{"id":3639,"date":"2026-09-16T11:11:33","date_gmt":"2026-09-16T08:11:33","guid":{"rendered":"https:\/\/www.defencemetal.com\/index.php\/en\/aisi-431\/"},"modified":"2026-09-25T21:15:15","modified_gmt":"2026-09-25T18:15:15","slug":"aisi-431","status":"publish","type":"page","link":"https:\/\/www.defencemetal.com\/index.php\/en\/aisi-431\/","title":{"rendered":"AISI 431 \/ (1. 4057)"},"content":{"rendered":"

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AISI 431 \/ (1.4057) \/ UNS S43100 \/ AMS 5628<\/h1>\n
DEFENCE METAL<\/span><\/p>\n
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AISI 431<\/div>\n
UNS S43100 \u00b7 W.Nr. 1.4057 \u00b7 X17CrNi16-2 \u00b7 BS 431S29. This is a MARTENSITIC stainless steel: it transforms to martensite on austenitising and quenching and is then TEMPERED. It does NOT precipitation harden; there is NO H900 \/ H1025 type ageing step. It is the HIGHEST CHROMIUM hardenable grade of the family (15-17%, against 12-14% in 410, 416 and 420). The nickel here is not there for strength but FOR THE STRUCTURE: 16% chromium on its own makes the structure ferritic, and a ferritic structure does not harden by heat treatment; 1.25-2.50% nickel keeps the austenite field open and lets martensite form on quenching. EN 10088-3 for 1.4057: C 0.12-0.22% – Si 1.00% max – Mn 1.50% max – P 0.040% max – S 0.030% max – Cr 15.0-17.0% – Ni 1.50-2.50%. ASTM A276 \/ the Carpenter type analysis: C 0.20% max (THERE IS NO FLOOR) – Mn 1.00% max – P 0.040% max – S 0.030% max – Si 1.00% max – Cr 15.00-17.00% – Ni 1.25-2.50%. EN sets a carbon FLOOR (0.12%) and a higher nickel floor (1.50%); ASTM sets neither. Aubert & Duval give a nominal C 0.16% – Cr 17.00% – Ni 2.00% for their own APX grade.<\/p>\n
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Not to be confused with<\/div>\n

AISI 410<\/a><\/div>\n<\/div>\n<\/div>\n

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For what<\/div>\n
Bought for parts that need high strength together with the best corrosion resistance available inside the martensitic family: pump and propeller shafts, valve stems, marine hardware and fasteners, aircraft fittings and attachments, turbine parts, plastics processing moulds and screws, chemical and\u2026<\/div>\n<\/div>\n
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Forms<\/div>\n
Round bar, flat bar, plate, sheet, pipe, forging, wire. All forms are supplied to order.<\/div>\n<\/div>\n
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Standards<\/div>\n
AMS: 5628 – ‘Steel, Corrosion-Resistant, Bars, Wire, Forgings, and Tubing, 16Cr – 2.5Ni (SAE 51431)’. ASTM: A276 \/ SA-276 (bars and shapes). EN: 1.4057 \u00b7 EN 10088-3 (bars, wire, sections; +A, +QT800 and +QT900 conditions). Welding procedure: ASME Section IX P-No 6.
NOT AN AMS 5628 TRAP BUT AN AMS 5682 TRAP: some stockist pages list this grade under the heading ‘Alloy 431 \/ AMS 5682’, while the body of those same pages quotes only AMS 5628. That AMS 5682 belongs to 431 COULD NOT BE VERIFIED IN ANY SOURCE;<\/span><\/div>\n<\/div>\n
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Advantage<\/div>\n
IT HAS THE HIGHEST CORROSION RESISTANCE OF THE HARDENABLE MARTENSITIC GRADES, and it delivers that together with a tensile strength in the 1345-1580 MPa class.<\/div>\n<\/div>\n
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Welding<\/div>\n
IT CAN BE WELDED BUT IT IS DIFFICULT, and it is not done WITHOUT preheat and a postweld treatment. PREHEAT: 200-316 \u00b0C. Carpenter gives 204-316 \u00b0C (400-600 \u00b0F), the Engineering.com specification summary 204-316 \u00b0C, AZoM 200-300 \u00b0C and Abrams 100-300 \u00b0C. POSTWELD TREATMENT: about 649-650 \u00b0C.<\/div>\n<\/div>\n
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Limits<\/div>\n
1) FORBIDDEN TEMPERING BAND: 400-600 \u00b0C. Aubert & Duval state it most plainly: ‘we do not recommend using this steel in the tempering range from 400 \u00b0C to 600 \u00b0C’ – the reason given is unfavourable impact strength. Carpenter states that 371-565 \u00b0C (700-1050 \u00b0F) ‘will adversely affect impact strength and corrosion properties’;<\/div>\n<\/div>\n
REQUEST A QUOTE<\/a>All stainless steels →<\/a>TECHNICAL DETAILS ↓<\/span><\/div>\n
Compiled from manufacturer data sheets \u00b7 confirm against the current specification before ordering<\/div>\n<\/div>\n<\/div>\n

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