Stainless Steel: Exploring AMS 5659, AMS 5862, and BMS7-240 Specifications


Stainless Steel Specifications

Stainless steel, an alloy renowned for its robustness and corrosion resistance, has become a cornerstone in various industries, from construction to aerospace. Within this vast domain, certain specifications like AMS 5659, AMS 5862, and BMS7-240 have been developed to cater to specific requirements. These specifications delineate the chemical composition, mechanical properties, and other critical characteristics that ensure the material’s suitability for particular applications.

This exploration focuses on these specialized stainless steel specifications, shedding light on their unique features and the implications for their respective applications. By understanding the nuances of each specification, professionals across industries can make informed decisions when selecting materials for their projects.

Overview of AMS 5659: Composition and Characteristics


  • Primary Elements: The core elements of AMS 5659 include iron, chromium, nickel, and molybdenum. Chromium contributes to the corrosion resistance, while nickel enhances the material’s formability and strength.
  • Trace Elements: Minor components such as carbon, manganese, silicon, phosphorus, sulfur, and nitrogen are also present. These elements are carefully controlled to enhance specific properties like hardness and machinability.


  • Mechanical Properties: AMS 5659 stainless steel exhibits high strength and toughness, particularly at elevated temperatures. It maintains its structural integrity under stress and has excellent fatigue resistance.
  • Corrosion Resistance: Thanks to its chromium content, this steel offers superior resistance to oxidation and corrosion, making it ideal for harsh environments.
  • Heat Treatment: This specification includes detailed guidelines for heat treatment processes to achieve the desired mechanical properties. The steel is typically subjected to solution annealing, followed by precipitation hardening.

Applications: Given its robust characteristics, AMS 5659 stainless steel finds extensive use in aerospace components, such as turbine blades, shafts, and fasteners, where strength and corrosion resistance are paramount.

AMS 5862: Properties and Industrial Applications

AMS 5862, another pivotal Aerospace Material Specification, outlines the standards for a specific stainless steel variant, distinct in its composition and intended for demanding industrial applications. This specification is tailored for steel that requires a unique combination of strength, corrosion resistance, and durability, particularly in high-stress environments.


  • Chemical Composition: AMS 5862 stainless steel primarily consists of iron, chromium, nickel, and molybdenum. The precise ratios of these elements are critical in conferring the steel’s unique properties.
  • Mechanical Strength: This steel is known for its exceptional strength and ability to withstand high pressure and temperatures. It is often used in situations where structural integrity is paramount.
  • Corrosion Resistance: The chromium content in AMS 5862 provides excellent resistance to oxidation and corrosion, making it suitable for use in environments that are corrosive or oxidizing.
  • Heat Treatment and Fabrication: The specification also includes guidelines for heat treatment to optimize the material’s mechanical properties. The steel can be welded, formed, and machined with standard methods, making it versatile for various applications.

Industrial Applications:

  • Aerospace Industry: AMS 5862 is extensively used in the manufacture of aerospace components such as engine parts, exhaust systems, and landing gear, where durability and resistance to extreme conditions are required.
  • Medical Devices: Its biocompatibility makes it suitable for medical implants and surgical instruments.
  • Energy Sector: Components in power generation equipment, particularly in high-temperature environments, often utilize AMS 5862 steel.

Understanding BMS7-240

BMS7-240, standing for Boeing Material Specification 7-240, is a unique stainless steel variant specifically developed to meet the stringent requirements of the aerospace industry, particularly in aircraft manufacturing.

Composition and Characteristics:

  • Composition: BMS7-240 comprises a blend of iron, chromium, nickel, and molybdenum, with precise control over elements like carbon, manganese, and silicon.
  • Durability: This steel is known for its exceptional durability and ability to maintain structural integrity under various stress conditions.
  • Corrosion Resistance: Like other stainless steels, BMS7-240 has excellent resistance to corrosion and oxidation, a crucial factor in aircraft applications.


