SAE 4140 Round Bar Specification and Properties

42crmo4 Steel Bar Properties

Properties	Imperial
Density	0.280 lb/in³ (7750 kg/m³ )
Specific Gravity	7.75
Machinability	65-70% of 1% Carbon steel
Thermal Diffusivity	12 mm²/s
Chromium (%)	0.8 to 1.1
Manganese (%)	0.75 to 1.0

Quenching and Tempering Steel AISI 4140 Steel bar as per EN-10083-1

quenching and tempering steel aisi 4140 steel bar

AISI 4140 Bar Specification
AISI 4140 Bar stock / Types
Equivalent Standards of SAE 4140 Steel Round Bar
Chemical Composition of AISI 4140 Steel Round Bar
AISI 4140 Round Bar Mechanical Properties
Thermal Properties of SAE 4140 Hex Bar
4140 Alloy Steel Flat Bar Electrical Properties
4140 HT Alloy Square Bar Forming Option
Heat-treatment Option of 4140 Tool Steel Hex Bar
AISI 4140 Alloy Steel Square Bar Surface Option
4140 Steel Annealed Flat Bar Mechanical Properties
4140 Chromoly Steel Application
AISI 4140 42CrMo4 Hex Bar Welding
Mechanical Properties of 4140 Q&T Steel Square Bar
AISI 4140 HT Round Bar Machining Allowances
Hardenability Diagram of AISI 4140 HRC Round Bar

AISI 4140 Bar Specification

Specifications	A108-13, ASTM A331, 1.7225, SCM440
Workability	Cut and Machine, Moderate to Weld
Stock Sizes	12ft, 8ft, 6ft, 4ft, 2ft, or Cut to Size

AISI 4140 Bar stock / Types

AISI 4140 Round Bar

4140 Steel Bright Bar

AISI 4140 HT Hex Bar

AISI 4140 Steel Flat Bar

4140 Q&T Steel Square Bar

AISI 4140 Alloy Rectangular bars

Equivalent Standards of SAE 4140 Steel Round Bar

American (ASTM)	ASTM A29/A29M Grade 1040 ASTM A108 Grade 1040
European (EN)	EN 10083-2 C40E EN 10277 C45 EN 10083-1 C45E
British Standard (BS)	BS 970 080M40 BS 970 080A42
German (DIN)	DIN 17200 C40 DIN 17200 C45 DIN 1652-2 CK40
Italian (UNI)	UNI C40 UNI C45 UNI C45E
Japanese (JIS)	JIS G4051 S40C JIS G4051 S45C
Indian Standard (IS)	IS 1570 C40 IS 1570 C45 IS 5517 40C8

Chemical Composition of AISI 4140 Steel Round Bar

Element	Content (%)
Iron (Fe)	96.8 to 97.8
Chromium (Cr)	0.8 to 1.1
Manganese (Mn)	0.75 to 1.0
Carbon (C)	0.38 to 0.43
Silicon (Si)	0.15 to 0.35
Molybdenum (Mo)	0.15 to 0.25
Sulfur (S)	0 to 0.040
Phosphorus (P)	0 to 0.035

AISI 4140 Round Bar Mechanical Properties

Brinell Hardness	200 to 310
Elastic Modulus	190 Gpa (27 x 10⁶ psi)
Elongation at Break	11 to 26 %
Fatigue Strength	360 to 650 Mpa (53 to 94 x 10³ psi)
Poisson’s Ratio	0.29
Shear Modulus	73 Gpa (11 x 10⁶ psi)
Shear Strength	410 to 660 Mpa (60 to 96 x 10³ psi)
Tensile Strength	590 to 990 Mpa (85 to 140 x 10³ psi)

Thermal Properties of SAE 4140 Hex Bar

Latent Heat of Fusion	250 J/g
Maximum Temperature	420 °C (790 °F)
Melting Completion	1460 °C (2660 °F)
Melting Onset	1420 °C (2580 °F)
Specific Heat Capacity	470 J/kg-K (0.11 BTU/lb-°F)
Thermal Conductivity	43 W/m-K (25 BTU/h-ft-°F)
Thermal Expansion	13 µm/m-K

4140 Alloy Steel Flat Bar Electrical Properties

Electrical Conductivity	7.3 % IACS
Electrical Conductivity (Specific)	8.4 % IACS

4140 HT Alloy Square Bar Forming Option

Hot Rolling Process

Hot Forging

Heat-treatment Option of 4140 Tool Steel Hex Bar

Forging	926 to 1205°C (1700 to 2200°F)
Hot Working	816 to 1038°C (1500 to 1900°F)
Annealing	872°C (1600°F)
Tempering	205 to 649°C (400 to 1200°F)

