AISI 4140 Alloy Steel

AISI 4140 Alloy Steel (UNS G41400)

Alloy steels are designated by AISI four-digit numbers and comprise different kinds of steels, each with a composition which exceeds the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va set for carbon steels.

AISI 4140 alloy steel is a chromium-, molybdenum-, and manganese-containing low alloy steel. It has high fatigue strength, abrasion and impact resistance, toughness, and torsional strength. The following datasheet gives an overview of AISI 4140 alloy steel.

 

AISI 4140 Steel equivalent

Country	China	Japan	Germany	USA	British
Standard	GB/T 3077	JIS G4105	DIN (W-Nr.) EN 10250	AISI/ASTM ASTM A29	BS 970
Grade	42CrMo	SCM440	42crmo4/1.7225	4140	EN19/709M40

 
AISI 4140 steel chemical composition

Grade	C	Si	Mn	P	S	Cr	Mo	Ni
42CrMo	0.38-0.45	0.17-0.37	0.5-0.80	≤0.035	≤0.035	0.9-1.2	0.15-0.25	-
SCM440	0.38-0.43	0.15-0.35	0.6-0.85	≤0.035	≤0.04	0.9-1.2	0.15-0.30	-
42crmo4/1.7225	0.38-0.45	≤ 0.4	0.6-0.9	≤0.025	≤0.035	0.9-1.2	0.15-0.30	-
4140	0.38-0.43	0.15-0.35	0.75-1.00	≤0.035	≤0.04	0.8-1.1	0.15-0.25	-
EN19/709M40	0.35-0.45	0.15-0.35	0.5-0.80	≤0.035	≤0.035	0.9-1.5	0.2-0.40	-

 
AISI 4140 steel mechanical properties(for guidance only)

Grade	Tensile strength σb(MPa)	Yield strength σs (MPa)	Elongation δ5 (%)	Reduction ψ (%)	Impact Value Akv (J)	Hardness
4140	≥1080	≥930	≥12	≥45	≥63	28-32HRC

  
AISI 4140 steel overviews

Size	Round	Dia 6-1200mm
	Plate/Flat/Block	Thickness 6mm-500mm
		Width 20mm-1000mm
Heat treatment	Normalized ; Annealed ; Quenched ; Tempered
Surface condition	Black; Peeled; Polished; Machined; Grinded; Turned; Milled
Delivery condition	Forged; Hot rolled; Cold drawn
Test	Tensile strength, Yield strength, elongation, area of reduction, impact value, hardness, grain size, ultrasonic test, US inspection, magnetic particle testing, etc.
Payment terms	T/T;L/C;/Money gram/ Paypal
Trade terms	FOB; CIF; C&F; etc..
Delivery time	30-45 days
Application	AISI 4140 steel finds many applications as forgings for the aerospace,oil and gas,automotive, agricultural and defense industries etc. Typical applications for 4140 steel uses include:forged gears,spindles,fixtures,jigs,collars,Axles,conveyor parts,crow bars,logging parts,shafts,sprockets,studs,pinions,pump shafts, rams, and ring gears etc

Physical Properties

The physical properties of AISI 4140 alloy steel are highlighted in the following table.

Properties	Metric	Imperial
Density	7.85 g/cm3	0.284 lb/in³
Melting point	1416°C	2580°F

Mechanical Properties

The following table outlines the mechanical properties of AISI 4140 alloy steel.

Properties	Metric	Imperial
Tensile strength	655 MPa	95000 psi
Yield strength	415 MPa	60200 psi
Bulk modulus (typical for steel)	140 GPa	20300 ksi
Shear modulus (typical for steel)	80 GPa	11600 ksi
Elastic modulus	190-210 GPa	27557-30458 ksi
Poisson's ratio	0.27-0.30	0.27-0.30
Elongation at break (in 50 mm)	25.70%	25.70%
Hardness, Brinell	197	197
Hardness, Knoop (converted from Brinell hardness)	219	219
Hardness, Rockwell B (converted from Brinell hardness)	92	92
Hardness, Rockwell C (converted from Brinell hardness. Value below normal HRC range, for comparison purposes only)	13	13
Hardness, Vickers (converted from Brinell hardness)	207	207
Machinability (based on AISI 1212 as 100 machinability)	65	65

Thermal Properties

The thermal properties of AISI 4140 alloy steel are given in the following table.

Properties	Metric	Imperial
Thermal expansion coefficient (@ 0-100°C/32-212°F)	12.2 µm/m°C	6.78 µin/in°F
Thermal conductivity (@ 100°C)	42.6 W/mK	296 BTU in/hr.ft².°F

Other Designations

Other designations equivalent to AISI 4140 alloy steel are listed in the following table.

AMS 6349	ASTM A193 (B7, B7M)	ASTM A506 (4140)	ASTM A752 (4140)
AMS 6381	ASTM A194 (7, 7M)	ASTM A513	ASTM A829
AMS 6382	ASTM A29 (4140)	ASTM A513 (4140)	SAE J1397 (4140)
AMS 6390	ASTM A320 (L7, L7M, L7D)	ASTM A519 (4140)	SAE J404 (4140)
AMS 6395	ASTM A322 (4140)	ASTM A646 (4140)	SAE J412 (4140)
AMS 6529	ASTM A331 (4140)	ASTM A711

Fabrication and Heat Treatment

Machinability 

AISI 4140 alloy steel has good machinability in the annealed condition.

Forming

AISI 4140 alloy steel has high ductility. It can be formed using conventional techniques in the annealed condition. It requires more pressure or force for forming because it is tougher than plain carbon steels.

Welding

AISI 4140 alloy steel can be welded using all conventional techniques. However, the mechanical properties of this steel will be affected if it is welded in the heat-treated condition, and post-weld heat treatment should be performed.

Heat Treatment

AISI 4140 alloy steel is heated at 845°C (1550°F) followed by quenching in oil. Before hardening, it can be normalized by heating it at 913°C (1675°F) for a long period of time, followed by air cooling.

Forging

AISI 4140 alloy steel is forged at 926 to 1205°C (1700 to 2200°F)

Hot Working

AISI 4140 alloy steel can be hot worked at 816 to 1038°C (1500 to 1900°F)

Cold Working

AISI 4140 alloy steel can be cold worked using conventional methods in the annealed condition.

Annealing

AISI 4140 alloy steel is annealed at 872°C (1600°F) followed by slowly cooling in the furnace.

Tempering

AISI 4140 alloy steel can be tempered at 205 to 649°C (400 to 1200°F) depending upon the desired hardness level. The hardness of the steel can be increased if it has a lower tempering temperature. For example, a tensile strength of 225 ksi can be achieved by tempering at 316°C (600°F), and tensile strength of 130 ksi can be achieved by tempering at 538°C (1000°F).

Hardening

AISI 4140 alloy steel can be hardened by cold working, or heating and quenching.