If you’re in the manufacturing, ingénierie, or any industry that requires high – performance metals, 4140 annealed cold rolled steel is a material you should know well. This alloy offers a unique blend of strength, dureté, et machinabilité, making it suitable for a wide range of applications. Dans ce guide, we’ll explore everything from its material properties and composition à industrial applications et supply chain options, helping you make informed decisions for your projects.
1. Propriétés des matériaux & Composition
Composition chimique
4140 steel is a medium – carbone, chrome – molybdenum alloy. The main alloying elements include:
- Carbone (C): Around 0.38 – 0.43%, which contributes to the steel’s hardness and strength.
- Chrome (Croisement): Environ 0.80 – 1.10%, enhancing wear resistance and hardenability.
- Molybdène (MO): Avec 0.15 – 0.25%, it improves the steel’s toughness, especially at high temperatures, and also contributes to hardenability.
- Manganèse (MN): In the range of 0.75 – 1.00%, it helps with strength and hardenability as well.
Propriétés mécaniques
| Propriété | Valeur | Unit |
| Résistance à la traction 4140 annealed CR | 600 – 800 | MPA |
| 4140 annealed yield strength | 380 – 550 | MPA |
| Élongation | 15 – 20 | % |
| Reduction of area | 40 – 50 | % |
| Dureté (BNN) 4140 annealed cold rolled | 170 – 210 | BNN |
| Density of 4140 acier | 7.85 | g / cm³ |
| Impact toughness 4140 recuit | Modéré – Haut (depends on heat treatment) | J/cm² |
Par exemple, in a manufacturing plant producing hydraulic cylinders, le 4140 annealed cold rolled steel’s yield strength of 400 MPA (a value within the range) ensures that the cylinder rods can withstand the internal pressure without deforming.
2. Heat – Treatment Response & Performance mécanique
Heat Treatment Methods
- Recuit: Heating the 4140 steel to around 840 – 870°C and then slowly cooling it. This process softens the steel, reduces internal stresses, and refines the grain structure, enhancing machinabilité.
- Quenching and Tempering: Heating the steel to austenitizing temperature (autour 840 – 860° C pour 4140) followed by rapid cooling (quenching) in oil or water. Alors, it is tempered at 550 – 650°C to balance hardness and toughness. Le hardenability curve 4140 acier shows how the depth of hardening varies with cooling rate.
- Normalizing: Heating above the critical temperature (similar to austenitizing) and air – refroidissement. It improves the grain structure and mechanical properties’ uniformity.
Comparison of Hardness
| Traitement thermique | Dureté (approximate) |
| 4140 recuit | 170 – 210 BNN |
| Quenched & Tempered | 40 – 50 HRC (équivalent à 388 – 477 BNN) |
A manufacturer of high – stress bolts may choose quenched and tempered 4140 steel for its high hardness and strength, while for parts that require more formability and less hardness, the annealed version is preferred.
3. Machinabilité, Formabilité & Finition de surface
Machinabilité
- Machinability rating: 4140 annealed has a good machinability rating, which is better than some higher – alloy steels. Compared to 1045 acier, 4140 annealed has a rating of around 60 – 70% (where 1018 hot rolled = 100%).
- Recommended cutting speeds: For turning operations with high – speed steel (HSS) outils, cutting speeds of 60 – 90 m/min are recommended. When using carbide tools, speeds can be increased to 150 – 250 m / mon.
- Chip control: Due to its relatively soft nature in the annealed state, chip control can be achieved with proper tool geometry. Par exemple, using tools with positive rake angles helps in breaking the chips into smaller pieces during machining.
Formabilité
- Cold forming limits: 4140 annealed can be cold – formed, but it requires more force compared to low – carbon steels. Le bending radius 4140 annealed cold rolled depends on the thickness of the material. Pour un 5 – mm thick sheet, a minimum bending radius of about 1.5 times the thickness (7.5 MM) is typically recommended.
- Soudabilité: 4140 steel has fair weldability. Preheating to 150 – 250°C and post – traitement thermique (tempering) are often required to prevent cracking. MIG or TIG welding with appropriate filler metals like ER80S – G can be used.
Finition de surface
The surface finish achievable on 4140 CR can be as low as Ra 0.2 – 0.8 µm. This smooth surface finish is beneficial for applications where friction needs to be minimized, such as in shafts and hydraulic cylinder rods.
4. Applications industrielles & End – Cas d'utilisation
- Automobile: Automotive crankshafts made from 4140 annealed cold rolled steel can withstand the high – stress cyclic loading during engine operation. Aussi, haut – stress bolts & attaches in engines are often made of 4140 steel due to its strength.
