive service
Fabrication notes
Machining
Austenitic grades work harden quickly, so use positive rake tooling, rigid setups, generous feed and flood coolant rather than light dwelling cuts. Martensitic and precipitation hardening grades machine most easily in the annealed or solution treated condition and are aged after rough machining.
Welding
Weldable by GTAW, GMAW, resistance and electron beam methods with matching or over alloyed filler. Stabilized and low carbon grades resist sensitization in the weld zone. Precipitation hardening grades are normally welded in the solution treated condition and aged afterward.
Forming
Sheet and strip form well in the annealed condition; cold worked tempers trade formability for strength. Allow for springback and, where specified, an intermediate anneal between draws.
431 compared with similar grades
410
Lower alloy martensitic grade, less corrosion resistant.
17-4 PH
Precipitation hardening with less distortion and higher strength options.
Designations and cross reference
- Material family
- Stainless Steel
- UNS number
- S43100
- Werkstoff (W.Nr)
- 1.4057
Working from an obsolete, foreign or superseded designation? Send it over and we will cross reference it to a current grade and specification.
Quality, testing and traceability
Supplied with mill test reports and heat traceability, with penetrant dye, ultrasonic, chemical assay, hardness, corrosion and mechanical testing available on request.
We are AS9100D and ISO 9001:2015 registered. If our stock does not already carry the inspection your specification requires, we can quote the material with that work performed. More on our quality system
Available forms
Custom sizes converted from billet, plus saw cut, waterjet and near-net blanks. See custom conversions
431 frequently asked questions
What is 431?
431 is a martensitic stainless with higher chromium and a nickel addition, which gives it better corrosion resistance than 410 or 420 while still hardening by quench and temper to high strength.
What forms is 431 available in?
We supply 431 in bar, forging. Custom sizes are converted from billet, and we can provide saw cut, waterjet or near net blanks so material arrives closer to your finished part.
What is the UNS or equivalent designation for 431?
431 is designated UNS S43100, Werkstoff 1.4057. If your drawing calls out an obsolete or foreign designation we can cross reference it and confirm the equivalent before you order.
What specifications can 431 be supplied to?
Commonly ordered specifications include AMS 5628, ASTM A276, MIL-S-18732, UNS S43100. Material is released to the specification and condition on your purchase order, with mill test reports supplied as standard.
What conditions can 431 be ordered in?
We can supply Annealed, Q&T 1100F. If our stock is not already in the condition you need, we can quote it with the heat treatment performed before shipment.
Can you cut 431 to size?
Yes. Saw cutting, waterjet, laser and shearing are available, along with trepanning, gun drilling, lathe turning and CNC machining, so you can order blanks or rough machined pieces rather than full lengths.
Do you provide test reports and additional testing on 431?
Every order ships with mill test reports and heat traceability. If your print calls for ultrasonic inspection, penetrant dye, magnetic particle, chemical assay, micrography, hardness or mechanical testing and our stock does not already carry it, we can quote the material with that work performed.
Can 431 be supplied to DFARS domestic melt requirements?
Tell us at quote stage if the order is DFARS or domestic melt restricted and we will confirm availability against that requirement before you commit.
What do you need to quote 431?
Grade, form, dimensions, quantity, specification and condition, plus any testing or certification requirements and the date you need it. Send a drawing if you have one. Quotes are typically ready within 24 hours.
How does 431 compare with 410?
Lower alloy martensitic grade, less corrosion resistant.