AISI 4140 Alloy Steel
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.
Supplying Size:
Rolled: Diameter 40-200mm
Forged: Diameter 80-600mm
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 | |
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)
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.
