ThePipingMart Blog Grades AISI 8640 Alloy Steel (UNS G86400) – Properties Uses and Composition

AISI 8640 Alloy Steel (UNS G86400) – Properties Uses and Composition

AISI 8640 Steel

AISI 8640 steel is a versatile medium-carbon, nickel, chromium and molybdenum alloy that has proven its value as a reliable steel in a wide range of industrial applications and its properties make it suitable for automotive part types, shafts and gears. AISI 8640 alloy steel, also known as SAE-AISI 8640 steel, is a low alloy steel primarily used in the manufacture of machinery and equipment These steels consist of carbon, manganese, silicon, chromium, nickel and molybdenum. The unique structure of AISI 8640 Alloy Steel gives it superior strength, toughness and wear resistance. The steel is easily heat treated to improve its properties, making it an excellent choice for applications requiring high strength and durability Because of its low carbon content it is possible to weld softened without risk of cracking. Overall, AISI 8640 alloy steel, also known by its UNS G86400 designation, is an excellent choice for applications requiring strength, durability and weldability.

What Forms of AISI 8640 is Available at Piping Mart?

  • Nut
  • Bar
  • Bolt
  • Pipe
  • Screw
  • Tubing
  • Valves
  • Washers
  • Flanges
  • Fasteners
  • Electrodes
  • Stud Bolts
  • Sheet Plates
  • Pipe Fittings
  • Forged Fitting
  • Instrumentation Fittings

AISI 8640 Chemical Composition

AISI 8640 is a low-grade steel alloy with chemical compositions of Carbon (0.37-0.43%), Manganese (0.60-0.90%), Chromium (0.40-0.70%), and Nickel (0.40-0.40%). 0.70%), Molybdenum (0.15-0.25%), Silicon (0.15-0.30%), and Sulfur (0.040% max). It is known for its durability, which is suitable for applications requiring high strength with fatigue and shock resistance.

Element Content (%)
Manganese, Mn 0.75-1.00
Nickel, Ni 0.40-0.70
Chromium, Cr 0.40-0.60
Carbon, C 0.38-0.43
Silicon, Si 0.15-0.30
Molybdenum, Mo 0.15-0.25
Sulfur, S 0.04 (max)
Phosphorus, P 0.035 (max)

AISI 8640 Physical Properties

AISI 8640, a low-alloy steel, exhibits a density of around 7.85 g/cm³. This moderate density makes it suitable for diverse applications, balancing strength and weight. Engineers often favor AISI 8640 for components requiring durability and resilience. The steel’s density influences its performance in structural elements and mechanical parts, offering a combination of robustness and efficiency. This physical property enhances its versatility in industries where a precise equilibrium of material characteristics is paramount.

Properties Metric Imperial
Density 7.7-8.03 g/cm3 0.278-0.290 lb/in3

AISI 8640 Mechanical Properties

AISI 8640 exhibits an elastic modulus, reflecting its stiffness, typically around 190-210 GPa. The Poisson’s ratio, indicating material deformation behavior, ranges between 0.27 and 0.30. These mechanical properties are crucial for understanding the steel’s response to stress and strain in structural and engineering applications.

Properties Metric Imperial
Elastic modulus 190-210 GPa 27557-30458 ksi
Poisson’s ratio 0.27-0.30 0.27-0.30

AISI 8640 Equivalent

DIN 1.6546 UNI 40 NiCrMo 2 KB B.S. Type 7 ASTM A322 ASTM A331
ASTM A506 ASTM A519 SAE J404 SAE J412 SAE J770

AISI 8640 Uses

8640 Alloy Steel is typically used in applications such as crankshafts, couplings, and other automotive parts; shafts for machinery; and gears. It is also used in oil refineries and petrochemical plants due to its excellent corrosion resistance. Additionally, it can be used for various components in aircraft construction, such as landing gear frames, supports for engines and transmissions, cowlings, propeller shafts, and more.

AISI 8640 Uses in Industries

  • Automotive Industry
  • Aerospace Industry
  • Oil and Gas Industry
  • Construction Industry
  • Manufacturing Industry

AISI 8640 Corrosion Resistance

AISI 8640 is a low-alloy steel with fair corrosion resistance. While not specifically designed for highly corrosive environments, it performs satisfactorily in mild conditions. Protective coatings or corrosion inhibitors may be applied to enhance its longevity in harsh settings. Considering environmental factors is crucial when choosing AISI 8640 for applications requiring resistance against corrosion.

AISI 8640 Heat Resistance & Heat Treatment

AISI 8640 steel also offers good heat resistance due to the presence of nickel and chromium. These two elements combine to create an alloy that can withstand temperatures up to 1200°F (650°C). Heat treatment can be used to further strengthen this type of steel by increasing hardness as well as improving wear resistance and fatigue strength. However, care must be taken not to overheat the material during heat treatment as this could lead to cracking or distortion of the material’s shape or structure.

AISI 8640 Machining

Machining AISI 8640 steel requires special attention due to its hardening behaviour during machining operations. It should only be machined with tools designed specifically for hard materials, such as carbide-tipped tools with positive rake angles (generally 10 degrees) and slow cutting speeds (around 50 feet per minute). Additionally, coolants should always be used when machining this type of steel to help reduce friction between the tool and workpiece while also preventing heat buildup, which can lead to distortion or cracking if not properly controlled.


AISI 8640 steel has repeatedly proven itself in numerous industrial applications thanks to its combination of corrosion resistance, heat resistance, machinability, strength, ductility and durability under a wide range of working conditions. From automotive components like crankshafts and gears through aircraft components like supports for engines and transmissions – there really isn’t much this versatile medium-carbon nickel-chromium-molybdenum alloy cannot do! So if you’re looking for an all-purpose metal that will provide long-lasting performance no matter what environment you may find yourself working in, look no further than AISI 8640!

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