  • Aircraft Manufacturing: BMS7-240 is predominantly used in the construction of aircraft components. Its ability to withstand high stresses and corrosive environments makes it ideal for parts such as fuselage frames, wing structures, and landing gear components.
  • High-Stress Components: Any aerospace component that requires a combination of high strength, toughness, and corrosion resistance is a potential application for BMS7-240 steel.

AMS 5659 vs. AMS 5862 vs. BMS7-240

When comparing AMS 5659, AMS 5862, and BMS7-240, it’s important to understand that while they are all high-performance stainless steel grades, each has been developed with specific properties and applications in mind. This comparative analysis will help in understanding the nuances that distinguish each specification.

AMS 5659 vs. AMS 5862:

  • Composition: Both AMS 5659 and AMS 5862 primarily comprise iron, chromium, nickel, and molybdenum. However, the specific ratios and presence of additional trace elements can vary, leading to different mechanical properties.
  • Mechanical Properties: AMS 5659 is known for its balance between strength and toughness, especially at high temperatures, making it suitable for aerospace components. AMS 5862, while also strong, is designed to withstand even higher pressures and temperatures, and is used in more critical aerospace and medical applications.
  • Corrosion Resistance: Both specifications offer excellent corrosion resistance, but the exact resistance levels can vary based on the exact chemical composition and heat treatment processes.

AMS 5659 vs. BMS7-240:

  • Aerospace Focus: While AMS 5659 is widely used in aerospace for its balanced properties, BMS7-240 is more specifically tailored for aircraft manufacturing, with a focus on durability and resistance to stress.
  • Application Scope: AMS 5659 finds broader application in both aerospace and other industries, while BMS7-240 is more narrowly focused on the specific needs of aircraft construction.

AMS 5862 vs. BMS7-240:

  • Strength and Durability: Both specifications are designed for high-stress environments, but AMS 5862 is often preferred in applications where higher mechanical strength is required, such as in engine parts. BMS7-240, while also strong, is optimized for the unique requirements of aircraft construction.
  • Industry Utilization: AMS 5862 sees usage across a wider range of industries, including aerospace, medical, and energy sectors, whereas BMS7-240 is primarily used in aerospace.

AMS 5659: Mechanical Properties and Performance

Mechanical Properties:

  • Strength: AMS 5659 is characterized by high strength and toughness, which is maintained even at elevated temperatures. This is crucial for parts that experience significant stress and heat.
  • Hardness: The steel under this specification can achieve a high level of hardness, especially after heat treatment, which is essential for wear resistance.
  • Elongation and Ductility: Despite its strength, AMS 5659 retains good elongation and ductility, allowing it to withstand deformation under stress without fracturing.

Performance Metrics:

  • Fatigue Resistance: AMS 5659 has excellent fatigue resistance, making it suitable for components that experience cyclic loading.
  • Corrosion Resistance: The chromium content in AMS 5659 imparts superior resistance to oxidation and corrosion, which is vital for parts exposed to harsh environments.
  • Thermal Stability: This steel maintains its mechanical properties over a wide range of temperatures, which is beneficial for components exposed to varying thermal conditions.

Heat Treatment Processes of AMS 5862

AMS 5862 stainless steel, tailored for high-strength and corrosion-resistant applications, requires specific heat treatment processes to achieve its desired properties. The heat treatment of AMS 5862 is a critical step in ensuring that the material meets the necessary performance standards for its intended industrial applications.

Heat Treatment Processes of AMS 5862:

  1. Solution Treatment:
  • Purpose: This initial step involves heating the steel to a high temperature to dissolve the alloying elements and homogenize the microstructure.
  • Process: The steel is typically heated to a temperature range of 1900°F to 1950°F (1038°C to 1066°C).
  • Cooling: After holding at the solution temperature, rapid cooling or quenching is performed to prevent the precipitation of unwanted phases.
  1. Precipitation Hardening (Aging):
  • Purpose: This step aims to precipitate fine particles within the steel matrix, which significantly enhances its strength and hardness.
  • Process: After solution treatment, the steel is reheated to a lower temperature, usually between 900°F and 1150°F (482°C to 621°C), depending on the desired properties.
  • Duration: The material is held at this temperature for a period, which can vary based on the required mechanical properties. This duration is critical in controlling the size and distribution of the precipitates.
  1. Cooling:
  • Post Aging: Following the aging process, the material is cooled down slowly to room temperature.
  • Controlled Cooling: The cooling rate can be controlled to influence the final properties of the material.

