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Demystifying Metal Specifications

In the simplest terms, materials specifications are like rules that say how materials should be made and what properties they need to have. Different organizations and authorities make sure that these rules are followed to ensure the materials are safe, reliable, and suitable for their intended use. In this article we will breakdown, simplify, and explain how specifications impact the material you buy.


What are materials specifications and who enforces them?

Materials specifications typically include information such as chemical composition, mechanical properties, dimensional tolerances, surface finish, heat treatment requirements, testing methods, and other relevant parameters. They provide guidelines for manufacturers, suppliers, and users to ensure consistent quality, performance, and safety of materials.

The enforcement of materials specifications varies depending on the industry and the specific context. Some key Industry-specific organizations are the American Society for Testing and Materials (ASTM), Society of Automotive Engineers (SAE), American Iron and Steel Institute (AISI), and Aerospace Material Specifications (AMS).

While ASTM, SAE, AISI, and AMS have their distinct areas of focus, there can be instances of collaboration or overlap where they may reference each other's standards or work together on specific projects or initiatives related to common areas of interest.

ASTM: develops standards and specifications covering a broad range of materials, products, and industries beyond just iron and steel.

AISI: primarily focuses on standards and specifications for iron and steel products.

SAE: develops standards and specifications for various aspects of mobility engineering, including materials used in the automotive, aerospace, and commercial vehicle industries.

AMS: stands for Aerospace Material Specification. It is a set of standards and specifications developed by the SAE (Society of Automotive Engineers) for materials used in aerospace applications.

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What is ASTM?

ASTM (American Society for Testing and Materials) is a globally recognized organization that develops and maintains standards and specifications across a wide range of industries and materials. ASTM covers diverse areas such as metals, construction materials, textiles, petroleum, plastics, and more.

An example specification is ASTM A193, and it covers the requirements for alloy steel and stainless-steel bolting materials for high-temperature or high-pressure service.

A193: The number "193" is the numerical designation assigned to this specific ASTM specification. Each ASTM specification has a unique numerical identifier. ASTM A193 covers two types of bolting materials—alloy steel and stainless steel.

ASTM A193 is specifically designed for bolting materials intended for use in environments with high temperatures. It's important to note that ASTM A193 also includes various grades (e.g., A193 B7, A193 B8, A193 B8M) that specify different material compositions and properties to suit specific applications and service conditions.

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What is AISI?

AISI (American Iron and Steel Institute) is an industry association that focuses specifically on the iron and steel industry. It represents and advocates for the interests of North American steel producers. AISI develops standards and specifications primarily related to steel and iron products.

AISI 4340 serves as an example of an AISI specification for alloy steel. The designation "4340" is a numerical identifier assigned by AISI to this specific alloy steel composition. The first two digits signify a Nickel-Chromium-Molybdenum alloy steel, while the last two digits indicate a carbon content of approximately 0.4 percent. By referencing AISI 4340, manufacturers, suppliers, and users can confidently select the suitable alloy steel that possesses the desired properties for their applications. This ensures that the chosen alloy steel meets the necessary requirements and performs effectively in the intended use case.

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What is SAE?

SAE (Society of Automotive Engineers) is another industry association that focuses on mobility engineering. While SAE is known for its involvement in the automotive industry, it covers a broader range of industries, including aerospace, commercial vehicles, and more. SAE develops standards and specifications related to various aspects of mobility, including materials, components, systems, and processes.

An example of an SAE specification is SAE 660, and it refers to a type of bronze material specifically used for bearings. Bearings are components that support moving parts and reduce friction between them. The SAE 660 designation helps users identify and specify the appropriate bearing bronze material for their applications, ensuring compatibility, performance, and reliability.

What is the difference between AISI & SAE?

Both organizations develop standards and specifications, but AISI's focus is on steel, while SAE's focus extends to multiple sectors within mobility engineering.

Both AISI and SAE collaborated to develop and maintain the same alloy number system, ensuring consistency and compatibility across industries. This system provides a common language for manufacturers, suppliers, and users to refer to specific alloy compositions and properties.

For example, alloy steel grade 4140 is designated as AISI 4140 and SAE 4140. The same applies to other alloy steel grades such as 4340 (AISI 4340, SAE 4340), 316 stainless steel (AISI 316, SAE 316), and so on.

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What is AMS?

AMS (Aerospace Material Specification) is a set of standards and specifications developed by the SAE (Society of Automotive Engineers) for materials used in aerospace applications. These specifications cover a wide range of materials, including metals, alloys, composites, plastics, and more.

AMS specifications provide detailed requirements for materials in terms of their chemical composition, mechanical properties, manufacturing processes, testing methods, and quality control measures. They are designed to ensure that materials used in aerospace applications meet stringent performance, reliability, and safety standards.

AMS 5510 specifically pertains to a type of stainless steel known as 301 Full Hard. By referring to AMS 5510, manufacturers, suppliers, and users in the aerospace industry can ensure the proper selection and utilization of stainless steel 301 Full Hard that meets the specified requirements and performance standards.

An example specification AMS-QQ-A-225/6 refers to an Aerospace Material Specification for aluminum alloy 2024.

Here's a breakdown of the specification:

AMS: Aerospace Material Specification

QQ: Formerly used to indicate Federal Specifications

A: Indicates aluminum alloy materials

225: Represents the specific alloy within the series

/6: Denotes the specific revision or amendment of the specification

AMS-QQ-A-225/6 covers the requirements for aluminum alloy 2024 in the form of sheet, plate, and rolled or cold-finished bar. Aluminum alloy 2024 is a high-strength, heat-treatable alloy commonly used in aerospace applications due to its excellent strength-to-weight ratio.

*It's important to refer to the latest revision of the specification to ensure accurate and up-to-date information regarding the specific requirements for aluminum alloy 2024.

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Other Specs You Might See

DMS - McDonnell Douglas Specification refers to a set of technical requirements and standards established by the former aerospace manufacturer McDonnell Douglas Corporation. McDonnell Douglas was a major American aerospace company that later merged with Boeing in 1997. Since the merger with Boeing, the McDonnell Douglas Specifications have largely been superseded or integrated into Boeing's own specifications and standards.

BMS - Boeing Material Specifications (BMS) cover a wide range of areas, including materials, finishes, coatings, fasteners, adhesives, electrical components, and more. Each BMS specification is identified by a unique alphanumeric code, such as BMS 8-121, with each code representing a different area of focus.

MIL - Military specifications, often referred to as "MIL-SPEC," are a set of standards established by various branches of the United States military to define the requirements and expectations for materials, equipment, and systems used by the military. These specifications cover a wide range of areas, including materials, manufacturing processes, performance criteria, and testing procedures.

NACE - A standard developed by the National Association of Corrosion Engineers (NACE) International. NACE standards cover a wide range of industries and applications, including oil and gas, chemical processing, water treatment, infrastructure, and more. These standards provide guidelines, specifications, and recommended practices to address various aspects of corrosion, such as material selection, coatings, cathodic protection, corrosion monitoring, and corrosion management.

IPC - IPC (Institute for Interconnecting and Packaging Electronic Circuits) standards cover various aspects of electronic manufacturing, including design guidelines, materials selection, fabrication processes, assembly methods, and quality control. These standards help ensure consistency, reliability, and quality in the production of electronic devices and PCBs.


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