SAE 4140 Flat Bars

SAE 4140 flat bar is a chromium-molybdenum alloy steel flat, rolled and then hardened and tempered for machine parts that carry load and wear.

20 to 150 mm wide Alloy steel Made to order

HRAP FLAT BARS

SAE 4140 flat bar

SAE 4140 flat bar is a hot rolled bar of rectangular section in the chromium-molybdenum through-hardening steel that SAE J404 defines and ASTM A322 tabulates. Carbon of 0.38 to 0.43 percent sets the hardness a quench and temper can reach, and the chromium and molybdenum carry that hardness into the middle of a thick section instead of a thin surface layer. The same steel is 42CrMo4 in European practice, material number 1.7225, and EN 19 in BS 970. SAE 4130 holds less carbon and tempers to a lower strength in heavy flats. SAE 4340 adds nickel and hardens deeper again, so 4140 is the grade chosen when the section does not need it.

The flat is supplied annealed or normalised, the condition most machine shops work from, or hardened and tempered to a BS 970 condition such as T, U or V so that the strength band is fixed before cutting. Pickling is a stainless finishing step and does not apply here, so scale comes off by machining or blasting. The grade has no corrosion resistance, and a finished part is painted, plated or oiled. Welding calls for preheat and a temper afterwards, because the carbon and the alloy harden the weld zone. Flats run 20 to 150 mm wide, 5 to 50 mm thick and up to 6.4 metres long, for machine guides and gib strips, die and bolster plates, wear plates and clamp plates. Laxcon Steels rolls every size to order.

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 flat bar supply conditions

Length: Up to 6.4 metres
Supply condition: Hot rolled, annealed or normalised
Tolerance: EN 10058
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 10058: Hot rolled flat steel bars for general purposes: dimensions and tolerances on shape and dimensions.
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

Width (mm)	Thickness (mm)	kg per metre
20	15	2.35
20	16	2.51
21	17.5	2.88
22 / 22.8	11	1.90
22 / 22.8	13	2.25
22 / 22.8	16	2.76
22 / 22.8	17	2.94
22 / 22.8	18	3.11
22 / 22.8	19.5	3.37
23.5	14.5	2.67
25/25.4	8	1.57
25/25.4	10	1.96
25/25.4	12	2.35
25/25.4	12.7	2.49
25/25.4	15	2.94
25/25.4	20	3.92
26	11	2.25
26	13	2.65
26	16	3.27
26	21	4.29
28.5	14	3.13
30	6	1.41
30	8	1.88
30	10	2.35
30	12	2.83
30	15	3.53
30	16	3.77
30	20	4.71
31.75/32	9	2.24
31.75/32	11	2.74
31.75/32	12.7	3.17
31.75/32	13	3.24
31.75/32	15	3.74
31.75/32	16	3.99
31.75/32	20	4.98
31.75/32	21	5.23
35	6	1.65
35	8	2.20
35	10	2.75
35	15	4.12
35	20	5.49
36	23	6.50
36	27.5	7.77
38	23.5	7.01
38.1	6.35	1.90
40	5	1.57
40	6	1.88
40	8	2.51
40	10	3.14
40	12	3.77
40	15	4.71
40	16	5.02
40	20	6.28
40	25	7.85
40	30	9.42
42	11	3.63
42	13	4.29
42	16	5.28
42	22	7.25
42	26	8.57
42	32	10.55
45	6	2.12
45	8	2.83
45	10	3.53
45	15	5.30
45	20	7.06
45	25	8.83
50/50.8	5	1.96
50/50.8	6	2.35
50/50.8	8	3.14
50/50.8	10	3.92
50/50.8	12	4.71
50/50.8	12.7	4.98
50/50.8	15	5.89
50/50.8	16	6.28
50/50.8	20	7.85
50/50.8	25	9.81
50/50.8	30	11.77
50/50.8	40	15.70
52	11	4.49
52	16	6.53
52	21	8.57
52	26	10.61
52	32	13.06
52	42	17.14
55	5	2.16
55	6	2.59
55	8	3.45
55	10	4.32
55	12	5.18
55	15	6.48
55	16	6.91
55	20	8.63
55	25	10.79
57	32	14.32
60	6	2.83
60	8	3.77
60	10	4.71
60	15	7.06
60	20	9.42
60	25	11.77
60	30	14.13
60	32	15.07
60	35	16.48
60	40	18.84
63/63.5	11	5.44
63/63.5	13	6.43
63/63.5	15	7.42
63/63.5	16	7.91
63/63.5	20	9.89
63/63.5	21	10.39
63/63.5	25	12.36
63/63.5	30	14.84
63/63.5	32	15.83
63/63.5	42	20.77
65	8	4.08
65	10	5.10
65	15	7.65
65	16	8.16
65	20	10.20
65	25	12.76
65	30	15.31
65	32	16.33
65	35	17.86
65	40	20.41
70	8	4.40
70	20	10.99
70	25	13.74
70	30	16.48
70	40	21.98
72	11	6.22
72	21	11.87
75/76.2	5	2.94
75/76.2	8	4.71
75/76.2	10	5.89
75/76.2	12	7.06
75/76.2	12.7	7.48
75/76.2	15	8.83
75/76.2	20	11.77
75/76.2	25	14.72
75/76.2	30	17.66
80	8	5.02
80	10	6.28
80	15	9.42
80	20	12.56
80	25	15.70
80	30	18.84
80	35	21.98
80	40	25.12
80	50	31.40
82	11	7.08
82	13	8.37
82	16	10.30
82	21	13.52
82	31	19.95
90	8	5.65
90	10	7.06
90	15	10.60
90	20	14.13
90	30	21.19
90	40	28.26
90	50	35.32
100/101.6	6	4.71
100/101.6	6.35	4.98
100/101.6	8	6.28
100/101.6	10	7.85
100/101.6	11	8.63
100/101.6	12	9.42
100/101.6	12.7	9.97
100/101.6	13	10.20
100/101.6	15	11.77
100/101.6	20	15.70
100/101.6	25	19.62
100/101.6	30	23.55
100/101.6	40	31.40
120	10	9.42
120	12	11.30
120	15	14.13
120	16	15.07
150	10	11.77
150	12	14.13
150	15	17.66
150	16	18.84
150	20	23.55

Density 7.85 g/cm³, width x thickness x 0.00785. Where a width is listed with two values (25/25.4) the first is used.

Ordering SAE 4140 flat bar

An enquiry for this grade in this form states the grade and its governing standard, SAE 4140 to ASTM A322 or EN 19 to BS 970, the condition required, whether annealed, normalised, or hardened and tempered to a named BS 970 condition, the width, thickness and tolerance class to EN 10058, the cut length, the quantity, the certificate type to EN 10204, and any ultrasonic examination or hardness check.