431 Stainless Steel

431 stainless steel stockholders and suppliers. 431 is a martensitic stainless steel with a 17% chromium and 2.5% nickel content available in round and flat bar with delivery to the whole of the UK. It is usually supplied in the hardened but still machineable condition. It offers good corrosion resistance in mild marine and industrial atmospheres where high tensile and yield strength with excellent toughness are required.

We welcome export enquiries for stainless steel. Contact our sales office and consult our shipping policy for further details.

Related Specifications

BS 970 431S29T 1.4057 X17CrNi16-2
X16CrNi16 AISI ASTM UNS S43100

Alternative stainless grades we supply

17/4PH | FV520B | S31254 | 904L | 310 | 316 | 321 | 440B | 440C | 420 | 410 | 416 | S31803 | S32760

Form of Supply

West Yorkshire Steel are  suppliers and stockholders of round and flat bar in grade 431. Diameters can be sawn to your required lengths as one offs or multiple cut pieces. 431 ground stainless steel bar can be supplied, providing a high quality stainless steel precision ground diameter bar to tight tolerances.

Click here to contact our experienced sales team who will assist you with your 431 stainless steel enquiry.

  • Flat
  • Diameter

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Used widely in the aircraft and marine industries, for components such as shafts, axles, pumps, valves, bolts and nuts. Suitable for applications requiring good strength, toughness combined with reasonable resistance to corrosion.

Carbon 0.12-0.20% Chromium 15.00-18.00%
Manganese 1.00% max Nickel 2.00-3.00%
Silicon 1.00% max Sulphur 0.030% max
Phosphorous 0.040% max

431 stainless steel offers the best corrosion resistance of all martensitic stainless steel grades. Optimum corrosion resistance is achieved when used in the hardened and tempered condition. Allowing oxygen to circulate freely on the surface will form an oxide film which protects the surface. Keeping the surface free of scale and foreign particles improves the corrosion resistance and finished components should be passivated. For best machining and corrosion 431 stainless steel is commonly supplied in the ‘T’ condition.

Pre heat carefully, then raise the temperature to 1150-1200°C, hold until temperature is uniform throughout the steel. Do not forge below 900°C. After forging cool slowly in furnace or warm ashes.

Heat slowly to 650-680°C hold until temperature is uniform through the steel. Soak well and allow to cool in the furnace.

Heat the component slowly to 950-1020°C and hold until the temperature is uniform throughout the steel. After adequate soaking time quench in oil or air cool. Temper as soon as tools are hand warm.

Heat carefully to a suitable tempering temperature. Soak as required and then allow to cool in air. Tempering between 590-680°C will achieve ‘T’ condition. Double tempering is recommended. 431 stainless can be tempered at lower temperatures to achieve higher tensile strengths but with lower impact properties. Tempering between 370-565°C is not advised as tempering within this range will seriously reduce impact properties and corrosion resistance.

Heat treatment temperatures, including rate of heating, cooling and soaking times will vary due to factors such as the shape and size of each component. Other considerations during the heat treatment process include the type of furnace, quenching medium and work piece transfer facilities. Please consult your heat treatment provider for full guidance on heat treatment of 431 stainless.

Condition Tensile (UTS)
(50.8mm) %
T 850-1000 635 11 34 248-302

Stainless steel 431 (431S29) grade is available with BS EN 10204 3.1 mill certificate, please request when placing any orders.

431 stainless steel is supplied in accordance with our ISO 9001:2015 registration.