What type of material is 431? 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 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 steel Mechanical Properties.Tempering Temperature (°C) | Tensile Strength (MPa) | Yield Strength 0.2% Proof (MPa) | Elongation (% in 50mm) | Hardness Brinell (HB) | Impact Charpy V (J) | Annealed * | 862 | 655 | 20 | 285 max | – | 204 | 1345 | 1055 | 20 | 388 | 50 | 316 | 1295 | 1035 | 19 | 375 | 53 | 427 | 1350 | 1080 | 19 | 388 | # | 538 | 1140 | 965 | 19 | 321 | # | 593 | 1015 | 770 | 20 | 293 | 64 | 650 | 960 | 695 | 20 | 277 | 84 | SS431 is frequently stocked and supplied in “Condition T”, with
specified tensile strength of 850 – 1000MPa. | * Annealed tensile properties are typical for Condition A of ASTM
A276; annealed hardness is the specified maximum. SS431 is only
rarely stocked in annealed Condition A. # Due to associated low impact resistance this steel should not be
tempered in the range 425-600°C |
stainless steel 431 equivalent & Specification ComparisonGrade | UNS No | Old British | Euronorm | Swedish SS | Japanese JIS | BS | En | No | Name | SS431 | S43100 | 431S29 | 57 | 1.4057 | X17CrNi16-2 | 2321 | SUS 431 | These comparisons are approximate only. The list is intended as a
comparison of functionally similar materials not as a schedule of
contractual equivalents. If exact equivalents are needed original
specifications must be consulted. |
431 stainless steel nearest possible GradesGrade | Why it might be chosen instead of 431 | SS410 | Only a lower hardened strength is needed. | SS416 | High machinability is required, and the lower hardened strength and
lower corrosion resistance of 416 is acceptable. | SUS 440C | A higher hardened strength or hardness than can be obtained from
420 is needed. |
stainless steel 431 Corrosion ResistanceExcellent resistance to a wide variety of corrosive media.
Reasonable resistance to salt water in cold southern waters but
less resistant than SUS316 in tropical waters. Overall the
corrosion resistance of SUS431 is approximately the same as or
slightly below that of SUS304.Performance is best with a smooth surface finish, in the hardened
and tempered condition.431 stainless steel Heat ResistanceResists scaling in intermittent service to 925°C and in continuous
service to 870°C, but is generally not recommended for use in
temperatures above the relevant tempering temperature, because of
reduction in mechanical properties.431 stainless steel Heat TreatmentFull anneal – not practical for this grade – it hardens even when
cooled slowly.Process Anneal – heat to 620-660°C and air cool.Hardened by heating to 980-1065°C, holding for about 1/2 hour then
quenching in air or oil. Pre-heating at 760-790°C may be useful for
complex parts or those already hardened. Temper to suit mechanical
requirements, at temperatures as indicated in the accompanying
table.The tempering range 425-600°C should be avoided due to reduced
impact toughness, although the effect is less marked than in most
other martensitic grades. |
