AISI 4145 Alloy Steel

AISI 4145 steel stockholders and suppliers. AISI 4145 is a chromium molybdenum alloy steel grade available as full bar lengths or cut pieces with delivery to the whole of the UK. It is widely used in the oil and gas sectors. Similar to AISI 4140 but with a higher carbon content. 4145 is more popular in larger diameters due to its increased strength and hardenability. AISI 4145 is commonly supplied quenched and tempered with a hardness of between 30 to 36HRc.

We welcome export enquiries for AISI 4145 steel. Contact our sales office and consult our shipping policy for further details.

Alternative grades we supply

4130 | 4140 | 4330V | 4340 | 8620 | 6150

Form of Supply

West Yorkshire Steel are AISI 4145 steel stockholders of round bar. Diameters can be supplied as full bar lengths or cut blanks. AISI 4145 ground steel bar can be supplied, providing a high quality steel precision ground bar to tight tolerances.

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  • Diameter

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AISI 4145 is commonly used for a variety of applications in the oil and gas sector. Used often for the manufacture of down hole drilling tools such as drill collars. Other applications include gears, shafts for hydraulic presses, rolls for paper mills, pump shafts and tool holders.

Carbon 0.43-0.49% Chromium 0.80-1.10%
Manganese 0.85-1.10% 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. AISI 4145 has good forging characteristics but care must be taken when cooling the steel due to its susceptibility to cracking.

Heat the steel 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 4145 steel is usually supplied ready heat treated to 30-36HRc. If further heat treatment is required annealed AISI 4145 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 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 values of this steel.

Proof Stress
of Area %
Min 140 120 14 40 30 286
Max 36 336

(*at room temperature heat treated to 30-36HRc)

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 4145 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 AISI 4145 alloy steel.

AISI 4145 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 4145 round bar is supplied in accordance with our ISO 9001:2015 registration.