AISI 4140 Alloy Steel

AISI 4140 steel stockholders and suppliers. AISI 4140 is a chromium molybdenum alloy steel available as full bar lengths or cut pieces with delivery to the whole of the UK. This specification widely used in the oil and gas industry. Similar to grade AISI 4130 but with a slightly higher carbon content. The higher carbon content of AISI 4140 gives greater strength and heat treatment capabilities in comparison to AISI 4130, however it does have inferior weldability characteristics. AISI 4140 machines well in the supply condition of 18-22HRc.

We welcome export enquiries for AISI 4140 steel. Contact our sales office and consult our shipping policy for further details.

Alternative oil and gas steel grades we supply

4130 | 4145 | 4330V | 4340 | 8620 | 6150

Form of Supply

West Yorkshire Steel are AISI 4140 steel stockholders of round bar. Diameters can be supplied as full bar lengths or cut pieces. AISI 4140 ground steel bar can be supplied, providing a quality alloy steel precision ground bar to tight tolerances.

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  • Diameter

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AISI 4140 is commonly used for a variety of applications in the oil and gas sector. Typical applications include components such as connection rods, collets, conveyor pins, gears, stem assemblies, pump shafts and tool holders.

Carbon 0.38-0.43% Chromium 0.80-1.10%
Manganese 0.75-1.00% Molybdenum 0.15-0.25%
Silicon 0.10-0.35% Phosphorous 0.035% max
Nickel 0.25% max Sulphur 0.040% max

Preheat the steel carefully, then raise the temperature to 1150-1200°C for forging. Do not forge below 850°C.

Heat the AISI 4140 slowly to 800-850°C and allow enough time for the steel to be thoroughly heated. Cool slowly in the furnace to 480°C followed by air cooling.

When parts are heavily machined, ground or otherwise subject to cold work, stress relieving will be beneficial prior to hardening.

AISI 4140 steel is usually supplied ready heat treated to 18-22HRC. If further heat treatment is required annealed AISI 4140 should be heated slowly to 840-875°C and after adequate soaking at this temperature quench in oil. Temper as soon as the tools reach room temperature.

Heat the AISI 4140 carefully to a suitable temperature selected by reference to a tempering chart or table (usually between 550-700°C, soak at the temperature for 2 hours per 25mm of ruling section, then allow to cool in air. Tempering between 250-375°C is not advised as tempering within this range will seriously reduce the impact value.

Proof Stress
of Area %
Min 100 80 20 40 18 217
Max 130 110 22 235

(*at room temperature heat treated to 18-22HRc)

Heat treatment temperatures, including rate of heating, cooling and soaking times will vary due to factors such as the shape and size of each AISI 4140 steel 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 alloy steel.

AISI 4140 alloy steel is available with a cast and analysis certificate or a BS EN 10204 3.1 mill certificate, please request when placing any orders.

AISI 4140 round bar is supplied in accordance with our ISO 9001:2015 registration.