- Aérospatial: Aerospace landing – gear components require materials with high strength – à – weight ratios. 4140 acier, especially in the heat – treated condition, can meet these requirements. Par exemple, the landing – gear struts can be made from 4140 steel to ensure durability during landing impacts.
- Oil and Gas: Drill collars 4140 acier are used in drilling operations. They need to withstand high torque and compressive forces, and the strength and wear resistance of 4140 steel make it an ideal choice.
- Machines industrielles: Engrenages & pinions, tool holders & luminaires, et arbres & essieux are commonly made from 4140 acier. In a gearbox, 4140 pre – hardened gears can transmit high torque efficiently.
5. Availability, Shapes & Supply Chain Options
Shapes and Sizes
- Round bar sizes: 4140 annealed cold rolled round bars are available in diameters ranging from 3 – 150 MM. Par exemple, a manufacturer of small – scale machinery may use 10 – mm diameter round bars for shafts.
- Flat bar: Thicknesses can range from 1 – 30 MM, and widths from 10 – 200 MM.
- Square & hex bar: Square bars with side lengths of 5 – 100 mm and hex bars with across – flats dimensions of 6 – 80 mm are commonly stocked.
Chaîne d'approvisionnement
- Précision – ground 4140 rod suppliers: There are many suppliers worldwide that offer precision – ground rods, ensuring tight tolerances. Par exemple, in the US, companies like XYZ Metals specialize in providing precision – ground 4140 tiges.
- Cut – à – longueur 4140 annealed service: Many suppliers offer cut – à – length services, allowing customers to order the exact lengths they need. This reduces waste and costs.
- Mill minimum order 4140 CR: The mill minimum order quantity can vary, but it’s often around 1 – 5 tons. Cependant, some suppliers may offer smaller quantities for customers with lower requirements.
- Domestic vs import 4140 availability: In the US, domestic suppliers can provide shorter lead times, généralement à l'intérieur 1 – 2 weeks for standard sizes. Imported 4140 steel may take 4 – 6 weeks but could be more cost – effective for large orders.
6. Normes, Certifications & Technical Documentation
- ASTM A331: This standard covers cold – finished alloy steel bars, y compris 4140 annealed cold – finished. It defines the chemical and mechanical property requirements.
- SAE 4140 grade equivalent chart: Helps in comparing 4140 steel with other grades from different standards. Par exemple, it shows the equivalent grades in the European EN system.
- AMS 6381 4140 annealed specification: Aerospace Material Specification (AMS) that details the requirements for 4140 annealed steel used in aerospace applications.
- DANS 1.7225 / 42CrMo4 vs 4140: DANS 1.7225 (42CRMO4) is the European equivalent of 4140 acier. While they have similar chemical compositions, there may be slight differences in mechanical properties due to manufacturing variations.
- Material test report (MTR) 4140: A document provided by the supplier that shows the test results for chemical composition and mechanical properties of the supplied 4140 acier.
- ISO 9001 & AS9100 certified 4140 supplier: ISO 9001 ensures quality management systems, and AS9100 is for aerospace – related quality. Suppliers with these certifications can provide more reliable products.
- REACH & RoHS compliance 4140 acier: REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) and RoHS (Restriction of Hazardous Substances) ensure that the 4140 steel does not contain harmful substances above the regulated limits.
Yigu Technology’s Perspective on 4140 Annealed Cold Rolled Steel
À la technologie Yigu, we’ve witnessed the versatility of 4140 annealed cold rolled steel in various projects. For applications that demand a balance of strength and machinability, like in the production of high – engrenages de précision, this material is a top choice. We often recommend it to clients in the automotive and machinery industries. Our team can assist in selecting the right heat – treated state and shape based on your project requirements, ensuring cost – efficiency and high – quality end – produits.
FAQ
- Peut 4140 annealed cold rolled steel be welded easily?
4140 steel has fair weldability. Cependant, preheating to 150 – 250°C and post – traitement thermique (tempering) are often required to prevent cracking. Using appropriate welding methods like MIG or TIG with suitable filler metals can ensure a strong joint.
- What is the difference between 4140 annealed and 4140 quenched and tempered?
4140 annealed is softer, with a hardness of 170 – 210 BNN, and is more suitable for applications requiring formability and ease of machining. 4140 quenched and tempered is much harder, with a hardness of 40 – 50 HRC (388 – 477 BNN), and is used for applications where high strength and wear resistance are crucial.
- Where can I find a reliable supplier for 4140 annealed cold rolled steel?
You can look for suppliers with ISO 9001 or AS9100 certifications, depending on your industry. Domestic suppliers may offer shorter lead times, while imported options could be more cost – effective for large orders. Requesting material test reports (Mtrs) can help ensure the quality of the supplied steel.
