Steel Suppliers and stockholders - KV Steel Services, Darlaston, West Midlands

EN24 and EN24T Steel

BS970: 1955 EN24, BS970/PD970: 1970 onwards 817M40.
Related European grades: 34CrNiMo6, Werkstoff No. 1.6582
US Grade: SAE (AISI) 4340.

EN24 is usually supplied in the finally heat treated condition (quenched and tempered to "T" properties) up to a limiting ruling section of 250mm, which is superior to grades 605M36, 708M40 or 709M40 - see properties below.  Please refer to our selection guide for comparisons.

EN24 is a very popular grade of through-hardening alloy steel, which is readily machinable in the "T" condition. (Refer to our machinability guide). EN24T is most suitable for the manufacture of parts such as heavy-duty axles and shafts, gears, bolts and studs.  EN24T can be further surface-hardened typically to 58-60 HRC by induction or nitride processes, producing components with enhanced wear resistance.

In addition to the above, EN24T is capable of retaining good impact values at low temperatures, hence it is frequently specified for harsh offshore applications such as hydraulic bolt tensioners and shipborne mechanical handling equipment.

EN24 sections larger than 250mm may still be available in the quenched and tempered condition, but it should be noted that a fall-off in mechanical properties may be apparent approaching the centre of the bar.

It is therefore recommended that larger sizes are supplied in the annealed (softened) condition, and that quenching and tempering is carried out after initial stock removal.  This should achieve better mechanical properties towards the core.

817M40 (EN24) Specification
Chemical composition
Carbon 0.36-0.44%
Silicon 0.10-0.35%
Manganese 0.45-0.70%
Sulphur 0.040 Max
Phosphorus 0.035 Max
Chromium 1.00-1.40%
Molybdenum 0.20-0.35%
Nickel 1.30-1.70%


817M40 (EN24) - mechanical properties in "T" condition
Max Stress 850-1000 n/mm2  
Yield Stress 680 n/mm2 Min (up to 150mm LRS)
Yield Stress 650 n/mm2 Min (over 150 to 250mm LRS)
0.2% Proof Stress 665 n/mm2 Min (up to 150mm LRS)
0.2% Proof Stress 635 n/mm2 Min (over 150 to 250mm LRS)
Elongation 13% Min (9% if cold drawn)
Impact KCV 50 Joules Min (up to 150mm LRS
Impact KCV 35 Joules Min (over 150 to 250mm LRS)
Hardness 248-302 Brinell (850-1000 n/mm2)


EN24 Equivalents
BS970: 1955 EN24
1970 onwards
European 34CrNiMo6
Werkstoff No. 1.6582
US SAE (AISI) 4340


KV Steel Services is a supplier of EN24 steel to local and national businesses. We stock EN24 in bright bar and blocks and black bar, square, flats and blocks.

EN24T Steel Bar