SAE 4140 Round Bars

SAE 4140 hot rolled round bar is a chromium molybdenum through hardening steel bar used for shafts, gears and forging stock.

16 to 125 mm Alloy steel Made to order

HOT ROLLED ROUND BARS

SAE 4140 hot rolled round bar

SAE 4140 hot rolled round bar is an alloy steel bar rolled from a chromium molybdenum steel that hardens through its whole section when it is quenched and tempered. The same steel is EN 19 in BS 970, 42CrMo4 in the German designations and 1.7225 in the European material numbers. Its carbon, close to 0.4 percent, sets the hardness the bar can reach; the chromium and the molybdenum carry that hardness into the middle of a thick bar instead of leaving it near the surface. A plain carbon bar of similar carbon hardens only in a shallow skin at these diameters. SAE 4130 holds less carbon and tempers to a lower strength. SAE 4340 adds nickel and hardens deeper again, and is kept for the heaviest sections.

The bar is supplied annealed or normalised for machining, or hardened and tempered to a BS 970 condition such as T, U or V. EN 10083-3 sets 650 MPa minimum yield and 900 to 1100 MPa tensile for 42CrMo4 quenched and tempered at 16 to 40 mm diameter, and lower bands for larger bars. Quenching is usually done in oil, which is gentler than water on a steel of this carbon level. Welding needs preheat, a low hydrogen consumable and a temper afterwards, or the heat affected zone cracks. The steel has no corrosion resistance and is painted, plated or oiled. Round bar in this grade becomes shafts, axles and spindles, gear and pinion blanks, tool holders, and forging stock for crankshafts and couplings.

Composition limits in weight percent are carbon 0.38 to 0.43, manganese 0.75 to 1.0, sulphur 0.04 maximum, phosphorus 0.035 maximum, silicon 0.15 to 0.35, chromium 0.8 to 1.1 and molybdenum 0.15 to 0.25.

SPECIFICATION

SAE 4140 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: SAE 4140 (4140, 42CrMo4, EN 19, 1.7225)
Family: Alloy steel
Supply: Made to order in this grade; every published size of the form

Composition of SAE 4140

Element	Symbol	Minimum %	Maximum %
Carbon	C	0.38	0.43
Manganese	Mn	0.75	1.0
Sulphur	S		0.04
Phosphorus	P		0.035
Silicon	Si	0.15	0.35
Chromium	Cr	0.8	1.1
Molybdenum	Mo	0.15	0.25

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

Equivalents of SAE 4140

Standard	Designation
DIN	42CrMo4
British EN	EN 19

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 SAE 4140 hot rolled round bar

An enquiry for SAE 4140 hot rolled round bar states the grade and the standard it is ordered to, whether EN 10083-3, BS 970 or ASTM A322, the delivery condition, the diameter with the tolerance to EN 10060 or ASTM A29, the surface as rolled or ground, the cut length, the quantity, the certificate type to EN 10204, and any test required, such as ultrasonic examination or positive material identification. Laxcon Steels rolls every size to order.