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.

Advantages:

1 QTC Qualification Test Coupon Passed

2 Superior Hardenability

3 Optimize chemical component

Smelting Option

1 EAF: Electric Arc Furnace

2 EAF+LF+VD: Refined-smelting and vacuum degassing

Forming Option

1 Hot rolling process

2 Hot Forging: Electro-hydraulic; High-speed-hydraulic; Oil-hydraulic; Precision-forging

Heat-treatment Option

1 +A: Annealed (full/soft/spheroidizing)

2 +N: Normalized

3 +NT: Normalized and tempered

4 +QT: Quenched and tempered (water/oil)

Suface Option

1 Black Surface

2 Grounded: Bright but rough ; Not precision

3 Machining for plate: Bright and precision; Little turning scar

4 Peeled/Turned: Bright and precision; Little turning scar

5 Polished: Very Bright and precision size; Not turning scar

Other Services

1 Cutting: Small pieces

2 CNC Machine: Produce as your drawing

3 Package: Bare/Nylon/Canvas/Wooden

4 Payment:T/T, L/C, O/A(request credit)

5 Transport:FOB/CFR/CIF/DDU/DDP (train/ship/Air)

Chemical Composition

The following table shows the chemical composition of AISI 4140 alloy steel.

Element	Content (%)
Chromium, Cr	0.80 – 1.10
Manganese, Mn	0.75 – 1.0
Carbon, C	0.380 – 0.430
Silicon, Si	0.15 – 0.30
Molybdenum, Mo	0.15 – 0.25
Sulfur, S	0.040
Phosphorous, P	0.035
Iron, Fe	Balance

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.

Designation by Standards

Brand Name	Ravne No.	Mat. No.	DIN	EN	AISI
42CRMOS4	792	1.7227	42CrMoS4	42CrMoS4	4140

Chemical Composition (in weight %)

C	Si	Mn	Cr	Mo	Ni	V	W	Others
0.41	max. 0.40	0.75	1.05	0.28	–	–	–	–

Applications

High and moderately stressed components for automobile industry and mechanical engineering – shafts, connecting rods, crankshafts, screws, etc.
Physical properties (avarage values) at ambient temperature
Modulus of elasticity [103 x N/mm2]: 210
Density [g/cm3]: 7.80<
Soft Annealing
Heat to 680-720oC, cool slowly in furnace. This will produce a maximum Brinell hardness of 241.

Normalizing
Temperature: 840-880oC.

Hardening
Harden from a temperature of 820-860oC followed by oil or water quenching.

Tempering
Tempering temperature: 540-680oC.

Mechanical Properties in Quenched and Tempered Condition

Diameter (mm)	0.2 proof stress (N/mm2)	Tensile stregth (N/mm2)	Elongation (%)	Reduction (%)	Impact energy (J)
Up to 16	900	1100-1300	10	40	30
17-40	750	1000-1200	11	45	35
41-100	650	900-1100	12	50	35
101-160	550	800-950	13	50	35
161-250	500	750-900	14	55	35

Hardenability in the end-quench test

Quenching temperature in the end-quench test is 850oC

Hardness	1.5	3	5	7	9	11	13	15	20	25	30	35	40	45	50
H max.	61	61	61	60	60	59	59	58	56	53	51	48	47	46	45
H min.	53	53	52	51	49	43	40	37	34	32	31	30	30	29	29
HH max.	61	61	61	60	60	59	59	58	56	53	51	48	47	46	45
HH min.	56	56	55	54	52	48	46	44	41	39	38	36	36	35	34
HL max.	58	58	58	57	56	54	53	51	49	46	44	42	41	40	40
HL min.	53	53	52	51	49	43	40	37	34	32	31	30	30	29	29

Forging
Hot forming temperature: 1050-850oC.

What is 4140 Steel?

AISI 4140 steel is a low alloy steel containing chromium, molybdenum, and manganese. It is widely used across numerous industries and is an excellent material choice due to its toughness, high fatigue strength, and abrasion and impact resistance. Not many grades can match the versatility and usefulness of 4140.

4140 Grade Designation

When discussing AISI 4140, it is important to understand what the grade number means:

Number	Meaning
4	Designates that 4140 steel is molybdenum steel, indicating that it possesses higher amounts of molybdenum than other steels, such as the 1xxx series.
1	Designates that 4140 steel has additions of chromium as well; more so than 46xx steel for example.
40	Used to differentiate 4140 Steel from other steels in the 41xx series.

How is 4140 Steel Made?

AISI 4140 is made by placing iron, carbon, and other alloying elements into an electric furnace or oxygen furnace. The major alloying elements added to AISI 4140 are: Chromium Manganese Molybdenum Once the iron, carbon, and other alloying elements have been mixed together in liquid form, it is allowed to cool. The steel may then be annealed; possibly several times.

After the annealing is complete, the steel is heated to a molten phase again so that it can be poured into the desired form and can either be hot worked or cold worked through rollers or other tools to reach the desired thickness. Of course, there are other special operations that can be added to this to reduce mill scale or improve mechanical properties.

Mechanical Properties of 4140 Steel

AISI 4140 is a low alloy steel. Low alloy steels rely on elements other than just iron and carbon to enhance their mechanical properties. In AISI 4140, additions of chromium, molybdenum, and manganese are used to increase the strength and hardenability of the steel. The additions of chromium and molybdenum are why AISI 4140 is considered a “chromoly” steel.

There are several important mechanical properties of AISI 4140, including: Tensile Strength: AISI 4140 steel typically has a target ultimate tensile strength of around 95,000 psi. Toughness Ductility Hardenability

Mechanical Properties of AISI Alloy 4140 Steel Bar, Plates, Square

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

AISI 4140 Rounds Hot Rolled

Size (mm)	40	50	60	70	75	80	85	90	95	100	105	110
115	120	125	130	140	150	160	170	180	190	200	220
240	260	280	300	320	350	400

AISI 4140 Rounds Bright Drawn

Size (inches)	5/16	3/8	7/16	1/2	9/16	5/8	3/4	7/8	15/16	1	1 1/8	1 1/4	1 3/8	1 1/2
1 5/8	1 3/4	2	2 1/4	2 1/2	2 3/4	3	3 1/2	4
Size (mm)	10	12	15	16	18	20	25	30	35	40	45	50	60

4140 TOOL STEEL SHAPES AND SIZES

4140 tool steel is available in the following thickness sizes and standard width sizes depicted in the tables below. Any non-standard thickness and width is available upon request.

Thickness Sizes*
1/4	1-3/4
3/8	2
1/2	2-1/4
5/8	2-1/2
3/4	2-3/4
7/8	3
1	3-1/2
1-1/8	4
1-1/4	4-1/2
1-3/8	5
1-1/2	6

*Non-standard thickness available upon request.

Standard Width Sizes**
1	7
1-1/2	8
2	10
2-1/2	12
3	14
3-1/2	16
4	18
5	24
6

**We will also cut any width required.