Views: 7 Author: Site Editor Publish Time: 2025-05-08 Origin: Site
AISI 4140 alloy steel is a chromium-, molybdenum-, and manganese-containing low alloy steel.4140 alloy steel is characterized by high strength, good hardenability, good toughness and low deformation during quenching. It has high fatigue strength, abrasion and impact resistance, toughness, and torsional strength. Because of these special properties, 4140 alloy steel is impressively tough and has quite a high torsional and fatigue strength.
1) Melting
First, iron ore is melted together with scrap iron, molybdenum, chromium, and carbon. These are mixed in an electric or oxygen furnace and heated to 1500°C or higher. The result of the melting is molten steel.
2) Cooling
The molten steel is removed from the furnace and cooled in the open air or through quenching. The result is solidified steel. At this stage, the 4140 steel may develop internal stresses or hardness due to the rapid cooling.
3) Refining
The next step is refining. Hydrofluoric acid is suitable for removing rust and impurities such as sulfur or phosphorus that may be present on the surface of the 4140 steel.
4) Shaping
After the metal is cleaned, it is poured into molds to create shapes such as ingots, billets, or slabs.
5) Inspection
Throughout the process, the steel's chemical composition, mechanical properties (strength, toughness, hardness), and dimensional accuracy are tested to ensure it meets the 4140 specifications.
CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Mo | Cu |
AISI 4140 | MIN | 0.38 | 0.75 | 0.15 | 0.8 | 0.15 | ||||
MAX | 0.43 | 1 | 0.035 | 0.04 | 0.35 | 0.25 | 1.1 | 0.25 | 0.35 |
Properties | Metric | Imperial |
Density | 7.85 g/cm3 | 0.284 lb/in³ |
Melting point | 1416°C | 2580°F |
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 |
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 |
ASTM/AISI | UNS | JIS | KS | ISO | DIN | W-Nr. | NF EN/NF | EN | |
4140 | G41400 | SCM440 | SCM440 | 42CrMo4 | 42CrMo4 | 1.7225 | 42CD4 | 42CrMo4 | 1.7225 |
Annealing: Performed at 800–850°C followed by slow cooling to improve machinability.
Normalizing: Heated to 870–900°C and air-cooled to refine the grain structure and enhance mechanical properties.
Quenching and Tempering: Quenched in oil or water from 840–880°C, then tempered at 540–680°C to achieve the desired hardness and toughness.
Induction or Flame Hardening: Increases surface hardness for improved wear resistance while maintaining a tough core.
High Strength and Hardness:
After appropriate heat treatment (such as quenching and tempering), 4140 steel can achieve high strength and hardness, making it suitable for applications involving heavy loads and wear resistance.
Good Toughness:
Compared to higher carbon or higher strength steels, 4140 has good toughness, allowing it to absorb impact energy without brittle fracture. This makes it ideal for components subjected to shock loading.
Good Wear Resistance:
Its hardness gives it a certain level of wear resistance, especially after surface hardening treatments such as induction or flame hardening.
Good Hardenability:
4140 has excellent hardenability, meaning it can be uniformly hardened throughout its cross-section during quenching. This is particularly important for large-section components.
Relatively Good Machinability:
In the annealed or normalized condition, 4140 steel offers relatively good machinability, making it easy to turn, mill, and process.
Limited Corrosion Resistance:
While better than plain carbon steel, 4140 is not stainless steel and will still rust in humid or highly corrosive environments. Protective measures are required for corrosion resistance.
Relatively Poor Weldability:
Compared to low carbon steels, 4140 has poorer weldability and requires preheating and post-weld heat treatment to prevent cracking and ensure joint performance.
Decreased High-Temperature Strength:
The strength of 4140 steel decreases significantly at elevated temperatures, making it unsuitable for long-term service under high-temperature and high-load conditions.
1. Automotive and Transportation
2. Oil & Gas Industry
3. Heavy Machinery and Equipment
4. Aerospace (non-structural parts)
5. Tooling and Die Applications:
6. Construction and Structural Use
1. Is 4140 considered stainless steel?
No, 4140 is not considered stainless steel.
The definition of stainless steel hinges on its high chromium content, typically requiring at least 10.5% chromium to form a passive protective film that resists corrosion.
The typical chromium content range for 4140 alloy steel is between 0.80% and 1.10%, which is significantly lower than the standard for stainless steel. While its alloying elements like chromium and molybdenum give it better corrosion resistance than plain carbon steel, it will still rust, especially in humid or corrosive environments.
2. What is the difference between 4140 and 4340 steel?
4140 Steel: Good strength and hardness, easy to machine and weld, relatively low cost, suitable for most medium-strength applications.
4340 Steel: Higher strength, hardness, and toughness, especially better for applications requiring resistance to impact and fatigue loads, as well as those operating in low-temperature environments, but more difficult to machine and weld, and higher cost.
3. What is the difference between 4130 and 4140 alloy?
4130: Easier to weld and machine, good strength, and higher toughness. Often used in applications where these factors are critical, such as aircraft tubing and racing frames.
4140: Higher strength and hardness, but less weldable and machinable than 4130. Preferred for higher stress applications like gears, shafts, and fasteners.
4. Where can I buy 4140 steel?
You can buy 4140 steel from us at ZIZI ENGEERING CO LTD . We are a leading supplier of high-quality and affordable steel products for various industries. We can provide you with customized sizes and shapes of steel plates, bars, tubes, pipes, fittings, flanges, sheets, or customized sizes per drawings.
