Acier 4140 : composition, caractéristiques, méthodes de traitement et domaines d'application

Par: Walter
8 septembre 2022

Welcome to HDC Manufacturing, the steadfast ally in the bespoke fabrication of metallic components, boasting a reservoir of industry acumen spanning more than a decade. Nestled within our state-of-the-art facilities, adorned with avant-garde apparatus such as 4-axis and 5-axis machining centers, alongside meticulous inspection instruments like coordinate measuring machines, HDC Manufacturing proudly claims its stature as a preeminent purveyor of personalized metal resolutions.

The linchpin of our prowess resides in 4140 Steel Machining. Armed with a proficient cohort and advanced CNC machining prowess, HDC Manufacturing pledges the zenith of quality and precision in each endeavor. Be it intricate constituents or robust fragments, HDC Manufacturing’s unwavering allegiance to excellence ensures an apogee of outcomes when interfacing with 4140 Steel.

Embark upon an odyssey through the plethora of machining alternatives HDC Manufacturing proffers, spanning the gamut from CNC machining to casting, forging, laser incision, and metal stamping. Our pliable capabilities stand poised to attend to a myriad of requirements, delivering bespoke resolutions attuned to the distinctive needs of your undertakings. Select HDC Manufacturing for your metallic craftsmanship requisites, where erudition and ingenuity converge, breathing life into your visionary aspirations.

Qu'est-ce que l'acier 4140 ?

The 4140 steel is a low alloy steel part enriched by chromium, molybdenum and manganese, known for its distinctive quality of high toughness, high torsional strength and good fatigue strength. This composite structure provides with excellent toughness, strength, and wear resistance. The process of heat treatment, annealing and tempering, strengthens the steel for a specific use. 4140 steel’s robustness and durability make it a good choice for producing such components as gears, axles, and bolts where it is widely used across many industries like oil and gas, agriculture, defense and automotive for its ability to stay in good condition even under difficult conditions.

Comment l’acier 4140 est-il nommé selon quelle règle ?

L'acier 4140 est désigné selon le système de classification des aciers AISI/SAE, où le premier chiffre (4) désigne un alliage de molybdène, le deuxième chiffre (1) indique des éléments d'alliage supplémentaires comme le chrome et le molybdène, et les deux derniers chiffres (40) spécifient la teneur en carbone de l'acier à environ 0,40%. Cette nomenclature fournit une référence rapide à la composition chimique et aux propriétés de l'acier, soulignant son utilisation de molybdène pour une résistance, une ténacité et une résistance à l'usure améliorées, et le rendant facile à identifier pour les applications nécessitant des matériaux robustes.

Composition chimique de l'acier 4140

L'acier 4140 est classé comme un acier à faible teneur en carbone et faiblement allié avec une bonne résistance aux chocs, une bonne résistance à l'usure, une bonne trempabilité, une bonne ténacité structurelle, une bonne résistance et une légère résistance à la corrosion. Bien qu'il soit peu soudable, il doit être chauffé à plus de 800 °C pour le forger. Le 4140 est polyvalent, en tant qu'acier à outils naturel, certainement utilisé pour les outils et les pièces de machines industrielles soumises à de lourdes charges, telles que les vilebrequins, les essieux arrière, les clips à ressort, les collecteurs, les engrenages, pilotage etc.

Composant	Wt.%
Carbone (C)	0,38 – 0,43
Fer (Fe)	96,785 – 97,77
Chrome (Cr)	0,75 – 1,00
Manganèse (Mn)	0,60 – 0,90
Molybdène (Mo)	0,15 – 0,25
Phosphore (P)	0,0 – 0,035
Silicium (Si)	0,15 – 0,30
Soufre (S)	0,0 – 0,04

L'influence de la composition chimique sur les propriétés de l'acier 4140

One of the essential factors that determine the mechanical properties of the 4140 steel, with about 0.40% carbon, 0.80-1.10% chromium, 0.15-0.25% molybdenum and 0.75-1.0% manganese, is its chemical composition. Carbon gives a combination of strength and ductility, chromium adds additional strength, hardness, tensile strength, and corrosion resistance, molybdenum gives tensile strength at high temperatures as well as resistance to wear and tear, and manganese improves hardenability and imparts resistance cracking. Having such a unique alloy composition, the 4140 steel gains high strength, toughness, wear resistance, and the ability to undergo heat treatment and to be used in the applications which are not damaging and in which performance under stress is crucial, such as gears, axles, and shafts.

