EN 24 Round Bars

EN 24 hot rolled round bar is a nickel chromium molybdenum alloy steel bar used for shafts, axles and gears in heavy sections.

16 to 125 mm Alloy steel Made to order

HOT ROLLED ROUND BARS

EN 24 hot rolled round bar

EN 24 hot rolled round bar is an alloy steel bar rolled from a nickel chromium molybdenum engineering steel that hardens right through its section when it is quenched and tempered. The same steel is written EN24, and appears as 817M40 in BS 970, as 34CrNiMo6 in the German designations, as 1.6582 in the European material numbers and as 4340 in the American system. Carbon near 0.4 percent sets the hardness the bar can reach. Nickel of 1.3 to 1.8 percent, with the chromium and the molybdenum beside it, carries that hardness deep into a thick bar. EN 19 one step down holds no nickel and softens toward the centre of a large diameter. EN 30B holds more nickel again and is kept for sections heavier still.

The bar is supplied annealed, normalised, or hardened and tempered to a BS 970 condition, T, U, V or above, each letter naming a band of tensile strength. Annealed or normalised bar machines cleanly and suits a part that is heat treated after cutting; bar bought hardened and tempered is cut to size and used as it is. Quenching is done in oil for most diameters, which is gentler than water on a steel of this carbon level, and tempering follows at once. The steel has no corrosion resistance, so finished parts are painted, plated or oiled. Round bar in this grade becomes transmission shafts and axles, gear and pinion blanks, high tensile bolts and studs, and forging stock for crankshafts.

Composition limits in weight percent are carbon 0.35 to 0.45, manganese 0.45 to 0.7, sulphur 0.05 maximum, phosphorus 0.05 maximum, silicon 0.1 to 0.35, chromium 0.9 to 1.4, nickel 1.3 to 1.8 and molybdenum 0.2 to 0.35.

SPECIFICATION

EN 24 hot rolled round bar supply conditions

Size range: 16 mm - 125 mm (5/8" - 5")
Length: Up to 8 metres
Tolerances: EN10060
Heat treatment: Soft annealing or normalising; oil or water quenching and tempering
Grade: EN 24 (EN24, 817M40, 34CrNiMo6, 4340)
Family: Alloy steel
Supply: Made to order in this grade; every published size of the form

Composition of EN 24

Element	Symbol	Minimum %	Maximum %
Carbon	C	0.35	0.45
Manganese	Mn	0.45	0.7
Sulphur	S		0.05
Phosphorus	P		0.05
Silicon	Si	0.1	0.35
Chromium	Cr	0.9	1.4
Nickel	Ni	1.3	1.8
Molybdenum	Mo	0.2	0.35

Composition, weight percent, balance iron. From the Laxcon Steels grade reference.

Equivalents of EN 24

Standard	Designation
SAE	4340
DIN	34CrNiMo6

Equivalence means nearest counterpart, not identity: each standards body sets its own composition window, so the limits of the standard named on the order govern.

Governing standards

EN 10083-1: Steels for quenching and tempering, part 1: general technical delivery conditions for the bars, rods and sections supplied for heat treatment.
EN 10083-3: Steels for quenching and tempering, part 3: technical delivery conditions for alloy steels, 42CrMo4 and 34CrNiMo6 among them.
BS 970-1: Wrought steels for mechanical and allied engineering purposes, part 1: the British numbering behind the EN and M designations and the R to Z heat treatment conditions.
ASTM A29/A29M: Steel bars, carbon and alloy, hot-wrought: general requirements for delivery, the base every carbon and alloy bar order inherits.
ASTM A322: Steel bars, alloy, standard grades: the composition tables for the SAE alloy grades supplied as bar.
EN 10060: Hot rolled round steel bars for general purposes: dimensions and tolerances on shape and dimensions.
NACE MR0175 / ISO 15156: Materials for use in H2S-containing environments in oil and gas production: the sour-service limits on hardness and condition.
EN 10204: Metallic products, types of inspection documents: the 2.2 test report and the 3.1 and 3.2 inspection certificates a purchase order can call for.

Weight per metre

Diameter (mm)	kg per metre	Metres per tonne
16	1.58	633.5
17	1.78	561.2
18	2.00	500.6
19	2.23	449.3
20	2.47	405.5
21	2.72	367.8
22	2.98	335.1
23.2	3.32	301.3
24	3.55	281.6
25	3.85	259.5
26	4.17	239.9
27	4.49	222.5
28	4.83	206.9
30	5.55	180.2
32	6.31	158.4
34	7.13	140.3
36	7.99	125.1
37	8.44	118.5
38	8.90	112.3
40	9.87	101.4
42	10.88	91.9
45	12.49	80.1
47	13.62	73.4
48	14.21	70.4
50	15.41	64.9
53	17.32	57.7
56	19.34	51.7
57.5	20.39	49.1
60	22.20	45.1
63	24.47	40.9
66	26.86	37.2
67.5	28.09	35.6
70	30.21	33.1
73.5	33.31	30.0
75	34.68	28.8
77.5	37.03	27.0
80	39.46	25.3
83	42.48	23.5
85	44.55	22.4
88	47.75	20.9
90	49.94	20.0
93	53.33	18.8
95	55.65	18.0
98	59.22	16.9
100	61.66	16.2
105	67.98	14.7
106	69.28	14.4
110	74.61	13.4
115	81.54	12.3
120	88.79	11.3
125	96.34	10.4

Density 7.85 g/cm³, diameter squared x 0.006166. Sizes are the published range at the nominal diameters shown.

Ordering EN 24 hot rolled round bar

An enquiry for EN 24 in this form states the grade with the standard it is bought to, BS 970, EN 10083-3 or ASTM A322, the condition wanted, the diameter with its tolerance to EN 10060, the surface as black, spot ground or fully ground, the cut length, the quantity, the EN 10204 certificate type, and any test called for, such as ultrasonic testing or PMI confirmation of the grade. Laxcon Steels rolls every size to order.