ThePipingMart Blog Grades AMS 4140 Alloy Steel – Composition, Properties and Uses

AMS 4140 Alloy Steel – Composition, Properties and Uses

AMS 4140

AMS4140 is a versatile alloy steel that finds widespread use in various applications that demand high strength, toughness, and wear resistance. Also known as AISI4140, this steel meets stringent international standards such as AMS 6382, AMS 6390, and AMS 6349. This blog post delves deeper into AMS 4140, discussing its composition, physical and mechanical properties, hardness, heat treatment, and typical applications.

What is AMS 4140?

AMS 4140 (also known as AISI 4140 Alloy Steel)  is a type of alloy steel widely used in manufacturing. It is known for its excellent strength, toughness, and wear resistance properties, making it ideal for making machine parts, gears, and other similar components. AMS4140 is also known as Chromoly or Chrom-Moly, due to its chromium and molybdenum content. Furthermore, it can be heat-treated to enhance its mechanical properties, making it a sought-after material in various industrial applications. Whether you want to create high-strength machinery or durable parts that can withstand tough conditions, AMS 4140 is an excellent choice that will not disappoint.

What Form Is AMS 4140 Available at Piping Mart?

  • Bars

AMS 4140 Composition

AMS 4140 is a low-alloy steel that contains significant amounts of chromium, molybdenum, and carbon. The composition typically ranges from 0.38-0.43% carbon, 0.75-1.00% manganese, 0.15-0.35% silicon, 0.80-1.10% chromium, 0.15-0.25% molybdenum, with trace amounts of phosphorus, sulfur, and other elements. The high carbon content contributes to its strength and hardness, while the alloying elements provide excellent wear resistance and toughness.

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

AMS 4140 Physical Properties

AMS 4140 has a density of 7.85 g/cm3 and a melting point of 1416°C. The thermal conductivity of this steel is around 42.6 W/mK, while its coefficient of thermal expansion is 12.3 μm/m°C. In terms of electrical conductivity, this steel has a conductivity of around 40% IACS (International Annealed Copper Standard).

Properties Metric Imperial
Density 7.85 g/cm3 0.284 lb/in³
Melting point 1416°C 2580°F

AMS 4140 Mechanical Properties

One of the key selling points of AMS 4140 is its exceptional mechanical properties. In the quenched and tempered condition (hardness range of 28-32 HRC), this steel exhibits a tensile strength of 930-1200 MPa and a yield strength of 640-850 MPa. Its elongation and reduction in the area range from 12-20% and 40-50%, respectively. The high fatigue strength and impact toughness of AMS 4140 make it an ideal choice for demanding applications such as aerospace components, automotive parts, and oil and gas drilling tools.

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

AMS 4140 Equivalents

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

AMS 4140 Uses

AMS 4140 is a popular choice for a wide range of applications. Its high strength, toughness, and wear resistance make it an ideal material for gears, shafts, spindles, couplings, and other critical machine components. It is also used extensively in the oil and gas industry for downhole drilling tools, such as drill bits, drilling jars, stabilizers, and subs. Other applications include automotive components, such as axles, crankshafts, and steering components, and structural applications requiring high strength.

AMS 4140 Hardness

AMS 4140 has a typical hardness range of 22-35 HRC (Rockwell C scale) in the annealed condition and 28-32 HRC (Rockwell C scale) in the quenched and tempered condition. It is high hardness and excellent wear resistance makes it ideal for applications requiring abrasion resistance, such as cutting tools and roller bearings.

AMS 4140 Heat Treatment

The heat treatment of AMS 4140 involves austenitizing the steel at 815-900°C, followed by quenching in oil or water. This produces a martensitic microstructure that provides high hardness and high strength. The steel is then tempered to achieve the desired balance of toughness and hardness. The exact heat treatment conditions depend on the application and desired properties of the steel.


AMS 4140 material is a versatile low-alloy steel that offers an excellent balance of strength, toughness and wears resistance. Its outstanding mechanical properties and a broad range of applications make it a popular choice for automotive, aerospace, and oil and gas industries. Understanding the composition, properties, and heat treatment of AMS 4140 is critical for selecting the right material for a specific application. With this comprehensive guide, you are now equipped with the knowledge to make an informed decision when choosing AMS 4140.

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