Propriétés mécaniques de l'acier 4140

Propriétés mécaniques	Métrique	Anglais
Résistance à la traction ultime	1020 MPa	148000 psi
Résistance à la traction	655 MPa	95000 psi
Allongement à la rupture	17.7 %	17.7 %
Réduction de la superficie	46.8 %	46.8 %
Dureté, Brinell	302	302
Dureté, Knoop	328	328
Dureté, Rockwell B	99	99
Dureté, Rockwell C	32	32
Dureté, Vickers	319	319
Module d'élasticité	205 GPa	29700 ksi
Module de masse	160 GPa	23200 ksi
Module de cisaillement	80,0 GPa	11600 ksi
Coefficient de Poisson	0.29	0.29
Usinabilité	65 %	65 %

Propriétés physiques de l'acier 4140

Propriétés physiques	Évaluer
Densité	7,85 g/cc
Point de fusion	2 580-2 650 °F
Chaleur spécifique	1,13 x 10^-1 BTU/lb-°F
Conductivité thermique	296 BTU-in/hr-ft^2-°F

Matériaux équivalents Acier 4140

UE	Etats-Unis	Allemagne	France	Italie	Espagne	Inter
FR	–	DIN,WNr	AFNOR	Uni	UNE	ISO
42CrMoS4 (1.7227)	4140	42CrMoS4	42CD4u	42CrMo4	40CrMo41	42CrMoS4

Le prix de l’acier 4140

The price of 4140 steel is somewhat volatile to changes that are brought about by factors that include market demand, raw material costs, supply levels, and overall economy. It depends on the steel’s form (e.g., bars, plates, and sheets), size, and other operations such as heat treatment and so on. Because the prices are variable, at any given time, for the most correct and the latest pricing, it is advised to contact steel suppliers or study recent market reports directly. Steel is priced per pound or per metric ton primarily, and cost reductions could be possible on per-unit basis for large volume purchases. Furthermore, passing through the retailers may include shipping, handling, and other fees.

Quelles sont les limites de l'acier 4140 ?

4140 steel, despite its multiple advantages in strength, toughness, and versatility facing the limits such as the reduced weldability requesting special welding procedures to stop cracking, lower corrosion resistance compared to the stainless steels hence protective coatings are required, and the technical problems in machining behaviour due to its hardness which causes a rise in manufacturing costs. Also, its alloying elements add, not only the material but also the processing expenses, thus making it more pricey than the simplest carbon steels. Furthermore, thicker sections are tougher to treat for homogenous properties and, thus, may crack if not tempered properly. Moreover, some specific sizes of 4140 steel are not readily available making customized options time-consuming and costly, leading to delays and extra expenses. Weighing these factors against the benefits is a big decision that is made for each given application.

Méthodes de traitement courantes utilisées pour l'acier 4140

The properties of 4140 steel will be improved by different methods of processing it to suit various applications. By forging the steel the structure is strengthened and made tougher, while annealing is done to lower hardness and remove internal stresses which makes the steel more easy to work with (more workable). Normalization adds refinement to the grain structure, and thus improving toughness and uniformity come together. Hardening, which is the process of heating and quenching followed by tempering, increases durability and resistance to wear but decreases the toughness to avoid brittleness. Instead, the carburizing process hardens the surface for parts, where the core must be tough and outside parts must be hard. Though fairly tough, 4140 can be machined using proper tools and conditions. The process collectively makes 4140 steel customizable, thus it meets the expected performance of specific applications, such as the required mechanical strength, toughness and wear resistance.