STAINLESS STEEL 431 / S43100/ 1.
4057 SS 431
431 is a high chromium-low nickel high hardenability Martensitic stainless steel with high strength and good corrosion
resistance, as generally supplied hardened and tempered in the tensile range 850 - 1000 Mpa (condition T) Brinell range 248 -
302. Characterised by very good corrosion resistance in general atmospheric corrosive environments, good resistance to mild
marine and industrial atmospheres, resistant to many organic materials, nitric acid and petroleum products coupled with high
tensile and high yield strength plus excellent toughness in the hardened and tempered condition.
431 due to its excellent hardenability is capable of being through hardened up to Rc44, depending upon carbon content and
section size. Small sections can be air cooled and larger sections oil quenched for maximum through hardness. Pre hardened
and tempered 431 will also respond readily to nitriding achieving a typical surface hardness of over Rc65. The nitriding process
however reduces the corrosion resistance and is therefore not generally recommended except for critical applications where the
benefit outweighs all other considerations. Used extensively for parts requiring a combination of high tensile strength, good
toughness and good corrosion resistant properties.
This heat treatable martensitic, nickel-bearing grade has the best corrosion resistance properties of all the martensitic grades. It
has excellent tensile and torque strength, and good toughness, making it ideally suited to shafting and bolt applications. It can
be hardened to approximately 40HRC. Because of its high yield strength, this grade is not readily cold worked and is therefore
not recommended for use in operations such as cold heading, bending, deep drawing or spinning. Martensitic stainless steels
are optimised for high hardness, and other properties are to some degree compromised. Fabrication must be by methods that
allow for poor weldability and usually also allow for a final harden and temper heat treatment. Corrosion resistance is generally
lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-
zero temperatures and loss of strength by over-tempering at elevated temperatures.
431 stainless was formulated to provide better corrosion resistance and toughness in a quench- hardenable, stainless steel. It
maintains good strength and corrosion resistance and hardness, in temperatures from -100 to 1200 degress f (-73/ 650c). It has
the best corrosion resistance of the conventional martensitic stainless grades.
Availability :
Alloy 431 is available as round / flat / sheet / hexagonal / plate/ square / coil / pipe & fittings.
Corrosion Resisting Alloy 4S80 / 5S80 / 6S80 7S80
SPECIFICATION
• AISI 431
• T431 SS
• UNS S43100 AMS2303
• AMS-5628 HI SHEAR #115 (CHEM ONLY)
• AMS-S-18732
• ASTM-A-276
• DMS-1565 EXC. SONIC
• MIL-S-18732
• QQS-763 EXC HARDNESS & IZOD
Chemical Composition
Weight % C Si Mn P+S max Cr Ni Others (max)
4- S80 5- Mo 0.3 / Co 0.05 / Cu 0.3 / Nb 0.05/
1.00 1.00 0.030P 2.00 /
S80 6- S80 0.12/0.20 15.00/18.00
max max 0.025S 3.00
7- S80 Bar Sn 0.02 / Ti 0.05 / V 0.20 / W 0.05
Applications of Stainless 431
• Marine components
• Aircraft Parts and Components
• Bolts and Nuts
• Fasteners
• Pump Shafts
• Propeller Shafts
• Studs
• Valve Parts etc.
Machinability of Stainless 431
• Carbide tools recommended
• Machine with carbide tools at higher speeds than high-speed tools
Heat Treatment of Stainless 431
• Process anneal at 1150° to 1225°F (621° to 663°C) before air cooling
• Harden by heating to 1800° to 1950°F (982° to 1066°C) for 30 minutes, then oil quench
• Temper by heating to 400° to 1200°F (204° to 649°C), then air cool
• Heat to 800° to 1700°F (427° to 927°C) to help eliminate stress corrosion cracking.
Avoid intergranular corrosion by performing stress relief from 450° to 750°F (232° to 399°C)
Workability of Stainless 431
• Forge and hot form from 1500° to 2150°F (816° to 1177°C)
• Easy to cold work sheet and small bars
• Extreme flanging and bending of heavy pieces at 1350° to 1550°F (732° to 843°C)
431 S43100 431S29 1.4057 X17CrNi16-2 2321 SUS 431
Heat Treatment
Annealing: typical Heat uniformly 1200/1250f (650/677c) remove from furnace and cool in air. Brinell hardness expected
approximately 270. This is the best condition for overall machining.
Hardening: Heat 1800/1950f (982/1066c) soak at heat, quench in oil. You may also harden in air.
Tempering: In the range of 700/1050f (371/565c), to achieve desired mechanical properties. Soak at hest for at least one hour,
longer for larger pieces and cool in air.
Typical Room Temperature Tensile Properties
Hardened at 1800f (982c) and oil quenched, followed by tempering at indicated temperature
and air cooled.
Ultimate
Temper Yield % Elongation % Charpy
Tensile Brinell
Temperature Strength in 2" Reduction V-notch
Strength Hardness
{50.8mm} of Area
F C ksi Mpa ksi Mpa ft-lb J
anneale
95 655 125 655 20 280 55 50 68
d
500 280 149 1027 196 1365 16 415 55 40 76
700 371 163 1123 202 1393 16 429 55 25 34
900 482 174 1200 204 1407 16 415 51 12 16
1100 593 115 793 140 965 19 302 57 48 65
1300 649 99 683 129 889 20 269 60 51 69
Hardened at 1900f (1038c) and oil quenched, followed by tempering at indicated temperature
and air cooled.
Ultimate
Temper Yield % Elongation % Charpy
Tensile Brinell
Temperature Strength in 2" Reduction V-notch
Strength Hardness
{50.8mm} of Area
F C ksi Mpa ksi Mpa ft-lb J
anneale
95 655 125 655 20 280 55 50 68
d
500 280 148 1020 193 1331 17 388 40 52 71
700 371 145 1000 188 1282 21 388 53 60 61
900 482 156 1076 200 1379 18 415 62 42 57
1100 593 113 779 150 1034 18 321 55 32 43
1300 649 98 676 140 965 18 263 53 45 61
Machinability:
431 in the annealed condition can gall and build up on the cutting tool which can result in poor finishes.
Specifications:
AMS 5628 ASTM A276 ASTM A314 ASTM A479 QQS 763 PWA LCS EN10204 DIN3.1B
Shapes Manufactured
Flat Bars, Square Bars, Round Bars, Rings, Hollows, Discs, Blocks and special Shapes. Send us a drawing to see how
we can save you material and Machining time!
The information in this data sheet is for information only and should not be used for engineering.