AISI 4140 Alloy Steel Square Bar Surface Option

Option	Description
Black Surface
Grounded	Bright but rough
Machining for plate	Bright and precision
Peeled/Turned	Bright and precision
Polished	Very Bright and precision size

4140 Steel Annealed Flat Bar Mechanical Properties

Brinell Hardness	200
Poisson’s Ratio	0.29
Elongation at Break	26%
Fatigue Strength	480 Mpa 70 x 10³ psi
Shear Strength	470 Mpa 69 x 10³ psi
Shear Modulus	73 Gpa 11 x 10⁶ psi
Tensile Strength	660 Mpa 95 x 10³ ps
Elastic Modulus	190 Gpa 27 x 10⁶ psi

4140 Chromoly Steel Application

Axles

Stud Bolts

Ordinary Shafts

Pinions

Gears

Tool Shanks

AISI 4140 42CrMo4 Hex Bar Welding

Methods		Electrode
SAW	Submerged arc	Low Hydrogen
FCAW	Flux-Cored Arc
SMAW	Shielded metal arc
GTAW	Gas Tungsten Arc
GMAW	Gas Metal Arc

Mechanical Properties of 4140 Q&T Steel Square Bar

Elastic Modulus	190 Gpa 27 x 106 psi
Fatigue Strength	650 Mpa 94 x 103 psi
Shear Modulus	73 Gpa 11 x 106 psi
Tensile Strength	990 Mpa 140 x 103 psi
Shear Strength	660 Mpa 96 x 103 psi
Poisson’s Ratio	0.29
Elongation at Break	16%
Brinell Hardness	310

AISI 4140 HT Round Bar Machining Allowances

Bar Diameter	Black (Hot Rolled or Forged)		Bright (Drawn or Peeled Bar)
Bar Diameter	if Len. <120mm	if Len. >120mm	if Len. <120mm	if Len. >120mm
0 – 50	1.5mm	1.5 + 6mm/m	1.0mm	1.0 + 4mm/m
50 – 100	2.3mm	2.3 + 6mm/m	1.0mm	1.0 + 4mm/m
100 – 150	4.5mm	4.5 + 6mm/m	1.0mm	1.0 + 4mm/m
150 – 210	6.5mm	6.5 + 6mm/m	1.5mm	1.5 + 4mm/m
210 – 450	–	–	1.5mm	1.5 + 6mm/m

Hardenability Diagram of AISI 4140 HRC Round Bar

AISI 4140 HT/ HRC Round Bars Standard Size & Length

Diameter(in.)	Lbs per ft.	Diameter(in.)	Lbs per ft.	Diameter(in.)	Lbs per ft.
5/8	1.044	1-1/2	6.012	2-3/8	15.258
3/4	1.500	1-5/8	7.056	2-1/2	16.896
7/8	2.040	1-3/4	8.172	2-5/8	18.724
1	2.676	1-7/8	9.384	2-3/4	20.533
1-1/8	3.384	2	10.680	2-7/8	22.426
1-1/4	4.176	2-1/8	12.234	3	24.409
1-3/8	5.052	2-1/4	13.704	3-1/8	26.463
3-1/4	28.606	6-3/4	123.078	11-1/2	360.874
3-3/8	30.833	7	133.779	12	392.584
3-1/2	33.143	7-1/4	143.397	12-1/2	427.665
3-5/8	35.692	7-1/2	153.348	13	462.124
3-3/4	38.175	7-3/4	163.631	13-1/2	497.918
4	43.394	8	174.251	14	535.047
4-1/4	48.939	8-1/4	185.204	14-1/2	573.511
4-1/2	54.822	8-1/2	197.170	15	613.310
4-3/4	61.243	8-3/4	208.818	15-1/2	654.444
5	67.804	9	220.816	16	696.913
5-1/4	74.699	9-1/4	233.100	17	785.856
5-1/2	81.928	9-1/2	245.741	18	880.139
5-3/4	90.203	9-3/4	258.716	19	979.762
6	98.146	10	273.753	20	1084.725

Heat Treatment and Machinability of Hot Forged 42crmo4 Round Bars

Treatments	furnace	Time	Next Steps
Annealing	1450 – 1600°F.	1 hour	Allow to Cool
Normalizing	1600 – 1700°F.	30 minutes	Allow to Cool in ambient air
Hardening & Quenching	1550 – 1600°F	30 minutes	When cooled 150°F do Tempering
Tempering	400 – 1200°F	15 minutes	Allow to Air Cool