EN8, EN19, EN24 Steel Explained: British Grades and Their Modern Equivalents

📋 Datasheets for the grades in this guide: C45 → (≈EN8) · 42CrMo4 → (≈EN19) · 34CrNiMo6 → (≈EN24)

What Do EN8, EN19 and EN24 Mean?

They are the old grade codes of the British BS 970 standard. The "EN" prefix does not mean European Norm — it comes from the "Emergency Number" series of the wartime standard issued in 1941. So EN8 is not "European standard no. 8"; it is steel no. 8 of the British war emergency standard. BS 970 later changed the codes (EN8 → 080M40), and the modern European EN 10083 system uses entirely different names — but workshop language never changed: in the UK, in India and across Middle Eastern industries built on the British school, people still ask "have you got EN8?"

This guide ties the most-searched British grades to their modern counterparts in a single table.

Quick Equivalence Table (BS 970 → Modern)

Old EN code	BS 970 (later code)	Modern EN equivalent	W.-Nr.	AISI/SAE (≈)	Our datasheet
EN1A	230M07	11SMn30	1.0715	1213	11SMn30
EN3B	070M20	≈ C22 / S235	~1.0402	1020	S235JR (close)
EN8	080M40	≈ C40 / C45	~1.0511	1040	C45
EN9	070M55	≈ C55	~1.0535	1055	—
EN19	708M40	42CrMo4	1.7225	4140	42CrMo4
EN24	817M40	34CrNiMo6	1.6582	4340	34CrNiMo6
EN31	534A99	100Cr6	1.3505	52100	100Cr6
EN32	080M15	≈ C15	~1.0401	1015	C15

⚠️ These mappings are "nearest equivalents", not identical twins. Analysis ranges differ slightly; on critical projects the ordering standard's values govern. For all cross-standard systems use our Steel Grade Equivalents tool.

The Big Three: EN8, EN19, EN24

EN8 (080M40) ≈ C45 — general-purpose medium-carbon steel

The bread-and-butter grade of the British system. Unalloyed, medium carbon (typically C 0.36–0.44%, Mn 0.60–1.00%): shafts, axles, bolts, keys, general machine parts. Normalised it gives roughly 550–700 MPa tensile strength; it can be quenched and tempered, but hardenability is limited — thick sections will not harden through to the core. Its modern counterpart lives with full values in our C45 datasheet.

EN19 (708M40) ≈ 42CrMo4 — chromium-molybdenum Q&T steel

Steps in where EN8 runs out: the addition of Cr ~0.90–1.20% + Mo ~0.15–0.25% boosts hardenability and fatigue resistance. Usually sold as "EN19T" (T condition), supplied quenched and tempered. Gears, crankshafts, high-tensile studs, injection screws — it is the British name for 42CrMo4/4140, the world's most used alloy steel.

EN24 (817M40) ≈ 34CrNiMo6 — nickel-chrome-moly heavy-duty steel

The champion of the trio: the Ni ~1.3–1.7% addition delivers uniform through-hardening to the core even in very large sections, plus superior toughness. "EN24T" is the most common supply condition. Heavy shafts, landing gear, defence and energy components — known today as 34CrNiMo6 (≈AISI 4340).

BS 970 Condition Letters (R, S, T, U…)

In the British system, the letter after the grade tells you the tensile strength band of the heat-treated material — as in "EN24T":

Condition	Tensile strength (MPa)
R	700–850
S	775–925
T	850–1000
U	925–1075
V	1000–1150

The T band is by far the most common ordering condition (EN19T, EN24T). To see it in hardness terms, use the Hardness Converter (850–1000 MPa ≈ 248–302 HB).

Three Practical Rules When Ordering

1. Confirm with the modern standard. Rather than ordering "EN8", write "C45 / 1.0511, EN 10083-2" and keep the British code in brackets. The number-one source of supply-chain confusion is two different readings of the same old code.
2. Ask for the mill certificate. An old code does not mean old tolerances — whichever standard the material was actually made to, those ranges apply. Check incoming material against the ranges with our Chemical Composition tool.
3. State the condition. Asking for EN19 is not enough — EN19T, or annealed? If the treatment band isn't specified, the supplier ships the cheapest state.

Supply from Aktif Çelik

Aktif Çelik stocks EN8/C45, EN19/42CrMo4 and EN24/34CrNiMo6 as hot-rolled bar and bright (cold-drawn) bar, and EN1A/11SMn30 within our free-cutting steel programme. We translate your British-coded specification into its modern equivalent and quote with 3.1 certification — contact our team for analysis reports and cutting to size.