Key Considerations in Heat Treatment:

  • Uniformity: Ensuring uniform heating and cooling during the treatment processes is vital to avoid thermal stresses and distortions in the material.
  • Atmosphere Control: The treatment is often conducted in a controlled atmosphere to prevent surface oxidation and scaling.
  • Repeatability: Consistency in heat treatment is crucial for ensuring that each batch of AMS 5862 steel meets the same high standards.

Impact of Heat Treatment on Properties:

  • Increased Strength and Toughness: The primary outcome of this process is an increase in the yield and tensile strength of the steel, making it suitable for high-stress applications.
  • Improved Corrosion Resistance: Proper heat treatment also enhances the corrosion resistance of the steel, an essential attribute for its use in corrosive environments.
  • Optimized Mechanical Properties: By adjusting the heat treatment parameters, different sets of mechanical properties can be targeted, making AMS 5862 versatile for various applications.

Fabrication and Machinability Aspects of BMS7-240

BMS7-240, a specialized stainless steel variant developed primarily for aerospace applications, presents unique challenges and considerations in terms of fabrication and machinability. Understanding these aspects is crucial for manufacturers and engineers who work with this material.

Fabrication Aspects:

  1. Weldability: BMS7-240 is generally considered to have good weldability, allowing for the construction of complex structures without compromising the material’s integrity. However, appropriate welding techniques and parameters must be employed to avoid issues like distortion or weakening at weld joints.
  2. Formability: This alloy can be formed into various shapes, which is essential for aerospace components. However, its high strength and hardness may require more force or specialized tooling compared to softer materials.
  3. Heat Treatment: Post-fabrication, BMS7-240 often undergoes heat treatment to relieve stresses and enhance its mechanical properties. This step is critical in maintaining the material’s performance characteristics, especially in high-stress aerospace environments.

Machinability Aspects:

  1. Cutting and Machining: While BMS7-240 can be machined using standard tooling, its high strength and hardness may lead to increased tool wear. Utilizing tools made from carbide or other hard materials is often advisable.
  2. Coolants and Lubricants: Employing appropriate coolants and lubricants is crucial to prevent overheating and to maintain tool life during machining processes.
  3. Surface Finish: Achieving a high-quality surface finish may require fine-tuning of machining parameters like speed, feed rate, and depth of cut.

How These Alloys Serve Different Industries

AMS 5659, AMS 5862, and BMS7-240 in Various Industries:

  • Aerospace Industry: All three alloys are extensively used in the aerospace industry, but for different components based on their specific properties. AMS 5659 is often used for turbine blades and other engine components due to its high strength and corrosion resistance. AMS 5862 finds application in critical high-stress parts like landing gears and exhaust systems. BMS7-240, with its unique combination of durability and stress resistance, is ideal for structural elements of aircraft.
  • Medical Industry: AMS 5862, in particular, is utilized in the medical field for surgical instruments and implants due to its excellent strength and biocompatibility.
  • Energy Sector: In power generation, particularly in environments with high temperatures and pressures, AMS 5862’s superior strength and corrosion resistance make it a preferred choice.
  • General Engineering and Manufacturing: While BMS7-240 is primarily used in aerospace, AMS 5659 and AMS 5862, with their versatile properties, find broader applications in general engineering and manufacturing sectors, including automotive and chemical processing industries.

In summary, while all three alloys – AMS 5659, AMS 5862, and BMS7-240 – are high-performance stainless steels, they each have distinct properties that make them suitable for specific applications across different industries. Understanding their fabrication and machinability aspects is crucial for effective utilization in these varied sectors.

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