Introduction to the ASTM Designation System

ASTM specifications represent a consensus among producers, specifiers, fabricators, and users of steel mill products. ASTM’s designation system for metals consists of a letter (A for ferrous materials) followed by an arbitrary sequentially assigned number. These designations often apply to specific products, for example A548 is applicable to cold-heading quality carbon steel wire for tapping or sheet metal screws.

 

Steel standards are instrumental in classifying, evaluating, and specifying the material, chemical, mechanical, and metallurgical properties of the different types of steels, which are primarily used in the production of mechanical components, industrial parts, and construction elements. The most widely used standard specifications for steel products in the United States are those published by ASTM (American Society for Testing and Materials).

 

ASTM specifications represent a consensus among producers, specifiers, fabricators, and users of steel mill products. In many cases, the dimensions, tolerances, limits, and restrictions in the ASTM specifications are similar to or the same as the corresponding items in the standard practices contained in the AISI Steel Products Manuals.

 

Many of the ASTM specifications have been adopted by the American Society of Mechanical Engineers (ASME) with little or no modification; ASME uses the prefix S and the ASTM designation for these specifications. For example, ASME-SA213 and ASTM A 213 are identical.

 

ASTM’s designation system for metals consists of a letter (A for ferrous materials) followed by an arbitrary sequentially assigned number. These designations often apply to specific products, for example A548 is applicable to cold-heading quality carbon steel wire for tapping or sheet metal screws. Metric ASTM standards have a suffix letter M.

Examples of the ASTM ferrous metal designation system, describing its use of specification numbers and letters, are shown below:

 

Example - ASTM A 582/A 582M-95b (2000), Grade 303Se-Free-Machining Stainless Steel Bars:

• ‘A’ describes a ferrous metal, but does not sub classify it as cast iron, carbon steel, alloy steel, tool steel, or stainless steel;
• 582 is a sequential number without any relationship to the metal’s properties;
• M indicates that the standard A582M is written in rationalized SI units (the M comes from the word Metric), hence together 582/A582M includes both inch-pound and SI units;
• 95 indicates the year of adoption or last revision and a letter b following the year indicates the third revision of the standard in1995;
• (2000), a number in parentheses, indicates the year of last re-approval;
• Grade 300Se indicates the grade of the steel, and in this case, it has a Se (selenium) addition.

 

Within the steel industry, the terms Grade, Type, and Class are generally defined as follows: Grade is used to describe chemical composition; Type is used to define the deoxidation practice; and Class is used to indicate other characteristics such as strength level or surface finish. However, within the ASTM standards, these terms were adopted and used to identify a particular metal within a metal standard and used without any strict definition. Although there are differences between the ASTM and traditional definitions of these terms ASTM have applied some loose rules to the use of this terminology in their designation system :

 

Example 1 - ASTM A 106-02a Grade A, Grade B, Grade C - Seamless Carbon Steel Pipe for High-Temperature Service:

• Typically an increase in alphabet (such as letters A, B, C) results in higher tensile or yield strength steels, and if it’s an unalloyed carbon steel, an increase in carbon content;
• In this case: Grade A:0.25%C (max), 48 ksi tensile strength (min); Grade B: 0.30%C (max), 60 ksi tensile strength (min); Grade C 0.35%C (max), 70 ksi tensile strength (min).

 

Example 2 - ASTM A 276-03, Type 304, 316, 410 – Stainless and Heat Resisting Steel Bars and Shapes:

 

Types 304, 316, 410 and others are based on the SAE designation system for stainless steels (see SAE and former AISI description that follows).

 

Another use of ASTM grade designators is found in pipe, tube, and forging products, where the first letter P refers to pipe, T refers to tube, TP may refer to tube or pipe, and F refers to forging.

 

Examples are found in the following ASTM specifications:

• ASTM A 335/A335-03, Grade P22; Seamless Ferritic Alloy-Steel Pipe for High Temperature Service;
• ASTM A 213/A213M-03a, Grade T22; Seamless Ferritic and Austenitic Alloy Steel Boiler, Superheater and Heat-Exchanger Tubes;
• ASTM A 312/A312M-03, Grade TP304; Seamless and Welded Austenitic Stainless Steel Pipe;
• ASTM A 336/A336M-03a, Class F22-Steel Forgings, Alloy, for Pressure and High-Temperature Parts.

 

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